Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY
A revley o f the regional geoiopy and tectonics o f southeastern Alaska
George E. ~ e h r e l r l and Henry C. 0erg2
Open-Fil e Report 88-659
Thfs r e p o r t i s pre l iminary and has not been reviewed f o r conformity wi th U.S. Geological Survey e d i t o r i a l standards and s t r a t i graphic nomenclature.
l0epartment o f Geosciences Univers i ty o f Arizona Tucson, Arizona 85721
*115 Ma1 vern Ave. F u l l e r ton , Cal i f o r n i a 92632
INTRODUCTION
Southeastern (SE) Alaska, a l so known as the "panhandle" o f Alaska, i s an
approximately 52,000 square m i l e area of i n t e n s e l y g l ac ia ted and h e a v i l y
forested mountains t h a t r i s e ab rup t l y from a complex system o f deep f i o r d s and
i n 1 and marine waterways. Primary physiographic fea tures i n SE A1 aska inc lude
the Coast Mountains, which u n d e r l i e the easternmost p a r t o f the panhandle, and
a myriad of small and l a r g e i s l a n d s t o the west which comprise the Alexander
a rch ipe l ago.
The panhandle i s under la in by an exceedingly complex and heterogeneous
assemblage of rocks, and i s c u t by an i n t r i c a t e network o f t h rus t , normal, and
s t r i ke-sl i p f a u l t s (Buddington and Chapin, 1929; Gehrel s and Berg, 1984).
These rocks record a l ong and n e a r l y complete geologic h i s t o r y beginning i n
the Proterozoic, represent ing every Phanerozoic per iod, and con t i nu ing through
the Holocene. We here in d j v i d e these rocks i n t o f i v e terranes t h a t apparent ly
conta in d i s t i n c t geologic records, and a v a r i e t y o f s t r a t i f i e d , p l u t o n i c , and
metamorphic assemblages t h a t are i n depos i t fona l , i n t r u s i v e , o r unknown
contac t w i t h the terranes. The d i s t r i b u t i o n o f these terranes and assemblages
i s discussed below i n reference t o the Coast Range b a t h o l i t h , which under l i es
the western Coast blountains and serves as a prominent geologic marker i n the
panhandle.
This r e p o r t begins w i t h a summary o f the reg iona l geology of SE Alaska
which i s der fved p r i m a r i l y from the synthesis o f Gehrels and Berg (1984) and
from more recent s tudies. Next, we discuss the components and c h a r a c t e r i s t i c s
o f each o f the terranes and 1 i t h i c assemblages t h a t comprise the panhandle and
then o u t l i n e s i m i l a r i t i e s and d i f fe rences among the terranes. We then present
a general overview o f the tec ton i c evo lu t i on o f SE Alaska.
SUmARY OF REGIONAL GEOLOGY
S t r a t i f i e d rocks
Pre-Jurass ic s t r a t i f i e d rocks i n SE Alaska ( f i g . 1) c o n s t i t u t e a s e r i e s
o f nor thwest -e longate b e l t s t h a t va ry i n depos i t i ona l age and I n degree of
deformat ion and metamorphism. These b e l t s occur a long t h e eas t and west
f l anks o f t h e Coast Range b a t h o l i t h ( f i g . 2 ) and on t he i s l a n d s t o t he west.
Rocks e a s t of t he b a t h o l i t h i n c l u d e a r e l a t i v e l y narrow b e l t of P ro te rozo i c (? )
sch i s t , gneiss, and marb le (Werner, 1977, 1978; Monger and Berg, 1987) and
Devonian, Carboniferous, Permian, and T r i a s s i c sedimentary and vo l can i c rocks
( S t i k i n e t e r r a n e ) t h a t extend eastward i n t o t he i n t e r i o r o f B r i t i s h Columbia.
Rocks ad jacen t t o t h e bath01 i t h on t he west i n c l u d e a narrow and p o o r l y known
assemblage o f moderate ly t o s t r o n g l y deformed Permian and T r i a s s i c
metasedimentary and metavolcanic rocks (Taku t e r r a n e ) . The most ex tens i ve
assemblage o f p r e J u r a s s i c s t r a t a occurs on i s l a n d s t o t he west, where a
v i r t u a l l y complete s e c t i o n o f sedimentary and vo l can i c rocks ranges from the
1 a t e s t P ro te rozo i c (? ) -Cambri an through the La te T r i a s s i c (A1 exander t e r rane ) . Upper Mesozoic s t r a t a i n c l ude Jura-Cretaceous graywacke and ma f i c -
i n t e rmed ia te vo l can i c rocks bo th eas t and west o f t he b a t h o l i t h . S t r a t a on
t he west (Gravina b e l t ) ove r l ap bo th b e l t s o f p re -Jurass ic rocks and grade
f rom r e l a t i v e l y nondeformed on t he west t o high-grade s c h i s t and gneiss toward
the east . A t h i r d upper Mesozoic assemblage (Chugach t e r rane ) occurs a long
the west coas t o f no r t he rn SE Alaska and c o n s i s t s o f s t r o n g l y deformed and
d i s r u p t e d Cretaceous graywacke and vo l can i c rocks. Cenozoic s t r a t a a re
widespread and occur on bo th s ides of t he b a t h o l i t h . They range from
Paleocene t o Holocene i n age, w i t h some vo l can i c rocks e r u p t i n g as r e c e n t l y as
360 +/- 60 years ago ( E l l i o t t and o thers , 1981).
With in the Coast Range b a t h o l i t h , m e t a s t r a t i f i e d rocks occur as pendants
of amphibol i te- t o g ranu l i t e - fac ies sch i s t , gneiss, and marble der ived from
p re -Te r t i a ry p r o t o l i t h s . Some o f these rocks may be c o r r e l a t i v e w i t h
Pro terozo ic (?) metamorphic rocks along the eastern f l a n k o f the b a t h o l i t h ,
some were probably der ived from Cretaceous and o l d e r s t r a t i f i e d rocks t o the
eas t and west, and some p r o t o l i t h s may n o t occur elsewhere i n SE Alaska.
I n t r u s i v e rocks
I n t r u s i v e rocks ( f i g . 1) range i n age from Cambrian t o Miocene b u t most
are Cretaceous-early T e r t i a r y i n age. Paleozoic p l utons occur on the i s l ands
west of the Coast Range bathol i t h and inc lude: (1) small bodies o f Cambrian
metagranodior i t e and metad ior i t e , ( 2 ) Ordovician-Early S i 1 u r i a n calc-a1 ka l i n e
gran i t o ids , ( 3 ) mid-Si l u r i a n t o e a r l i e s t Devonian trondhjemi t e and
l e u c o d i o r i t e , and ( 4 ) Pennsylvanian-Permian syen i te and d i o r i t e . T r i a s s i c
p lu tons inc lude a pyroxene gabbro on Duke I s l a n d and a l a r g e g ranod lo r i t e body
eas t o f the Coast Range b a t h o l i t h . Jurass ic p lu tons occur i n a b e l t from
Baranof I s l a n d t o the west sfde o f G lac ie r Bay, on southern Pr ince o f Wales
I s1 and, and perhaps i n c lose assoc ia t ion w i t h Jura-Cretaceous s t r a t a a1 ong the
west f l ank of the Coast Range b a t h o l i t h . Most o f the pre-Cretaceous i n t r u s i v e
su i tes i n the panhandle appear t o be cogenetic w i t h vo lcan ic rocks which occur
nearby . Cretaceous-earl y T e r t i a r y p l utons i ncl ude: (1) grani t o i ds o f E a r l y
Cretaceous and e a r l y T e r t i a r y age on i s l ands west o f the Coast Range b a t h o l i t h
and along i t s eastern f lank , ( 2 ) b e l t s o f mid-Cretaceous u l t r a m a f i c bodies and
Late Cretaceous granod ior i t i c p l utons west o f the bathol S th , ( 3 ) Cretaceous-
e a r l y T e r t i a r y p lu tons t h a t are the pr imary cons t i t uen ts o f the Coast Range
b a t h o l i t h , and (4 ) Oligocene-Miocene a l k a l i c g r a n i t o i d s which t rend west-
northwest across the batholith and belts t o the west.
Regional metamorphism and deformation
Several phases of deformation and metamorphism have punctuated the
. evolution of SE Alaska ( f ig . 1 ) . The most significant and widespread event
occurred during Late Cretaceous-early Tertiary time, when strat if ied
protol i ths w i t h i n the Coast Range bathol t h (now pendants) and a1 ong i t s
western f l a n k were regionally metamorphosed t o amphi bol i te-granul i t e facies,
strongly deformed, and intruded by a variety of plutonic suites. Rocks east
of the bathol i t h (Sti kine terrane) were metamorphosed original ly prior to mid-
Paleozoic time and uplifted, eroded, and perhaps deformed during the Middle
Triassic Tahl t a n orogeny (Souther, 1971; Monger, 1977). Metamorphic rocks
along the west flank of the batholith progressively decrease in metamorphic
grade and degree of deformation toward the west. In the lower grade
assemblages, pre-Cretaceous tectonic events are recorded. An unconformity a t
the base of the Jura-Cretaceous section (Gravi na be1 t) indicates t h a t Triassic
and older strata b o t h along the west flank of the bathol i th ( T a k u terrane) and
on the islands t o the west (Alexander terrane) were up1 ifted and eroded, and
a t least locally deformed and metamorphosed, between Late Triassic and Late
Jurassic time (Gehrel s and Berg, 1984; McClel land and Gehrel s, 1987b). West
of the belt of Jura-Cretaceous strata, Paleozoic rocks (Alexander terrane)
record deformational and metamorphic events during Middle Cambrian-Early
Ordovician and middle Sil urian-earl i e s t Devonian time, and an up1 i ft and
erosional event during the L a t e Permian(?)-Triassic.
Faults
The most conspicuous structural features in SE Alaska are regional
strike-slip fault zones t h a t c u t the bedrock into a great jigsaw pattern ( f ig .
2; Twenhofel and Sainsbury, 1958). Three major s t r i k e - s l i p systems dominate.
On the west, t he panhandle i s t runcated a t the North American cont inenta l
margin by the Fairweather f a u l t system. Fau l t s of thSs system are known from
geologic mapping and from marine and onshore geophysical s tud ies t o be a c t i v e
r i g h t - 1 a t e r a l s t ruc tu res wf t h considerable displacement. To the south they
connect w i t h the Queen Char lo t te f a u l t system; t o the no r th they splay i n t o a
se t o f compt ex t h r u s t f a u l t s (P la fker , 1967). The second major s t r i k e - s l i p
system i s the Chatham S t r a i t f a u l t , which o f f s e t s rocks as young as mid-
T e r t i a r y by as much as 150 km (Lathram, 1964; Hudson and others, 1982a). This
f a u l t i s apparent ly t runcated t o the southwest by the Fa i rweather-Queen
Char lo t te f a u l t system and connects northward w i t h the Denal i f a u l t system.
The d i f f e r e n c e i n displacement between the Chatham St ra f t f a u l t (150 km) and
the Denal i f a u l t (350 km?: Lanphere, 1978; Nokleberg and others, 1985) i s an
unresolved problem. The t h i r d major s t r i k e - s l i p system i n SE Alaska i s the
Clarence S t r a i t f a u l t , which coinc ides w i t h a major topographic l ineament b u t
has on ly approximately 15 km o f dex t ra l displacement (Gehrels and others,
1987).
I n a d d i t i o n t o these s t r i k e - s l i p f a u l t s , t h rus t , low-angle normal, and
steep d i p - s l i p f a u l t s are s i g n i f i c a n t . The o l d e s t known o f these are
southwest-vergent t h r u s t s i n the southern panhandle whjch moved du r ing middle
S i l u r f a n - e a r l i e s t Devonian time. They were fo l lowed by normal movement on
gen t l y d ipp ing f a u l t s on southern Pr ince o f Wales I s l a n d (Keete I n l e t f a u l t o f
Redman, 1981) probably dur ing L a t e Permian(?)-Tr iass ic t ime (Gehrels and
Sal eeby, 1987a) . Southwest-vergent t h r u s t f au l t s have been mapped on l y
l o c a l l y along the west f l ank o f the Coast Range b a t h o l i t h (Berg and others,
1988; Rubin and Saleeby, 1987a; Gehrel s and McClelland, 1988), b u t probably a re
much more widespread. Such f a u l t s along the west coast o f B r i t i s h Columbia,
j u s t south of the panhandle, reg iona l 1 y juxtaposed high-grade metamorphic
rocks southwestward over lower-grade rocks dur ing Late Cretaceous-early
T e r t i a r y t ime (Crawford and others, 1987). Fau l t s of s i m i l a r age and s t y l e
b u t steeper- o r i e n t a t i o n have a1 so been recognized a1 ong the eas t f l ank o f the
Coast Range b a t h o l i t h (Berg and others, 1978; Crawford and others, 1987).
Soon a f t e r movement on these t h r u s t f au l t s , the Coast Range b a t h o l i t h and
adjacent rocks t o the west were up1 i f t e d along high-angle f a u l t s , one o f which
i s r e f e r r e d t o as the Coast Range megalineament (Brew and Ford, 1978).
TERRANES AND LITHIC ASSEMBLAGES
The rocks o f SE Alaska were i n i t i a l l y d i v i d e d i n t o reg iona l geologic
be1 t s o r assemblages by Buddington and Chapin (1929). Schuchert ( 1923) noted
t h a t rocks i n one o f these b e l t s record a geologic h i s t o r y which i s
s i g n i f i c a n t l y d i f f e r e n t from o ther regions o f the nor thern C o r d i l l e r a -- t h i s
assemblage he r e f e r r e d t o as the "Alexandrian embayment" w i t h i n the
Cordi 11 eran Geosyncl i ne. Geosyncl i nal theory dominated syntheses o f
southeastern Alaska geology u n t i l : (1) J.T. Wilson (1968) recogn i ted t h a t
Paleozoic rocks o f the panhandle occur outboard o f coeval miogeocl i nal s t r a t a
and must there fore have been accreted t o North America; (2) Monger and Ross
(1971) documented the Tethyan o r equator ia l a f f i n i t y o f Permian fusul i n i d
faunas inboard of southeastern Alaska; and ( 3 ) Berg and others (1972)
recognized t h a t the pre-Jurassic rocks o f southeastern Alaska belong t o
several d i s t i n c t t e c t o n i c fragments, ' terranes ,I1 t h a t have d ispara te geologic
records. The te r rane concept was app l i ed i n a more comprehensive fashion by
Berg and o thers (19781, wherein they d i v ided a l l rocks of SE Alaska i n t o (1 )
fundamental 1 y d i s t i n c t , f au l t-bounded tec ton i c fragments ( t ec tonos t ra t i g raph ic
ter ranes) , and ( 2 ) assemblages t h a t were emplaced i n t o o r deposited on more
than one te r rane and are accord ing ly i n t e r p r e t e d t o have formed a f t e r adjacent
fragments were juxtaposed.
I n t h i s r e p o r t we subdivide the rocks o f SE Alaska i n t o a v a r i e t y o f
t ec ton i c assemblages ( f i g u r e s 1 and 2). F i ve of these are i d e n t i f i e d as
terranes because they apparent ly have d i s t i n c t geologic records. These
inc lude the A1 exander, Chugach, S t i k i n e ( S t i k i n i a ) , Taku, and Wrangell i a
terranes. The o ther assemblages of SE Alaska c o n s i s t of metamorphic rocks o f
unknown t e c t o n i c a f f i n i t y , and of rocks t h a t a re known o r reasonably
i n t e r p r e t e d t o be i n depos i t iona l o r i n t r u s i v e con tac t w i t h the terranes.
Such l i t h i c assemblages inc lude: (1) Jura-Cretaceous s t r a t a o f the GravSna # be1 t ( p a r t o f the Gravina-Nutzot in be1 t o f Berg and others, 1972); ( 2 )
metamorphic pendants and screens o f unknown t e c t o n i c a f f i n i t y i n the Coast
Range bath01 i th ; ( 3 ) Cretaceous-early T e r t i a r y p l u t o n i c s u i t e s i n the
b a t h o l i t h ; ( 4 ) p l u t o n i c s u i t e s west o f the b a t h o l i t h o f Early, mid-, and Late
Cretaceous, Eocene-01 i gocene, and 01 jgocene-Miocene age; and ( 5 ) Quaternary-
T e r t i a r y s t r a t a t h a t are d i s t r i b u t e d throughout SE A1 aska.
Alexander te r rane (Ac and Aa on f i g . 2 )
The Alexander te r rane comprises a v a r i e t y o f s t r a t 4 f f ed, metamorphic,
and p l u ton i c rocks o f 1 a t e s t Precambrian(?)-Cambrian through Midd le(?)
Jurass ic age t h a t u n d e r l i e much o f the Alaskan panhandle and cont inue
northward i n t o the Sa in t E l i a s Mountains reg ion o f B r i t i s h Columbia and Yukon
(Berg and others, 1972; Churkin and Eber le in, 1977; Gehrels and Saleeby,
1987a). Vol c a n i c l a s t i c t u r b i d i tes, s h a l l ow-marine carbonate, and subordinate
conglomerate o f S i l u r i a n age a re the most widespread u n i t s i n the terrane.
Pre-S i lu r ian rocks occur p r i m a r i l y i n the southern p a r t o f SE Alaska, upper
Paleozoic rocks occur i n r e l a t i v e l y r e s t r i c t e d areas, and Upper T r i a s s i c
s t r a t a crop o u t i n a f a i r l y narrow b e l t along the eastern margin of the
terrane,
The o l d e s t rocks recognized are arc- type rnetasedimentary and metavolcanic
rocks (Wales Group) t h a t were metamorphosed and deformed dur ing the Middle
Cambrian-Early Ordovic ian Wales orogeny (Gehrels and Saleeby, 1984, 1987a).
These rocks form t h e depos i t iona l and i n t r u s i v e basement t o an arc-type
volcanic-p lutonic-sedimentary complex o f E a r l y Ordovician-Early S i l u r i a n age
which under l i es much o f the southern p a r t o f the terrane. Ordovician c h e r t
and a r g i l l i t e on Admira l ty I s l a n d and marine c l a s t i c s t r a t a and carbonate i n
northernmost SE Alaska and the Sa in t E l i a s Mountains reg ion are i n t e r p r e t e d t o
have formed i n a deep- t o shallow-marine bas in behind t h i s arc system (Gehrels
and Saleeby, 1987a). This phase of arc-type a c t i v i t y ceased w i t h onset o f t he
middle S i l u r i a n - e a r l i e s t Devonian Klakas orogeny, whtch i s mani fest i n the
southern p a r t o f the terrane as: (1) southwest-vergent t h rus t i ng ; ( 2 ) reg iona l
metamorphism and deformation i n some areas; ( 3 ) u p l i f t ( l o c a l l y >5 km) and
eros ion of the arc complex; and ( 4 ) generat ion o f a n a t e c t i c ( ? ) t rondhjemite
and 1 eucodi o r i t e bodies . Upper Paleozoic s t r a t a i n much o f the Alexander terrane cons i s t p r i m a r i l y
of shal low-marine carbonate, c l a s t i c s t r a t a , and subordinate mafic-
in te rmed ia te vo lcan ic rocks. These s t r a t a now occur i n r e s t r i c t e d eros ional
remnants b u t probably were much more widespread o r i g i n a l l y . The predominance
of shallow-marine l imestone, the lack of r e g i o n a l l y s i g n i f i c a n t unconformi t ies
o r t h i c k conglomerate i n t h e sect ion, and r e s t r i c t i o n of vo lcanic rocks t o the
Middle and Upper Devonian and the Lower Permian suggest t h a t the te r rane
evolved i n a t e c t o n i c a l l y s tab le environment compared t o the e a r l y Paleozoic
orogenic and magmatic activity . Upper Triassic strata over1 i e the Permian and 01 der rocks on a regional
unconformity. In the southern part of the terrane, the section generally
consists, from bottom t o t o p , of basal conglomerate and sedimentary breccia,
rhyolite and rhyol i t i c tuff , massive 1 imestone, calcareous argill i te , and
basal tic-andesi t i c pi 11 ow flows and breccia. Toward the northwest, the amount
of rhyolite and conglomerate decreases and the proportion of mafic-
intermediate volcanic rock increases. These strata and their subjacent
unconformity are interpreted t o have formed in a r i f t environment based on:
(1) the bimodal (basal t-rhyol i t e ) composition of the volcanic rocks; ( 2 )
occurrence of the section in a relatively narrow belt along the eastern margin
of the terrane; (3) stratigraphic evidence for syndeposi tional faul ting; and
( 4 ) evidence for Late Permian(?)-Triassic up1 i f t and erosion without
accompanying deformation and metamorphism (Gehrels and others, 1986).
The youngest component of the terrane i s the Bokan Mountain Granite,
which i s a Middle(?) Jurassic peralkaline ring-dike complex on southern Prince
of Wales Island (Thompson and others, 1982; Saint-Andre and others, 1983;
Armstrong, 1985). The tectonic significance of this body i s as yet unknown.
The Alexander terrane was subdivided by Berg and others (1978) and Monger
and Berg (1987) into the Craig, Annette, and Admiralty subterranes based
primarily on regional variations in stratigraphy and in degree and age of
metamorphism and deformation. Gehrels and others (1987) suggest t h a t the
Annette and Craig subterranes should no t be differentiated, however, because
they: (1) share similar pre-Middle Devonian and Triassic l i th ic assemblages;
( 2 ) record the same early Paleozoic tectonic histories; and (3) b o t h lack
upper Paleozoic strata. We accordingly i ncl ude rocks of the Annette
subterrane w i t h rocks o f t he C ra ig subterrane.
Re la t i ons among t h e Admi ra l t y (Aa on f i g . 2 ) and C r a i g (Ac on f i g . 2 )
subter ranes a r e more d i f f i c u l t t o assess because rocks o f the Admi ra l t y
subterrane: ( 1 ) have o n l y l o c a l l y been s tud ied i n d e t a i l ; ( 2 ) have y i e l d e d few
f o s s i l s ; and ( 3 ) a r e r e g i o n a l l y metamorphosed and deformed i n most areas.
However, s t ud ies t o date on Kupreanof I s l a n d (Mu f f l e r , 1967; Brew and others ,
1984; McCle l land and Gehrels, 1987a, b ) and Admi ra l t y I s l a n d (Lathram and
o thers , 1965) and i n t h e C h i l k a t Range (Lathram and o thers , 1959; Brew and
others , 1985; Forbes and o thers , 1987) suppor t t h e i n t e r p r e t a t i o n t h a t
Paleozoic s t r a t a o f t h e Admi ra l t y subter rane reco rd a d i f f e r e n t h i s t o r y f rom
coeval r ocks i n t h e r e s t o f the te r rane . I n general , t he Admi ra l t y subter rane
c o n s i s t s o f Ordov ic ian and Devonian t o T r i a s s i c bas ina l c l a s t i c s t r a t a , maf i c -
i n t e rmed ia te vo l can i c rocks, and subord ina te 1 imestone ( f i g . 1 ) . An
assemblage o f metasedimentary and metavolcanic rocks i n t he no r the rn C h i l k a t
Range (Four Winds complex o f Forbes and o thers , 1987) i s h e r e i n i n t e r p r e t e d t o
be p a r t o f t h e Admi ra l t y subter rane based on apparent s i m i l a r i t i e s w i t h rocks
on Admi ra l t y and Kupreanof I s l ands . Forbes and o the rs (1987) argue t h a t
metamorphism o f a t l e a s t some rocks i n t he Four Winds complex occur red d u r i n g
La te Devonian-Early M i s s i s s i p p i a n t ime. The t i m i n g o f t h i s event and t he
o v e r a l l bas ina l cha rac te r o f Adm i ra l t y s t r a t a c o n t r a s t w i t h t h e h i s t o r y o f t he
C ra ig subter rane and suppor t t h e i r d i s t i n c t i o n as two subterranes.
The e a r l i e s t re1 i a b l e 1 i n k between the two subter ranes occurs d u r i n g
Permian t ime, when c l a s t s o f c h e r t from t h e Admi ra l t y assemblage were
depos i ted on C ra ig s t r a t a and then t h e Pybus Dolomi te was deposi ted over bo th
subter ranes (Muf f le r , 1967; Berg and o thers , 1978; Jones and o thers , 1981).
T r i a s s i c s t r a t a of t he two subter ranes a re apparen t l y c o r r e l a t i v e ( M u f f l e r ,
1967; Gehrels and others, 1986). Thus, p r i o r t o Permian time, the Admira l ty
subterrane may have been a basinal , vo l can i c - r i ch fac ies adjacent t o a
t e c t o n i c a l l y stab1 e, dominantly s h a l l ow-marine fac ies (Cra ig subterrane) , o r
i t may have been a d i s t i n c t t ec ton i c fragment. \
The displacement h i s t o r y of the Alexander te r rane p r i o r t o i t s Mesozoic
accretion i s poo r l y constra ined and i s a sub jec t o f considerable speculat ion.
Apparent ly re1 f a b l e cons t ra in t s on i t s pal eoposi t i o n i n c l ude: (1) Nd-Sr
i s o t o p i c data which i n d i c a t e t h a t the te r rane comprises j uveni 1 e c r u s t a l
ma te r i a l s and was n o t i n p rox im i t y t o a l a r g e cont inenta l landmass p r i o r t o
Jurass ic t ime (Samson and others, 1987, 1988); ( 2 ) paleomagnetic data which
suggest t h a t the te r rane evolved near the paleoequator from Ordovician through
Pennsylvanian t ime (Van der Voo and others, 1980); ( 3 ) biogeographic
i n d i c a t i o n s o f a l a t e Paleozoic p o s i t i o n between eastern and western P a c i f i c
faunal realms (Mamet and Pinard, 1985); (4 ) the low p a l e o l a t i t u d e and eastern
P a c i f i c a f f i n i t y o f T r i a s s i c b i va l ves o f the te r rane (Tozer, 1982; Newton,
1983; S i l b e r l f n g , 1985); and ( 5 ) occurrence o f the te r rane outboard o f the
Cache Creek terrane, which conta ins Permian f u s u l i n i d faunas of Tethyan
( e q u a t o r i a l ) a f f i n i t y (Monger and Ross, 1971) and apparent ly remained i n an
oceanic s e t t i n g i n t o Jurassic t ime (Cordey and others, 1987). Accret ion
aga ins t the western margin of inboard terranes probably began dur ing Ear ly -
Middle Jurassic t ime (McClelland and Gehrel s, 1987b) and was completed by the
e a r l y T e r t i a r y (Monger and others, 1982).
Chugach te r rane ( C on f i g . 2)
The Chugach te r rane has two s t r u c t u r a l components ( P l a f k e r and others,
1977; Johnson and K a r l , 1985; Gehrel s and Berg, 1984): (1) a s t rong ly deformed
b u t coherent assemblage o f fl yschoidal graywacke, a r g i l l i t e , and s l a t e o f
probable E a r l y Cretaceous age; and ( 2 ) a deformed and d i s r u p t e d assemblage
(me1 ange) of b l ocks o f bas ic vo l can i c rocks, r ad io1 a r i a n che r t , u l t r a m a f i c
rocks, l imestone, and p l u t o n i c rocks i n a m a t r f x of cher ty , tu f faceous
a r g i l l i t e . The composi t ion and age o f some b locks suggest t h a t they p robab ly
were de r i ved f rom Permo-Carboniferous and T r i a s s i c s t r a t a o f Wrangel l ia .
Greenschis t - t o amph ibo l i t e - f ac i es reg iona l metamorphism o v e r p r i n t s l o c a l
remnants of b l u e s c h i s t - f a c i e s metamorphism. Rad io l a r i ans i n c h e r t i n t h e
m a t r i x o f t he melange a re g e n e r a l l y E a r l y Cretaceous i n age. The two
assemblages a r e s t r u c t u r a l l y i n t e r l e a v e d i n many places, b u t i n general t he
d i s r u p t e d assemblage tends t o l i e s t r u c t u r a l l y above and eas t o f t h e coherent
f l y s c h assernbl age.
J u x t a p o s i t i o n o f t he t e r r a n e aga ins t inboard assemblages i s thought t o
have occur red d u r i n g Late Cretaceous-ear ly T e r t i a r y t ime (Decker and o thers ,
1980), a1 though Cowan ( 1982) hypothes izes t h a t t he t e r rane was d i sp l aced
nor thward f rom an o r i g i n a l p o s i t i o n near Vancouver I s l a n d a f t e r 40 Ma.
S t i k i n e t e r r a n e ( S t i k i n i a : S on f i g . 2)
The most s i g n i f i c a n t components o f S t i k i n e t e r r a n e i n and ad jacen t t o SE
Alaska I n c l u d e Devonian carbonate, Carboni ferous a rc - type vo l can i c and
sedimentary rocks, Lower Permian bas ina l s t r a t a , Upper Permian p la t f o rma l
l imestone, and Upper T r f a s s i c t o M idd le Ju rass i c a rc - type vo lcan ic , p l u t o n i c ,
and c l a s t i c sedimentary rocks ( f i g . 1) (Monger, 1977; Gehrels and Berg, 1984;
Robert G. Anderson, o r a l commun., 1987). Most of t he t e r r a n e i n B r i t i s h
Col umbia i s covered by Jura-Cretaceous sedimentary and vo l can i c rocks;
T r i a s s i c and o l d e r s t r a t a c rop o u t p r i m a r i l y a long t h e eas te rn f l a n k of t h e
Coast Range b a t h o l i t h . The boundary between these s t r a t a and high-grade
metamorphic rocks i n t h e b a t h o l i t h i s i n most areas o b l i t e r a t e d by p l u tons o f
the batholith. In some regions, however: (1) a steep west-side-up fault
juxtaposes high-grade rocks against s trata of the Stikine terrane; ( 2 ) strata
be1 onging to the S t i kine terrane grade w i t h increasing metanorphi sm and
deformation into the high-grade rocks; and ( 3 ) Upper Triassic strata
apparently overlie high-grade metamorphic rocks (Souther, 1971; Berg and
others, 1978; Werner, 1977, 1978; Bultman, 1979; Monger and Berg, 1987; Brew
and others, 1985; Hill and others, 1985; Crawford and others, 1987)
Rocks of the Stikine terrane are known t o have been displaced because
they occur outboard of Cache Creek rocks containing Permian fusulinid faunas
of Tethyan or equatorial affinity (Monger and Ross, 1971), and their primitive
Nd-Sr i sotopic signature precludes primary relations with North America
(Samson and others, 1987). Their accretionary hi story remains en4 gmatic,
however, because: (1) paleomagnetic d a t a from Permian and Triassic rocks of
Stikine do not record significant latitudinal transport relative t o North
America (May and Butler, 1986; Irving and Monger, 1987); ( 2 ) the Cache Creek
terrane apparently remained in an oceanic setting through Early to Middle
Jurassic time (Cordey and others, 1987); and ( 3 ) paleomagnetic data from
Cretaceous rocks and from older rocks with interpreted Cretaceous magnetic
signatures record large-scale northward transport in Cretaceous-early Tertiary
time (Irving and others, 1985; Marquis and Globerman, 1987).
Taku terrane ( T on fig. 2)
The Taku terrane i s a poorly known assemblage of deformed and
metamorphosed strata of Early Permian, Middle and Late Triassic, and perhaps
pre-Permian age (Sil berl i ng a n d others, 1982; Brew and Grybeck, 1984). A s
mapped on figure 2, the terrane also contains a significant proportion of
Upper Jurassic t o mid-Cretaceous strata of the Gravina belt (Gehrels and Berg,
1984; Rubin and Saleeby, 1987b) and lower Paleozoic rocks o f the Alexander
t e r r a n e (Sal eeby, 1987). Regional l y s i g n i f i c a n t p re -Jurass ic components
inc lude : Permian c r i no ida l marble i n t e r c a l a t e d w i t h pe l i t i c p h y l l i t e and
f e l s i c m e t a t u f f ; Permian(?) b a s a l t i c me ta tu f f , agglomerate, and p i l l o w f lows;
Midd le and Upper T r i a s s i c carbonaceous 1 imestone, s l a t e , and p h y l l i te ; undated
q u a r t z i t e and q u a r t z o f e l dspa th ic gneiss presumably de r i ved f rom f e l SIC
volcan i c rocks; and metaconglomerate c o n t a i n i n g c l a s t s of g r a n i t i c rocks,
q u a r t z i t e , and f i ne -g ra ined c l a s t i c s t r a t a (Berg and o thers , 1978, 1988; Brew
and Grybeck, 1984; Brew and o thers , 1984, 1985; Rubjn and Saleeby, 1987a, b;
Gehrel s and McClel land, 1988; FlcClel l a n d and Gehrel s, 1988). Rocks o f
probable Jura-Cretaceous age i n c l u d e g reensch is t - and amph ibo l i t e - f ac i es
metagraywacke, meta-argi 11 i t e , metabasal t i c p i 11 ow f lows and b recc ia , and
metacongl omerate.
Rocks o f the Taku t e r r a n e can be subd iv ided i n t o t h r e e assemblages, t h e
r e l a t i o n s among which a re as y e t unknown (Monger and Berg, 1987). To t h e
northwest, Permian(?) -Tr iass ic metabasal t i c p i 11 ow f l ows predominate and a re
o v e r l a i n unconformably by less-deformed Jura-Cretaceous f l y s c h o f t he Gravina
b e l t (Redman, 1984; Gehrels and Berg, 1984). Near Haines ( f i g . 2 ) , Upper
T r i a s s i c b a s a l t and o v e r l y i n g T r i a s s i c - J u r a s s i c ( ? ) sediments a re r e p o r t e d t o
be geochemical l y and b i o s t r a t i g r a p h i c a l l y s i m i l a r t o Wrangell i a n s t r a t a i n
western B r i t i s h Col umbia and southern A1 aska ( P l a f k e r and Hudson, 1980; Davis
and Plafker , 1985; P la f ke r and o thers , 1988). I n southern SE Alaska,
T r i a s s i c ( ? ) metasedimentary rocks predominate b u t con tac t r e l a t i o n s w i t h Jura-
Cretaceous s t r a t a a r e obscured by Late Cretaceous-ear ly T e r t i a r y deformat ion
and metamorphism. Rubin and Saleeby (1987a, b ) and Saleeby (1987) r e p o r t t h a t
much of what has been mapped as t he southern Taku t e r r a n e c o n s j s t s o f lower
Paleozoic metasedimentary and metavolcanic rocks o f t he Alexander te r rane. In
c e n t r a l SE A1 aska, the te r rane inc ludes both Permian-Triassic metasedimentary
and metavolcanfc rocks and a t h i c k sequence of metarhyo l i te , metabasalt, and
qua r t z - r i ch metagraywacke o f unknown age and a f f i n i t y (Gehrel s and McCl e l 1 and,
1988; McCl e l 1 and and Gehrel s, 1988).
Contact r e l a t i o n s w i t h adjacent terranes are poo r l y known. To the
southwest, the te r rane i s general 1 y t h r u s t southwestward over Jura-Cretaceous
s t r a t a o f the Gravina b e l t . To the nor theast , rocks o f the te r rane increase
i n metamorphic grade t o amphiboli t e and l o c a l l y granul i t e f ac ies and are
i n t ruded by p lu tons o f t he Coast Range bathol i t h . We t e n t a t j v e l y draw the
eastern boundary along the western edge o f t h e bathol i th, a1 though metamorphic
rocks w i t h i n the b a t h o l i t h a re 1 i t h f c a l l y i nd i s t f ngu ishab le from high-grade
members of the Taku terrane.
Wrangel l ia te r rane ( W on f i g . 2)
A coherent sequence o f u n f o s s i l i f e r o u s s t r a t a on Chichagof and Baranof
Is lands i s i n t e r p r e t e d t o be a fragment o f Wrangel l ia on the bas is of
s i m i l a r i t i e s i n l i t h i c types and age ( P l a f k e r and others, 1976; Jones and
others, 1977; Berg and others, 1978). The sequence i s d i s t i ngu i shed by: (1 )
t h i c k , ma in ly subaeri a1 b a s a l t f lows (Goon Dip Greenstone) s imi 1 a r t o those o f
the Middle o r Upper T r i a s s i c N i k o l a i Greenstone i n southern Alaska (Jones and
others, 1977); ( 2 ) shallow- t o deep-marine carbonate (Whi t e s t r i p e Marble) t h a t
i s s i m i l a r t o the Upper T r i a s s i c Ch i t i s tone Limestone; and ( 3 ) p e l i t i c
sedimentary rocks s i m i l a r t o the Upper T r i a s s i c and Jurassic McCarthy
Formation. Jurass ic tonal i t i c p l utons are t he youngest components o f the
terrane, The sequence apparent ly o v e r l i e s a heterogeneous assemblage o f
upper(?) Paleozoic mafic vo lcanic rocks, pyroc l a s t i c rocks, c l a s t i c
sedimentary rocks, and minor c h e r t and marble rang ing i n metamorphic grade
f rom g reensch i s t t o amph ibo l i t e f ac i es .
The con tac t s between these rocks and ad jacen t t e r ranes a re p o o r l y known.
To t he e a s t they a r e apparen t l y jux taposed a g a i n s t rocks o f t he Alexander
t e r rane a long t h e Perf 1 S t r a i t f a u l t , a r i g h t - l a t e r a l f a u l t w i t h T e r t i a r y
o f f s e t , b u t t h e o r i g i n a l boundary between t h e two i s d i f f i c u l t t o i d e n t i f y due
t o abundant Jurass ic(?) -Cretaceous p lu tons and widespread metamorphism and
deformat ion a1 ong t h e boundary. E l sewhere Wrangell i a i s jux taposed a g a i n s t
rocks o f t h e Chugach t e r r a n e a long t he Border Ranges f a u l t , which i s
i n t e r p r e t e d as a west-vergent t h r u s t (P l a f k e r and o thers , 1976).
I f c o r r e l a t i o n s w i t h rocks i n o t h e r p a r t s o f Wrange l l i a a re c o r r e c t , then
the rocks i n SE Alaska must a1 so have been t r anspo r ted cons iderab le d is tances
nor thward s i nce La te T r i a s s i c t ime (Jones and o thers , 1977; H i l l h o u s e and
Gromme, 1984; Tozer, 1982).
Gravina b e l t (G on f i g . 2 )
The Gravina b e l t comprises Upper Ju rass i c t o mid-Cretaceous marine
a r g i l l i t e and graywacke, in te rbedded a n d e s i t i c t o b a s a l t i c vo l can i c and
vo lcan ic1 a s t i c rocks, subord inate p o l y m i c t i c conglomerate, and perhaps p l u tons
rang ing f rom qua r t z d i o r i t e t o d u n i t e and p e r i d o t i t e (Berg and others , 1972,
1978; Gehrel s and Berg, 1984). These s t r a t a occur i n a narrow be1 t sepa ra t i ng
t he Alexander and Taku te r ranes and reco rd the t r a n s i t i o n from lower-grade
rocks on t h e wes t t o h igher-grade rocks a long t h e f l a n k o f t he Coast Range
b a t h o l i t h . I n genera l , t h e metamorphic grade increases from greensch is t o r
sub-greenschis t fac ies on t he west t o amph ibo l i t e and l o c a l l y g r a n u l i t e f a c i e s
toward t h e east . Contact r e l a t i o n s w i t h ad jacen t t e r ranes a re uncer ta in .
Al though s t r a t a o f t h e Gravina b e l t a re i n t e r p r e t e d t o d e p o s i t i o n a l l y o v e r l i e
rocks o f t h e Alexander t e r rane (Berg and o thers , 1972), depos i t i ona l con tac t s
between t h e two assemblages a re appa ren t l y preserved o n l y on Gravina I s l a n d
(Berg, 1973) and Kupreanof I s 1 and (McClel l a n d and Gehrel s, 1987a). I n
- con t ras t , Gravina rocks a re known t o d e p o s i t i o n a l l y o v e r l i e metamorphosed and
deformed rocks of t h e Taku t e r r a n e i n no r t he rn SE Alaska (Redman, 1984).
S i m i l a r r e l a t i o n s may a l s o occur i n southern SE Alaska (Gehre ls and Berg,
1984; McClel l a n d and Gehrels, 1987b; Char les Rubin, o r a l commun., 1987).
The eas te rn marg in o f t he Gravina b e l t i s i n most areas d i f f i c u l t t o
identify. I n southern SE Alaska, high-grade metamorphic rocks assigned t o t h e
Taku t e r r a n e were p robab ly de r i ved i n p a r t f rom Gravina be1 t p r o t o l i t h s . To
the nor th , Gravina s t r a t a a re bound t o t he e a s t by eas t -d i pp ing t h r u s t
(Gehrel s and McClel land, 1988) and perhaps s t r i k e - s l i p f a u l t s , and may l o c a l l y
be i n t r u d e d by p l u tons be long ing t o t h e western p a r t o f t h e Coast Range
ba tho l i th,
Regional r e l a t i o n s suggest t h a t t h e Gravina b e l t i s p a r t o f a bas ina l
assemblage t h a t accumulated a long t he eas te rn marg in o f a p r e v i o u s l y
jux taposed Alexander t e r r a n e and Wrange l l i a and con t inued eastward across Taku
t e r r a n e (Berg and o thers , 1972, 1978). The c o n t i n u a t i o n o r c o r r e l a t i v e o f
Gravina s t r a t a eas t o f t he Taku t e r r a n e has n o t y e t been i d e n t i f i e d ,
Metamorphic rocks o f t he Coast Range ba tho l i t h (M on f i g . 2)
Metasedimentary and metavolcanic rocks comprise n e a r l y 50% o f t h e Coast
Range ba tho l i t h and c o n s i s t p r i m a r i l y o f pe l i t i c , semi-pel i t i c , and
quar tzo fe l dspa th ic s c h i s t and gnei ss and subord ina te amphi b o l i te , q u a r t z i t e ,
marble, and c a l c - s i l i c a t e . P r o t o l i t h s a re i n t e r p r e t e d by most workers t o be
a r g i l l aceous marine s t r a t a , 1 imestone and ( o r ) do lomi te , che r t , and
subord inate ma f i c t o f e l s i c vo l can i c rocks. Some rocks may a l s o have been
de r i ved from p l u t o n i c p r o t o l i ths. P r o t o l i t h ages o f Cretaceous(?) ,
J u r a s s i c ( ? ) , T r i a s s i c , Permian(?), Carboni ferous(?) , and P ro te rozo i c (? ) a re
i n d i c a t e d by: ( 1 ) r e l a t i o n s n o r t h and e a s t o f Juneau which suggest t h a t t he
metamorphic rocks grade eastward i n t o T r i a s s i c and o l d e r s t r a t a o f S t i k i n i a ,
and a re a t l e a s t l o c a l l y o v e r l a i n by t he T r i a s s i c s t r a t a (Souther, 1971;
Werner, 1977, 1978; Bul tman, 1979; Brew and o thers , 1985); ( 2 ) a p r e l i m i n a r y
Rb-Sr i sochron o f P ro te rozo i c apparent age determined on high-grade
metamorphic rocks a1 ong t h e A1 aska-Br i t i sh Col umbia border n o r t h o f Juneau
(L.J. Werner and R.L. Armstrong, i n Monger and Berg, 1987; Werner, 1977, -
1978); and ( 3 ) r e l a t i o n s i n t h e Coast Range b a t h o l i t h southeast o f SE Alaska
whfch suggest t h a t s i m i l a r metamorphic rocks were de r i ved f rom Cretaceous and
Ju rass i c s t r a t a (Douglass, 1986), from t h e Ju rass i c Bowser Lake Group
(Woodsworth and others , 1983), and f rom s t r a t a o f probable Permian (H i 11 ,
1985) and pre-Permian (Hutchison, 1982) age (Hi11 and o thers , 1985).
Regional amph ibo l i te - and l o c a l l y g r a n u l i t e - f a c i e s metamorphism occur red
p r i m a r i l y d u r i n g La te Cretaceous-ear ly T e r t i a r y t ime, a1 though metamorphism
p r i o r t o d e p o s i t i o n o f Jura-Cretaceous s t r a t a o f t h e Gravina b e l t , p r i o r t o
T r i a s s i c t ime, and between Carboniferous and P ro te rozo i c t ime may have
p r e v i o u s l y a f fec ted va r i ous p a r t s o f t h e Coast Range b a t h o l i t h .
I n t r u s i v e s u i t e s of t he Coast Range b a t h o l i t h
P lu tons o f t he Coast Range b a t h o l i t h comprise t h ree d i s t i n c t s u i t e s t h a t
become p r o g r e s s i v e l y younger toward t he east , and a l a r g e u n i t of und iv ided
g ranod io r i t i c rocks rang ing i n age from E a r l y ( ? ) Cretaceous t o Paleocene
( f i g u r e s 1 and 2). The o l d e s t s u i t e c o n s i s t s o f narrow b u t ve ry l o n g sheet-
l i k e masses of hornblende-dominant t o n a l i t e and qua r t z d i o r i t e t h a t extend i n
a l i n e a r f ash ion a long t he western margin o f t he b a t h o l i t h . These t a b u l a r
bodies form a complex of tonal i t i c s i l l s (Brew and Ford, 1981) and are
interpreted as marking a fundamental tectonic boundary within the batholith
(Berg and others, 1978; Brew and Ford, 1981; Gehrel s and Berg, 1984). Strong
foliation and lineation within the bodies and the i r contact relations with
country rocks suggest t h a t they were intruded during the l a t e r stages of
regional metamorphism and deformation within the Coast Range batholith. U-Pb
(zircon) dates on individual bodies appear t o young southward from near 70 Ma
i n northern southeastern Alaska (Barker and others, 1986), through 67-64 Ma in
central SE Alaska (Gehrels and others, 19841, t o approximately 60 Ma jus t
south of the panhandle (Armstrong and Runkle, 19791,
East of the tona l i t ic s i l l s are discrete plutons to large batholithic
complexes of Paleocene tonal i te-granodiori t e . These bodies are commonly
elongate b u t appear to have been emplaced a f t e r most of the deformation in the
batholith. In southern SE Alaska these bodies engulf the tonali t i c s i l l s and
constf tute most of the bathol i t h . The youngest and vol umetrical 1 y most
significant su i te in the bathol i t h consists of huge bodies of bioti te-dominant
granodiorite of Eocene age (Gehrels and others, 1984; Gehrels and Berg, 1984).
These rocks were apparently empl aced a t shallow crustal levels, as the i r
volcanic cover (Sloko Volcanics) i s locally preserved adjacent t o the pl utons.
Barker and Arth (1984), Barker and others (19861, and Arth and others
(1988) conclude t h a t plutons in the batholith are the roots of an Andean-type
arc formed in response to subduction of oceanic crust . In contrast , Monger
and others (1982), Kenah and Holl i s t e r (19831, and Crawford and others (1987)
indicate tha t some components may be anatectic me1 ts generated during the main
phase of deformation and metamorphism in the Coast Range batholith.
Intrusive sui tes west of the Coast Range batholith
Intrusive bodies west of the Coast Range batholith belong t o several
suites, including, from 01 dest t o youngest:
(1) Large, generally is01 ated granodiori te pl utons t h a t intrude A1 exander
and Wrangell i a . K-Ar dates on these bodies are generally Early Cretaceous,
b u t some bodies may be coeval with similar plutons i n the Saint Elias
Mountains region t h a t yield Jurassic K-Ar dates. Berg and others (1972)
suggest t h a t these intrusions formed in response t o plate convergence along
the western margin o f A1 exander and Wrangel 1 ia terranes.
( 2 ) Zoned ul tramaflc complexes ranging in composition from duni te,
commonly in the centers of the complexes, t o cl inopyroxeni te (Taylor, 1967;
Irvine, 1967, 1974). These bodies yield K-Ar dates o f Early to mid-Cretaceous
(Lanphere and Eberlein, 1966). The ul tramafic bodies intrude Triassic and
older rocks of the Alexander terrane, Permo-Triassic(?) rocks of Taku terrane,
and probably Jura-Cretaceous strata of the Gravina be1 t. I t has been argued
that the pl utons are subvolcanic t o m a f i c , cl inopyroxene-bearing flows in the
Gravina be1 t ( Irvine, 1973, 1974). They may have been formed in response to
plate convergence along the Pacific margin (Berg and others, 19721, o r in a
transtensional environment within which the Gravina basin was local ized
(Gehrel s and Sal eeby, 1985 1.
(3) Granodiori t i c , tonal i t i c , and subordinate quartz monzoni te to quartz
diorite bodies immediately west of the Coast Range batholith t h a t intrude
strata of the Taku terrane and Gravina bel t . Most intrusions contain bioti te
and(or) hornblende, many contain garnet, muscovite, and primary epidote, and
some are pyroxene-beari ng. K - A r , 4 0 ~ r / 3 9 ~ r , and U-Pb dates indicate
emplacement primarily during mid-Cretaceous time (Saleeby, 1987; Rubin and
Saleeby, 1987a, b; Sutter and Crawford, 1985). Geobarometric studies of epidote
and garne t i n these bodies suggest t h a t they c r y s t a l l i z e d a t mid- t o l owe r
c r u s t a l l e v e l s (Zen and Hammarstrom, 1984a, b) . A r t h and o the rs (1988)
conclude t h a t these p lu tons formed i n a subduc t fon- re la ted i s l a n d a r c based on
geochemical and i s o t o p i c analyses i n t h e Ketch ikan area, b u t Crawford and
o the rs (1987) argue t h a t they formed i n response t o c r u s t a l ana tex is d u r i n g
mid-Cretaceous compressional deformat ion.
( 4 ) Large g ranod io r i t i c bodies o f probable Eocene-01 igocene age t h a t
f n t r u d e Chugach, Wrangell i a , and A1 exander t e r ranes i n nor thwestern SE A1 aska.
The rocks range f rom muscovi te and 1 ocal l y garne t -bear ing g r a n o d i o r i te ,
g r a n i t e , and t ona l i t e i n t he Baranof I s l and -G lac ie r Bay area, t o b i o t i t e - and
hornbl ende-bearSng qua r t z d i o r i t e and g r a n o d i o r i t e i n t h e C h j 1 k a t Range.
(5) Stocks o f b i o t i t e - , hornblende-, and pyroxene-bearing g ran i t e , a1 k a l i
gran i te , qua r t z monzoni t e , g r a n o d i o r i t e , and d i o r i t e , and o f 1 ayered and
l o c a l l y toned bodies of gabbro, qua r t z gabbro, and o t h e r ma f i c -u l t r ama f i c
i n t r u s i v e s . These s tocks occur i n two d i s t i n c t reg ions, one ex tend ing f rom
the Coast Range b a t h o l i t h eas t o f Ketch lkan northwestward t o t he no r the rn t i p
o f Ku iu I s l and , and t h e o t h e r i n no r t he rn SE Alaska on Chichagof I s l a n d and i n
the G l a c i e r Bay area. K - A r dates on these bodies a r e g e n e r a l l y Ol igocene and
Miocene. The bodies i n southern and c e n t r a l SE Alaska i n t r u d e t he Coast Range
b a t h o l i t h , Gravina b e l t , and t h e Taku te r ranes , whereas t h e no r the rn
assembl age i n t r u d e s A1 exander , Wrangell , and Chugach te r ranes .
Qua te rna ry -Te r t i a r y s t r a t a ( Q T on f i g . 2)
Qua te rna ry -Te r t i a r y s t r a t a u n d e r l i e l a r g e reg ions o f Kupreanof, southern
Admira l ty , and western Baranof I s l ands and occur i n many o the r more r e s t r i c t e d
areas throughout SE Alaska. F i g u r e 2 shows the d i s t r i b u t i o n o f these strata
o n l y where they cover l a r g e reg ions. I n c e n t r a l SE Alaska these s t r a t a
i n c l u d e t h e e a r l y t o m idd le T e r t i a r y Kootznahoo Format ion (non-marine
sandstone, shale, and congl omerate) and Admiral ty I s 1 and Vol can ics ( basal t and
andesi t e ) , and younger basal t i c t o r hyo l i t i c v o l c a n i c rocks and assoc ia ted
sediments. West o f G l a c i e r Bay, 01 igocene t o Miocene s t r a t a ( n o t shown on
f i g . 2 ) be long t o t he Cenotaph Volcanics ( b a s a l t ) and t h e Topsy Format ion
(mar ine ca lcareous sandstone and s i l t s t o n e ) . Quaternary and T e r t i a r y basal t i c
t o r h y o l i t i c vo l can i c rocks and subord ina te sediments a l s o occur a t M t ,
Edgecumbe (west o f S i t k a ) , i n t he Coast Range bath01 i t h eas t o f Ketch ikan and
Petersburg, i n t h e western Pr ince o f Wales I s l a n d reg ion , on i s l a n d s i n Cross
Sound, and i n many o t h e r areas.
RELATIONS AMONG TERWES
The p r ima ry and present-day r e l a t i o n s among t h e t e r ranes o f southeastern
Alaska a r e c o n t r o v e r s i a l . U n c e r t a i n t i e s about t h e i r s i m i l a r i t i e s and
d i f ferences and about the ex is tence and na tu re of boundaries between them
a r i s e f rom t h e f a c t t h a t t he geology o f much of t h e panhandle has been s tud ied
o n l y i n reconnaissance fash ion, and because many c r i t i c a l r e l a t i o n s w i t h i n and
between t e r r a n e s a r e obscured by Cretaceous-ear ly T e r t i a r y metamorphism,
deformation, and ( o r ) p l utonism. To date, two fundamenta l ly d i f f e r e n t
i n t e r p r e t a t i o n s o f t h e t e c t o n i c framework o f SE Alaska have been proposed.
Berg and o the rs (1978) and Monger and Berg (1987) be1 $eve t h a t the Alexander,
Chugach, S t i k i n e , Taku, and Wrangell i a te r ranes , and t h e metamorphic r ocks o f
the Coast Range b a t h o l i t h , each have d i s t i n c t l i t h i c components and t e c t o n i c
h i s t o r i e s , and t h a t each i s ( o r was) f a u l t bounded. I n con t ras t , o t h e r
workers ( f o r example, Brew and Ford, 1983, 1984) b e l i e v e t h a t t he d i f f e r e n c e s
between most o f these te r ranes r e s u l t f rom f a c i e s changes w i t h i n a s i n g l e
c r u s t a l fragment. For example, Brew and Ford (1984) suggest t h a t Permo-
T r i a s s i c rocks o f t h e Taku and S t i k i n e t e r ranes a re f ac i es -equ i va len t s of t h e
upper p a r t s o f t he Alexander t e r rane , and t h a t t h e metamorphic rocks of t h e
Coast Range b a t h o l i t h and t he o l d e r rocks o f S t i k i n i a a re f a c i e s equ i va len t s
o f t h e lower p a r t s o f t he Alexander te r rane .
I n t he f o l l o w i n g sec t i ons we assess what i s known about t h e s i m i l a r i t i e s
and d i f f e r e n c e s among Alexander, Taku, Wrange l l i a , and S t i k i n e t e r ranes and
the metamorphic rocks i n t he Coast Range b a t h o l i t h , and o f f e r some t e n t a t i v e
i n t e r p r e t a t i o n s about p r imary r e l a t i o n s among the te r ranes .
A1 exander-Wrangel 1 i a re1 a t i o n s
The Alexander and Wrange l l i a t e r ranes were o r i g i n a l l y i n t e r p r e t e d as
separate t e c t o n i c e n t i t i e s p r i o r t o t h e i r j u x t a p o s i t f o n d u r i n g Ju rass i c t ime
(Berg and o thers , 1978; Coney and o thers , 1980). Th i s i n t e r p r e t a t i o n needs t o
be m o d i f i e d because Pennsyl vani an-Permian d i o r i t i c and syeni t i c i n t r u s i v e
bodies a r e "ow known t o i n t r u d e b o t h t e r ranes and t h e i r boundary i n southern
Alaska and southwestern Yukon (MacKevett and o thers , 1986). These r e l a t i o n s
i n d i c a t e t h a t Alexander and Wrange l l i a have been i n p r o x i m i t y s ince a t l e a s t
Pennsylvanian-Permian t ime. I n a d d i t i o n , i t i s 1 i k e l y t h a t Upper T r i a s s i c
rocks o f t he Alexander t e r rane a r e f a c i e s equ i va len t s o f t h e Upper T r i a s s i c
r i f t assemblage i n Wrangell i a (Gehrel s and o thers , 1986).
Pre-Pennsyl vanian re1 a t i o n s between t he two ter ranes, however, a r e as y e t
uncer ta in . The Devonian through Permian v o l c a n i c and bas ina l sedimentary
assemblages t h a t c h a r a c t e r i z e Wrange l l i a (Jones and others , 1977; Brandon and
others , 1986) a r e d i f f e r e n t f rom the carbonate-dominated upper Paleozoic rocks
o f much o f t h e Alexander t e r rane ( C r a i g subter rane) . It i s poss ib l e t h a t they
c o r r e l a t e w i t h d i s t a l sedimentary and vo l canogenic components o f t h e Admi ra1 t y
subterrane, b u t a r i g o r o u s comparison of these two assemblages must a w a i t more
d e t a i l e d s t u d i e s o f t he Admi ra l t y subterrane.
A1 exander-Taku re1 a t i o n s
Rigorous comparisons between t he Taku t e r r a n e and ad jacen t assemblages
a re h indered by a l a c k o f age c o n s t r a i n t s on most p r o t o l j t h s o f Taku. Recent
s tud ies have a l s o shown t h a t , i n many areas, rocks p r e v i o u s l y assigned t o t he
Taku t e r r a n e a re p a r t s o f o t h e r assemblages. I n t he Ketch ikan area, f o r
example, Saleeby (1987) and Rubin and Saleeby (1987a, b ) conclude t h a t t h e Taku
t e r rane o f Berg and o the rs (1978) c o n s i s t s o f lower Paleozoic rocks o f t he
Alexander terrane, Jura-Cretaceous s t r a t a of the Gravina b e l t , and Permo-
T r i a s s i c metasedimentary and metavolcanic rocks o f t r u e Taku a f f i n i t y . I n
cont ras t , i n nor thern SE Alaska, P l a f k e r and Davis (1985) and Plafker and
others (1988) argue on the bas is o f geochemical and b i o s t r a t i g r a p h i c
s i m i l a r i t i e s t h a t T r i a s s i c s t r a t a o f the Taku te r rane are c o r r e l a t i v e w - i i
Wrangell i a basal t s and ove r l y i ng sediments. These re1 at ions, the prox imi ty o f
Taku rocks t o o l d e r Alexander te r rane s t r a t a near Ketchikan, and the pre-
T r i a s s i c l i nkage of Alexander te r rane and Wrangel l ia are cons j s ten t w i t h a
scenario i n which the T r i a s s i c rocks i n Alexander, Wrangel l ia, and Taku
terranes are p a r t s o f a once-contiguous r i f t assemblage. The d i f f e rences i n
Upper T r i a s s i c rock types among the th ree terranes may r e f l e c t vary ing
pos i t i ons i n the extensional envjronment: bimodal vo lcan ics and coarse
conglomerate o f the Alexander te r rane may have formed on th i cke r , more evolved
c r u s t near the basin margin; f lood basal t s of Wrangell i a may be the r e s u l t o f
extension w i t h i n ensimat ic o r less-evol ved c rus t ; and b a s a l t and f ine-gra ined
c l a s t i c s t r a t a o f Taku may have formed w i t h i n an e n t i r e l y basinal regime.
The p r i n c i p l e arguments aga ins t pr imary 1 i n k s between Alexander and Taku
are tha t : (1 ) Permian rocks are known i n o n l y two r e s t r i c t e d regions of the
Alexander te r rane i n the panhandle but apparent ly c o n s t i t u t e much of the Taku
terrane; ( 2 ) i n s p i t e o f t h e i r present-day c lose prox imi ty , T r i a s s i c l i t h i c
types and s t r a t i g r a p h i c r e l a t i o n s i n the two terranes are q u i t e d i f f e ren t ; and
( 3 ) z i r con populat ions i n U-Pb samples from the Alexander te r rane do n o t show
evf dence o f i n h e r i tence (Gehrel s and Saleeby, 1987b; Gehrel s and others,
19871, whereas Cretaceous i n t r u s i v e s i n the Taku terr8ane have i n h e r i t e d
s i g n i f i c a n t Precambrian z i rcon components (Rubin and Saleeby, 1987a, b ) .
Current data are thus general 1 y cons i s ten t w i t h a scenario i n which
A1 exander, Wrangell i a, and Taku nay have been c l o s e l y associated du r ing
T r i a s s i c and perhaps Permian time. The data do not, however, r u l e ou t the
p o s s i b i l i t y t h a t Taku remained fundamentally separate from Alexander and
Wrangel l ia i n t o Jurassic t ime.
C o r r e l a t i o n o f metamorphic rocks o f the Coast Range b a t h o l i t h
The h igh metamorphic grade, pene t ra t i ve deformation, and l ack o f
p r o t o l i t h age c o n t r o l 1 i m i t arguments concerning the reg f onal t ec ton i c
a f f i n i t y o f metamorphic rocks o f the Coast Range b a t h o l i t h . Most r e l a t i o n s
i nd i ca te , however, t h a t rocks along the eastern margin o f t he b a t h o l i t h e i t h e r
are metamorphic equivalents o f S t i k i ne s t r a t a o r be1 ong t o a metamorphic
complex t h a t i s o v e r l a i n and i n t ruded by T r i a s s i c rocks o f S t i k i ne . These
metamorphic rocks are apparent ly i n d i s t i n g u i s h a b l e from rocks i n t he western
p a r t of the b a t h o l i t h and i n the eastern, h igh grade, p a r t o f Taku terrane.
I n add i t i on , i n h e r i t e d Precambrian z i r con components a l so occur i n i n t r u s i v e
bodies i n bo th the Taku te r rane (Rubin and Saleeby, 1987a, b ) and the Coast Range
bathol i t h (Gehrel s and others, 1984). Thus, a1 though tonal i t i c s i l l s and ( o r )
the Coast Range mega1 ineament may mark the pr imary boundary between the
bathol i t h and the Taku te r rane (Berg and others, 1978; Brew and Ford, 1978,
1984; Gehrel s and Berg, 1984), i t i s n o t y e t poss ib le t o document a
s i g n i f i c a n t change i n p r o t o l i t h content across e i t h e r one. As i n most
prev ious syntheses, we draw the boundary w i t h i n the t o n a l i t i c s i l l s because
they mark the on l y recognized major d i s c o n t i n u i t y between metamorphic rocks t o
the eas t and the west.
Brew and Ford (1984) have suggested t h a t metamorphic rocks i n the Coast
Range b a t h o l i t h a re the metamorphic equ iva len ts of s t r a t a i n the lower p a r t o f
the Alexander terrane. Beyond a crude comparison of p ropor t ions o f general
rock types, t h i s p o s s i b i l i t y i s d i f f i c u l t t o t e s t g e o l o g i c a l l y because so
l i t t l e i s known about the p r o t o l i t h age of the metamorphic rocks.
I s o t o p i c a l l y , however, the two can be d i s t i ngu i shed on the bas is of the: (1)
presence o f i n h e r i t e d t i rcon components i n the bath01 i t h (Gehrel s and others,
1984) b u t n o t i n the Alexander te r rane (Gehrel s and Saleeby, 1987b, Gehrels
and others, 19871, and (2) s i g n i f i c a n t l y more p r i m i t l v e 87~ r /86~r and
143~d /144~d i n 1 t i a l r a t i o s i n the A1 exander te r rane (Samson and others, 1987,
1988) than i n i n t r u s i v e bodies o f the Coast Range b a t h o l i t h (Barker and
others, 1986; A r th and others, 1988).
TECTONIC H I STORY OF SOUTHEASTERN ALASKA
The c u r r e n t l y decipherable tec ton i c h i s t o r y o f SE A1 aska begins dur f ng
l a t e s t Pro terozo ic (?) -Ear ly Cambrian t ime w i t h the format ion o f an arc- type
basement f o r t he Alexander terrane. Arc-type a c t i v i t y , punctuated by Late
Cambrian-Early Ordovician and middle S i l u r i a n - e a r l i e s t Devonian orogenic
events, cont inued through S i l u r i a n and perhaps i n t o Devonian time. The e a r l y
Paleozoic paleoposi t i o n o f the te r rane wS thSn t h f s t e c t o n i c a l l y ac t i ve , i n t r a -
oceanic regime i s problematic. Gehrels and Saleeby (1984, 1987a) argue t h a t
the te r rane bears tec ton i c s i m i l a r i t i e s w i t h orogenic systems t h a t formed
along the pa leo-Pac i f i c margins o f Aus t ra l i a , Antarc t ica , and c r u s t a l
fragments now r e s i d i n g i n Asia, and hypothesize t h a t the te r rane may have
formed w i t h i n the western p a r t of the pa leo-Pac i f i c Ocean basin. As noted by
Savage (1987), however, e a r l y Paleozoic faunas o f the A1 exander te r rane are
d i f f e r e n t from faunas found i n eastern Aus t ra l i a , and more c l o s e l y resemble
North American forms. I n apparent c o n t r a s t t o bo th comparisons, Nd-Sr
i s o t o p i c data i n d i c a t e t h a t t he te r rane i s cons t ruc ted of j u v e n i l e c r u s t a l
m a t e r i a l s and t h a t i t was n o t near any con t i nen ta l landmasses dur ing e a r l y
Paleozoic t ime (Samson and others, 1987, 1988).
P ro te rozo i c (? ) rocks a long the eastern margin o f t he Coast 4ange
b a t h o l i t h d i f f e r f rom those i n Alexander te r rane because they are dominated by
qua r t z - r i ch c l a s t i c s t r a t a and y i e l d Rb-Sr i s o t o p i c data cons i s ten t w i t h an
age o f approx imate ly 900 Ma (L.J. Werner and R.L. Armstrong, - i n Monger and
Berg, 1987). These rocks may have formed i n a con t i nen ta l margin environment
and are repo r ted by Werner (1977, 1978) and Bul tman (1979) t o form the
depos i t iona l basement t o T r i a s s i c rocks o f t he S t i k i n e te r rane. The p r i m i t i v e
Nd-Sr i s o t o p i c s ignature o f o t h e r rocks o f the S t i k i n e te r rane i nd i ca tes ,
however, e i t h e r t h a t t h i s o l d e r metamorphic basement does no t extend eastward
beneath t h e main p a r t o f S t i k i n i a , o r t h a t t he T r i a s s i c s t r a t a o v e r l y i n g the
metamorphic rocks are n o t p a r t o f S t i k i n i a .
Beginning i n Devonian t ime, Wrangell i a , S t i k i n i a , and the Admira l ty
subterrane o f t he Alexander t e r rane a1 1 evolved i n an environment
charac ter ized by arc- type vo lcan ic rocks, bas ina l marine c l a s t i c sediments,
and subord inate carbonate. I n con t ras t , upper Paleozoic rocks o f t he Cra ig
subterrane record t e c t o n i c s t a b i li t y through a t l e a s t 1 a t e Pennsylvanian t ime
and perhaps through the mid-Permian. Wrangel l ia and the Cra ig and Admi ra l ty
subterranes were probably i n c l o s e p rox im i t y du r i ng most o f t h i s t ime
(MacKevett and others, 1986; M u f f l e r , 1967; Berg and others, 1978; Jones and
others, 1981). These r e l a t i o n s , combined w i t h Nd-Sr i s o t o p i c data from upper
Paleozoic rocks o f the Cra ig subterrane and S t i k i n e ter rane, r e q u i r e the l a r g e
tectonic fragments in and adjacent t o the panhandle to have evolved i n an
intraoceanic realm th rough 1 ate Paleozoic ti me. Similarities between
Alexander terrane faunas and b o t h North American and Tethyan forms (Mamet and
Pinard, 1985; Ross and Ross, 1983, 1985) are consistent w i t h an intraoceanic
post tion within the paleo-Pacific basin.
Triassic rocks of the Alexander terrane and Wrangellia are interpreted to
have formed in a r i f t environment (Jones and others, 1977; Gehrels and others,
1986). In Wrangellia, huge volumes of tholei i t ic flood basalt covered the
terrane, whereas in Alexander terrane a bimodal volcanic suite was erupted
along the eastern margin of the terrane. Triassic basalt and andesite of the
Stikine terrane are interpreted t o have erupted within a volcanic arc
environment, presumably related t o subduction a1 ong the eastern (inboard)
margin of the terrane (Monger and ROSS, 1971). The tectonic environment of
Triassic rocks of the Taku terrane i s unknown.
The tectonic history o f SE Alaska after Triassic time i s dominated by
accretion of Alexander and Wrangell ia against Stikinia or other inboard
terranes. An unconformi t y separating Upper Jurassic to mi d-Cretaceous strata
of the Gravina be1 t from underlying Triassic and older rocks i s the f f r s t
evidence of this accretionary activity, Prior t o Late Jurassic time, Permo-
Triassic rocks of the Taku terrane were deformed and regionally metamorphosed
( ~ e h r e l s and Berg, 19841, and rocks of the eastern Alexander terrane were
deformed and disrupted a long the Duncan Canal shear tone on Kupreanof Island
(McClel land and Gehrel s , 1987a). This deformation i s interpreted to record
either the northward movement o f the Alexander-Wrangellia terrane along the
Cal ifornia-Washington continental margin (Gehrel s and Saleeby, 19851, or the
i n i t i a l j u x t a p o s i t i o n aga ins t t h e western marg in o f S t i k i n i a (McCl e l 1 and and
Gehrel s, 1987b) . Rocks o f t h e Gravina b e l t accumulated a long t h e western margin o f a
marine b a s i n o f unknown w id th . As proposed by Berg and o t h e r s ( 1972),
vo lcanism w i t h j n t h i s bas in was p robab ly d i s t a l l y r e l a t e d t o g r a n i t i c
p l u ton i sm i n t h e Alexander t e r rane , t o f o rma t i on o f the Chugach acc re t i ona ry
complex, and t o p l a t e convergence a long t h e outboard marg in o f Alexander and
Wrangell i a , The Gravina be1 t as a depos i t i ona l b a s i n may have formed as: (1)
a back-arc bas in o r r i f t behind a wes t - fac ing a r c (Berg and others , 1972; Brew
and Ford, 1983), ( 2 ) a c o l l a p s i n g sedimentary b a s i n t h a t records c l o s u r e o f
t he su tu re between t h e Alexander and S t i k i n e t e r ranes ( P a v l i s , 1982); ( 3 ) a
western c o n t i n u a t i o n o f the Jura-Cretaceous mar ine bas in t h a t formed on t h e
S t l k i n e t e r r a n e (Mu l l e r , 1977); o r ( 4 ) as a p u l l - a p a r t s t r u c t u r e i n a r i g h t -
l a t e r a l t r ans fo rm system a long which t h e outboard t e r ranes were t r anspo r ted
nor thward (Gehrel s and Saleeby, 1985). Wi thout a d d i t i o n a l i n f o rma t i on , a1 1 of
these scenar ios apparen t l y r e n a i n v i ab le .
S t r u c t u r a l a c c r e t i o n o f t he Alexander t e r r a n e a g a i n s t t h e western marg in
of S t i k i n i a began soon a f t e r d e p o s i t i o n o f mid-Cretaceous s t r a t a of t h e
Gravina b e l t (Berg and o thers , 1972, 1978; Coney and o thers , 1980; Monger and
others , 1982). Th i s acc re t i ona ry event i s recognized as movement on west-
vergent t h r u s t f a u l t s , widespread deformat ion and reg iona l metamorphism o f
rocks w i t h i n t h e Coast Range bath01 i t h and a long i t s western f l a n k , and
a n a t e c t i c ( ? ) p l u ton ism w i t h i n t h e su tu re zone sepa ra t i ng Alexander and
S t i k i n i a (Monger and o thers , 1982). These events apparen t l y cu lm ina ted
between approx imate ly 95 Ma and 65 Ma, and were f o l l o w e d soon a f t e r by r a p i d
up1 i ft of the Coast Range bath01 1 th . Thermobarometric s tud ies w i t h i n the
b a t h o l i t h i n d i ca te t h a t up1 i f t ra tes o f 2 m/yr were achieved a t about 55 Ma,
b r i n g i n g rocks t h a t formed a t over 20 km depth t o the surface ( H o l l i s t e r ,
1982; Crawford and others, 1987). Although the p e t r o l o g i c evidence f o r r a p i d
and la rge-sca le u p l i f t f s compell ing, the d e t r i t u s shed from the u p l i f t e d
orogen has n o t been i d e n t i f i e d , and the major s t ruc tu res along which the
b a t h o l i t h was u p l i f t e d have been recognized i n on l y a few areas.
I n t r u s i o n o f Oligocene-Miocene gabbro and g r a n i t e having low i n i t i a l
87~r /86~r , and of swarms o f lanprophyre and quar tz porphyry d ikes suggest
s t i l l younger post-accret ionary tectonism, poss ib l y tapping mantle sources.
These i n t r u s i o n s t rend west-northwester ly, across the reg iona l northwest
t rends of the Coast Range b a t h o l i t h , Taku terrane, Gravina b e l t , and Alexander
te r rane . Southeastern A1 aska cont inues t o be t e c t o n i c a l l y ac t i ve , w i t h Holocene
f a u l t i n g and up1 i f t (Hudson and others, 1982b), and e rup t i on o f l ava f lows as
r e c e n t l y as about 360 +/- 60 years ago ( E l 1 i o t t and others, 1981).
REFERENCES
Armstrong, R.L., 1985, Rb/Sr d a t i n g o f t h e Bokan Mountain g r a n i t e complex and i t s coun t r y rocks: Canadian Journal o f E a r t h Sciences, v. 22, p. 1233-1236.
Armstrong, R.L., and Runkle, D i t a , 1979, Rb-Sr geochronometry o f t h e E c s t a l l , K i t k i a t a , and Quot toon p lu tons and t h e i r coun t r y rocks, P r i nce Rupert reg ion, Coast P l u t o n i c complex, B r i t i s h Columbia: Canadian Journal o f E a r t h Sciences, V. 16, p. 387-399.
Ar th , J.G., Barker, Fred, and Stern, T.W., 1988, Coast b a t h o l i t h and Taku p lu tons near Ketchikan, Alaska: petrography, geochronology, geochemistry, and i s o t o p i c charac te r : American Journal of Science, i n press.
Barker, Fred, and Ar th , J .G. 1984, Pre l im ina ry r e s u l t s , Cent ra l Gneiss Complex of t h e Coast Range b a t h o l i t h , southeastern Alaska: t h e r o o t s o f a high-K c a l c - a1 k a l i n e arc?: phys ics o f t he E a r t h and P lane ta ry I n t e r i o r s , v. 35, p. 191- 198.
Barker, Fred, Ar th , J.G., and Stern, T.W., 1986, E v o l u t i o n o f t h e Coast bath01 i t h a1 ong t h e Skagway t r ave rse , A1 aska and B r i ti sh Col unbi a: American M ine ra log i s t , v. 71, p. 632-643.
Berg, H.C., 1973, Geology o f Gravina I s l and , Alaska: U.S. Geolog ica l Survey B u l l e t i n 1373, 41 p.
Berg, H.C., E l l i o t t , R.L., and Koch, R.D., 1988, Geologic map of t h e Ke tch i kan and P r i nce Rupert quadrangles, southeastern A1 aska: U.S. Geolog ica l Survey M i s c e l l aneous Geologic I n v e s t i g a t i o n Map 1-1807, sca le 1: 250,000.
Berg, H.C., Jones, D.L., and Coney, P.J., 1978, Map showing pre-Cenozoic t e c t o n o s t r a t i g r a p h i c t e r ranes o f southeastern Alaska and ad jacen t areas: U.S. Geol og i c a l Survey Open-Fi 1 e Repor t 78-1085.
Berg, H.C. , Jones, D.L., and R i ch te r , D.H., 1972, Grav ina-Nutzot in be1 t -- t e c t o n i c s i g n i f i c a n c e o f an upper Mesozoic sedimentary and vo l can i c sequence i n southern and southeastern Alaska: U.S. Geolog ica l Survey Profess ional Paper 800-0, p. Dl-D24.
Brandon, M.T., Orchard, M.J., Par r i sh , R.R., Sutherland-Brown, A. and Yorath, C.J., 1986, F o s s i l ages and i s o t o p i c dates from the Paleozoic S i cke r Group and assoc ia ted i n t r u s i v e rocks, Vancouver I s l and , B r i t i s h Columbia: Geolog ica l Survey of Canada Paper 86-lA, p. 683-696.
Brew, D.A., and Ford, A.B., 1978, Megalineament i n southeastern Alaska marks southwest edge o f Coast Range b a t h o l i t h i c complex; Canadian Journal o f E a r t h Sciences, v. 15, p. 1763-1772.
Brew, D.A., and Ford, A.B., 1981, The Coast p l u t o n i c complex s i l l , southeastern Alaska, i n A l h e r t , N.R.D., and Hudson, T.L., eds., The U.S. Geolog ica l Survey i n ATaska: Accomplishments d u r i n g 1980: U.S. Geolog ica l Survey C i r c u l a r 823-8. pp. 896-898.
Brew, D.A., and Ford, A.B., 1983, Comment on Tectonic acc re t i on and the o r i g i n o f the two major metamorphic and p l u t o n l c we1 t s i n the Canadian Cord i l l e r a : Geology, v. 11, p, 427-429.
Brew, D.A., and Ford, A.B., 1984, Tec tonost ra t ig raph ic terrsanes i n the Coast plutonic-metamorphjc complex, southeastern Alaska, i n Bartsch-Winkler, Susan, and Reed, K.M., ed., The U.S. Geological Survey i n maska: Accomplishments dur ing 1982: U,S, Geological Survey C i r c u l a r 939, p. 90-93,
Brew, D.A., Ford, A.B., and Garwin, S.L., 1985, F o s s i l i f e r o u s Middle and(or) Upper T r i a s s i c rocks w i t h i n the Coast plutonic-metamorphic complex southeast o f Skagway, i n Bartsch-Winkler, Susan, ed., The U.S. Geological Survey i n Alaska: Acco? ishments dur ing 1984: U.S. Geological Survey C i r c u l a r 967, p. 86-89.
Brew, D.A., and Grybeck, Dona1 d, 1984, Geology o f t he Tracy Arm-Fords Ter ror wi lderness study area and v i c i n i t y , Alaska: U.S. Geological Survey B u l l e t i n 1525-A, p.21-52.
Brew, D.A., Ovenshine, A.T., Ka r l , S.M., and Hunt, S.J., 1984, Pre l im inary reconnaissance geologic map of the Petersburg and p a r t s o f the Por t Alexander and Sumdum quadrangles, southeastern Alaska: U.S. GeologScal Survey Opoen-File Report 84-405.
Buddington, A.F., and Chapin, Theodore, 1929, Geology and mineral deposi ts o f southeastern Alaska: U.S. Geological Survey B u l l e t i n 800, 398 p,
Bul tman, TOR., 1979, Geology and tec ton i c h i s t o r y of the Whitehorse t rough west of At1 Sn, B r i t i s h Columbia: unpubl {shed Ph.D. thes is , Yale Un ivers i ty , New Haven, Connecticut, 284 p.
Churkin, Michael, Jr., and Eber le in, G.D., 1977, Ancient border land te r ranes o f the North American C o r d i l l e r a : c o r r e l a t i o n and microp la te tec ton ics : Geological Society o f America B u l l e t i n , v. 88, p. 769-786.
Coney, P o J * , Jones, D.L., and !longer, J.W.H., 1980, C o r d i l l e r a n suspect terranes: Nature, v. 288, p. 329-333.
Cordey, F., Mortimer, N., DeWever, P., and Monger, J.W.H., 1987, S ign i f i cance o f Jurass ic r a d i o l a r i a n s from the Cache Creek terrane, B r i t i s h Columbia: Geology, v. 15, p. 1151-1154.
Cowan, D.S., 1982, Geological evidence f o r post-40 m.y. B.P. large-scale northwestward .displacement of p a r t o f southeastern ~ l a s k a : ~ e o l o g y , v. 10, p. 309-313.
Crawford, M.L., H o l l i s t e r , L.S., and Woodsworth, G.J., 1987, Crusta l deformation and reg iona l metamorphism across a te r rane boundary, Coast p l u t o n i c complex, B r i t i s h Columbia: Tectonics, v. 6, p. 343-361.
Davis, A l i ce , and P la fker , George, 1985, Comparative geochemistry of T r i a s s i c b a s a l t i c rocks from the Taku te r rane on the C h i l k a t Peninsula and Wrangel l ia: Canadian Journal o f Ear th Sciences, v. 22, p. 183-194.
Decker, J .E., Wilson, F.H., and Turner, D.L., 1980, Mid-Cretaceous subduct ion event i n southeastern A1 aska: Geolog ica l S o c ~ e t y o f America Abs t rac ts w i t h Programs, v. 12, p. 103.
Douglass, B.J., 1986, Deformat ional h i s t o r y of an o u t l i e r o f metasedirnentary rocks, Coast P l u t o n i c Complex, B r i t i s h Col umbia, Canada: Canadian Journal of Ea r th Sciences, v. 23, p. 813-826.
E l l i o t t , R.L., Koch, R.D., and Robinson, S.GI., 1981, Age o f b a s a l t f l ows i n t h e Blue R i v e r v a l l e y , B r a d f i e l d Canal quadrangle, i n A lbe r t , N.R.D., and Hudson, T. L., eds., The U.S. Geolog ica l Survey i n AlTska: Accompl i shments d u r i n g 1979: U .S. Geolog ica l Survey C i r c u l a r 823-B, p. B115-116.
Forbes, R.B., G i l b e r t , W.G., and Redman, E.C., 1987, The Four Winds complex; A newly recognized Paleozoic metamorphic complex i n southeastern Alaska: Geolog ica l Soc ie ty o f America Abs t rac t s w i t h Programs, v. 19, p. 378.
Gehrels, G.E., and Berg, H.C., 1984, Geologic map o f southeastern Alaska: U.S. Geolog ica l Survey Open-File Report 84-886 ( rep1 aced by Map 1-1867 i n 1988).
Gehrels, G.E., Brew, D.A., and Saleeby, J.B., 1984, Progress r e p o r t on U/Pb ( t i r con) geochronol o g i c s tud ies i n t h e Coast p l utonic-metamorphic complex eas t o f Juneau, southeastern Alaska, i n Bar tsch-Wink ler , Susan, and Reed, K.M., ed., The U.S. Geolog ica l Survey in Alaska: Accompl ishments du r i ng 1982: U.S. Geo log ica l - Survey C i r c u l a r 939, p. 100-102.
Gehrel s, G.E. Dodds, C.J., and Campbell, R.B., 1986, Upper T r i a s s i c rocks of the Alexander te r rane , SE Alaska & t h e S a i n t E l i a s Mountains of B.C. and Yukon: Geo log ica l Soc ie t y o f America Abs t rac t s w i t h Programs, v. 18, p. 109.
Gehrels, G.E., and McClel land, W.C., 1988, O u t l i n e o f t h e Taku t e r r a n e and Gravina b e l t i n t h e Cape Fanshaw-Windham Bay r e g i o n o f c e n t r a l southeastern Alaska: Geo log ica l Soc ie ty o f America Abs t rac t s w i t h Programs, v. 20, p. 163.
Gehrels, G.E., and Saleeby, J.B., 1984, Paleozoic geo log ic h i s t o r y o f t h e Alexander t e r rane , and comparisons w i t h o t h e r orogenic be1 t s : Geolog ica l Soc ie ty o f America Abs t rac t s w i t h Programs, v. 16, p. 516.
Gehrels, G.E., and Saleeby, J.B., 1985, Cons t ra i n t s and specu la t ions on t h e displacement and accretionary h i s t o r y o f t he Alexander-Wrangel l ia-Peninsular super ter rane: Geolog ica l Soc ie ty o f America Abs t rac t s w i t h Programs, v. 17, p. 356.
Gehrel s, G.E., and Sal eeby, J .B., 1987a, Geologic framework, t e c t o n i c e v o l u t i o n , and displacement h i s t o r y o f t he Alexander te r rane : Tecton ics, v. 6, p. 151-173.
Gehrels, G.E., and Saleeby, J.B., 1987b, Geology o f southern Pr ince of Wales I s l and , southeastern Alaska: Geolog ica l Soc ie ty of America Bul l e t i n , v. 98, p. 123-137.
Gehrel s, G.E., Saleeby, J.B., and Berg, H.C., 1987, Geology o f Annette,
3 4
Gravi na, and Duke I s 1 ands, southeastern A1 aska: Canadian Journal o f Ea r th Sciences, v. 24, p. 866-881.
H i l l , M.L., 1985, Remarkable f o s s i l l o c a l i t y : c r i n o i d stems from migmati t e o f t he Coast p l u t o n i c complex, B r i t i s h Columbia: Geology, v. 13, p. 825-826.
H i l l , M,L,, Woodsworth, G.J., and van der Heyden, Peter , 1985, The Coast p l u t o n i c compl ex near Terrace, B .C, : a metamorphosed western ex tens ion o f S t i k i n i a : Geolog ica l Soc ie ty of America Abs t rac t s w i t h Programs, v. 17, p. 362.
Hi1 1 house, J .W., and Gromme, C.S., 1984, Northward d isp lacement and a c c r e t i o n of Wrangell i a : new paleomagnetic evidence from Alaska: Journa l o f Geophysical Research, v. 89, p. 4461-4477.
H o l l i s t e r , L.S. , 1982, Metamorphic evidence f o r r a p i d ( 2 mn/yr) u p l i f t o f a p o r t i o n o f t h e Cent ra l Gneiss Complex, Coast Mountains, B.C. : Canadian M ine ra log i s t , v. 20, p. 319-332.
Hudson, T r a v i s, P l a fker , George, and Dixon, K i r k , 1982a, Ho r i zon ta l o f f s e t h i s t o r y o f t h e Chatham S t r a i t f a u l t , i n Coonrad, W.L., ed,, The U,S, Geolog ica l Survey i n Alaska: Accompl i 5 m e n t s d u r i n g 1980: U.S. Geolog ica l Survey C i r c u l a r 844, p. 128-132.
Hudson, TravSs, Dixon, K i r k , and P la f ke r , George, 1982b, Regional u p l i f t i n southeastern Alaska, i n Coonrad, W.L., ed., The U.S. Geolog ica l Survey i n A1 aska: Accompl i shments du r i ng 1980: U.S, Geologica l Survey C i r c u l a r 844, p. 132-135.
Hutch i son, W.W., 1982, Geology o f t he Pr ince Rupert-Skeena Map area, B r i t i s h Columbia: Geolog ica l Survey o f Canada Memoir 394, 116 p.
I r v f n e , TON., 1967, The Duke I s l a n d u l t r a m a f i c complex, southeastern Alaska, i n Wy l l i e , P.J., ed., U l t r a m a f i c and r e l a t e d rocks: New York, John Wi ley and x n s , Inc., p, 84-97.
I r v i n e , T.N. 1973, B r i d g e t Cove vo lcan ics , Juneau area, Alaska: Poss ib l e paren ta l magma o f A1 askan-type u l t r a m a f i c complexes: Carnegie I n s t i t u t e o f Washington Yearbook v. 72, p. 478-491.
I r v i n e , T.N., 1974, Pe t ro logy o f t he Duke I s l a n d u l t r a m a f i c complex, southeastern Alaska: Geolog ica l Soc ie ty o f America Memoir 138, 240 p.
I r v i n g , E., and Monger, J.W.H., 1987, P re l im ina ry paleomagnetic r e s u l t s f rom the Permian A s i t k a Group, B r i t i s h Columbia; Canadian Journal o f E a r t h Sciences, v. 24, p. 1490-1497.
I r v i n g , E., Woodsworth, G.J., Wynne, P.J., and Morr ison, A., 1985, Paleomagnetic evidence f o r displacement f rom the south o f t he Coast p l u t o n i c complex, B r i t i s h Columbia: Canadian Journal o f E a r t h Sciences, v. 22, p. 584- 598.
Johnson, B.R., and K a r l , S.M., 1985, Geologic map o f western Chichagof and
Yakobi I s l ands , sou theas te rn A1 aska: U.S. Geological Survey Miscell aneous Geologic Inves t i ga t ions Map 1-1506.
Jones , D.L. , S i l b e r l i n g , N.J., and Hil lhouse, John, 1977, Wrangellia -- a d i sp laced t e r r a n e In northwestern North America: Canadian Journal of Earth Sciences, v . 14, p. 2565-2577.
Kenah, C , , and H o l l i s t e r , L,S., 1983, Anatexis i n t h e Central Gneiss Complex, B r i t i s h Columbia, i n Atherton, M.P., and Gribble , C.D., eds. , Migmatites, Me1 t i n g , and Metamzphism: Shiva Pub1 i s h i n g Ltd., Cheshire , U K , p. 142-162,
Lanphere, M.A., 1978, Displacement h i s t o r y of t h e Denali f a u l t system, Alaska and Canada: Canadian Journal of Earth Sc iences , v. 15, p. 817-822.
Lanphere, M.A., and Ebe r l e in , G.D. , 1966, Potassium-argon ages of magnetite- bear ing ul tramafic complexes i n sou theas t e rn A1 aska: Geological Soc ie ty of America Special Paper 87, p. 94.
Lathram, E, . H . , 1964, Apparent r i g h t - l a t e r a l s epa ra t i on on C h a t h a m S t r a i t f a u l t , sou theas te rn Alaska: Geological Society o f America B u l l e t i n , v. 75, p. 249-252.
Lathram, E.H., Loney, R.A., Condon, W.H., and Berg, H.C., 1959, Progress map of t h e geology of t h e Juneau quadrangle , Alaska: U.S. Geological Survey Miscellaneous Geological Inves t i ga t ions Map 1-303, s c a l e 1:250,000.
Lathram, E.H., Pomeroy, J.S., Berg, H.C., and Loney, R.A. , 1965, Reconnaissance geology of Admiralty Is1 and, A1 aska: U .S. Geological Survey B u l l e t i n 1181-R, p. R1-R48.
MacKevett, E.M., Gardner, M.C., Bergman, S.C., Cushing, G. , and McClel l and , W.C., 1986, Geologic evidence f o r Late Pennsylvanian jux t apos i t i on of Wrangell i a and t h e Alexander t e r r a n e , Alaska: Geological Soc ie ty of America Abs t r ac t s with Programs, v, 18 , p. 128.
Mamet, B.L., and Pinard, S. 1985, 9 Carboniferous Algae from t h e Pera t rov ich Formation, sou theas te rn Alaska, i n Toorney, D.F., and Ni teck i , K.H. , eds . , Paleoal go1 ogy: Contemporary research and appl i c a t i o n s : Springer-Verl ag , New York, p. 91-100.
Marquis, Guy, and Globerrnan, B . R . , 1987, Paleornagnetism of t h e Upper Cretaceous Carmacks Group, west of T i n t i n a Trench f a u l t , Yukon and B r i t i s h Columbia: EOS, v. 68, p. 1254.
May, S.R:, and Bu t l e r , R.F., 1986, North American J u r a s s i c apparent po l a r wander: Imp1 i c a t i o n s f o r pl a t e motion, pal eogeography, and Cord i l l e ran t e c t o n i c s : Journal o f Geophysical Research, v. 91, p. 11,519-11,544.
McClelland, W.C., and Gehrels, G.E. , 1987a, Analysis o f a major shear zone i n Duncan Canal , Kupreanof Is1 and, sou theas te rn A1 aska: Geological Soc ie ty of America Abs t r ac t s w i t h Programs, v . 19, p. 430.
McClel l and , W.C., and Gehrel s , G . E . , 1987b, Evidence f o r Early-Middl e J u r a s s i c
deformation and metamorphism a1 ong the inboard margin of the A1 exander terrane, SE Alaska: Geological Society of.America Abst rac ts w i t h Programs, v. 19, p. 764.
McClel land, W.C., and Gehrel s, G.E., 1988, Charac te r i s t i cs o f the Taku terrsane (TT) and Gravina b e l t (GB) i n the Petersburg regton, c e n t r a l southeastern Alaska: Geological Society o f America Abst rac ts w i t h Programs, v. 20, p. 211.
Monger, J.W.H., 1977, Upper Paleozoic rocks o f the western Canadian C o r d i l l e r a and t h e i r bear ing on Cordi 11 eran evol u t i o n : Canadian Journal o f Ear th Sciences, v, 14, p. 1832-1859.
Monger, J.W.H., and Berg, H.C., 1987, L i t h o t e c t o n i c t e r rane map o f western Canada and southeastern Alaska, i n S i l b e r l i n g , N.J., and Jones, D.L., eds., L i t h o t e c t o n i c te r rane maps o f t h e o r t h American C o r d i l l e r a : U.S. Geological Survey Miscellaneous F i e l d Studies Map MF-1874-B, scale 1:2,500,000.
Monger, J.W.H., Pr ice , R.A., and Ternpelman-Kluit, D.J., 1982, Tectonic acc re t i on and the o r i g i n of the two major metamorphic we l t s i n the Canadian C o r d i l l e r a : Geology, v. 10, p. 70-75.
Monger, J.W.H., and Ross, C.A., 1971, D i s t r i b u t i o n o f Fusulinaceans i n t he western Canadian C o r d i l l e r a : Canadian Journal o f Ear th Sciences, v. 8, p. 259- 278.
Muff ler, L.J.P., 1967, S t ra t ig raphy o f the Keku I s l e t s and neighbor ing p a r t s o f Kuiu and Kupreanof I s1 ands, southeastern A1 aska: U.S. Geological Survey B u l l e t i n 1241-C, 52 p.
Mu l le r , J.E., 1977, Evo lu t i on o f the P a c i f i c margin, Vancouver Is land, and adjacent reglons: Canadian Journal o f Ear th Sciences, v. 14, p. 2062-2085.
Newton, C.R., 1983, Paleozoogeographic a f f i n i t i e s of Morian b i va l ves from the Wrangell tan, Peninsular, and Alexander terranes, i n Stevens, C.H., ed., Pre- Jurass ic rocks i n western North American suspect te r ranes: P a c i f i c Section, Society o f Economic Pa leonto log is ts and Minera log is ts , Los Angeles, p. 37-48.
Nokleberg, W.J., Jones, D.L., and S i l b e r l i n g , N.J., 1985, O r i g i n and t e c t o n i c evo lu t i on of the Maclaren and Wrangel l ia terranes, eastern Alaska Range, Alaska: Geologfcal Society o f America B u l l e t i n , v. 96, p. 1251-1270.
Pav l is , T.L., 1982, O r i g i n and age of the Border Ranges f a u l t o f southern Alaska and i t s bear ing on the Late Mesozoic e v o l u t i o n o f Alaska: Tectonics, v. 1, p. 343-358;
Plafker, George, 1967, Geologic map o f the Gulf of Alaska T e r t i a r y Province, Alaska: U.S. Geological Survey F l i sce l l aneous Geologic I nves t i ga t i ons Map I- 484.
P l afker, George, Blome, C. D., and S i l b e r l ing, N.J., 1988, Re in te rp re ta t i on o f lower Mesozoic rocks on the Chi1 k a t Peninsula, Alaska: Closer l i n k s w i t h Wrangel l ia: Geology, v. 16, i n press.
P l a f k e r , George, and Hudson, T rav i s , 1980, Regional i m p l i c a t i o n s o f Upper T r i a s s i c metavolcanic and metasedimentary rocks on t he C h i l k a t Peninsula, southeastern Alaska: Canadian Journal o f E a r t h Sciences, v. 17, p. 681-689.
P l a f k e r , George, Jones, 0. L., Hudson, T rav is , and Berg, H.C., 1976, The Border Ranges f a u l t system i n t h e S a i n t E l i a s Mountains and Alexander Archipelago, i n Cobb, E.H., The U.S. Geolog ica l Survey i n A1 aska: Accompl i shments du r i ng 1 9 7 F U.S. Geolog ica l Survey C i r c u l a r 733, p. 14-16.
P l a f k e r , George, Jones, D.L., and Pessagno, E.A., Jr., 1977, A Cretaceous acc re t i ona ry f l y s c h and melange t e r rane a long t h e G u l f o f Alaska margin, i n Blean, K.M., ed., The 1J.S. Geologica l Survey i n Alaska: Accomp1ishments du r i ng 1976: U.S. Geolog ica l Survey C i r c u l a r 751-B, p. B41-B43.
Redman, E a r l , 1981, The Keete I n l e t t h r u s t f a u l t , P r i nce o f Wales I s l and : Alaska D i v i s i o n o f Geolog ica l and Geophysical Surveys Report 73, p. 17-18.
Redman, E a r l , 1984, An unconformi ty assoc ia ted w i t h conglomerat ic sediments i n t h e Berners Bay area o f southeastern Alaska: Alaska D i v i s i o n o f Geolog ica l and Geophysical Surveys Pro fess iona l Repor t 86, p. 1-4.
Ross, C.A., and Ross, J.R.P., 1983, La te Paleozoic acc re ted te r ranes of western Nor th America, i n Stevens, C.H., ed., Pre-Jurass ic rocks i n western Nor th American suspect te r ranes : P a c i f i c Sect ion, Soc ie ty o f Economic P a l e o n t o l o g i s t s and M ine ra log i s t s , Los Angel es, p. 7-22.
Ross, C.A., and Ross, J.R.P., 1985, Carboni ferous and E a r l y Permian biogeography: Geology, v. 13, p. 27-30.
Rubin, C.M., and Saleeby, J.B., 1987a, The i n n e r boundary zone of t h e Alexander te r rane , southern SE Alaska - a newly d l scovered t h r u s t be1 t: Geolog ica l Soc ie ty o f America Abs t rac t s w i t h Programs, v. 19, p. 445.
Rubin, C.M., and Saleeby, J.B., 1987b, The i n n e r boundary zone o f t h e Alexander t e r r a n e i n southern SE Alaska, P a r t 1: Cleveland Penninsul a t o southern Rev i l l ag igedo I s l and ; Geolog ica l Soc ie ty o f America Abs t rac t s w i t h Programs, v. 19, p. 826.
Saint-Andre, Bruno de, Lancelot , J.R., and C o l l o t , Bernard, 1983, U-Pb geochronol ogy o f the Bokan Mountain p e r a l k a l i n e g ran i t e , southeastern A1 aska: Canadian Journal o f E a r t h Sciences, v. 20, p. 236-245.
Saleeby, J.B., 1987, The i n n e r boundary zone o f t he Alexander t e r rane i n southern SE Al.aska, P a r t 11: Southern R e v i l l ag igedo I s l a n d (RI t o Cape Fox (CF): Geologica l Soc ie ty o f America Abs t rac t s w i t h Programs, v. 19, p. 828.
Samson, S.D., McClel land, W.C., Gehrels, G.E., Pa tche t t , P.J., and Anderson, R.G., 1987, Nd i so topes and t h e o r i g i n o f t he accre ted Alexander and S t i k i n e te r ranes i n t h e Canadian C o r d i l l e r a : EOS, v. 68, p. 1548.
Samson, S.D., McClel land, W.C., Gehrels, G.E., and Pa tche t t , P.J., 1988, The Alexander t e r rane , Nd and Sr i s o t o p i c evidence f o r a p r i m i t i v e magmatic h i s t o r y : Geolog ica l Soc ie ty o f America Abs t rac ts w i t h Programs, v. 20, p. 227.
Savage, N.M., 1987, Eastern A u s t r a l i a i s an u n l i k e l y source te r rane f o r t he A1 exander te r rane o f southeastern A1 aska : Geol og i c a l Society o f America Abstracts w i t h Programs, v. 19, p. 830.
Schuchert, Charles, 1923, Sf t es and nature of the North American geosyncl ines: Geological Society o f America B u l l e t i n , v. 34, p. 151-230.
S i l b e r l ing, N.J., 1985, Biogeographic s ign i f i cance o f the Upper T r i a s s i c b i v a l v e Monotis i n Circum-Pacif ic suspect terranes, i n Howell, D.G., ed, , T e c t o n o s ~ a p h i c terranes of the Circum-Paci f i c reg ion : Circum-Paci f i c Council f o r Energy and Mineral Resources, Houston, Texas, p. 63-70.
S i l b e r l i n g , N.J., Wardlaw, B.R., and Berg, H.C., 1982, New pa leonto log ic age determinat ions from the Taku terrane, Ketchikan area, southeastern Alaska, i n - Coonrad, W.L., ed., The U.S. Geological Survey i n Alaska: Accomplishments dur ing 1980: U.S. Geological Survey C i r c u l a r 844, p, 117-119.
Souther, J.G., 1971, Geology and mineral deposi ts o f t he Tulsequah map area, B r i t i s h Columbia: Geological Survey o f Canada Memoir 362, 84 pp.
Sut te r , J.F., and Crawford, M.L., 1985, Timing o f metamorphism and u p l i f t i n the v i c i n i t y o f Pr ince Rupert, B r i t i s h Col umbla and Ketchi kan, Alaska: Geological Society o f America Abstracts w i t h Programs, v, 17, p. 411.
Taylor, H.P. Jr., 1967, The toned u l t r a m a f i c complexes of southeastern Alaska, i n Wyl l ie , P.J., ed., U l t ramaf ic and r e l a t e d rocks: New York, John Wiley and S n s , Inc., p. 96-118.
Thompson, T.B., Pierson, J.R., and L y t t l e , T., 1982, Petro logy and petrogenesis of the Bokan Mountain Grani te Complex, southeastern Alaska: Geological Society o f America B u l l e t i n , v. 93, p . 898-908.
Tozer, E.T., 1982, Marine T r i a s s i c faunas of North America: t h e i r s i gn i f i cance f o r assessing p l a t e and te r rane movements: Geologische Rundschau, v., 71, p. 1077-1104.
Twenhofel , W.S:, and Sainsbury, C.L., 1958, F a u l t pa t te rns i n southeastern Alaska: Geological Society o f America B u l l e t i n , v . 69, p. 1431-1442.
Van der Voo, R., Jones, M., Gromme, C.S., Eber le in, G.D., and Churkin, M., Jr., 1980, Paleozoic pal eomagneti sm and northward d r i f t o f the Alexander terrane, southeastern Alaska: Journal o f Geophysical Research, v. 85, p. 5281- 5296.
Werner, L.J., 1977. Metamorphic terrane, nor thern Coast Mountains west o f At1 i n iake, B r i t i s h ~ o l u m b i a : ~ e o l o g i c a l Survey o f Canada Paper 77-lA, p. 267- 269.
Werner, L.J., 1978, Metamorphic terrane, nor thern Coast Mountains west o f A t l i n Lake, B r i t i s h Columbia: Geological Survey o f Canada Paper 78-lA, p , 69- 70.
Wilson, J.T., 1968, S t a t i c o r mob i le ear th , t h e c u r r e n t s c i e n t i f i c r e v o l u t i o n : Proceedings of the American Ph i l osoph i ca l Soc ie ty , v. 112, p. 309-320.
Woodsworth, G.J., Crawford, M.L., and H o l l i s t e r , L.S., 1983, Metamorphism and s t r u c t u r e o f t he Coast p l u t o n i c complex and ad jacen t b e l t s , P r i nce Rupert and Terrace areas, B r i t i s h Columbia: Geolog ica l Assoc ia t i on o f Canada F i e l d T r i p Guide No. 14, 62 pp.
Zen, E-an, and Hammarstrom, J.M., 1984a, Minera logy and a pe t rogene t i c model f o r t h e t ona l i t e a t Bushy Po in t , Rev i l l ag igedo I s l and , Ketch ikan 1 x 2 quadrangle, southeastern Alaska, i n Bar tsch-Wink ler , Susan, and Reed, K.M., eds., The U.S. Geolog ica l Survey K A1 aska : Accompl i shments d u r i n g 1982: U.S. Geolog ica l Survey C i r c u l a r 939, p . 118-123.
Zen, E-an, and Hammarstrom, J.M., 1984b, Magmatic ep ido te and i t s p e t r o l o g i c s i g n i f i c a n c e : Geology, v. 12, p. 515-518.
George E. Gehrel s Department o f Geosciences Un i ve rs i ty o f Ar izona Tucson, Ar i zona 85721 (602) 621-6026
Henry C. Berg 115 Malvern Ave. F u l l e r ton , Cal i f o r n i a 92632 (714) 870-6395
Jones, D.L., Berg, H.C., Coney, Peter , and Ha r r i s , An i ta , 1981, S t r u c t u r a l and s t r a t i g r a p h i c s i g n i f i c a n c e o f Upper Devonian and M i s s i s s i p p i a n f o s s i l s f rom the Cannery Formation, Kupreanof I s l and , southeastern Alaska, i n The U.S.
/ ' ~ e o l o g i c a l Survey i n Alaska: Accompl ishrnents d u r i n g 1979, e d i t 3 by N.R.D. ; A l b e r t , and T r a v i s Hudson, pp. 109-112: U.S. Geolog ica l Survey C i r c u l a r 823-B.
-7 \ . -1 *,-, y 2 r-!,- .-- 2 0 @- 1, - , . * i ., .