PIR 2008-1C 25

INTRODUCTIONThe Colville Basin in northern Alaska is a large east-trending foreland basin that developed north of the Brooks

Range fold and thrust belt in the Early Cretaceous (Mull, 1985; Bird and Molenaar, 1992; fi gs. 1–2). The southern margin of the basin is generally regarded as gas-prone, although it remains underexplored relative to the rest of the North Slope (Houseknecht and Bird, 2006). Seismic data are poor throughout this belt (Molenaar, 1988), leading to uncertainty regarding regional stratigraphic relationships.

The purpose of this paper is to examine the poorly understood stratigraphic relationship between the Fortress Mountain and Nanushuk2 Formations—two of the most prospective siliciclastic units exposed in the inner foot-hills. Many previous workers have interpreted the two units as discrete depositional cycles, often separated by a “tongue” of mudstone-dominated Torok Formation (Mull, 1985; Moore and others, 1994; fi g. 3). However, in the fi eld the relationship between the two formations is unclear and the two distinct belts of resistant exposures are never observed in close spatial association (fi g. 2). To date, it has been diffi cult to prove the two units did not overlap in time, leading some workers to entertain the hypothesis that the uppermost Fortress Mountain Formation graded northward into the lower Nanushuk Formation (Kelley, 1990). In addition to ambiguous fi eld relationships, available biostratigraphic constraints have largely proven insuffi cient to address this question. This study takes an alternate approach, testing the stratigraphic continuity of the two units on the basis of their provenance character-istics—specifi cally, the novel application of detrital zircon geochronology. Preliminary results strongly suggest the two units represent different depositional sequences.

1Alaska Division of Geological & Geophysical Surveys, 3354 College Rd., Fairbanks, Alaska 99709-3707Email for Marwan A. Wartes: marwan.wartes@alaska.gov

2The Nanushuk has historically been ascribed Group status (Detterman, 1956). However, in a comprehensive revision and simplifi cation of Brookian stratigraphic nomenclature, Mull and others (2003) suggested the Nanushuk be demoted to formation rank.

EVALUATION OF STRATIGRAPHIC CONTINUITY BETWEEN THE FORTRESS MOUNTAIN AND NANUSHUK FORMATIONS IN THE CENTRAL BROOKS RANGE FOOTHILLS—ARE THEY PARTLY

CORRELATIVE?by

Marwan A. Wartes1

Fig. 2PK & IG

EK

Miles0

0 50 100 200

30 60 120

Kilometers

Figure 1. Regional location map of northern Alaska. Initials refer to localities outside of the study area that are mentioned in the text (PK & IG = Poko Mountain and Igloo Mountain; EK = Ekakevik Mountain).

26 PIR 2008-1C Preliminary results, fi eld investigations, Brooks Range foothils & North Slope, Alaska

Figure 2. Generalized geologic map of the east-central foothills (modifi ed slightly from C.G. Mull, unpublished mapping). Numbered locations refer to samples in this study (see table 1).

Okpikruak Formation(Neocomian)

Ko

Etivluk Group(Permian - Jurassic)

JPu

Lisburne Group( Pennsylvanian)Mississippian -

IPMI

Endicott Group(L )ower Mississippian - Devonian

MDu

Kayak Shale(Lower Mississippian)

Mk

Basalt sills and dikesba

Colville Group(Upper Cretaceous)

Kc

Nanushuk Formation(middle Albian - Cenomanian)

Kn

Torok Formation(Aptian - Albian)

Kt

Fortress Mountain Formation(Barremian(?) - early Albian)

Kf

0 5Kilometers

IPMIIPMI

IPMI

IPMI

IPMI

IPMI

IPMIIPMI

IPMIIPMI

IPMI

IPMI

IPMI

IPMI IPMI

IPMI

IPMI

Mk

Mk

ba

ba

ba

ba

ba

baba

ba

ba

ba

ba

ba

ba

Ko

Ko

KoKo

Ko

Ko

Ko

Ko

Ko

Ko

Ko

Ko

Ko

Ko

Ko

Ko

KoKoKo

Ko

Ko

Ko KoKo

Kf

Kf

Kf

Kf

Kf

Kf

Kf

Kf

KfKf

Kf

Kf

Kf

Kf

Kf

Kf

Kt

Kt

Kt

Kt

Kt

Kt

Kt

Kt

Kt

Kt

Kt

MDu MDu

JPu

JPu

JPu

JPu

JPu

JPuJPu

JPu

JPu

JPu

JPu

JPuJPu

JPu

JPu

JPu

JPu

JPu

JPu JPu

JPu

JPu

JPu

JPu

JPu

JPu

JPu

JPu

JPu

JPu

JPu

JPu

JPu

Kn

Kn

Kn

Kn

Kn

Kn

Kc

Kc

Kcrevi

Rkayiy

A

reviRreldnahC

reviR

kupkiski

S

reviR

agalu

T

reviR

kuvutkan

A

JPu

IPMI

JPu

JPu JPu

Ko

JPu

?

Tuktu Escarpment

Kfm-Kto contact

?

Kt

Kf

(1)(2)

(3)(4)

(5)

CastleMountain

GunsightMountain

Desolation CreekFault zone

“HoaryMarmot”Mountain

“ThumbprintSyncline” “Rumpled Rug Folds”

FortressMtn.

10

Stratigraphic continuity between the Fortress Mountain and Nanushuk Formations 27

EXISTING CONSTRAINTSMap relationships

Early reconnaissance mapping recognized that at a regional scale progressively younger Brookian units typi-cally crop out from south to north (Patton and Tailleur, 1964). This general observation supports the interpretation that the southerly belt of Fortress Mountain Formation is older than the more northerly Nanushuk Formation trend. However, the top of the Fortress Mountain Formation is almost never exposed. Moreover, the two units are never observed together, but are instead separated by a poorly exposed, low-relief succession of fi ner-grained Torok Formation (fi gs. 2 and 4). The broad zone of Torok Formation exhibits locally complex deformation with variable fold vergence (Peapples and others, 2007). The northerly part of the Torok belt is generally interpreted as a structurally thickened triangle zone beneath a south-vergent roof thrust near the base of the Nanushuk Forma-tion (Moore and others, 2004; Wallace and others, 2006). The uplift and subsequent erosion of post-Torok rocks has obscured the relationship between the Fortress Mountain Formation and proximal reaches of the Nanushuk Formation (fi g. 4).

Upper

Low

er

Cre

taceous

140

120

110

100

130

FortressMtn.

Nanushuk Fm.

Fm.

Figure 3. Chronostratigraphy of middle Cretaceous units in northern Alaska showing revised stratigraphic nomen-clature (modifi ed from Mull and others, 2003). cs = cob-blestone sandstone (informal unit); ms = manganiferous shale unit (informal).

Roof thrust zone

Poorly exposed andcomplexly folded Torok Fm

Ge

og

rap

hic

se

pa

ratio

nfo

resh

ort

en

ed

for

pu

rpo

se

of

sch

em

atic

illu

str

atio

n

CASTLEMOUNTAIN GUNSIGHT

MOUNTAIN

02MAW006

?

??

?

02MAW020

02MAW009

05WKW082

05ASD053

?

upper Fortress Mountain FormationFan delta - Alluvial fan/braided fluvial

lower Fortress Mountain FormationDeep water sediment gravity flows (slope)

upper Nanushuk FormationDominantly nonmarine (fluvial)

lower Nanushuk FormationDominantly marine shoreface to deltaic

Fortress Mountain Formation Nanushuk Formation

SW NE

Kfmu

Kfml

Knu

Knl

Kfmu

Kfml

Knu

Knl

Figure 4. Schematic cross section illustrating the geography of the Fortress Mountain and Nanushuk trends and the stratigraphic uncertainty of their relationship. Note the relative location of samples in this study.

28 PIR 2008-1C Preliminary results, fi eld investigations, Brooks Range foothils & North Slope, Alaska

Stratigraphic RelationshipsThe Fortress Mountain Formation includes a variety of facies ranging from deep marine basin fl oor up through

alluvial fan environments (Wartes, 2008, this volume; Houseknecht and others, 2007; Crowder, 1989; Molenaar and others, 1988; Hunter and Fox, 1976). The type section of the Fortress Mountain Formation consists of a series of discontinuous exposures in the Castle Mountain area (fi g. 2; Patton and Tailleur, 1964). This ~3,000–m-thick section is considerably thicker than any other known outcrop of the formation and is interpreted to grade from basin fl oor(?) to slope facies up through fan delta, alluvial fan, and braided fl uvial facies (Molenaar and others, 1988; Crowder, 1987).

The Nanushuk Formation records deposition in marine shelf, deltaic, and fl uvial environments (Ahlbrandt, 1979; Huffman, 1985; LePain and others, 2008). Seismic data clearly indicate that Nanushuk topsets transition basinward (to the northeast) into clinoforms of the Torok Formation (Molenaar, 1988; Houseknecht and Schenk, 2001). In the east-central foothills, where the samples for this study were collected, the Nanushuk is approximately 1,600 m thick (Patton and Tailleur, 1964) and is subdivided into a marine lower part and a dominantly nonmarine upper part (fi g. 3; Mull and others, 2003).

Regionally, the Fortress Mountain formation rapidly fi nes northward and locally grades into rocks assigned to the lower Torok Formation (Patton and Tailleur, 1964; Molenaar and others, 1988; fi g. 3). However, at Castle Mountain the upper 350 m of section includes the most proximal nonmarine facies interpreted as alluvial fan and braided fl uvial. The northerly equivalent of this nonmarine succession is not known and it remains possible that it graded northward into the marine facies of the lower Nanushuk. The uncertain relationship between the two units is schematically illustrated in fi gure 4.

Sandstone CompositionIn hand sample, sandstones of the Nanushuk Formation are often lighter colored and appear less lithic rich

than darker greenish-gray-weathering Fortress Mountain Formation sandstones. This qualitative observation is borne out by regional petrographic data that indicate that Nanushuk samples from the central and eastern foothills average about 58 percent total quartz (Bartsch-Winkler and Huffman, 1988), whereas Fortress Mountain samples average only 32 percent quartz in the east-central outcrop belt (Molenaar and others, 1988). An additional notable difference documented in these studies is captured in the metamorphic lithics, which average 15 percent for the Nanushuk samples as compared to only 1 percent for Fortress Mountain samples. This stark difference was also noted by Johnsson and Sokol (2000), who documented as much as 30 percent metamorphic lithic fragments in the easternmost exposures of the Nanushuk Formation.

BiostratigraphyThe Fortress Mountain Formation is generally ascribed an Aptian(?) to early Albian age, whereas the Na-

nushuk Formation is regarded as middle Albian to Cenomanian (fi g. 3). These assignments largely refl ect detailed megafossil work done by the USGS in the 1950s and 1960s, most notably Imlay (1961). The shallow marine Nanushuk Formation has generally yielded a more diverse fauna and the biostratigraphic range can be considered more robust than the Fortress Mountain Formation. The majority of the biostratigraphic control for the Fortress Mountain Formation came from the lower third of the unit (Patton and Tailleur, 1964), leaving the upper limit of the formation in question.

Bivalves identifi ed as similar to Inoceramus anglicus and Inoceramus altifl uminis were reported from both the Fortress Mountain and Nanushuk Formations by Imlay (1961). In Alberta and British Columbia, these species were generally regarded as no older than middle Albian (McLearn, 1945). On the basis of the entire fossil assemblage from the Fortress Mountain Formation, particularly ammonite specimens, Imlay (1961) favored an interpretation that these Inoceramids must have ranged down into the early Albian in northern Alaska. More recently, Kelley (1990) reported additional specimens of I. anglicus from the Fortress Mountain Formation at Hoary Marmot Mountain (informal name; fi g. 2). He interpreted an age no older than middle Albian and concluded the exposure was likely coeval with the lower part of the Nanushuk Formation.

Palynological and foraminiferal data generally offer limited biostratigraphic resolution for any of the Fortress, Nanushuk, or Torok Formations, and typically yield a signifi cant number of “Aptian–Albian” or “Lower Cretaceous undifferentiated” age assignments (unpublished DGGS micropaleontology reports). However, there is a general observation that can be gleaned from the subset of samples that do preserve abundant age-diagnostic microfos-sils: the Fortress Mountain Formation samples do not appear to produce ages younger than Aptian to early Albian and the Nanushuk Formation in the central foothills does not yield ages older than middle to late Albian (written commun., M. Mickey, 2006; LePain and others, 2008).

Stratigraphic continuity between the Fortress Mountain and Nanushuk Formations 29

SampleNumber Map # Description Latitude / Longitude

05ASD053 (1)Gunsight MountainTop of Nanushuk Fm. N 68.71775 W 151.83504

05WKW082 (2)Siksikpuk RiverBase of Nanushuk Fm. N 68.72206 W 151.88918

02MAW009 (3) Castle Mountain summitTop of Fortress Mountain Fm.

N 68.56649 W 152.58198

02MAW020 (4) Castle Mountain baseupper Fortress Mountain Fm.

N 68.56365 W 152.60785

LOCATION

Table 1. Sample location information; note map number that refers to sample notation in fi gure 4.

NEW DATAAs outlined in the preceding sections, existing constraints have proven inadequate to defi nitively assess the

stratigraphic relationship between the Fortress Mountain and Nanushuk Formations. The following new data attempts to address the question by focusing on the provenance of the two units, specifi cally the U-Pb ages of detrital zircons.

Detrital Zircon GeochronologyZircon is a common heavy mineral in most siliciclastic systems and is highly resistant to weathering and dia-

genesis (Fedo and others, 2003). Recent advances in analytical technology have allowed for the rapid acquisition of a large number of U-Pb ages from individual detrital zircons (Gehrels and others, 2006). The addition of this geochronologic component is revolutionizing studies of sedimentary provenance, particularly regional paleogeo-graphic and tectonic studies (Gillis and others, 2005; Dickinson and Gehrels, 2003).

Sample Selection and MethodsIn order to assess the population of detrital zircon ages from each formation, samples were selected from some

of the thicker, more continuous exposures in the foothills. In the case of the Fortress Mountain Formation, three samples were selected from the type section at Castle Mountain, one from the lower and two from the upper part of the formation (fi gs. 2 and 4; table 1). This section is particularly appropriate as it likely contains the stratigraphi-cally highest Fortress Mountain Formation exposed anywhere in the foothills. Two Nanushuk Formation samples were analyzed from well-exposed bluffs where the Siksikpuk River cuts across the Tuktu escarpment area; one sample is from the very base of the formation, the other from upper Nanushuk on Gunsight Mountain (fi gs. 2 and 4; table 1).

Zircons were separated at the Apatite-to-Zircon, Inc. laboratory using heavy liquid and magnetic separation techniques. Grains were mounted in epoxy and polished to expose grain interiors for analysis. One-hundred grains were selected at random and dated for each sample, a number commonly sought by most workers and one that reduces the probability of missing any given provenance components to <5 percent (Dodson and others, 1988). Uranium, thorium, and lead isotope data were collected at the Washington State University Geoanalytical Labora-tory on a ThermoFinnigan Element2 magnetic sector double-focusing ICP–MS (inductively coupled plasma–mass spectrometer). Each grain underwent laser ablation using a New Wave Research UP-213 system. See Chang and others (2006) for additional details regarding laboratory procedures such as standards and error corrections.

30 PIR 2008-1C Preliminary results, fi eld investigations, Brooks Range foothils & North Slope, Alaska

Detrital zircon populationsAppendix C-1 includes isotopic ratio and age data for 500 individual U-Pb zircon analyses. Only one grain from

sample 02MAW020 produced strongly discordant data and was rejected. For ages up to 1000 Ma, the 206Pb/238U age is selected as the most precise; those greater than 1000 Ma are taken from the 206Pb/207Pb ages (see Gehrels and others, 2006). The age distribution data for each of the fi ve samples are plotted in a histogram format and cumulative probability curves (fi gs. 5–9). Histograms illustrate the number of ages that fall into each 50 Ma bin. Cumulative probability curves, which are a common method for displaying detrital zircon data, represent the normalized sum of probability distributions for all analyses from a sample. Age peaks are only considered statistically signifi cant if defi ned by several analyses. All plots were created using Isoplot/Ex v. 3.32 (Ludwig, 2005).

DISCUSSIONThe detrital zircon data reveal statistically signifi cant differences between the two formations. This is best

illustrated by comparing selected groups of grain ages (table 2, fi gs. 10 and 11). All three Fortress Mountain For-mation samples include abundant Permian grains (10–19 percent), whereas the Nanushuk samples yielded only one Permian grain between both samples. Typically the parent lithology of individual zircons is diffi cult to assess. However, in the case of the Permian age spike, U-Pb zircon ages from igneous clasts within the Fortress Mountain Formation (Wartes and others, 2006) indicate the detrital population observed in this study was derived from an unknown tonalitic–dacitic igneous complex.

Late Neoproterozoic to Cambrian ages (500–665 Ma) form a prominent peak in both Nanushuk samples (aver-age 23 percent) but are much less abundant, on average, in the Fortress Mountain samples (7 percent). Nanushuk samples also contain a discrete pulse of early Neoproterozoic ages (850–950 Ma) that is much less common in the Fortress Mountain samples. Similarly, Mesoproterozoic ages (~1000–1300 Ma) form prominent peaks in both Nanushuk samples (average 20 percent), while the Fortress Mountain samples include a very weak record of this provenance (average 5 percent). Finally, although the Nanushuk Formation samples contain signifi cantly larger proportion of Precambrian grains, the Fortress Mountain samples average almost three times more early Proterozoic grain ages (Orosirian period 1800–2050 Ma).

If the Fortress Mountain and Nanushuk Formations were in part correlative, it seems probable that the up-permost Fortress Mountain sample (02MAW009) would have been most similar to the basal Nanushuk sample (05WKW082). In fact, these two samples produced some of the starkest contrasts in several groupings of detrital grain ages (table 2; fi gs. 10 and 11). The two formations clearly have a different provenance for zircons and the

Table 2. Comparison of signifi cant detrital-age groupings highlighting noteworthy differences between the Nanushuk and the Fortress Mountain Formations. Age groupings are listed as numbers of ages within each “bin”, although since ~100 grains were dated for each sample, these numbers are effectively percentages as well.

Sample No. 251-299 Maa 500-665 Mab 850-950 Mac 1.00-1.35 Gad 1.80-2.05 Gae > 542 Ma

05ASD053 1 14 12 24 6 7605WKW082 0 32 14 16 4 82

AVERAGE 0.5% 23% 13% 20% 5% 79%

02MAW009 19 2 5 4 10 4002MAW020 18 14 3 7 13 5802MAW006 10 5 3 4 20 54

AVERAGE 16% 7% 4% 5% 14% 51%

dGlobally significant orogenic episode in the Mesoproterozoic (e.g. McLelland and others, 1996)eOrosirian period of the Paleoproteroic, based on timescale of Ogg (2004)

aPermian period, based on timescale of Ogg (2004)bGlobally significant orogenic episode spanning the late Neoproterozoic - Cambrian (e.g. Murphy and Nance, 1991)cPart of the early Neoproterozoic

SIGNIFICANT GROUPINGS OF DETRITAL AGES

NANUSHUK FORMATION

FORTRESS MOUNTAIN FORMATION

Stratigraphic continuity between the Fortress Mountain and Nanushuk Formations 31

02468

10

12

14

16

18

20

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

Number

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

RelativeProbability

Up

pe

rF

ortr

es

sM

ou

nta

inF

orm

ati

on

(02

MA

W0

20

)

273

602

1813

329

371

Figu

re 6

. His

togr

am (5

0 M

a bi

ns) a

nd re

lativ

e pro

babi

lity

plot

s of

det

rita

l zirc

on a

ges

from

the

uppe

r Fo

rtre

ss

Mou

ntai

n Fo

rmat

ion.

Figu

re 5

. His

togr

am (5

0 M

a bi

ns) a

nd re

lativ

e pr

obab

ility

pl

ots

of d

etri

tal z

ircon

age

s fro

m th

e lo

wer

For

tress

M

ount

ain

Form

atio

n.

02468

10

12

14

16

18

20

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

Number

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

RelativeProbability

Lo

wer

Fo

rtr

ess

Mo

un

tain

Fo

rm

ati

on

(02M

AW

006)

17

85

28

5

46

5

42

0

Figu

re 7

. His

togr

am (5

0 M

a bi

ns) a

nd re

lativ

e pro

babi

lity

plot

s of d

etrit

al zi

rcon

age

s fro

m th

e top

of t

he F

ortre

ss

Mou

ntai

n Fo

rmat

ion.

02468

10

12

14

16

18

20

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

Number

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

RelativeProbability

To

pF

ortr

es

sM

ou

nta

inF

orm

ati

on

(02

MA

W0

09

)

48

1

18

20

26

0

44

2

32 PIR 2008-1C Preliminary results, fi eld investigations, Brooks Range foothils & North Slope, Alaska

Figu

re 8

. His

togr

am (5

0 M

a bi

ns) a

nd re

lativ

e pr

obab

il-ity

plo

ts o

f det

rita

l zirc

on a

ges

from

the

base

of t

he

Nan

ushu

k Fo

rmat

ion.

02468

10

12

14

16

18

20

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

Number

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

RelativeProbability

Ba

se

Na

nu

sh

uk

Fo

rm

ati

on

(05

WK

W0

82

)

355

635 8

85

1655

565

Figu

re 9

. His

togr

am (5

0 M

a bi

ns) a

nd re

lativ

e pro

babi

lity

plot

s of

det

rita

l zirc

on a

ges

from

the

top

of th

e N

a-nu

shuk

For

mat

ion.

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

RelativeProbability

02468

10

12

14

16

18

20

05

00

10

00

15

00

20

00

25

00

30

00

Ag

e(M

a)

Number

To

pN

an

ush

uk

Fo

rm

ati

on

(05A

SD

053)

34

142

0

50

8

90

1

10

85

14

53

Stratigraphic continuity between the Fortress Mountain and Nanushuk Formations 33

Permian ages(~251 - 299 Ma)

late Neoproterozoic - Cambrian “Pan-African” ages(~500 - 665 Ma)

0

2

4

6

8

10

12

0 100 200 300 400 500 600 700

Age (Ma)

Nu

mb

er

0

2

4

6

8

10

12

0 100 200 300 400 500 600 700

Age (Ma)

Nu

mb

er

0

2

4

6

8

10

12

0 100 200 300 400 500 600 700

Age (Ma)

Nu

mb

er

0

2

4

6

8

10

12

0 100 200 300 400 500 600 700

Age (Ma)

Nu

mb

er

0

2

4

6

8

10

12

0 100 200 300 400 500 600 700

Age (Ma)

Nu

mb

er

Na

nu

sh

uk

Fo

rma

tio

nF

ort

res

sM

ou

nta

inF

orm

ati

on

05ASD053Top of Kn

05WKW082Base of Kn

02MAW009Top of Kfm

02MAW020Upper Kfm

02MAW006Lower Kfm

Figure 10. Histograms (20 Ma bins) depicting a subset of grain age popu-lations (0–700 Ma). Samples are stacked in interpreted stratigraphic order. Highlighted groupings illustrate the signifi cant differences between Fortress Mountain and Nanushuk Formation samples (see also table 2). “Pan-African” refers to a globally signifi cant orogenic episode (Murphy and Nance, 1991).

balance of these results favors an interpretation that the two units do not represent parts of a single clastic wedge.

Very little U-Pb zircon geochronologic data exists for the Brooks Range and precise correlations between these detrital ages and specifi c units in the fold-and-thrust belt is premature and beyond the scope of this paper. Instead, the more salient, fi rst order result from this study is that the Fortress Mountain and Nanushuk Formations were clearly tapping unique and dif-ferent source areas and represent discrete phases in the unroofi ng sequence. This agrees with existing conventional petrographic point-count data noted earlier, which indicated clear differences in framework grain composition between the two formations (Bartsch-Winkler and Huffman, 1988; Molenaar and others, 1988). However, in some respects, the zircon data provide a more robust and quantitative comparison of the two units. It has long been recognized that sandstone mineralogy can be strongly infl uenced by transport distance (Pettijohn, 1957), particularly the labile components (Mack, 1978) that are abundant in both units. Given the geographic separation of the Fortress Moun-tain and Nanushuk outcrop belts, it remains possible that the observed differences were simply a function of transport biases. In contrast, durable zircons are unlikely to undergo signifi cant weathering or fractionation along a depositional profi le (Morton and Smale, 1991).

Ultimately, these provenance differences have stratigraphic implications and suggest the youngest exposed Fortress Mountain Formation is not correlative with the basal Nanushuk Formation. This interpretation is consistent with most depictions of Creta-ceous stratigraphy, which show a tongue of the Torok Formation separating the sandstone-rich Fortress Mountain and Nanushuk sequences (Mull and others, 2003; fi gs. 3 and 12). The upper-most Fortress Mountain Formation at Castle Mountain records alluvial fan and braided fl uvial deposition (Molenaar and others, 1988; Crowder, 1987). Thus, if a succession of Torok mudstones originally overlay this interval, it would represent a transgressive sequence (fi g. 12b). This hypothesis is diffi cult to evaluate due

34 PIR 2008-1C Preliminary results, fi eld investigations, Brooks Range foothils & North Slope, Alaska

Mesoproterozoic “Grenville” ages(~1000 -1350 Ma)

Paleoproterozoic Orosirian Period ages(~1800 - 2050 Ma)

early Neoproterozoic ages(~850 - 950 Ma)

0

2

4

6

8

700 950 1200 1450 1700 1950 2200

Age (Ma)

Nu

mb

er

0

2

4

6

8

700 950 1200 1450 1700 1950 2200

Age (Ma)

Nu

mb

er

0

2

4

6

8

700 950 1200 1450 1700 1950 2200

Age (Ma)

Nu

mb

er

0

2

4

6

8

700 950 1200 1450 1700 1950 2200

Age (Ma)

Nu

mb

er

0

2

4

6

8

700 950 1200 1450 1700 1950 2200

Age (Ma)

Nu

mb

er

Nan

ush

uk

Fo

rmati

on

Fo

rtre

ss

Mo

un

tain

Fo

rmati

on

05ASD053Top of Kn

05WKW082Base of Kn

02MAW009Top of Kfm

02MAW020Upper Kfm

02MAW006Lower Kfm

Figure 11. Histograms (50 Ma bins) depicting a subset of grain age populations (700–2250 Ma). Samples are stacked in interpreted stratigraphic order. Highlighted groupings illustrate the signifi cant differences between Fortress Mountain and Nanushuk Formation samples (see also table 2). “Grenville” refers to a globally sig-nifi cant orogenic episode (McLelland and others, 1996); Orosirian is a Mesoproterozoic period (Ogg, 2004).

to the lack of exposed formation tops in Fortress Moun-tain exposures (fi g. 12a; see also fi gure 4a of Bird and Molenaar, 1992). However, a few regional observations have cited evidence for an upward deepening at the top of the Fortress Mountain Formation. For example, in the Ekakevik Mountain area (fi g. 1), Hunter and Fox (1976) noted that the formation generally fi nes upward and, where best exposed, the top of the formation was characterized by transgressive shallow marine facies overlying nonmarine conglomerate. Farther west, be-tween Poko and Igloo mountains (fi g. 1), Mull (1985) inferred a gradational contact between the Fortress Mountain Formation and overlying fi ne-grained facies of the Torok Formation.

A major fl ood back of Torok slope facies over nonma-rine–marginal marine Fortress Mountain Formation was recently recognized in the Siksikpuk River area (labeled as Kfm–Kto contact on fi g. 2; Houseknecht and others, 2007; Peapples and others, 2007). However, this section is here interpreted as relatively low in the composite Fortress Mountain succession (Patton and Tailleur, 1964), suggesting that the transgressive event is intra-Fortress Mountain, rather than marking the regional top of the formation. It is also possible there is regional variation in the position of the top of the Fortress Mountain Forma-tion and that fl ooding of the Torok Formation across the Fortress Mountain Formation was diachronous locally, varying according to paleotopography across the complex orogenic wedge (Wartes and Swenson, 2005). Similarly complex relationships are known from the better-studied Upper Cretaceous foreland basin strata of the Western Interior Seaway (Krystinik and DeJarnett, 1995).

Existing data do not unequivocally rule out a scenario whereby now-eroded sections of the Fortress Mountain Formation once existed above Castle Mountain and formed part of a unifi ed prograding clastic wedge that

Stratigraphic continuity between the Fortress Mountain and Nanushuk Formations 35

Non

-dep

ositi

on(?

)

upper Kingak Shaleequivalent

UpperTorok Fm.

OkpikruakFormation

?

Allochthonous(?)

LowerTorok Fm.

Valanginian

Berriasian

Barremian

Ma

upper Kingak Shaleequivalent

UpperTorok Fm.

Hauterivian

140

120

110

Ne

oco

mia

n

Lo

we

r

Cre

taceo

us

Cenomanian

Aptian

Up

pe

r

Albian

100

130

OkpikruakFormation

?

Proximal

SSW NNE

Distal

AG

E

SER

IES

STA

GE

Allochthonous(?)

Pebble Shale equivalent

LowerTorok Fm.

Eroded

Valanginian

Berriasian

Barremian

Ma

Hauterivian

140

120

110

Ne

oco

mia

n

Lo

we

r

Cre

tac

eo

us

Cenomanian

Aptian

Up

pe

r

Albian

100

130

Valanginian

Berriasian

Barremian

Ma

Hauterivian

140

120

110

Ne

oco

mia

n

Lo

we

r

Cre

tac

eo

us

Cenomanian

Aptian

Up

pe

r

Albian

100

130

?

A

B

C

Non

-dep

ositi

on(?

)

upper Kingak Shaleequivalent

UpperTorok Fm.

OkpikruakFormation

?

Allochthonous(?)

LowerTorok Fm.

NanushukFormation

Formation

FortressMountain

FortressMountain

NanushukFormation

Formation

NanushukFormation

Formation

FortressMountain

Pebble Shale equivalent

Pebble Shale equivalent

Figure 12. Chronostratigraphic diagrams illustrating relationships between the Fortress Mountain, Nanushuk, and Torok Formations discussed in the text. Approximate sample positions shown by red dots. (A) Depiction of the observed spatial context of Fortress Mountain and Nanushuk exposures, highlighting the ambiguity of proposed stratigraphic correlations between the two units. This diagram contrasts with the common schematic representation of Early Cretaceous stratigraphy (Mull and others, 2003; fi g. 3) and emphasizes that the top of the Fortress Mountain Formation is a Holocene erosion surface and that the Nanushuk Formation cannot be demonstrated to overlie the Fortress Mountain Forma-tion based on fi eld evidence alone. On the basis of the available constraints discussed in the text, this fi gure interprets the exposed Fortress Mountain Formation as entirely older than the Nanushuk Formation in this area. (B & C) Portrayal of two possible strati-graphic scenarios as they would have appeared at the close of Nanushuk deposition: (B) proposes a retrogradational tongue of Torok separated the Fortress Mountain and Nanushuk Formations (model favored in this study), while (C) illustrates a model where the Fortress Mountain and Nanushuk Formations represent a continuous northward-prograding clastic wedge (see also fi gure 25.3c in Molenaar, 1988).

graded northward into the lower Nanushuk deltas (fig. 12c; see also figure 25.3c in Molenaar, 1988). However, if such a section existed, then a substantial upsection change in provenance would be required within the uppermost proximal Fortress Mountain For-mation. Based on available data (including that presented here), it seems more probable that the Fortress Mountain and Nanushuk Formations are regionally separated by an intervening tongue of the Torok Formation (fi g. 12b), possibly recording a basin-scale change in the balance between sediment sup-ply and newly created accommodation.

The Torok Formation can be generi-cally subdivided into lower and upper parts, roughly corresponding to proximal Fortress Mountain and Nanushuk Formations, re-spectively (Mull and others, 2003; fi g. 3). If a tongue of Torok separates these two progradational sequences (fi g. 12b)—an in-terpretation that is favored here—then it may prove useful to consider a tripartite genetic subdivision of the formation (fi g. 13). It is diffi cult to evaluate this proposed subdivi-sion in the outcrop belt where distinctions between lower, middle, and upper parts of the formation are hampered by: (1) inadequate biostratigraphic resolution, (2) non-unique, fi ne-grained facies, (3) discontinuous expo-sures, and (4) complex structure (Patton and Tailleur, 1964; Mull, 1985; Molenaar and others, 1988; Houseknecht and Schenk, 2007; Houseknecht and others, 2007). Regional seismic and well data indicate that an older succession of Brookian rocks exists beneath the Nanushuk-related Torok clinoforms (Molenaar, 1988). In the northern foothills, Houseknecht and Schenk (2001) document that this older Torok “foredeep wedge” was derived from the west and traced individual Torok clinoforms into Nanushuk topsets. However, this wedge continues to thicken dramatically southward, probably including southerly sourced Fortress Mountain-related lower(?) Torok facies (Cole and others, 1997; Molenaar, 1988). Regardless, in light of the strong differences in detrital zircon ages within the proximal Fortress Mountain and Nanushuk Formations, it seems likely that the affi nity of isolated Torok samples could be reliably assessed with the technique outlined in this study.

The new provenance data presented here confi rm that the Fortress Mountain and

36 PIR 2008-1C Preliminary results, fi eld investigations, Brooks Range foothils & North Slope, Alaska

Nanushuk Formations were clearly derived from different sources. Provided the two units both record unroofi ng of the nearby ancestral Brooks Range, it follows that the exposed Fortress Mountain Formation represents an entirely older depositional system than the Nanushuk topsets (as shown in fi g. 12a). However, it remains possible that the two units are partly coeval and that the detrital zircon data refl ects two different major sediment dispersal systems—transverse, Brooks Range-derived Fortress Mountain Formation and axially fed Nanushuk facies tapping a different source region to the west. Even in better-studied foreland basins, identifying the relative roles of axial versus transverse systems is diffi cult (Clevis and others, 2004). Farther north, in central NPRA (fi g. 1), seismi-cally mapped shelf margins indicate the Nanushuk–Torok depositional system is fed principally out of the west (Molenaar, 1988; Houseknecht and Schenk, 2001). However, the origin of Nanushuk topsets in the area sampled in this study were most likely sourced from transverse, north-fl owing rivers as indicated by paleocurrent data as well as contrasting deltaic style and provenance relative to the demonstrably western-sourced axial deltaic system (Huffman and others, 1988; Molenaar, 1988; LePain and others, in press).

The focus of this paper has been the stratigraphic implications of a modest new detrital zircon data set. Future papers will examine the potential sources of various zircon age populations and the broader tectonic implications of these data. However, it is worth noting that the marked change in provenance outlined in this study occurred at approximately the early to middle Albian boundary, a time characterized by signifi cant tectonic events in the Brooks Range hinterland (Vogl, 2002). In other words, the provenance changes may refl ect discrete tectonically-driven exhumation and orogen-wide reorganization of drainages.

CONCLUSIONSNew detrital zircon age data indicate the Fortress Mountain and Nanushuk Formations in the central Brooks

Range foothills were sourced from unique and different provenances. Signifi cantly different populations of grain ages suggest the Fortress Mountain and Nanushuk depositional systems were not part of a unifi ed north–northeast-erly prograding clastic wedge. Instead, the youngest exposed Fortress Mountain Formation is here interpreted to be entirely older than the Nanushuk Formation. Based on available data, it is inferred that the Fortress Mountain and Nanushuk Formations are separated by a transgressive tongue of the Torok Formation, although more data are needed to defi nitively reject alternate hypotheses. In particular, additional subsurface information will be required to document stratigraphic relationships that are presently ambiguous.

Figure 13. Schematic cross section of the Colville Basin (modifi ed from Mull, 1985, and Houseknecht and Schenk, 2001). The middle Torok is speculated to be a retrogradational package separating the Fortress Mountain and Nanushuk Forma-tions.

Kfm = Fortress Mountain Formation

Tecto

nic

Wedge

Kfm

Paleozoic &

seicafdesnednocnisabdevratS

Umiat

SSouthernFoothills

NorthernFoothills

Coastal Plain

~100 km

U. Cretaceous strata

N

Kto = Torok Formation (informal subdivision: Ktol=lower; Ktom=middle; Ktou=upper)

Ktol

Kto

m Ktou

Transgressive flooding surface (hypothesized)

Nanushuk FormationAllochthonous

Mesozoic Rocks

?

Stratigraphic continuity between the Fortress Mountain and Nanushuk Formations 37

ACKNOWLEDGMENTSThe impetus for this study came from a number of outcrop discussions with A. Carroll, who, unbiased by any

North Slope geological dogma, posed a number of insightful questions regarding established Brookian stratigraphic relationships, including, “Are you sure the Fortress Mountain and Nanushuk Formations aren’t, in part, correla-tive?” The ideas presented here also benefi ted from numerous discussions with D. LePain, R. Gillis, T. Moore, P. Decker, G. Mull, R. Reifenstuhl, R. Swenson, W. Wallace, D. Houseknecht, and P. O’Sullivan. A version of fi gure 13 was kindly provided by D. LePain. Funding for part of the original work in the Castle Mountain area was generously supplied to the University of Wisconsin by Anadarko Petroleum Corporation. DGGS studies in the foothills are supported by industry contributions from Anadarko, FEX, BG Alaska, Chevron, Petro-Canada, Pioneer Natural Resources, ENI, Shell, and ConocoPhillips. Funding for DGGS geologic mapping in the Siksikpuk River area was provided by the state of Alaska and the U.S. Geological Survey National Cooperative Geologic Mapping Program (award numbers 04HQAG0061 and 05HQAG0025). This paper benefi tted from constructive review comments by Bob Gillis.

REFERENCESAhlbrandt, T.S., ed., 1979, Preliminary geologic, petrologic, and paleontologic results of the study of Nanushuk

Group rocks, North Slope, Alaska: U.S. Geological Survey Circular 794, 163 p.Bartsch-Winkler, S., and Huffman, A.C., Jr., 1988, Sandstone petrography of the Nanushuk Group and Torok

Formation, in Gryc, George, ed., Geology and exploration of the National Petroleum Reserve in Alaska, 1974 to 1982: U.S. Geological Survey Professional Paper 1399, p. 801–831.

Bird, K.J., and Molenaar, C.M., 1992, The North Slope foreland basin, Alaska, in Macqueen, R.W., and Leckie, D.A., eds., Foreland basins and fold belts: AAPG Memoir 55, p. 363–393.

Chang, Z., Vervoort, J.D., McClelland, W.C., and Knaack, C., 2006, U-Pb dating of zircon by LA-ICP-MS: Geo-chemistry, Geophysics, Geosystems, v. 7, no. 5, Q05009.

Clevis, Q., DeBoer, P.L., and Nijman, W., 2004, Differentiating the effect of episodic tectonism and eustatic sea-level fl uctuations in foreland basins fi lled by alluvial fans and axial deltaic systems: insights from a three-dimensional stratigraphic forward model: Sedimentology, v. 51, p. 809–835.

Cole, F.E., Bird, K.J., Toro, J., Roure, F., O’Sullivan, P.B., Pawlewicz, M.J., and Howell, D.G., 1997, An integrated model for the frontal Brooks Range and Colville Basin 250 km west of the Trans-Alaska Crustal Transect: Journal of Geophysical Research, v. 102, p. 20,685–20,708.

Crowder, R.K., 1987, Cretaceous basin to shelf transition in northern Alaska; deposition of the Fortress Mountain Formation, in Tailleur, I.L., and Weimer, P., eds., Alaskan North Slope geology: Pacifi c Section, SEPM, Ba-kersfi eld, CA, v. 50, p. 449–458.

———Deposition of the Fortress Mountain Formation, in Mull, C.G., and Adams, K.E., eds., Dalton Highway, Yukon River to Prudhoe Bay, Alaska: Alaska Division of Geological & Geophysical Surveys Guidebook 7, v. 2, p. 293–301.

Detterman, R.L., 1956, New and redefi ned nomenclature of Nanushuk Group: AAPG Bulletin, v. 40, p. 233–244.

Dickinson, W.R., and Gehrels, G.E., 2003, U-Pb ages of detrital zircons from Permian and Jurassic eolian sandstones of the Colorado Plateau, USA; paleogeographic implications: Sedimentary Geology, v. 163, p. 29–66.

Dodson M.H., Compston, W., Williams, I.S., and Wilson, J.F., 1988, A search for ancient detrital zircons in Zim-babwean sediments: Journal of the Geological Society of London, v. 145, p. 977–983.

Fedo, C.M., Sircombe, K.N., and Rainbird, R.H., 2003, Detrital zircon analysis of the sedimentary record: Reviews in Mineralogy and Geochemistry, v. 53, p. 277–303.

Gehrels, G.E., Valencia, V., and Pullen, A., 2006, Detrital zircon geochronology by laser-ablation multicollector ICPMS at the Arizona Laser-Chron Center, in Olszewski, T., and Huff, W., eds., Geochronology; Emerging opportunities: Philadelphia, Pennsylvania, Paleontological Society Short Course, p. 1–10.

Gillis, R.J., Gehrels, G.E., Ruiz, J., and de Dios Gonzalez, L.A.F., 2005, Detrital zircon provenance of Cam-brian–Ordovician and Carboniferous strata of the Oaxaca terrane, southern Mexico: Sedimentary Geology, v. 182, p. 87–100.

Houseknecht, D.W, and Schenk, C.J., 2001, Depositional sequences and facies in the Torok Formation, National Petroleum Reserve–Alaska (NPRA), in Houseknecht, D.W., ed., NPRA Core Workshop; Petroleum Plays and Systems in the National Petroleum Reserve Alaska: SEPM Core Workshop (June 2001), no. 21,, p. 179–199.

38 PIR 2008-1C Preliminary results, fi eld investigations, Brooks Range foothils & North Slope, Alaska

Houseknecht, D.W, and Schenk, C.J., 2007, Outcrops of turbidite channel facies in the Torok Formation; reservoir analogs for the Alaska North Slope, in Nilsen, T., Shew, R.D., Steffens, G.S., and Studlick, J.R.J., eds., An Atlas of Deepwater Outcrops; Models and Analogs: American Association of Petroleum Geologists Studies in Geology v. 56, p. 373–377.

Houseknecht, D.W., and Bird, K.J., 2006, Oil and gas resources of the Arctic Alaska petroleum province: U.S. Geological Survey Professional Paper 1732-A, 11 p.

Houseknecht, D.W., Schenk, C.J., and Wartes, M.A., 2007, Sedimentology and sequence stratigraphy of the Lower Cretaceous Fortress Mountain and Torok Formations exposed along the Siksikpuk River, north-central Alaska, in Haeussler, P.J., and Galloway, J.P., eds., Studies by the U.S. Geological Survey in Alaska, 2006: U.S. Geo-logical Survey Professional Paper 1739-D, 27 p., 1 plate.

Huffman, A.C., Jr., ed., 1985, Geology of the Nanushuk Group and related rocks, North Slope, Alaska: U.S. Geo-logical Survey Bulletin 1614, 129 p.

Huffman, A.C., Jr., Ahlbrandt, T.S., and Bartsch-Winkler, Susan, 1988, Sedimentology of the Nanushuk Group, North Slope, in Gryc, George, ed., Geology and exploration of the National Petroleum Reserve in Alaska, 1974 to 1982: U.S. Geological Survey Professional Paper 1399, p. 281–298.

Hunter, R.E., and Fox, J.E., 1976, Interpretation of depositional environments in the Fortress Mountain Formation, central Arctic Slope: U.S. Geological Survey Circular 733, p. 30–31.

Imlay, R.W., 1961, Characteristic Lower Cretaceous megafossils from northern Alaska: U.S. Geological Survey Professional Paper 335, 74 p.

Johnsson, M.J., and Sokol, N.K., 2000, Stratigraphic variation in petrographic composition of Nanushuk Group sandstones at Slope Mountain, North Slope, Alaska, in Kelley, K.D., and Gough, L.P., eds., Geologic studies in Alaska by the U.S. Geological Survey, 1998: U.S. Geological Survey Professional Paper 1615, p. 83–100.

Kelley, J.S., 1990, Generalized geologic map of the Chandler Lake Quadrangle, north-central Alaska: U.S. Geo-logical Survey Miscellaneous Field Studies Map 2144A, 1 sheet, 19 p.

Krystinik, L.F., and DeJarnett, B., 1995, Lateral variability of sequence stratigraphic framework in the Campan-ian and Early Maastrichtian of the Western Interior Seaway, in Van Wagoner, J.C., and Bertram, G.T., eds., Sequence stratigraphy of foreland basin deposits; Outcrop and subsurface examples from the Cretaceous of North America: American Association of Petroleum Geologists Memoir, no. 64, p. 11–26.

LePain, D.L., McCarthy, P.J., and Kirkham, R., 2008, Sedimentology and sequence stratigraphy of the Nanushuk Formation in the central Brooks Range foothills, northern Alaska: Alaska Division of Geological & Geophysi-cal Surveys Report of Investigation, in press.

Ludwig, K.R., 2005, Isoplot/EX rev. 3.32; A geochronological toolkit for Microsoft Excel: Berkeley Geochronol-ogy Center Special Publication 4.

Mack, G.H., 1978, The survivability of labile light-mineral grains in fl uvial, aeolian, and littoral marine environments; the Permian Cutler and Cedar Mesa formations, Moab, Utah: Sedimentology, v. 25, no. 5, p. 587–603.

McLearn, F.H., 1945, Revision of the Lower Cretaceous of the western interior of Canada: Geological Survey of Canada Paper 44-17 (2nd ed.), 14 p., 2 tables, 12 plates.

McLelland, J., Daly, J.S., and McLelland, J.M., 1996, The Grenville Orogenic Cycle (ca. 1350–1000 Ma); an Adirondack perspective: Tectonophysics, v. 265, p. 1–28.

Molenaar, C.M., 1988, Depositional history and seismic stratigraphy of Lower Cretaceous rock in the National Petroleum Reserve in Alaska and adjacent areas, in Gryc, G., editor, Geology and exploration of the National Petroleum Reserve in Alaska, 1974–1982: U.S. Geological Survey Professional Paper 1399, p. 593–621.

Molenaar, C.M., Egbert, R.M., and Krystinik, L.F., 1988, Depositional facies, petrography, and reservoir poten-tial of the Fortress Mountain Formation (Lower Cretaceous), central North Slope, Alaska, in Gryc, G., ed., Geology and Exploration of the National Petroleum Reserve in Alaska, 1974–1982: U.S. Geological Survey Professional Paper 1399, p. 257–280.

Moore, T.E., Wallace, W.K., Bird, K.J., Karl, S.M., Mull, C.G., and Dillon, J.T., 1994, Geology of northern Alaska, in Plafker, G., and Berg, H.C., eds., The Geology of North America, v. G-1, The Geology of Alaska: Boulder, CO, Geological Society of America, p. 49–140.

Moore, T.E., Potter, C.J., O’Sullivan, P.B., Shelton, K.L., and Underwood, M.B., 2004, Two stages of deformation and fl uid generation for the central Brooks Range fold and thrust belt, northern Alaska, in Swennen, R.A.J., Roure, Francois, and Granath, J.W., eds., Deformation, fl uid fl ow, and reservoir appraisal in foreland fold and thrust belts: AAPG Hedberg Series, no. 1, p. 157–186.

Stratigraphic continuity between the Fortress Mountain and Nanushuk Formations 39

Morton, A.C., and Smale, D., 1991, The effects of transport and weathering on heavy minerals from the Cascade River, New Zealand: Sedimentary Geology, v. 68, p. 117–123.

Mull, C.G., 1985, Cretaceous tectonics, depositional cycles, and the Nanushuk Group, Brooks Range and Arctic Slope, Alaska, in Huffman, A.C., ed., Geology of the Nanushuk Group and related rocks, North Slope, Alaska: U.S. Geological Survey Bulletin 1614, p. 7–36.

Mull, C.G, Houseknecht, D.W., and Bird, K.J., 2003, Revised Cretaceous and Tertiary stratigraphic nomenclature in the Colville Basin, northern Alaska: U.S. Geological Survey Professional Paper 1673, 51 p.

Murphy, J.B., and Nance, R.D., 1991, Supercontinent model for the contrasting character of Late Proterozoic orogenic belts: Geology, v. 19, p. 469–472.

Ogg, J.G., 2004, Status of divisions of the International Geologic Time Scale: Lethaia, v. 37, p. 183–199.Patton, W.W., and Tailleur, I.L., 1964, Geology of the Killik–Itkillik region, Alaska: U.S. Geological Survey

Professional Paper 303G, p. 409–500.Peapples, P.R., Wallace, W.K., Wartes, M.A., Swenson, R., Mull, C.G., Dumoulin, J.A., Harris, E.E., Finzel, E.S.,

Reifenstuhl, R.R., and Loveland, A.L., 2007, Geologic map of the Siksikpuk River area, Brooks Range north-ern foothills, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2007-1, 1 sheet, scale 1:63,360.

Pettijohn, F.J., 1957, Sedimentary Rocks: 2nd ed., New York, Harper and Bros., 718 p.Vogl, J.J., 2002, Late-orogenic backfolding and extension in the Brooks Range collisional orogen, northern Alaska:

Journal of Structural Geology, v. 24, p. 1,753–1,776.Wallace, W.K., Duncan, A.S. Peapples, P.R., Swenson, R.F., Wartes, M.A., O’Sullivan, P.B., and Finzel, E.S., 2006,

Geometry and evolution of the frontal part of an orogenic wedge, central Brooks Range Foothills, Alaska: Geological Society of America Abstracts with Program, v. 38, no. 5, p. 24.

Wartes, M.A., 2008, Measured section and facies analysis of the Lower Cretaceous Fortress Mountain Formation, Atigun Syncline, northern Alaska, in Wartes, M.A., and Decker, P.L., eds, Preliminary results of recent geologic fi eld investigations in the Brooks Range foothills and North Slope, Alaska: Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2008-1, p. 11–24, 1 sheet.

Wartes, M.A., and Swenson, R.F., 2005, New constraints on the structural and stratigraphic development of the proximal Colville foreland basin; Implications for burial history and oil and gas exploration in the central Brooks Range foothills, northern Alaska, in GSA, Cordilleran Section, 101st annual meeting: AAPG, Pacifi c Section, 80th annual meeting, Abstracts with Programs, v. 37, no. 4, p. 92–93.

Wartes, M.A., O’Sullivan, P.B., and Carroll, A.R., 2006, Enigmatic Permian U-Pb zircon ages from igneous clasts found in mid-Cretaceous deposits of the Colville Foreland Basin, northern Alaska: Geological Society of America Abstracts with Programs, v. 38, no. 5, p. 89.

This page has intentionally been left blank.

Text for reports with appendices: This appendix is included in this PDF document for the reader’s convenience. In the full publication, the appendices and sheets are placed at the conclusion of all of the text. The separation of the appendices and sheets from their chapter in the full publication determines the page numbers; thus, you will find that the page numbers for this smaller piece of the larger document are not sequential.

Appendix C-1 179

APPENDIX C-1

ANALYTICAL DATA AND CALCULATED AGES

180 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

±285

234-

370.

0920

0.00

360.

0139

0.00

030.

0479

0.00

1989

.35

3.49

89.2

51.

7792

.16

3.68

89.2

51.

7785

234-

330.

0888

0.00

740.

0135

0.00

060.

0476

0.00

4186

.39

7.18

86.6

33.

5479

.50

6.82

89.6

33.

5485

234-

340.

2220

0.01

030.

0320

0.00

070.

0503

0.00

2420

3.57

9.45

202.

934.

4821

1.03

10.1

020

2.93

4.48

8523

4-28

0.31

920.

0300

0.04

450.

0014

0.05

210.

0050

281.

2626

.40

280.

478.

6728

7.70

27.7

028

0.47

8.67

8523

4-18

0.39

000.

0099

0.05

340.

0007

0.05

290.

0014

334.

398.

5033

5.59

4.67

326.

088.

5833

5.59

4.67

8523

4-32

0.39

510.

0198

0.05

360.

0009

0.05

340.

0027

338.

1216

.91

336.

785.

9634

7.44

17.7

533

6.78

5.96

8523

4-11

0.40

460.

0202

0.05

460.

0015

0.05

370.

0028

345.

0117

.25

342.

779.

3636

0.11

18.9

734

2.77

9.36

8523

4-35

0.40

370.

0174

0.05

470.

0018

0.05

350.

0024

344.

3414

.87

343.

5811

.42

349.

7315

.38

343.

5811

.42

8523

4-45

0.47

310.

0104

0.06

280.

0010

0.05

460.

0013

393.

368.

6739

2.88

5.94

396.

359.

1239

2.88

5.94

8523

4-21

0.49

640.

0123

0.06

520.

0012

0.05

520.

0015

409.

2910

.18

407.

267.

2342

0.84

11.0

340

7.26

7.23

8523

4-93

0.51

390.

0409

0.06

680.

0022

0.05

580.

0046

421.

0933

.54

417.

1113

.52

442.

8136

.56

417.

1113

.52

8523

4-79

0.51

480.

0404

0.06

700.

0020

0.05

580.

0044

421.

6433

.12

417.

8212

.65

442.

5834

.97

417.

8212

.65

8523

4-7

0.50

980.

0139

0.06

710.

0011

0.05

510.

0015

418.

2811

.39

418.

727.

0741

5.95

11.6

641

8.72

7.07

8523

4-2

0.51

740.

0247

0.06

770.

0021

0.05

540.

0028

423.

3920

.20

422.

5213

.36

427.

8621

.31

422.

5213

.36

8523

4-92

0.52

710.

0143

0.06

880.

0013

0.05

550.

0016

429.

8911

.69

429.

178.

3743

3.88

12.5

542

9.17

8.37

8523

4-30

0.62

700.

0204

0.07

930.

0011

0.05

730.

0019

494.

2516

.11

492.

027.

0350

4.61

17.0

949

2.02

7.03

8523

4-84

0.64

660.

0528

0.08

160.

0026

0.05

750.

0048

506.

4041

.34

505.

7416

.10

509.

4942

.87

505.

7416

.10

8523

4-31

0.64

860.

0222

0.08

210.

0019

0.05

730.

0021

507.

6017

.34

508.

4012

.08

504.

0718

.12

508.

4012

.08

8523

4-22

0.65

400.

0251

0.08

220.

0013

0.05

770.

0023

510.

9219

.64

508.

978.

3351

9.79

20.4

150

8.97

8.33

8523

4-55

0.65

240.

0322

0.08

300.

0018

0.05

700.

0029

509.

9625

.18

513.

9410

.99

492.

1724

.94

513.

9410

.99

8523

4-10

00.

6816

0.02

520.

0846

0.00

190.

0584

0.00

2252

7.72

19.4

952

3.79

11.9

954

4.89

20.6

452

3.79

11.9

985

234-

230.

6835

0.04

470.

0847

0.00

210.

0585

0.00

3952

8.90

34.5

652

4.37

13.1

254

8.25

36.8

152

4.37

13.1

285

234-

620.

6791

0.03

790.

0848

0.00

250.

0581

0.00

3352

6.26

29.3

452

4.74

15.2

053

2.72

30.5

952

4.74

15.2

085

234-

130.

6866

0.08

210.

0854

0.00

520.

0583

0.00

7353

0.73

63.4

952

8.11

32.4

254

2.14

67.6

352

8.11

32.4

285

234-

900.

7131

0.02

830.

0886

0.00

170.

0584

0.00

2454

6.61

21.6

854

7.35

10.4

754

3.59

22.1

354

7.35

10.4

785

234-

740.

7212

0.04

970.

0909

0.00

430.

0575

0.00

3355

1.37

38.0

256

0.84

26.5

051

2.54

29.8

156

0.84

26.5

085

234-

80.

7892

0.01

970.

0952

0.00

190.

0601

0.00

1659

0.74

14.7

458

6.23

11.7

460

8.22

16.1

458

6.23

11.7

485

234-

510.

8547

0.02

910.

1016

0.00

190.

0610

0.00

2162

7.22

21.3

562

3.70

11.4

464

0.11

22.1

462

3.70

11.4

485

234-

40.

8614

0.02

630.

1029

0.00

240.

0607

0.00

2063

0.91

19.2

463

1.57

14.7

162

8.59

20.4

363

1.57

14.7

185

234-

490.

8956

0.02

290.

1052

0.00

170.

0617

0.00

1764

9.38

16.6

264

5.06

10.4

166

4.52

17.8

564

5.06

10.4

1

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

Sam

ple

05A

SD05

3 (u

pper

Nan

ushu

k Fo

rmat

ion)

App

endi

x C

-1. A

naly

tical

dat

a an

d ca

lcul

ated

age

s ge

nera

ted

from

lase

r ab

latio

n in

duct

ivel

y co

uple

d pl

asm

a m

ass

spec

trom

etry

. Bol

d ag

es a

re c

onco

rdan

t; bl

ue a

ges

indi

cate

min

or P

b lo

ss

(plo

ts ju

st b

elow

the

conc

ordi

a cu

rve,

equ

ival

ent t

o <

2 pe

rcen

t of t

he to

tal P

b); a

ges i

n re

d in

dica

te e

vide

nce

for U

loss

or P

b ga

in (p

lots

abo

ve th

e co

ncor

dia

curv

e); a

ges i

n gr

een

exhi

bit

sign

ifi ca

nt P

b lo

ss (p

lots

bel

ow th

e co

ncor

dia

curv

e, e

quiv

alen

t to

>2

perc

ent o

f the

tota

l Pb)

; rej

ecte

d ag

es in

dica

ted

by st

rike

thro

ugh.

Isot

ope

ratio

s are

cor

rect

ed fo

r Pb/

U fr

actio

natio

n by

co

mpa

riso

n w

ith st

anda

rd zi

rcon

s with

an

age

of 5

64 ±

4 M

a (2σ)

and

109

9 ±

8 M

a (2σ)

. Rep

orte

d er

rors

incl

ude

mea

sure

men

t and

frac

tiona

tion

erro

rs. D

ecay

con

stan

ts: 23

5 U=

9.84

85x1

0-10 ;

238 U

=1.

5512

5x10

-10 ;

238 U

/235 U

=13

7.88

; see

Cha

ng a

nd o

ther

s (20

06) f

or d

etai

led

labo

rato

ry p

roce

dure

s.

Appendix C-1 181

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)85

234-

701.

0422

0.03

490.

1190

0.00

360.

0635

0.00

2372

5.00

24.2

672

4.76

21.8

272

5.86

25.9

972

4.76

21.8

285

234-

591.

1666

0.02

650.

1305

0.00

210.

0648

0.00

1578

5.07

17.8

379

0.78

12.9

976

8.97

17.7

479

0.78

12.9

985

234-

691.

2842

0.11

840.

1391

0.01

130.

0670

0.00

6583

8.71

77.3

083

9.53

68.0

183

6.64

81.1

883

9.53

68.0

185

234-

531.

3158

0.05

830.

1421

0.00

340.

0672

0.00

3285

2.67

37.8

185

6.56

20.5

184

2.82

39.6

885

6.56

20.5

185

234-

291.

3488

0.04

450.

1423

0.00

280.

0687

0.00

2486

7.03

28.6

185

7.72

16.6

889

1.04

31.6

885

7.72

16.6

885

234-

541.

3593

0.06

010.

1440

0.00

500.

0685

0.00

3387

1.55

38.5

286

7.14

29.9

788

2.80

42.3

386

7.14

29.9

785

234-

121.

4018

0.04

590.

1477

0.00

390.

0688

0.00

2588

9.71

29.1

588

8.15

23.3

189

3.90

32.2

688

8.15

23.3

185

234-

161.

4271

0.03

100.

1489

0.00

200.

0695

0.00

1690

0.36

19.5

989

4.74

12.2

391

4.19

20.4

089

4.74

12.2

385

234-

721.

4407

0.02

550.

1497

0.00

200.

0698

0.00

1390

6.00

16.0

189

9.43

12.2

792

2.09

16.6

389

9.43

12.2

785

234-

911.

4696

0.04

820.

1510

0.00

320.

0706

0.00

2491

7.95

30.1

190

6.78

19.3

394

4.98

32.1

790

6.78

19.3

385

234-

461.

4637

0.02

530.

1522

0.00

220.

0697

0.00

1291

5.54

15.8

491

3.54

13.4

492

0.41

16.1

291

3.54

13.4

485

234-

881.

4946

0.07

750.

1545

0.00

440.

0702

0.00

3692

8.18

48.1

092

6.12

26.0

793

3.23

47.4

692

6.12

26.0

785

234-

421.

5543

0.05

710.

1580

0.00

300.

0714

0.00

2895

2.20

34.9

894

5.65

18.0

296

7.48

37.8

294

5.65

18.0

285

234-

611.

5548

0.03

870.

1585

0.00

340.

0711

0.00

2095

2.39

23.7

294

8.66

20.0

496

1.23

26.9

694

8.66

20.0

485

234-

571.

6969

0.04

620.

1705

0.00

290.

0722

0.00

2010

07.3

527

.42

1014

.70

17.2

699

1.52

28.0

699

1.52

28.0

685

234-

641.

6970

0.04

110.

1685

0.00

340.

0731

0.00

2010

07.3

924

.41

1003

.71

20.0

810

15.5

127

.44

1015

.51

27.4

485

234-

821.

6705

0.08

320.

1647

0.00

520.

0736

0.00

3899

7.37

49.6

698

2.91

30.9

610

29.3

252

.51

1029

.32

52.5

185

234-

631.

7990

0.06

300.

1772

0.00

550.

0736

0.00

2710

45.0

936

.60

1051

.70

32.7

110

31.3

438

.28

1031

.34

38.2

885

234-

651.

7576

0.06

090.

1710

0.00

540.

0746

0.00

2710

29.9

835

.71

1017

.63

31.8

510

56.4

438

.86

1056

.44

38.8

685

234-

581.

8709

0.04

950.

1804

0.00

370.

0752

0.00

2110

70.8

328

.34

1069

.01

21.6

610

74.6

829

.45

1074

.68

29.4

585

234-

761.

9541

0.06

470.

1882

0.00

480.

0753

0.00

2510

99.8

436

.44

1111

.38

28.4

710

77.1

936

.44

1077

.19

36.4

485

234-

681.

8176

0.05

220.

1750

0.00

430.

0753

0.00

2310

51.8

130

.19

1039

.53

25.3

010

77.4

232

.25

1077

.42

32.2

585

234-

981.

8361

0.05

100.

1755

0.00

460.

0759

0.00

2310

58.4

829

.40

1042

.22

27.4

510

92.2

233

.24

1092

.22

33.2

485

234-

961.

8995

0.03

830.

1805

0.00

350.

0763

0.00

1710

80.9

121

.77

1069

.71

20.5

311

03.5

924

.72

1103

.59

24.7

285

234-

782.

1439

0.06

800.

2010

0.00

510.

0774

0.00

2611

63.0

936

.90

1180

.79

29.8

411

30.3

737

.41

1130

.37

37.4

185

234-

521.

9567

0.08

130.

1826

0.00

710.

0777

0.00

3611

00.7

745

.72

1080

.89

42.0

411

40.2

552

.13

1140

.25

52.1

385

234-

892.

0296

0.06

860.

1892

0.00

310.

0778

0.00

2811

25.4

938

.05

1117

.29

18.0

611

41.4

040

.58

1141

.40

40.5

885

234-

812.

1849

0.05

690.

1971

0.00

420.

0804

0.00

2311

76.2

430

.61

1159

.71

24.5

012

06.8

635

.17

1206

.86

35.1

785

234-

832.

3725

0.04

860.

2095

0.00

380.

0821

0.00

1812

34.3

625

.30

1226

.18

22.1

312

48.6

726

.75

1248

.67

26.7

585

234-

192.

3642

0.05

720.

2087

0.00

420.

0821

0.00

2112

31.8

629

.80

1222

.07

24.7

312

49.0

531

.99

1249

.05

31.9

985

234-

392.

5211

0.05

540.

2169

0.00

310.

0843

0.00

1912

78.1

428

.10

1265

.27

18.0

012

99.8

629

.95

1299

.86

29.9

585

234-

252.

5231

0.07

200.

2164

0.00

380.

0846

0.00

2512

78.7

036

.48

1262

.82

21.9

313

05.5

039

.07

1305

.50

39.0

785

234-

502.

5870

0.06

280.

2213

0.00

340.

0848

0.00

2112

96.9

631

.50

1288

.77

19.8

913

10.5

432

.93

1310

.54

32.9

385

234-

62.

7596

0.08

850.

2327

0.00

600.

0860

0.00

3013

44.6

743

.14

1348

.65

34.8

413

38.3

546

.24

1338

.35

46.2

485

234-

772.

7996

0.07

970.

2357

0.00

460.

0861

0.00

2413

55.4

438

.56

1364

.55

26.7

113

41.2

537

.96

1341

.25

37.9

685

234-

102.

7950

0.13

600.

2324

0.00

860.

0872

0.00

4613

54.2

065

.89

1347

.14

49.7

013

65.5

572

.06

1365

.55

72.0

6

Age

s (M

a)

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 05

AS

D05

3

Cor

rect

ed Is

otop

ic R

atio

s

182 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)85

234-

562.

7724

0.05

110.

2299

0.00

340.

0875

0.00

1713

48.1

424

.85

1333

.89

19.9

113

70.8

527

.02

1370

.85

27.0

285

234-

152.

7889

0.12

110.

2258

0.00

900.

0896

0.00

3713

52.5

758

.73

1312

.28

52.3

214

16.9

757

.99

1416

.97

57.9

985

234-

993.

0638

0.11

250.

2477

0.00

670.

0897

0.00

3514

23.6

952

.28

1426

.65

38.6

014

19.4

156

.01

1419

.41

56.0

185

234-

52.

9422

0.07

960.

2374

0.00

660.

0899

0.00

2913

92.8

437

.68

1373

.29

38.4

414

23.0

445

.58

1423

.04

45.5

885

234-

13.

1257

0.14

690.

2504

0.00

760.

0906

0.00

4314

39.0

467

.61

1440

.32

43.8

514

37.4

268

.07

1437

.42

68.0

785

234-

383.

1488

0.05

170.

2504

0.00

320.

0912

0.00

1514

44.7

123

.72

1440

.32

18.1

714

51.2

624

.03

1451

.26

24.0

385

234-

853.

1900

0.07

070.

2533

0.00

490.

0913

0.00

2114

54.7

432

.26

1455

.39

28.3

614

53.8

233

.85

1453

.82

33.8

585

234-

803.

4716

0.09

780.

2724

0.00

740.

0924

0.00

2815

20.7

842

.86

1553

.01

42.1

614

76.3

644

.88

1476

.36

44.8

885

234-

93.

1953

0.05

650.

2494

0.00

440.

0929

0.00

1814

56.0

325

.74

1435

.34

25.5

814

86.4

729

.55

1486

.47

29.5

585

234-

243.

3209

0.10

290.

2587

0.00

700.

0931

0.00

2914

85.9

746

.05

1483

.31

40.3

514

90.0

245

.53

1490

.02

45.5

385

234-

673.

5184

0.13

330.

2694

0.00

910.

0947

0.00

3815

31.3

658

.00

1537

.79

52.1

115

22.6

061

.30

1522

.60

61.3

085

234-

973.

5781

0.10

420.

2734

0.00

560.

0949

0.00

2815

44.6

844

.98

1558

.25

31.9

915

26.2

245

.53

1526

.22

45.5

385

234-

713.

7208

0.15

430.

2778

0.00

570.

0971

0.00

4215

75.8

565

.34

1580

.32

32.3

115

69.9

467

.15

1569

.94

67.1

585

234-

863.

5918

0.06

510.

2676

0.00

410.

0974

0.00

1915

47.7

228

.07

1528

.37

23.4

315

74.2

530

.20

1574

.25

30.2

085

234-

873.

6447

0.08

360.

2701

0.00

520.

0979

0.00

2515

59.3

635

.75

1541

.27

29.5

315

84.0

940

.85

1584

.09

40.8

585

234-

953.

7106

0.11

280.

2744

0.00

630.

0981

0.00

3015

73.6

647

.85

1563

.16

36.0

815

87.7

249

.06

1587

.72

49.0

685

234-

413.

9316

0.06

590.

2890

0.00

420.

0987

0.00

1816

20.2

127

.17

1636

.44

23.7

215

99.2

728

.40

1599

.27

28.4

085

234-

944.

0812

0.09

440.

2959

0.00

650.

1000

0.00

2616

50.5

538

.17

1671

.00

36.4

716

24.7

641

.34

1624

.76

41.3

485

234-

264.

0183

0.09

680.

2862

0.00

610.

1018

0.00

2716

37.9

139

.47

1622

.34

34.8

516

58.0

643

.96

1658

.06

43.9

685

234-

404.

2691

0.10

910.

3011

0.00

600.

1028

0.00

2716

87.4

243

.12

1696

.98

33.5

716

75.5

744

.04

1675

.57

44.0

485

234-

144.

4528

0.12

160.

3113

0.00

770.

1038

0.00

2917

22.2

247

.03

1746

.89

43.1

816

92.4

746

.86

1692

.47

46.8

685

234-

364.

2478

0.13

520.

2961

0.00

740.

1041

0.00

3416

83.3

153

.56

1671

.84

41.8

116

97.7

355

.78

1697

.73

55.7

885

234-

734.

3037

0.07

450.

2961

0.00

460.

1054

0.00

1916

94.0

729

.34

1671

.77

26.0

417

21.8

030

.84

1721

.80

30.8

485

234-

174.

3858

0.07

210.

3006

0.00

430.

1058

0.00

1817

09.6

628

.09

1694

.36

24.3

917

28.4

828

.72

1728

.48

28.7

285

234-

444.

8601

0.11

380.

3205

0.00

550.

1100

0.00

2817

95.3

642

.05

1792

.14

30.9

817

99.2

445

.19

1799

.24

45.1

985

234-

485.

3383

0.11

360.

3393

0.00

590.

1141

0.00

2518

75.0

139

.89

1883

.34

32.4

818

65.8

840

.05

1865

.88

40.0

585

234-

435.

6514

0.14

510.

3547

0.00

720.

1156

0.00

3219

23.9

849

.40

1957

.10

40.0

018

88.5

851

.63

1888

.58

51.6

385

234-

275.

7355

0.13

460.

3538

0.00

700.

1176

0.00

2919

36.7

345

.45

1952

.70

38.8

619

19.8

247

.26

1919

.82

47.2

685

234-

205.

8321

0.11

500.

3578

0.00

610.

1182

0.00

2519

51.1

938

.47

1971

.75

33.6

219

29.5

540

.36

1929

.55

40.3

685

234-

665.

7032

0.11

240.

3495

0.00

730.

1184

0.00

2719

31.8

538

.07

1932

.06

40.4

219

31.6

144

.76

1931

.61

44.7

685

234-

311

.479

70.

3466

0.49

420.

0146

0.16

850.

0046

2562

.93

77.3

825

88.6

976

.68

2542

.73

68.5

925

42.7

368

.59

8523

4-60

13.3

156

0.39

820.

5265

0.01

400.

1834

0.00

6027

02.2

980

.81

2726

.54

72.4

026

84.2

987

.08

2684

.29

87.0

885

234-

7513

.377

10.

3025

0.50

820.

0105

0.19

090.

0043

2706

.64

61.2

126

49.0

054

.62

2750

.02

62.1

827

50.0

262

.18

8523

4-47

20.9

269

0.49

530.

6393

0.01

440.

2374

0.00

6031

35.2

174

.21

3186

.33

71.8

931

02.7

479

.06

3102

.74

79.0

6

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 05

AS

D05

3

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

Appendix C-1 183

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

±285

233-

70.

2225

0.00

670.

0321

0.00

060.

0503

0.00

1520

4.00

6.15

203.

613.

7520

8.74

6.17

203.

613.

7585

233-

60.

4054

0.03

400.

0548

0.00

110.

0537

0.00

4534

5.55

28.9

434

3.94

6.97

356.

6030

.08

343.

946.

9785

233-

630.

4057

0.01

400.

0549

0.00

090.

0536

0.00

1934

5.80

11.9

534

4.45

5.73

354.

9212

.70

344.

455.

7385

233-

700.

4156

0.01

220.

0562

0.00

080.

0537

0.00

1635

2.91

10.3

535

2.39

5.08

356.

4510

.77

352.

395.

0885

233-

100

0.41

650.

0161

0.05

640.

0009

0.05

350.

0021

353.

5413

.65

353.

895.

8635

1.10

13.8

835

3.89

5.86

8523

3-15

0.42

000.

0109

0.05

660.

0008

0.05

380.

0014

356.

079.

2735

4.91

5.27

363.

629.

5535

4.91

5.27

8523

3-4

0.43

840.

0230

0.05

870.

0009

0.05

410.

0029

369.

1219

.40

367.

915.

5437

6.43

20.2

436

7.91

5.54

8523

3-51

0.44

120.

0171

0.05

900.

0011

0.05

430.

0022

371.

1214

.36

369.

366.

5538

2.31

15.1

236

9.36

6.55

8523

3-36

0.47

090.

0158

0.06

240.

0015

0.05

480.

0020

391.

8013

.14

390.

029.

3340

2.37

14.5

439

0.02

9.33

8523

3-44

0.48

850.

0319

0.06

420.

0016

0.05

520.

0037

403.

8626

.39

401.

0710

.18

419.

6928

.00

401.

0710

.18

8523

3-9

0.49

080.

0162

0.06

460.

0010

0.05

510.

0019

405.

4913

.42

403.

786.

0041

5.50

14.1

540

3.78

6.00

8523

3-98

0.59

660.

0172

0.07

610.

0013

0.05

690.

0016

475.

0513

.74

472.

608.

1948

6.98

13.2

947

2.60

8.19

8523

3-61

0.62

620.

0353

0.07

900.

0018

0.05

750.

0034

493.

7427

.87

489.

9511

.01

511.

4730

.23

489.

9511

.01

8523

3-39

0.62

780.

0376

0.07

980.

0025

0.05

710.

0035

494.

7129

.61

494.

6815

.26

494.

7729

.90

494.

6815

.26

8523

3-12

0.66

060.

0201

0.08

260.

0016

0.05

800.

0018

514.

9615

.68

511.

499.

8353

0.17

16.6

351

1.49

9.83

8523

3-74

0.66

550.

0241

0.08

320.

0013

0.05

800.

0022

517.

9718

.77

515.

158.

0553

0.40

19.8

451

5.15

8.05

8523

3-54

0.67

170.

0142

0.08

430.

0012

0.05

780.

0013

521.

7611

.03

521.

567.

4052

2.61

11.6

752

1.56

7.40

8523

3-56

0.69

460.

0160

0.08

640.

0012

0.05

830.

0014

535.

5712

.36

534.

207.

4254

1.31

12.6

053

4.20

7.42

8523

3-81

0.74

110.

0121

0.09

120.

0011

0.05

890.

0010

563.

079.

1656

2.63

6.51

564.

969.

6256

2.63

6.51

8523

3-38

0.74

330.

0232

0.09

140.

0017

0.05

900.

0019

564.

3117

.58

563.

9710

.35

565.

5717

.80

563.

9710

.35

8523

3-42

0.75

050.

0323

0.09

170.

0014

0.05

940.

0026

568.

4924

.47

565.

428.

6258

0.94

25.8

756

5.42

8.62

8523

3-58

0.74

740.

0195

0.09

190.

0012

0.05

900.

0016

566.

7414

.80

566.

517.

4456

7.70

15.4

056

6.51

7.44

8523

3-84

0.75

300.

0340

0.09

200.

0019

0.05

940.

0028

569.

9525

.76

567.

4211

.58

580.

2227

.38

567.

4211

.58

8523

3-17

0.76

380.

0264

0.09

340.

0018

0.05

930.

0021

576.

1819

.91

575.

7710

.80

577.

9320

.63

575.

7710

.80

8523

3-90

0.76

380.

0243

0.09

390.

0017

0.05

900.

0019

576.

2118

.30

578.

8010

.55

566.

1818

.39

578.

8010

.55

8523

3-27

0.78

710.

0424

0.09

540.

0039

0.05

980.

0033

589.

5231

.76

587.

4723

.78

597.

3832

.94

587.

4723

.78

8523

3-62

0.78

930.

0241

0.09

650.

0019

0.05

930.

0019

590.

7518

.07

593.

6911

.49

579.

6118

.69

593.

6911

.49

8523

3-48

0.80

330.

0297

0.09

710.

0014

0.06

000.

0023

598.

6622

.16

597.

558.

5660

2.84

22.9

059

7.55

8.56

8523

3-57

0.80

390.

0371

0.09

730.

0027

0.05

990.

0028

599.

0427

.63

598.

3516

.55

601.

5828

.22

598.

3516

.55

8523

3-92

0.83

470.

0257

0.09

960.

0017

0.06

080.

0020

616.

2018

.98

612.

2810

.19

630.

4920

.72

612.

2810

.19

8523

3-67

0.83

220.

0219

0.10

050.

0019

0.06

010.

0017

614.

8316

.18

617.

3611

.39

605.

4716

.76

617.

3611

.39

8523

3-45

0.84

470.

0225

0.10

080.

0015

0.06

080.

0016

621.

7116

.57

619.

148.

9563

1.03

16.5

361

9.14

8.95

8523

3-93

0.85

290.

0338

0.10

150.

0016

0.06

090.

0025

626.

2524

.81

623.

269.

6663

7.13

25.7

062

3.26

9.66

App

endi

x C

-1 c

ontin

ued

Sam

ple

05W

KW

082A

(ba

sal N

anus

huk

Form

atio

n)C

orre

cted

Isot

opic

Rat

ios

Age

s (M

a)

184 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)85

233-

190.

8431

0.02

790.

1018

0.00

230.

0600

0.00

1962

0.87

20.5

562

5.19

13.8

260

5.16

19.3

662

5.19

13.8

285

233-

290.

8704

0.04

570.

1022

0.00

310.

0617

0.00

3463

5.79

33.3

662

7.58

18.9

166

5.28

36.1

962

7.58

18.9

185

233-

720.

8546

0.03

000.

1028

0.00

160.

0603

0.00

2262

7.17

21.9

863

0.84

9.94

613.

8622

.04

630.

849.

9485

233-

160.

8748

0.02

430.

1033

0.00

240.

0614

0.00

1863

8.14

17.7

563

3.76

14.8

265

3.61

19.3

563

3.76

14.8

285

233-

530.

8787

0.03

370.

1037

0.00

180.

0615

0.00

2564

0.28

24.5

763

5.87

11.0

765

5.98

26.2

963

5.87

11.0

785

233-

370.

8815

0.01

750.

1040

0.00

170.

0615

0.00

1464

1.81

12.7

663

8.05

10.3

865

5.06

14.5

663

8.05

10.3

885

233-

730.

8907

0.02

420.

1048

0.00

160.

0616

0.00

1764

6.73

17.5

464

2.62

9.51

661.

2418

.20

642.

629.

5185

233-

880.

8826

0.02

480.

1059

0.00

230.

0605

0.00

1764

2.40

18.0

464

8.82

14.2

061

9.89

17.8

964

8.82

14.2

085

233-

780.

9012

0.03

180.

1069

0.00

350.

0611

0.00

2165

2.35

23.0

465

4.63

21.5

664

4.46

22.5

065

4.63

21.5

685

233-

960.

9091

0.02

480.

1069

0.00

170.

0617

0.00

1765

6.57

17.8

965

4.66

10.3

966

2.99

18.5

365

4.66

10.3

985

233-

860.

9125

0.04

470.

1069

0.00

470.

0619

0.00

3465

8.41

32.2

365

4.96

28.7

167

0.47

36.3

565

4.96

28.7

185

233-

80.

9102

0.04

580.

1082

0.00

210.

0610

0.00

3265

7.14

33.0

966

2.34

12.9

863

9.50

33.0

866

2.34

12.9

885

233-

830.

9222

0.01

830.

1087

0.00

170.

0615

0.00

1366

3.54

13.1

566

5.41

10.5

065

7.20

13.8

966

5.41

10.5

085

233-

411.

0342

0.02

420.

1175

0.00

170.

0638

0.00

1572

1.03

16.9

071

6.29

10.5

473

5.70

17.6

271

6.29

10.5

485

233-

651.

3298

0.02

960.

1419

0.00

280.

0680

0.00

1885

8.80

19.1

485

5.25

16.7

086

8.07

22.5

385

5.25

16.7

085

233-

821.

3710

0.02

650.

1445

0.00

200.

0688

0.00

1487

6.59

16.9

687

0.11

12.2

289

3.02

18.2

387

0.11

12.2

285

233-

231.

3633

0.05

050.

1449

0.00

460.

0683

0.00

2787

3.30

32.3

487

2.21

27.4

587

6.16

35.2

087

2.21

27.4

585

233-

891.

3796

0.04

080.

1456

0.00

350.

0687

0.00

2188

0.27

26.0

687

6.39

21.0

289

0.05

27.7

587

6.39

21.0

285

233-

851.

4142

0.04

360.

1469

0.00

420.

0698

0.00

2389

4.92

27.6

188

3.63

25.3

192

2.93

29.8

788

3.63

25.3

185

233-

261.

4072

0.03

180.

1473

0.00

260.

0693

0.00

1689

1.98

20.1

888

5.79

15.8

390

7.29

21.4

088

5.79

15.8

385

233-

661.

3985

0.03

900.

1476

0.00

270.

0687

0.00

2088

8.28

24.7

788

7.35

16.4

989

0.85

26.2

788

7.35

16.4

985

233-

401.

4730

0.02

800.

1526

0.00

190.

0700

0.00

1491

9.37

17.4

691

5.30

11.4

892

9.18

18.0

491

5.30

11.4

885

233-

691.

4644

0.05

430.

1549

0.00

390.

0686

0.00

2791

5.84

33.9

492

8.13

23.4

288

6.12

34.6

592

8.13

23.4

285

233-

871.

5092

0.02

670.

1569

0.00

210.

0697

0.00

1293

4.10

16.5

493

9.70

12.6

292

0.91

15.8

093

9.70

12.6

285

233-

711.

5472

0.05

680.

1576

0.00

370.

0712

0.00

2794

9.38

34.8

594

3.51

21.9

796

2.98

36.0

594

3.51

21.9

785

233-

341.

5414

0.06

320.

1587

0.00

410.

0705

0.00

2994

7.08

38.8

394

9.31

24.4

594

2.00

39.4

094

9.31

24.4

585

233-

431.

5727

0.05

200.

1588

0.00

270.

0718

0.00

2595

9.50

31.7

595

0.19

16.2

398

0.84

33.6

895

0.19

16.2

385

233-

491.

5803

0.03

200.

1615

0.00

270.

0710

0.00

1696

2.50

19.4

796

5.11

16.1

295

6.50

21.6

396

5.11

16.1

285

233-

101.

6071

0.05

710.

1629

0.00

270.

0715

0.00

2697

3.00

34.5

797

3.03

16.1

197

3.13

35.4

697

3.03

16.1

185

233-

281.

7236

0.03

340.

1729

0.00

300.

0723

0.00

1510

17.3

819

.70

1028

.24

17.6

699

4.19

20.6

699

4.19

20.6

685

233-

31.

7002

0.04

770.

1684

0.00

400.

0732

0.00

2110

08.6

228

.32

1003

.41

23.5

310

20.0

928

.89

1020

.09

28.8

985

233-

251.

8540

0.02

970.

1811

0.00

270.

0742

0.00

1310

64.8

517

.06

1073

.25

16.1

510

47.6

718

.24

1047

.67

18.2

485

233-

641.

9404

0.04

360.

1833

0.00

250.

0768

0.00

1910

95.1

524

.60

1085

.23

14.8

611

14.9

627

.20

1114

.96

27.2

085

233-

681.

9488

0.03

220.

1841

0.00

220.

0768

0.00

1310

98.0

418

.12

1089

.47

13.1

011

15.0

419

.23

1115

.04

19.2

3

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 05

WK

W08

2A

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

Appendix C-1 185

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)85

233-

182.

0527

0.06

690.

1936

0.00

310.

0769

0.00

2611

33.2

036

.92

1140

.85

18.2

111

18.7

037

.61

1118

.70

37.6

185

233-

112.

0317

0.03

730.

1892

0.00

260.

0779

0.00

1511

26.1

920

.70

1116

.81

15.6

111

44.4

921

.97

1144

.49

21.9

785

233-

22.

0778

0.03

850.

1927

0.00

220.

0782

0.00

1511

41.5

021

.12

1136

.10

12.8

811

51.8

922

.45

1151

.89

22.4

585

233-

242.

2057

0.04

030.

2028

0.00

210.

0789

0.00

1511

82.8

421

.62

1190

.17

12.0

111

69.5

122

.26

1169

.51

22.2

685

233-

752.

1402

0.03

650.

1955

0.00

270.

0794

0.00

1511

61.9

019

.82

1151

.03

15.7

811

82.3

322

.86

1182

.33

22.8

685

233-

992.

3186

0.10

030.

2056

0.00

520.

0818

0.00

3812

18.0

152

.70

1205

.24

30.4

712

40.8

557

.02

1240

.85

57.0

285

233-

762.

3805

0.06

120.

2099

0.00

480.

0823

0.00

2412

36.7

531

.78

1228

.03

28.2

312

52.0

636

.55

1252

.06

36.5

585

233-

552.

3651

0.04

870.

2083

0.00

310.

0824

0.00

1712

32.1

225

.38

1219

.50

17.8

912

54.2

325

.82

1254

.23

25.8

285

233-

52.

4721

0.05

160.

2134

0.00

400.

0840

0.00

2012

63.9

226

.37

1246

.71

23.4

712

93.4

530

.09

1293

.45

30.0

985

233-

212.

6236

0.08

210.

2226

0.00

340.

0855

0.00

2813

07.2

640

.90

1295

.59

19.9

713

26.4

142

.71

1326

.41

42.7

185

233-

132.

8291

0.12

420.

2352

0.00

910.

0873

0.00

4113

63.2

859

.86

1361

.44

52.6

413

66.2

764

.61

1366

.27

64.6

185

233-

312.

8249

0.07

650.

2328

0.00

470.

0880

0.00

2513

62.1

636

.87

1349

.28

27.1

513

82.5

639

.86

1382

.56

39.8

685

233-

952.

9163

0.06

610.

2371

0.00

340.

0892

0.00

2113

86.1

431

.42

1371

.44

19.4

314

08.9

633

.77

1408

.96

33.7

785

233-

602.

9351

0.05

050.

2385

0.00

360.

0892

0.00

1713

91.0

223

.93

1379

.07

21.0

214

09.3

426

.31

1409

.34

26.3

185

233-

523.

0833

0.05

570.

2477

0.00

390.

0903

0.00

1514

28.5

525

.79

1426

.72

22.2

514

31.3

923

.70

1431

.39

23.7

085

233-

793.

2462

0.04

780.

2571

0.00

240.

0916

0.00

1414

68.2

621

.62

1474

.97

13.8

814

58.5

522

.46

1458

.55

22.4

685

233-

913.

4485

0.08

670.

2679

0.00

550.

0934

0.00

2515

15.5

238

.11

1530

.25

31.4

514

95.2

539

.74

1495

.25

39.7

485

233-

773.

3585

0.07

040.

2591

0.00

510.

0940

0.00

2214

94.7

631

.34

1485

.45

29.5

015

08.1

035

.82

1508

.10

35.8

285

233-

973.

5785

0.06

500.

2736

0.00

390.

0949

0.00

1815

44.7

728

.05

1559

.24

22.4

115

25.1

929

.07

1525

.19

29.0

785

233-

593.

8354

0.06

230.

2858

0.00

450.

0973

0.00

1916

00.2

025

.99

1620

.31

25.3

915

73.9

130

.27

1573

.91

30.2

785

233-

143.

8416

0.18

530.

2801

0.01

410.

0995

0.00

5416

01.5

177

.27

1591

.82

79.9

016

14.3

887

.55

1614

.38

87.5

585

233-

203.

9057

0.08

090.

2845

0.00

540.

0995

0.00

2216

14.8

533

.47

1614

.21

30.9

216

15.6

835

.29

1615

.68

35.2

985

233-

463.

8416

0.10

430.

2785

0.00

580.

1000

0.00

2916

01.5

243

.48

1583

.94

32.9

416

24.7

646

.51

1624

.76

46.5

185

233-

13.

9172

0.06

480.

2831

0.00

350.

1004

0.00

1816

17.2

426

.74

1606

.72

19.9

416

31.0

529

.12

1631

.05

29.1

285

233-

473.

9157

0.11

030.

2807

0.00

570.

1012

0.00

3016

16.9

345

.53

1595

.13

32.6

016

45.4

348

.23

1645

.43

48.2

385

233-

224.

1150

0.05

980.

2939

0.00

380.

1016

0.00

1716

57.2

824

.08

1660

.97

21.4

416

52.6

827

.27

1652

.68

27.2

785

233-

803.

9940

0.06

080.

2848

0.00

360.

1017

0.00

1416

32.9

824

.87

1615

.29

20.6

916

55.9

623

.09

1655

.96

23.0

985

233-

504.

2460

0.06

170.

3002

0.00

350.

1026

0.00

1616

82.9

624

.44

1692

.11

19.7

816

71.7

225

.99

1671

.72

25.9

985

233-

304.

5967

0.11

400.

3074

0.00

710.

1084

0.00

2817

48.6

643

.37

1728

.12

40.0

117

73.2

645

.03

1773

.26

45.0

385

233-

944.

8977

0.11

870.

3269

0.00

750.

1087

0.00

2918

01.8

643

.69

1823

.36

41.7

617

77.3

147

.28

1777

.31

47.2

885

233-

325.

0110

0.11

120.

3219

0.00

650.

1129

0.00

2718

21.1

840

.42

1798

.82

36.2

618

46.7

744

.26

1846

.77

44.2

685

233-

355.

2035

0.09

590.

3326

0.00

600.

1135

0.00

2218

53.2

034

.14

1851

.19

33.1

718

55.4

135

.98

1855

.41

35.9

885

233-

335.

0362

0.09

930.

3218

0.00

580.

1135

0.00

2518

25.4

336

.01

1798

.59

32.5

418

56.1

641

.06

1856

.16

41.0

6

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 05

WK

W08

2A

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

186 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

±248

502-

110.

2246

0.01

570.

0405

0.00

060.

0000

0.00

000.

000.

000.

000.

000.

000.

000.

000.

0048

502-

760.

1206

0.01

010.

0182

0.00

090.

0482

0.00

4111

5.65

9.70

116.

055.

9010

7.42

9.21

116.

055.

9048

502-

830.

1255

0.00

390.

0188

0.00

040.

0485

0.00

1512

0.00

3.71

119.

832.

2512

4.21

3.83

119.

832.

2548

502-

370.

1292

0.00

940.

0193

0.00

040.

0485

0.00

3612

3.39

8.94

123.

332.

3412

4.74

9.20

123.

332.

3448

502-

330.

1403

0.00

440.

0209

0.00

030.

0487

0.00

1513

3.33

4.14

133.

242.

1613

5.04

4.24

133.

242.

1648

502-

580.

1888

0.04

200.

0272

0.00

290.

0503

0.01

2317

5.62

39.1

117

3.21

18.1

720

8.36

51.0

317

3.21

18.1

748

502-

940.

2268

0.01

880.

0326

0.00

070.

0504

0.00

4320

7.58

17.2

220

7.01

4.53

214.

1618

.23

207.

014.

5348

502-

130.

2399

0.01

170.

0343

0.00

110.

0507

0.00

2621

8.30

10.6

221

7.35

6.79

228.

4211

.59

217.

356.

7948

502-

340.

2643

0.00

770.

0376

0.00

050.

0510

0.00

1523

8.14

6.97

237.

753.

3424

2.16

7.05

237.

753.

3448

502-

90.

2747

0.01

610.

0389

0.00

070.

0513

0.00

3124

6.47

14.4

424

5.71

4.73

253.

4515

.21

245.

714.

7348

502-

180.

2758

0.01

350.

0390

0.00

060.

0512

0.00

2624

7.35

12.0

824

6.85

3.69

251.

5412

.60

246.

853.

6948

502-

220.

2747

0.01

650.

0392

0.00

130.

0508

0.00

3224

6.42

14.8

324

7.95

7.95

232.

0114

.52

247.

957.

9548

502-

190.

2750

0.03

290.

0394

0.00

170.

0507

0.00

6324

6.71

29.5

024

8.81

10.9

322

7.05

28.2

624

8.81

10.9

348

502-

30.

2824

0.01

350.

0398

0.00

060.

0514

0.00

2525

2.57

12.0

425

1.83

4.08

259.

4012

.82

251.

834.

0848

502-

20.

2867

0.01

210.

0404

0.00

080.

0515

0.00

2325

5.94

10.8

325

5.05

5.15

264.

0511

.61

255.

055.

1548

502-

60.

2883

0.00

760.

0406

0.00

050.

0515

0.00

1425

7.25

6.76

256.

753.

1326

1.76

7.11

256.

753.

1348

502-

150.

2939

0.02

440.

0412

0.00

120.

0517

0.00

4426

1.63

21.7

526

0.28

7.87

273.

7423

.33

260.

287.

8748

502-

630.

2914

0.03

000.

0412

0.00

110.

0513

0.00

5425

9.66

26.7

126

0.49

6.92

252.

3026

.54

260.

496.

9248

502-

520.

2960

0.03

240.

0415

0.00

120.

0518

0.00

5826

3.28

28.7

926

2.08

7.27

274.

8130

.76

262.

087.

2748

502-

480.

2965

0.02

470.

0415

0.00

110.

0518

0.00

4426

3.65

22.0

026

2.33

7.24

275.

6523

.66

262.

337.

2448

502-

810.

2968

0.01

040.

0416

0.00

100.

0518

0.00

1926

3.93

9.20

262.

806.

4627

4.81

10.2

326

2.80

6.46

4850

2-44

0.29

920.

0287

0.04

190.

0009

0.05

170.

0051

265.

7725

.54

264.

865.

7227

3.90

26.8

326

4.86

5.72

4850

2-25

0.30

260.

0393

0.04

230.

0013

0.05

190.

0069

268.

4734

.87

266.

838.

2628

2.90

37.5

126

6.83

8.26

4850

2-56

0.30

280.

0240

0.04

230.

0014

0.05

200.

0043

268.

6021

.29

266.

908.

8028

3.66

23.6

326

6.90

8.80

4850

2-26

0.30

660.

0620

0.04

270.

0016

0.05

210.

0107

271.

5754

.92

269.

5610

.17

289.

1559

.22

269.

5610

.17

4850

2-16

0.30

470.

0123

0.04

280.

0007

0.05

160.

0021

270.

0510

.88

270.

424.

3326

6.80

11.0

127

0.42

4.33

4850

2-35

0.31

040.

0139

0.04

340.

0006

0.05

190.

0024

274.

5112

.31

273.

814.

0528

0.61

12.9

127

3.81

4.05

4850

2-87

0.31

150.

0099

0.04

360.

0004

0.05

180.

0017

275.

388.

7927

5.41

2.62

275.

278.

9727

5.41

2.62

4850

2-17

0.31

780.

0440

0.04

450.

0019

0.05

180.

0074

280.

1938

.77

280.

4011

.93

278.

4739

.77

280.

4011

.93

4850

2-64

0.32

320.

0153

0.04

520.

0011

0.05

190.

0025

284.

3413

.43

285.

006.

9327

9.16

13.6

528

5.00

6.93

4850

2-66

0.32

820.

0229

0.04

550.

0011

0.05

230.

0038

288.

2120

.10

286.

907.

0329

8.77

21.4

428

6.90

7.03

4850

2-21

0.33

020.

0425

0.04

560.

0018

0.05

250.

0070

289.

7537

.25

287.

4711

.38

308.

3041

.05

287.

4711

.38

4850

2-8

0.35

200.

0127

0.04

850.

0006

0.05

260.

0019

306.

2111

.07

305.

613.

9431

0.75

11.5

030

5.61

3.94

4850

2-95

0.36

020.

0058

0.04

950.

0006

0.05

270.

0009

312.

385.

0531

1.66

3.53

317.

925.

3731

1.66

3.53

4850

2-86

0.36

690.

0258

0.05

020.

0011

0.05

300.

0039

317.

3522

.33

315.

777.

1032

8.90

23.9

531

5.77

7.10

App

endi

x C

-1 c

ontin

ued

Sam

ple

02M

AW

009

(upp

erm

ost F

ortr

ess

Mou

ntai

n Fo

rmat

ion)

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

Appendix C-1 187

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)48

502-

390.

3748

0.00

770.

0515

0.00

050.

0528

0.00

1232

3.20

6.62

323.

543.

4132

0.82

7.02

323.

543.

4148

502-

550.

3892

0.02

360.

0528

0.00

140.

0535

0.00

3433

3.81

20.2

833

1.70

9.07

348.

4322

.46

331.

709.

0748

502-

970.

3903

0.05

620.

0537

0.00

330.

0527

0.00

7833

4.57

48.1

733

7.36

20.7

331

5.09

46.7

933

7.36

20.7

348

502-

620.

4019

0.03

260.

0542

0.00

200.

0538

0.00

4534

2.99

27.8

634

0.08

12.4

636

3.01

30.6

534

0.08

12.4

648

502-

670.

4213

0.01

690.

0573

0.00

140.

0533

0.00

2335

6.96

14.2

835

9.18

8.69

343.

4014

.54

359.

188.

6948

502-

690.

4558

0.02

200.

0605

0.00

140.

0546

0.00

2738

1.32

18.3

837

8.97

8.45

395.

6619

.88

378.

978.

4548

502-

420.

4637

0.01

460.

0617

0.00

070.

0545

0.00

1738

6.81

12.1

938

5.77

4.08

393.

3012

.62

385.

774.

0848

502-

410.

4813

0.01

890.

0642

0.00

100.

0544

0.00

2239

8.99

15.6

840

0.85

6.19

388.

2616

.05

400.

856.

1948

502-

740.

4950

0.02

780.

0647

0.00

200.

0555

0.00

3440

8.29

22.9

540

4.38

12.7

643

0.68

26.3

040

4.38

12.7

648

502-

70.

4964

0.01

760.

0651

0.00

140.

0553

0.00

2040

9.25

14.5

540

6.66

8.84

423.

8915

.61

406.

668.

8448

502-

310.

5148

0.02

000.

0673

0.00

100.

0555

0.00

2242

1.64

16.3

642

0.01

5.99

430.

6817

.03

420.

015.

9948

502-

730.

5318

0.02

770.

0697

0.00

130.

0553

0.00

3043

3.03

22.5

643

4.63

8.08

424.

7322

.74

434.

638.

0848

502-

650.

5445

0.03

880.

0707

0.00

280.

0559

0.00

4244

1.38

31.4

344

0.09

17.3

644

8.91

33.6

744

0.09

17.3

648

502-

820.

5493

0.02

260.

0711

0.00

120.

0561

0.00

2444

4.51

18.2

944

2.51

7.26

455.

0219

.36

442.

517.

2648

502-

430.

5511

0.02

390.

0713

0.00

110.

0561

0.00

2544

5.75

19.3

344

4.03

6.62

454.

7920

.38

444.

036.

6248

502-

960.

5559

0.03

060.

0717

0.00

130.

0562

0.00

3244

8.83

24.7

444

6.53

8.08

460.

5126

.29

446.

538.

0848

502-

140.

5602

0.02

320.

0721

0.00

150.

0564

0.00

2445

1.65

18.6

744

8.74

9.58

466.

5419

.98

448.

749.

5848

502-

320.

5665

0.01

470.

0730

0.00

080.

0563

0.00

1545

5.72

11.8

645

4.31

5.07

462.

9512

.45

454.

315.

0748

502-

270.

5832

0.01

970.

0751

0.00

130.

0564

0.00

1946

6.51

15.7

246

6.58

7.93

466.

3116

.07

466.

587.

9348

502-

450.

5920

0.01

680.

0755

0.00

150.

0569

0.00

1747

2.16

13.3

846

9.15

9.16

487.

0614

.51

469.

159.

1648

502-

930.

6107

0.02

220.

0777

0.00

100.

0570

0.00

2148

3.99

17.5

848

2.17

6.23

492.

7818

.57

482.

176.

2348

502-

750.

6129

0.01

990.

0778

0.00

130.

0572

0.00

1948

5.41

15.7

648

2.86

7.97

497.

6716

.87

482.

867.

9748

502-

720.

6122

0.01

710.

0779

0.00

090.

0570

0.00

1648

4.92

13.5

248

3.38

5.33

492.

4014

.20

483.

385.

3348

502-

980.

6277

0.02

130.

0793

0.00

140.

0574

0.00

2049

4.65

16.7

949

1.71

8.63

508.

4217

.98

491.

718.

6348

502-

910.

6361

0.02

780.

0803

0.00

150.

0574

0.00

2549

9.90

21.8

649

7.97

9.38

508.

8022

.52

497.

979.

3848

502-

510.

7650

0.07

710.

0927

0.00

230.

0599

0.00

6157

6.89

58.1

257

1.58

13.8

959

8.53

61.3

457

1.58

13.8

948

502-

10.

8221

0.02

750.

0983

0.00

190.

0607

0.00

2160

9.21

20.3

960

4.29

11.7

662

7.44

21.5

160

4.29

11.7

648

502-

681.

1222

0.03

330.

1248

0.00

210.

0652

0.00

2076

4.04

22.6

875

8.41

12.7

278

0.72

23.7

775

8.41

12.7

248

502-

291.

2781

0.03

890.

1385

0.00

270.

0669

0.00

2083

6.02

25.4

483

6.03

16.2

783

6.11

25.0

883

6.03

16.2

748

502-

701.

4159

0.04

080.

1470

0.00

330.

0699

0.00

2189

5.62

25.8

488

4.20

20.0

892

4.07

27.9

688

4.20

20.0

848

502-

100

1.48

100.

0315

0.15

250.

0022

0.07

050.

0016

922.

6619

.60

914.

7713

.47

941.

7021

.48

914.

7713

.47

4850

2-71

1.50

120.

0510

0.15

720.

0028

0.06

930.

0025

930.

8731

.60

940.

9616

.92

906.

9832

.56

940.

9616

.92

4850

2-57

1.55

290.

0668

0.15

770.

0036

0.07

140.

0031

951.

6640

.91

944.

2121

.27

968.

8642

.62

944.

2121

.27

4850

2-20

1.55

690.

0477

0.15

930.

0036

0.07

090.

0023

953.

2329

.18

952.

9021

.39

954.

0631

.36

952.

9021

.39

4850

2-80

2.01

260.

0563

0.18

770.

0027

0.07

780.

0023

1119

.78

31.3

411

08.9

116

.17

1140

.86

33.3

711

40.8

633

.37

4850

2-49

2.03

860.

0629

0.18

770.

0050

0.07

880.

0026

1128

.51

34.8

011

08.9

129

.41

1166

.61

38.7

711

66.6

138

.77

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 02

MA

W00

9

188 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)48

502-

52.

2718

0.05

780.

2030

0.00

300.

0812

0.00

2112

03.5

830

.64

1191

.36

17.3

812

25.5

531

.17

1225

.55

31.1

748

502-

842.

5447

0.05

700.

2185

0.00

270.

0845

0.00

2012

84.9

128

.80

1273

.88

15.5

313

03.5

630

.12

1303

.56

30.1

248

502-

902.

9043

0.07

350.

2365

0.00

330.

0891

0.00

2413

83.0

435

.02

1368

.27

18.8

414

05.7

938

.01

1405

.79

38.0

148

502-

463.

0699

0.11

080.

2413

0.00

690.

0923

0.00

3714

25.2

051

.45

1393

.50

39.5

614

73.0

158

.71

1473

.01

58.7

148

502-

473.

3507

0.05

220.

2586

0.00

230.

0940

0.00

1614

92.9

623

.24

1482

.42

13.2

115

08.1

024

.94

1508

.10

24.9

448

502-

543.

6430

0.06

260.

2767

0.00

380.

0955

0.00

1815

58.9

726

.77

1574

.74

21.8

515

37.6

728

.89

1537

.67

28.8

948

502-

363.

5448

0.04

810.

2668

0.00

280.

0964

0.00

1315

37.2

820

.88

1524

.35

15.9

215

55.2

121

.62

1555

.21

21.6

248

502-

923.

6982

0.08

960.

2765

0.00

460.

0970

0.00

2515

70.9

738

.08

1573

.81

26.3

215

67.0

839

.61

1567

.08

39.6

148

502-

793.

9885

0.06

030.

2874

0.00

380.

1007

0.00

1616

31.8

624

.68

1628

.31

21.8

016

36.3

925

.77

1636

.39

25.7

748

502-

403.

9827

0.07

570.

2845

0.00

340.

1015

0.00

2116

30.6

830

.98

1613

.85

19.3

616

52.6

033

.77

1652

.60

33.7

748

502-

504.

0582

0.10

950.

2882

0.00

660.

1021

0.00

2916

45.9

544

.42

1632

.78

37.1

916

62.7

946

.72

1662

.79

46.7

248

502-

534.

2542

0.05

840.

3006

0.00

390.

1026

0.00

1416

84.5

523

.11

1694

.30

22.1

816

72.3

322

.66

1672

.33

22.6

648

502-

774.

9632

0.09

580.

3268

0.00

410.

1101

0.00

2218

13.0

835

.01

1822

.96

22.7

618

01.6

435

.86

1801

.64

35.8

648

502-

614.

6768

0.22

510.

3080

0.00

630.

1101

0.00

5217

63.1

084

.88

1730

.76

35.5

118

01.6

885

.23

1801

.68

85.2

348

502-

894.

9786

0.10

870.

3277

0.00

490.

1102

0.00

2518

15.6

939

.64

1827

.26

27.0

718

02.3

541

.70

1802

.35

41.7

048

502-

244.

8253

0.07

470.

3147

0.00

490.

1112

0.00

1817

89.3

227

.71

1764

.03

27.5

718

19.0

030

.20

1819

.00

30.2

048

502-

105.

0801

0.10

180.

3272

0.00

420.

1126

0.00

2318

32.7

936

.71

1824

.82

23.5

418

41.8

537

.88

1841

.85

37.8

848

502-

605.

1463

0.08

290.

3270

0.00

390.

1142

0.00

1918

43.7

929

.72

1823

.58

21.8

018

66.8

030

.63

1866

.80

30.6

348

502-

385.

2663

0.10

280.

3307

0.00

430.

1155

0.00

2418

63.4

136

.37

1841

.59

24.0

518

87.9

739

.40

1887

.97

39.4

048

502-

125.

8684

0.10

380.

3494

0.00

470.

1218

0.00

2219

56.5

734

.59

1931

.69

25.7

219

82.9

936

.59

1982

.99

36.5

948

502-

305.

9316

0.13

610.

3513

0.00

470.

1225

0.00

2919

65.8

745

.12

1940

.99

26.0

119

92.3

047

.66

1992

.30

47.6

648

502-

786.

0442

0.16

470.

3544

0.00

670.

1237

0.00

3519

82.2

454

.02

1955

.62

36.9

420

10.2

356

.63

2010

.23

56.6

348

502-

996.

6795

0.09

740.

3765

0.00

570.

1287

0.00

2220

69.9

130

.19

2059

.94

31.2

420

79.9

335

.59

2079

.93

35.5

948

502-

287.

5484

0.14

010.

3988

0.00

610.

1373

0.00

2721

78.7

540

.43

2163

.61

33.1

021

93.2

042

.51

2193

.20

42.5

148

502-

597.

7740

0.14

600.

4071

0.00

720.

1385

0.00

2822

05.2

041

.41

2201

.78

38.7

022

08.3

744

.59

2208

.37

44.5

948

502-

858.

1958

0.20

500.

4111

0.00

580.

1446

0.00

3622

52.8

856

.35

2219

.98

31.5

522

82.8

757

.63

2282

.87

57.6

348

502-

888.

5974

0.25

860.

4210

0.00

900.

1481

0.00

4622

96.2

969

.08

2265

.11

48.2

423

24.0

771

.60

2324

.07

71.6

048

502-

239.

1388

0.20

320.

4452

0.00

860.

1489

0.00

3623

52.0

152

.29

2373

.71

46.0

023

33.3

256

.39

2333

.32

56.3

948

502-

411

.170

20.

1585

0.48

550.

0065

0.16

690.

0024

2537

.43

36.0

025

51.2

233

.94

2526

.59

36.8

225

26.5

936

.82

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 02

MA

W00

9

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

Appendix C-1 189

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

±248

506-

360.

1378

0.00

600.

0206

0.00

030.

0486

0.00

2113

1.10

5.70

131.

301.

9012

7.49

5.63

131.

301.

9048

506-

600.

1823

0.02

080.

0266

0.00

080.

0497

0.00

5817

0.02

19.3

616

9.37

4.83

178.

9920

.86

169.

374.

8348

506-

840.

2242

0.01

860.

0323

0.00

080.

0504

0.00

4320

5.43

17.0

520

4.66

4.94

214.

2318

.25

204.

664.

9448

506-

230.

2730

0.02

390.

0389

0.00

140.

0509

0.00

4624

5.07

21.4

924

5.88

8.94

237.

7321

.37

245.

888.

9448

506-

730.

2884

0.01

510.

0406

0.00

070.

0515

0.00

2725

7.27

13.4

525

6.77

4.22

262.

6014

.00

256.

774.

2248

506-

620.

2896

0.01

450.

0408

0.00

060.

0515

0.00

2625

8.28

12.9

125

7.79

3.67

263.

3713

.42

257.

793.

6748

506-

210.

2921

0.02

510.

0412

0.00

270.

0514

0.00

4526

0.20

22.3

226

0.46

17.0

825

7.80

22.4

726

0.46

17.0

848

506-

70.

2941

0.01

300.

0413

0.00

060.

0516

0.00

2326

1.79

11.5

526

1.11

3.62

267.

9412

.14

261.

113.

6248

506-

30.

2979

0.01

080.

0418

0.00

070.

0517

0.00

1926

4.77

9.64

264.

144.

3027

0.39

9.97

264.

144.

3048

506-

930.

2985

0.01

460.

0419

0.00

080.

0517

0.00

2626

5.25

12.9

926

4.36

5.26

273.

5913

.89

264.

365.

2648

506-

190.

3052

0.02

030.

0428

0.00

070.

0518

0.00

3527

0.49

17.9

726

9.94

4.29

275.

8018

.41

269.

944.

2948

506-

550.

3067

0.02

110.

0429

0.00

080.

0519

0.00

3627

1.65

18.6

527

0.67

5.33

280.

1519

.66

270.

675.

3348

506-

310.

3094

0.01

310.

0432

0.00

100.

0520

0.00

2327

3.75

11.5

627

2.48

6.20

284.

7312

.43

272.

486.

2048

506-

920.

3131

0.01

620.

0436

0.00

110.

0520

0.00

2727

6.60

14.2

927

5.31

7.16

287.

5515

.11

275.

317.

1648

506-

300.

3143

0.02

140.

0437

0.00

150.

0522

0.00

3727

7.50

18.9

127

5.70

9.28

292.

7420

.90

275.

709.

2848

506-

290.

3111

0.01

640.

0439

0.00

150.

0514

0.00

2827

4.99

14.4

827

7.05

9.40

257.

8713

.83

277.

059.

4048

506-

750.

3221

0.03

870.

0446

0.00

160.

0524

0.00

6528

3.55

34.0

528

1.42

10.2

430

1.28

37.3

828

1.42

10.2

448

506-

110.

3235

0.01

030.

0449

0.00

110.

0522

0.00

1928

4.57

9.07

283.

256.

8229

5.41

10.6

028

3.25

6.82

4850

6-18

0.32

780.

0207

0.04

530.

0017

0.05

250.

0035

287.

9118

.17

285.

8010

.70

305.

4820

.46

285.

8010

.70

4850

6-12

0.32

480.

0162

0.04

550.

0007

0.05

180.

0027

285.

6114

.26

286.

594.

4527

7.56

14.2

728

6.59

4.45

4850

6-51

0.33

880.

0281

0.04

730.

0013

0.05

190.

0044

296.

2924

.58

298.

138.

3328

1.91

23.9

029

8.13

8.33

4850

6-66

0.34

540.

0188

0.04

740.

0020

0.05

280.

0030

301.

2616

.42

298.

5412

.71

322.

3418

.59

298.

5412

.71

4850

6-25

0.35

020.

0248

0.04

820.

0010

0.05

270.

0038

304.

8721

.61

303.

606.

4031

4.64

22.8

230

3.60

6.40

4850

6-49

0.35

120.

0142

0.04

840.

0008

0.05

260.

0021

305.

6312

.35

304.

855.

2231

1.58

12.6

530

4.85

5.22

4850

6-81

0.37

240.

0197

0.05

130.

0015

0.05

270.

0029

321.

4516

.99

322.

499.

5731

4.10

17.2

032

2.49

9.57

4850

6-95

0.37

370.

0207

0.05

150.

0009

0.05

270.

0030

322.

4317

.85

323.

615.

8531

4.10

18.0

932

3.61

5.85

4850

6-40

0.38

010.

0157

0.05

190.

0007

0.05

310.

0022

327.

1013

.51

326.

364.

1333

2.41

13.9

832

6.36

4.13

4850

6-87

0.38

230.

0125

0.05

220.

0007

0.05

310.

0018

328.

7410

.72

327.

834.

1533

5.16

11.3

932

7.83

4.15

4850

6-45

0.40

620.

0353

0.05

520.

0022

0.05

340.

0047

346.

1230

.07

346.

3013

.63

345.

0030

.25

346.

3013

.63

4850

6-5

0.42

790.

0220

0.05

730.

0015

0.05

410.

0028

361.

6918

.62

359.

369.

1437

6.66

19.7

735

9.36

9.14

4850

6-38

0.43

610.

0214

0.05

850.

0009

0.05

410.

0027

367.

5318

.02

366.

355.

5537

5.21

18.8

336

6.35

5.55

4850

6-94

0.44

420.

0245

0.05

920.

0013

0.05

440.

0031

373.

1920

.56

371.

018.

0638

6.66

22.3

737

1.01

8.06

4850

6-44

0.44

360.

0201

0.05

930.

0010

0.05

430.

0025

372.

7616

.91

371.

146.

0538

2.84

17.7

837

1.14

6.05

4850

6-2

0.48

980.

0458

0.06

510.

0015

0.05

460.

0052

404.

8137

.88

406.

499.

0939

5.66

37.7

240

6.49

9.09

4850

6-48

0.49

610.

0225

0.06

580.

0016

0.05

470.

0026

409.

0418

.55

411.

0010

.27

397.

9518

.73

411.

0010

.27

App

endi

x C

-1 c

ontin

ued

Sam

ple

02M

AW

020

(upp

er-m

iddl

e Fo

rtre

ss M

ount

ain

Form

atio

n)C

orre

cted

Isot

opic

Rat

ios

Age

s (M

a)

190 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)48

506-

420.

5290

0.02

770.

0686

0.00

190.

0559

0.00

3043

1.15

22.5

642

7.56

11.6

045

0.36

24.3

442

7.56

11.6

048

506-

680.

5427

0.03

240.

0704

0.00

140.

0559

0.00

3444

0.21

26.2

443

8.37

8.54

449.

9127

.74

438.

378.

5448

506-

10.

5617

0.01

210.

0728

0.00

070.

0560

0.00

1245

2.61

9.75

452.

744.

3645

2.19

10.0

245

2.74

4.36

4850

6-35

0.58

690.

0241

0.07

510.

0011

0.05

670.

0024

468.

8619

.27

466.

946.

6047

8.29

20.4

246

6.94

6.60

4850

6-99

0.63

540.

0374

0.08

010.

0015

0.05

760.

0035

499.

4529

.42

496.

439.

5551

3.23

31.1

549

6.43

9.55

4850

6-9

0.64

690.

0223

0.08

120.

0016

0.05

780.

0021

506.

5917

.50

503.

389.

8652

1.01

19.0

150

3.38

9.86

4850

6-50

0.69

650.

0259

0.08

750.

0020

0.05

770.

0023

536.

6919

.99

540.

7812

.65

519.

3320

.64

540.

7812

.65

4850

6-63

0.73

750.

0291

0.09

150.

0018

0.05

840.

0024

560.

9422

.11

564.

5311

.33

546.

3422

.53

564.

5311

.33

4850

6-8

0.75

860.

0173

0.09

240.

0015

0.05

950.

0014

573.

1813

.10

569.

679.

4758

7.23

13.7

356

9.67

9.47

4850

6-65

0.77

020.

0349

0.09

350.

0015

0.05

970.

0028

579.

8726

.26

576.

179.

2759

4.41

27.8

457

6.17

9.27

4850

6-56

0.77

250.

0253

0.09

400.

0010

0.05

960.

0020

581.

1819

.04

579.

166.

0458

9.07

19.8

257

9.16

6.04

4850

6-52

0.79

990.

0252

0.09

630.

0016

0.06

020.

0020

596.

7618

.80

592.

879.

9261

1.57

20.0

959

2.87

9.92

4850

6-41

0.81

530.

0176

0.09

810.

0010

0.06

030.

0013

605.

4213

.08

603.

116.

0961

4.09

13.6

260

3.11

6.09

4850

6-88

0.81

960.

0236

0.09

830.

0013

0.06

050.

0018

607.

8217

.48

604.

557.

7461

9.96

18.6

760

4.55

7.74

4850

6-47

0.82

140.

0327

0.09

960.

0031

0.05

980.

0025

608.

8524

.27

612.

1919

.11

596.

4725

.42

612.

1919

.11

4850

6-58

0.82

820.

1232

0.10

050.

0038

0.05

980.

0091

612.

6291

.16

617.

4223

.24

595.

0990

.27

617.

4223

.24

4850

6-13

0.87

390.

0226

0.10

360.

0010

0.06

120.

0016

637.

7116

.52

635.

306.

1864

6.36

17.1

063

5.30

6.18

4850

6-37

0.87

740.

0235

0.10

370.

0014

0.06

140.

0017

639.

6017

.15

635.

908.

5265

2.77

17.7

363

5.90

8.52

4850

6-77

0.91

680.

0249

0.10

740.

0016

0.06

190.

0017

660.

6517

.96

657.

759.

9267

0.47

18.7

565

7.75

9.92

4850

6-79

0.98

630.

0722

0.11

230.

0054

0.06

370.

0048

696.

8351

.01

686.

3633

.22

730.

6755

.63

686.

3633

.22

4850

6-43

1.09

440.

0220

0.12

270.

0018

0.06

470.

0014

750.

6315

.08

746.

3511

.22

763.

4716

.14

746.

3511

.22

4850

6-54

1.11

200.

0168

0.12

430.

0013

0.06

490.

0011

759.

1611

.50

755.

187.

8777

0.95

12.7

475

5.18

7.87

4850

6-6

1.11

550.

0465

0.12

620.

0028

0.06

410.

0028

760.

8031

.70

766.

1216

.83

745.

1632

.44

766.

1216

.83

4850

6-69

1.22

880.

0594

0.13

350.

0038

0.06

680.

0033

813.

8039

.31

807.

8723

.01

830.

1540

.72

807.

8723

.01

4850

6-46

1.45

510.

0563

0.15

050.

0024

0.07

010.

0028

911.

9735

.29

903.

8114

.20

931.

7836

.99

903.

8114

.20

4850

6-27

1.53

340.

0458

0.15

620.

0041

0.07

120.

0022

943.

8528

.18

935.

4224

.71

963.

6729

.61

935.

4224

.71

4850

6-32

1.55

250.

0364

0.15

910.

0026

0.07

080.

0017

951.

4722

.31

951.

6215

.38

951.

4623

.18

951.

6215

.38

4850

6-15

1.60

430.

0273

0.16

150.

0020

0.07

210.

0013

971.

8916

.53

964.

9811

.79

987.

5917

.92

964.

9811

.79

4850

6-28

1.61

040.

0933

0.16

310.

0048

0.07

160.

0044

974.

2556

.46

973.

8628

.52

975.

1159

.23

973.

8628

.52

4850

6-26

1.63

490.

0439

0.16

350.

0022

0.07

250.

0020

983.

7626

.44

976.

2012

.95

1000

.75

27.6

510

00.7

527

.65

4850

6-78

1.83

290.

0530

0.17

930.

0041

0.07

410.

0023

1057

.33

30.5

610

63.1

224

.26

1045

.34

31.8

010

45.3

431

.80

4850

6-83

1.96

730.

0410

0.18

760.

0029

0.07

610.

0016

1104

.39

22.9

911

08.2

217

.14

1096

.76

23.6

810

96.7

623

.68

4850

6-39

1.94

760.

0504

0.18

430.

0019

0.07

660.

0020

1097

.63

28.4

010

90.4

111

.07

1111

.98

29.5

411

11.9

829

.54

4850

6-14

2.04

260.

0623

0.19

190.

0031

0.07

720.

0025

1129

.82

34.4

611

31.4

818

.37

1126

.63

36.0

411

26.6

336

.04

4850

6-76

2.19

170.

0306

0.19

920.

0019

0.07

980.

0012

1178

.40

16.4

411

70.9

711

.30

1192

.02

18.0

111

92.0

218

.01

4850

6-82

2.75

960.

0535

0.22

920.

0032

0.08

730.

0019

1344

.70

26.0

713

30.4

418

.77

1367

.42

29.1

013

67.4

229

.10

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 02

MA

W02

0

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

Appendix C-1 191

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)48

506-

202.

9801

0.07

210.

2399

0.00

360.

0901

0.00

2314

02.5

633

.95

1386

.29

20.6

514

27.3

835

.85

1427

.38

35.8

548

506-

853.

0314

0.04

600.

2433

0.00

320.

0904

0.00

1514

15.5

521

.50

1403

.77

18.5

614

33.2

223

.84

1433

.22

23.8

448

506-

103.

1564

0.12

940.

2520

0.01

040.

0908

0.00

3914

46.5

659

.28

1448

.92

59.8

014

43.0

662

.50

1443

.06

62.5

048

506-

343.

6017

0.05

640.

2732

0.00

360.

0956

0.00

1515

49.9

024

.25

1557

.06

20.5

815

40.1

824

.90

1540

.18

24.9

048

506-

593.

5738

0.08

730.

2652

0.00

570.

0977

0.00

1915

43.7

237

.69

1516

.25

32.8

515

81.6

131

.02

1581

.61

31.0

248

506-

803.

7864

0.08

780.

2767

0.00

460.

0992

0.00

2315

89.8

636

.88

1574

.93

26.4

116

09.6

537

.48

1609

.65

37.4

848

506-

743.

8319

0.06

110.

2784

0.00

330.

0998

0.00

1715

99.4

825

.49

1583

.45

18.8

116

20.6

427

.45

1620

.64

27.4

548

506-

644.

2236

0.13

820.

3062

0.00

930.

1000

0.00

3316

78.6

354

.92

1722

.13

52.2

016

24.6

453

.49

1624

.64

53.4

948

506-

334.

0276

0.05

710.

2880

0.00

330.

1014

0.00

1516

39.7

823

.26

1631

.56

18.6

916

50.3

124

.75

1650

.31

24.7

548

506-

674.

0071

0.11

920.

2866

0.00

440.

1014

0.00

3116

35.6

348

.65

1624

.27

25.0

916

50.3

949

.67

1650

.39

49.6

748

506-

163.

9999

0.08

150.

2839

0.00

480.

1022

0.00

2216

34.1

833

.30

1611

.07

27.0

816

64.1

236

.21

1664

.12

36.2

148

506-

864.

2897

0.06

780.

3003

0.00

270.

1036

0.00

1716

91.3

926

.74

1692

.91

15.3

516

89.4

528

.16

1689

.45

28.1

648

506-

704.

2633

0.11

580.

2977

0.00

460.

1039

0.00

2716

86.3

045

.78

1679

.67

26.1

216

94.4

944

.75

1694

.49

44.7

548

506-

964.

5704

0.04

730.

3073

0.00

330.

1079

0.00

1317

43.8

918

.05

1727

.30

18.7

317

63.7

621

.20

1763

.76

21.2

048

506-

974.

6795

0.04

670.

3120

0.00

260.

1088

0.00

1217

63.5

817

.60

1750

.66

14.5

317

78.8

318

.89

1778

.83

18.8

948

506-

714.

7561

0.11

910.

3133

0.00

400.

1101

0.00

2817

77.1

944

.51

1757

.16

22.2

618

00.7

745

.91

1800

.77

45.9

148

506-

984.

8540

0.05

850.

3180

0.00

280.

1107

0.00

1417

94.3

121

.62

1780

.15

15.6

618

10.6

822

.17

1810

.68

22.1

748

506-

244.

9630

0.07

680.

3251

0.00

460.

1107

0.00

1918

13.0

428

.05

1814

.79

25.7

918

10.8

430

.66

1810

.84

30.6

648

506-

724.

8294

0.09

350.

3164

0.00

360.

1107

0.00

2217

90.0

434

.67

1772

.09

19.9

518

10.9

936

.36

1810

.99

36.3

648

506-

224.

8339

0.14

000.

3154

0.00

740.

1112

0.00

3317

90.8

151

.85

1767

.28

41.2

018

18.7

353

.99

1818

.73

53.9

948

506-

895.

0485

0.08

120.

3243

0.00

480.

1129

0.00

1918

27.4

929

.41

1810

.64

27.0

518

46.7

031

.55

1846

.70

31.5

548

506-

100

5.21

580.

0558

0.33

460.

0032

0.11

310.

0013

1855

.21

19.8

318

60.4

217

.58

1849

.29

21.2

618

49.2

921

.26

4850

6-53

5.37

840.

1552

0.33

420.

0054

0.11

670.

0035

1881

.42

54.3

018

58.4

929

.76

1906

.95

57.3

519

06.9

557

.35

4850

6-57

5.61

150.

1018

0.34

300.

0032

0.11

870.

0022

1917

.87

34.8

019

00.9

717

.97

1936

.21

36.1

619

36.2

136

.16

4850

6-91

6.05

890.

2154

0.36

580.

0122

0.12

010.

0045

1984

.35

70.5

420

09.6

466

.88

1958

.05

73.1

919

58.0

573

.19

4850

6-61

5.96

160.

1869

0.35

120.

0101

0.12

310.

0042

1970

.26

61.7

819

40.1

955

.56

2001

.99

68.9

720

01.9

968

.97

4850

6-17

6.48

480.

2056

0.37

440.

0095

0.12

560.

0041

2043

.83

64.8

020

50.2

151

.89

2037

.47

67.2

920

37.4

767

.29

4850

6-4

10.3

511

0.23

010.

4637

0.00

810.

1619

0.00

3824

66.6

954

.82

2455

.97

43.0

624

75.6

258

.73

2475

.62

58.7

348

506-

9011

.042

40.

2667

0.47

880.

0079

0.16

730.

0043

2526

.71

61.0

225

21.9

841

.47

2530

.65

65.5

825

30.6

565

.58

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 02

MA

W02

0

192 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

±248

509-

360.

1575

0.02

170.

0232

0.00

120.

0493

0.00

7114

8.55

20.4

814

7.76

7.77

161.

5923

.14

147.

767.

7748

509-

390.

1622

0.02

060.

0239

0.00

080.

0492

0.00

6315

2.59

19.3

615

2.18

4.84

158.

6920

.38

152.

184.

8448

509-

890.

1798

0.01

330.

0263

0.00

090.

0496

0.00

4016

7.92

12.3

816

7.28

5.80

177.

3114

.21

167.

285.

8048

509-

250.

2001

0.02

890.

0290

0.00

090.

0500

0.00

7318

5.23

26.7

518

4.56

5.99

193.

7128

.43

184.

565.

9948

509-

610.

2048

0.01

980.

0295

0.00

200.

0504

0.00

5118

9.21

18.2

518

7.38

12.4

321

1.49

21.5

818

7.38

12.4

348

509-

170.

2176

0.01

420.

0313

0.00

140.

0504

0.00

3719

9.90

13.0

419

8.73

8.72

213.

6215

.49

198.

738.

7248

509-

680.

2265

0.00

850.

0327

0.00

050.

0502

0.00

1920

7.32

7.79

207.

673.

3120

3.09

7.78

207.

673.

3148

509-

780.

2585

0.03

650.

0367

0.00

140.

0511

0.00

7423

3.48

33.0

023

2.09

8.63

247.

3535

.96

232.

098.

6348

509-

910.

2689

0.01

570.

0382

0.00

090.

0510

0.00

3124

1.80

14.0

924

1.98

5.74

240.

0214

.45

241.

985.

7448

509-

200.

2778

0.01

610.

0390

0.00

170.

0516

0.00

3224

8.89

14.4

324

6.92

10.7

126

7.33

16.6

524

6.92

10.7

148

509-

600.

3131

0.02

020.

0439

0.00

160.

0518

0.00

3327

6.61

17.8

327

6.75

9.93

275.

3417

.81

276.

759.

9348

509-

430.

3124

0.01

990.

0439

0.00

120.

0516

0.00

3427

6.04

17.5

727

7.07

7.35

267.

1817

.59

277.

077.

3548

509-

120.

3209

0.01

400.

0447

0.00

070.

0521

0.00

2428

2.63

12.3

328

1.73

4.71

289.

9213

.14

281.

734.

7148

509-

950.

3227

0.01

710.

0449

0.00

090.

0522

0.00

2928

4.01

15.0

728

2.91

5.94

292.

5916

.05

282.

915.

9448

509-

230.

3259

0.01

480.

0452

0.00

090.

0522

0.00

2528

6.44

13.0

428

5.27

5.43

295.

7213

.99

285.

275.

4348

509-

630.

3247

0.01

120.

0454

0.00

110.

0519

0.00

1828

5.49

9.84

286.

087.

0728

0.46

9.94

286.

087.

0748

509-

470.

3264

0.01

440.

0456

0.00

140.

0520

0.00

2328

6.80

12.6

828

7.16

8.56

283.

2812

.72

287.

168.

5648

509-

60.

3330

0.01

390.

0465

0.00

110.

0519

0.00

2229

1.84

12.1

529

3.10

6.72

281.

5211

.84

293.

106.

7248

509-

540.

3433

0.03

320.

0475

0.00

210.

0524

0.00

5329

9.69

29.0

029

9.17

13.4

930

4.03

30.8

329

9.17

13.4

948

509-

490.

3466

0.02

840.

0476

0.00

170.

0528

0.00

4530

2.16

24.7

729

9.76

10.6

332

1.04

27.5

429

9.76

10.6

348

509-

840.

3590

0.01

440.

0493

0.00

080.

0528

0.00

2231

1.44

12.5

231

0.19

5.23

320.

5913

.46

310.

195.

2348

509-

700.

3967

0.00

900.

0540

0.00

100.

0533

0.00

1333

9.22

7.69

338.

956.

4734

0.88

8.04

338.

956.

4748

509-

730.

3995

0.01

450.

0540

0.00

130.

0536

0.00

2134

1.26

12.3

533

9.26

8.19

354.

7713

.58

339.

268.

1948

509-

240.

4680

0.01

660.

0621

0.00

110.

0547

0.00

1938

9.83

13.8

138

8.17

6.80

399.

4014

.22

388.

176.

8048

509-

570.

4821

0.04

170.

0629

0.00

340.

0556

0.00

4839

9.52

34.5

339

3.49

21.4

343

4.42

37.4

939

3.49

21.4

348

509-

40.

4841

0.01

620.

0639

0.00

100.

0549

0.00

1840

0.90

13.3

839

9.35

6.33

409.

7013

.61

399.

356.

3348

509-

660.

5124

0.01

710.

0667

0.00

200.

0557

0.00

2042

0.09

14.0

341

6.27

12.4

544

0.90

15.9

141

6.27

12.4

548

509-

30.

5104

0.01

370.

0669

0.00

070.

0553

0.00

1541

8.72

11.2

541

7.53

4.48

425.

1111

.79

417.

534.

4848

509-

960.

5108

0.01

630.

0672

0.00

100.

0551

0.00

1841

8.98

13.3

341

9.22

6.09

417.

1013

.77

419.

226.

0948

509-

500.

5153

0.02

610.

0677

0.00

250.

0552

0.00

2742

1.98

21.3

642

2.10

15.6

142

1.22

20.8

242

2.10

15.6

148

509-

70.

5198

0.03

350.

0678

0.00

350.

0556

0.00

3742

5.02

27.4

142

2.89

22.0

143

6.40

28.9

842

2.89

22.0

148

509-

580.

5287

0.04

590.

0688

0.00

350.

0557

0.00

5043

0.93

37.4

342

9.04

21.7

744

0.52

39.5

542

9.04

21.7

748

509-

450.

5451

0.02

630.

0701

0.00

290.

0564

0.00

2944

1.80

21.3

043

6.55

18.0

346

9.06

23.8

643

6.55

18.0

348

509-

260.

5403

0.05

460.

0702

0.00

570.

0558

0.00

5843

8.60

44.3

643

7.35

35.6

044

4.72

46.2

743

7.35

35.6

048

509-

20.

5558

0.02

850.

0714

0.00

200.

0564

0.00

3044

8.78

23.0

544

4.70

12.6

546

9.51

25.0

744

4.70

12.6

5

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

App

endi

x C

-1 c

ontin

ued

Sam

ple

02M

AW

006

(low

er F

ortr

ess

Mou

ntai

n Fo

rmat

ion)

Appendix C-1 193

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)48

509-

100.

5576

0.02

480.

0724

0.00

150.

0559

0.00

2644

9.99

20.0

445

0.56

9.08

446.

9321

.03

450.

569.

0848

509-

650.

5752

0.02

250.

0736

0.00

210.

0566

0.00

2346

1.38

18.0

645

8.06

13.3

147

7.45

19.4

545

8.06

13.3

148

509-

800.

5778

0.01

640.

0741

0.00

110.

0565

0.00

1646

3.04

13.1

446

0.82

7.06

473.

9413

.77

460.

827.

0648

509-

190.

5768

0.01

960.

0744

0.00

140.

0562

0.00

2046

2.38

15.6

946

2.68

8.96

460.

5116

.44

462.

688.

9648

509-

990.

5821

0.02

080.

0746

0.00

160.

0566

0.00

2046

5.84

16.6

646

3.52

10.0

447

7.22

16.7

446

3.52

10.0

448

509-

870.

5879

0.02

730.

0747

0.00

260.

0571

0.00

2746

9.53

21.7

746

4.25

16.3

049

5.30

23.6

146

4.25

16.3

048

509-

310.

5936

0.02

030.

0765

0.00

180.

0562

0.00

2047

3.16

16.1

647

5.42

11.1

946

1.81

16.2

447

5.42

11.1

948

509-

790.

6129

0.02

990.

0785

0.00

310.

0566

0.00

2848

5.40

23.6

748

6.93

19.4

047

7.68

23.8

148

6.93

19.4

048

509-

460.

6229

0.03

360.

0798

0.00

150.

0566

0.00

3149

1.69

26.5

449

5.01

9.20

476.

0726

.44

495.

019.

2048

509-

710.

6410

0.03

290.

0810

0.00

270.

0574

0.00

3150

2.90

25.8

150

2.05

16.8

850

6.67

27.5

750

2.05

16.8

848

509-

560.

6559

0.04

410.

0836

0.00

410.

0569

0.00

3851

2.07

34.4

651

7.34

25.3

848

8.36

32.5

551

7.34

25.3

848

509-

900.

7186

0.02

370.

0883

0.00

190.

0590

0.00

1954

9.82

18.1

254

5.41

11.4

456

8.01

18.0

854

5.41

11.4

448

509-

130.

7763

0.02

920.

0955

0.00

170.

0590

0.00

2358

3.40

21.9

658

7.85

10.6

056

5.95

21.8

558

7.85

10.6

048

509-

640.

8991

0.02

910.

1050

0.00

290.

0621

0.00

2265

1.25

21.0

664

3.49

17.8

467

8.10

24.0

764

3.49

17.8

448

509-

831.

0565

0.11

460.

1183

0.00

520.

0648

0.00

7373

2.09

79.4

572

0.82

31.7

576

6.68

86.9

972

0.82

31.7

548

509-

411.

2096

0.03

840.

1321

0.00

170.

0664

0.00

2280

5.01

25.5

479

9.67

10.5

781

9.63

26.6

379

9.67

10.5

748

509-

421.

2155

0.04

380.

1322

0.00

240.

0667

0.00

2580

7.73

29.1

080

0.49

14.2

382

7.64

31.1

680

0.49

14.2

348

509-

551.

3338

0.09

890.

1430

0.00

820.

0676

0.00

4986

0.53

63.7

886

1.82

49.3

085

7.09

62.4

286

1.82

49.3

048

509-

821.

4073

0.03

700.

1475

0.00

240.

0692

0.00

1989

2.03

23.4

588

6.87

14.4

990

4.69

25.2

488

6.87

14.4

948

509-

921.

5499

0.05

430.

1616

0.00

410.

0696

0.00

2595

0.46

33.2

996

5.67

24.7

991

5.30

33.4

296

5.67

24.7

948

509-

401.

8951

0.05

110.

1796

0.00

380.

0765

0.00

2410

79.3

629

.09

1064

.56

22.7

811

09.2

834

.27

1109

.28

34.2

748

509-

162.

1436

0.06

070.

1940

0.00

500.

0801

0.00

2411

62.9

832

.91

1142

.89

29.2

512

00.5

636

.65

1200

.56

36.6

548

509-

482.

3177

0.03

360.

2094

0.00

230.

0803

0.00

1212

17.7

117

.63

1225

.81

13.4

212

03.2

317

.90

1203

.23

17.9

048

509-

972.

5908

0.05

930.

2246

0.00

450.

0837

0.00

2112

98.0

329

.72

1306

.37

26.2

112

84.6

032

.29

1284

.60

32.2

948

509-

943.

0974

0.06

890.

2473

0.00

510.

0909

0.00

2114

32.0

431

.83

1424

.33

29.5

114

43.4

833

.22

1443

.48

33.2

248

509-

593.

3994

0.13

130.

2649

0.00

960.

0931

0.00

3915

04.2

558

.10

1515

.00

55.1

514

89.4

163

.08

1489

.41

63.0

848

509-

813.

3380

0.07

200.

2563

0.00

400.

0945

0.00

2214

89.9

932

.13

1470

.92

23.2

415

17.1

434

.89

1517

.14

34.8

948

509-

113.

7943

0.10

800.

2866

0.00

780.

0960

0.00

2915

91.5

445

.28

1624

.76

44.3

815

48.0

046

.81

1548

.00

46.8

148

509-

853.

8283

0.08

640.

2787

0.00

290.

0996

0.00

2315

98.7

236

.09

1584

.70

16.4

916

17.0

937

.89

1617

.09

37.8

948

509-

444.

1071

0.08

960.

2898

0.00

300.

1028

0.00

2316

55.7

136

.14

1640

.58

17.2

416

74.8

837

.26

1674

.88

37.2

648

509-

514.

1867

0.09

870.

2947

0.00

640.

1030

0.00

2416

71.4

339

.39

1665

.12

36.3

716

79.2

338

.62

1679

.23

38.6

248

509-

694.

4646

0.07

090.

3043

0.00

430.

1064

0.00

1817

24.4

127

.38

1712

.35

24.4

417

38.9

329

.74

1738

.93

29.7

448

509-

304.

6855

0.12

250.

3171

0.00

770.

1072

0.00

2717

64.6

546

.13

1775

.48

43.3

617

51.7

143

.64

1751

.71

43.6

448

509-

724.

6662

0.10

040.

3133

0.00

530.

1080

0.00

2417

61.2

037

.88

1756

.96

29.6

717

65.8

438

.98

1765

.84

38.9

848

509-

214.

8185

0.06

820.

3224

0.00

400.

1084

0.00

1717

88.1

325

.31

1801

.65

22.4

617

72.3

128

.32

1772

.31

28.3

248

509-

224.

5415

0.13

130.

3026

0.00

670.

1088

0.00

3117

38.6

150

.27

1704

.28

37.9

617

80.0

949

.96

1780

.09

49.9

6

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 02

MA

W00

6

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)

194 PIR 2008-1 Preliminary results, fi eld investigations, Brooks Range Foothils & North Slope, Alaska

Ana

lysi

s #

207 P

b / 23

5 U±2

206 P

b / 23

8 U±2

207 P

b / 20

6 Pb

±220

7 Pb

/ 235 U

±220

6 Pb

/ 238 U

±220

7 Pb

/ 206 P

b±2

Bes

t Age

± M

a (2

)48

509-

294.

8188

0.06

190.

3199

0.00

270.

1092

0.00

1417

88.1

922

.98

1789

.29

15.1

517

86.8

022

.50

1786

.80

22.5

048

509-

935.

0996

0.13

080.

3355

0.00

840.

1102

0.00

2818

36.0

347

.10

1864

.83

46.7

718

03.4

445

.73

1803

.44

45.7

348

509-

764.

9707

0.09

890.

3257

0.00

610.

1107

0.00

2118

14.3

436

.09

1817

.56

33.7

718

10.5

334

.94

1810

.53

34.9

448

509-

864.

8599

0.07

540.

3164

0.00

450.

1114

0.00

1917

95.3

427

.84

1772

.12

25.2

218

22.3

230

.87

1822

.32

30.8

748

509-

625.

2287

0.11

650.

3393

0.00

720.

1117

0.00

2318

57.3

141

.40

1883

.46

39.7

318

28.0

437

.95

1828

.04

37.9

548

509-

355.

1806

0.10

750.

3303

0.00

510.

1138

0.00

2418

49.4

338

.36

1839

.72

28.6

018

60.2

440

.02

1860

.24

40.0

248

509-

385.

0389

0.11

230.

3210

0.00

610.

1138

0.00

2718

25.8

940

.68

1794

.53

33.8

518

61.7

144

.72

1861

.71

44.7

248

509-

675.

2666

0.12

880.

3344

0.00

680.

1142

0.00

2818

63.4

745

.59

1859

.63

37.9

118

67.6

446

.58

1867

.64

46.5

848

509-

155.

3160

0.09

820.

3320

0.00

440.

1161

0.00

2318

71.4

434

.57

1848

.14

24.5

918

97.2

837

.23

1897

.28

37.2

348

509-

536.

0951

0.19

400.

3711

0.00

840.

1191

0.00

4019

89.5

563

.31

2034

.57

46.2

919

42.9

464

.93

1942

.94

64.9

348

509-

95.

5672

0.15

250.

3385

0.00

600.

1193

0.00

3419

11.0

352

.35

1879

.55

33.2

019

45.2

355

.31

1945

.23

55.3

148

509-

345.

6310

0.14

500.

3394

0.00

700.

1203

0.00

3319

20.8

649

.46

1883

.77

39.0

219

61.0

053

.38

1961

.00

53.3

848

509-

756.

3113

0.16

100.

3758

0.00

850.

1218

0.00

2920

20.0

351

.55

2056

.54

46.4

419

82.8

047

.37

1982

.80

47.3

748

509-

885.

9387

0.09

780.

3521

0.00

420.

1223

0.00

2219

66.9

132

.38

1944

.55

23.3

119

90.4

335

.08

1990

.43

35.0

848

509-

325.

9575

0.19

510.

3519

0.00

760.

1228

0.00

4119

69.6

664

.51

1943

.57

41.8

619

97.0

767

.04

1997

.07

67.0

448

509-

100

5.92

950.

1714

0.34

710.

0083

0.12

390.

0038

1965

.57

56.8

219

20.8

746

.01

2012

.86

62.0

620

12.8

662

.06

4850

9-1

6.40

020.

0803

0.37

270.

0033

0.12

460.

0017

2032

.30

25.4

920

41.8

817

.95

2022

.55

27.0

120

22.5

527

.01

4850

9-5

6.17

230.

1297

0.35

660.

0064

0.12

550.

0029

2000

.53

42.0

419

66.1

835

.11

2036

.10

47.6

420

36.1

047

.64

4850

9-77

6.32

360.

0896

0.36

390.

0040

0.12

600.

0019

2021

.73

28.6

520

00.8

321

.82

2043

.04

31.1

720

43.0

431

.17

4850

9-37

7.29

940.

2882

0.39

940.

0148

0.13

260.

0056

2148

.74

84.8

421

66.3

880

.21

2132

.13

89.8

221

32.1

389

.82

4850

9-14

7.04

840.

1105

0.38

410.

0055

0.13

310.

0022

2117

.55

33.1

820

95.2

430

.24

2139

.21

34.8

621

39.2

134

.86

4850

9-8

8.71

160.

1988

0.42

280.

0092

0.14

950.

0037

2308

.30

52.6

822

73.2

149

.21

2339

.67

57.8

823

39.6

757

.88

4850

9-98

8.85

520.

3647

0.42

840.

0178

0.14

990.

0067

2323

.19

95.6

722

98.5

295

.25

2345

.16

104.

5223

45.1

610

4.52

4850

9-74

10.0

693

0.27

000.

4605

0.01

130.

1586

0.00

4324

41.1

665

.46

2441

.87

59.8

724

40.4

566

.91

2440

.45

66.9

148

509-

1812

.068

30.

1983

0.49

950.

0069

0.17

520.

0030

2609

.73

42.8

826

11.6

036

.12

2608

.19

44.9

826

08.1

944

.98

4850

9-27

11.9

622

0.35

940.

4922

0.01

140.

1763

0.00

6526

01.4

578

.16

2580

.00

60.0

026

18.1

096

.05

2618

.10

96.0

548

509-

2812

.431

20.

1686

0.49

820.

0067

0.18

100.

0027

2637

.54

35.7

726

06.0

034

.80

2661

.71

39.5

126

61.7

139

.51

4850

9-52

13.7

393

0.31

700.

5421

0.01

180.

1838

0.00

4327

31.9

163

.03

2792

.17

60.7

226

87.5

763

.23

2687

.57

63.2

348

509-

3313

.985

10.

3551

0.53

760.

0130

0.18

870.

0048

2748

.70

69.7

927

73.3

666

.82

2730

.52

70.0

927

30.5

270

.09

App

endi

x C

-1 c

ontin

ued

-- S

ampl

e 02

MA

W00

6

Cor

rect

ed Is

otop

ic R

atio

sA

ges

(Ma)