Understanding growth-faulted, intraslope subbasins by

AUTHORS

L. Frank Brown Jr. � Bureau of Economic Geol-ogy, John A. and Katherine G. Jackson School of Geo-sciences, University of Texas at Austin, UniversityStation Box X, Austin, Texas 78713-8924;[email protected]

Frank Brown received his B.S. degree in geology andchemistry from Baylor University in 1951 and his M.S.degree and his Ph.D. from the University of Wisconsin,Madison, in 1953 and 1955, respectively. Frank workedfor Standard Oil of Texas (Chevron) in 1955–1957,the Bureau of Economic Geology (BEG) in 1957–1960and 1966–1989, and as an international consultantin 1989–1999. From 1960 to 1966, he was associateprofessor at Baylor University. He was professor of geo-logical sciences at the University of Texas at Austinin 1971–1989 and emeritus professor in 1989–1999.Since 1999, he has been a research professor at BEG,where he continues his studies of the sequence stra-tigraphy of the Gulf Coast of Texas and Mexico.

Robert G. Loucks � Bureau of Economic Geology,John A. and Katherine G. Jackson School of Geosciences,University of Texas at Austin, University Station Box X,Austin, Texas 78713-8924; [email protected]

Robert Loucks is a senior research scientist at theBureau of Economic Geology, working on siliciclasticand carbonate reservoir characterization. He wasthe recipient of the 1999 AAPG Wallace E. Pratt Me-morial Award for Best Paper, the 1982 SEPM Excel-lence of Presentation Award, and the 1991 SEPMExcellence of Poster Presentation Award. Bob servedas the Mideast AAPG Dean A. McGee InternationalDistinguished Lecturer in 1999.

Ramon H. Trevino � Bureau of Economic Geology,John A. and Katherine G. Jackson School of Geo-sciences, University of Texas at Austin, UniversityStation Box X, Austin, Texas 78713-8924;[email protected]

Ramon Trevino received his B.S. degree in geology(Texas A&I University, 1983) and his M.S. degree ingeology (University of Texas at Arlington, 1988). Heworked for Mobil from 1988 to 1992 and receivedan M.B.A. degree from the University of Oklahomain 1994. Since 1995, he has worked on sequence-stratigraphic reservoir characterization at the Bureauof Economic Geology.

Ursula Hammes � Bureau of Economic Geology,John A. and Katherine G. Jackson School of Geo-sciences, University of Texas at Austin, UniversityStation Box X, Austin, Texas 78713-8924;[email protected]

Ursula Hammes obtained her diploma in geology fromthe University of Erlangen, Germany, in 1987, and herPh.D. from the University of Colorado at Boulder in1992. She spent 10 years in industry and joined theBureau of Economic Geology in 2002 as a research

Understanding growth-faulted,intraslope subbasins byapplying sequence-stratigraphicprinciples: Examples fromthe south Texas OligoceneFrio FormationL. Frank Brown Jr., Robert G. Loucks, Ramon H. Trevino,and Ursula Hammes

ABSTRACT

A detailed analysis of Oligocene Frio Formation intraslope, growth-

faulted subbasins in the Corpus Christi, Texas, area indicates that

deposition during relative lowstands of sea level was the main ini-

tiator, or trigger, of growth faulting. Lowstand depocenters on the

low-gradient, upper continental slope comprising basin-floor fan

facies, slope-fan systems, and prograding lowstand delta systems

exerted sufficient gravity stress to trigger major sections of outer

shelf and upper slope strata to fail and move basinward. The faults

sole out deep in the basin, and rotation of hanging-wall blocks mo-

bilized deep-water muds and forced the mud basinward and upward

to form mud (shale) ridges that constitute the basinward flank of

intraslope subbasins overlying footwall fault blocks.

Sedimentation associated with third-order relative falls of sea

level produced load stress that triggered a major regional syndeposi-

tional growth-fault system. Subbasins on the downthrown side of

each arcuate fault segment that constitute a regional fault system are

filled during the lowstands of sea level. Consequently, genetically

similar but noncontemporaneous lowstand depositional systems

filled each successive growth-faulted subbasin trend. The subbasin

stratigraphy becomes younger basinward because the subbasin de-

velopment and fill process extended the Frio shelf edge stepwise

into the Oligocene Gulf of Mexico Basin, coinciding with relative

third-order sea level cycles.

The subbasins have been prolific petroleum targets for decades

and are now the focus of prospecting for deep gas. Lowstand sand-

stones are principal reservoirs, and synsedimentary tectonics produced

AAPG Bulletin, v. 88, no. 11 (November 2004), pp. 1501–1522 1501

Copyright #2004. The American Association of Petroleum Geologists. All rights reserved.

Manuscript received February 23, 2004; provisional acceptance May 6, 2004; revised manuscriptreceived June 11, 2004; final acceptance July 1, 2004.

anticlinal and fault traps and associated stratigraphic pinch-out

traps on the flanks of the structures. Understanding the origin of

the faulted subbasins and their chronostratigraphic relationships

and depositional processes provides a perspective that can improve

deep gas exploration.

INTRODUCTION

Deltaic and other associated coastal reservoirs in the study area

(Figure 1) exhibit closures provided by rollover anticlines and shale

ridges inferred to have been activated by sediment discharge of river

systems and consequential progradation of deltaic systems. Complex

extensional fault systems associated with these anticlines also pro-

vide abundant fault-trap opportunities.

Sediment composing major global delta systems was supplied

by the world’s principal rivers, which, during the Tertiary, discharged

along thinned continental crustal margins (e.g., Niger, Amazon, and

ancestral Mississippi). Tertiary reservoirs and synsedimentary struc-

tures are the principal hydrocarbon components in the Niger Delta

and northern Gulf of Mexico Basin. Many smaller fluvial systems

also entered the northwestern margin of the Gulf of Mexico Basin

throughout the Tertiary. Most structures associated with these del-

taic systems are syndepositional, but postdepositional reactivation

of faults also produced traps for younger, onshelf, deltaic, and coastal

facies. The term ‘‘onshelf’’ is used herein instead of simply ‘‘shelf’’

to avoid connoting sediment deposited under actual shelf environ-

ments (i.e., below maximum storm-wave base). Wire-line log and

various vintages of two-dimensional (2-D) seismic data guided most

of the early exploration directed toward identifying shallow-buried

shelf structures.

Long-term oil and gas production in the Gulf of Mexico Basin

has significantly depleted reserves in traditional onshore and offshore

fields producing from shallow to medium depth ranges (i.e., 6000–

12,000 ft [2000–4000 m]) associated with regional growth-fault

systems (Figures 1–3). Nonetheless, deep gas reserves exist, and

because of increased demand and improved gas economics, these

deep gas reserves (i.e., >12,000 ft [>4000 m]) in lowstand sand-

stone reservoirs are currently being explored. However, finding

deep reserves requires modification of earlier conventional inter-

pretation techniques and concepts. Robust application of sequence-

stratigraphic and depositional principles is the recommended meth-

od to search for deeper gas targets.

Conventional wisdom indicates that deeper gas in growth-

faulted subbasins is restricted mostly to lowstand reservoirs in syn-

depositional structural and/or combination traps. During a relative

lowstand of sea level, sediments were deposited basinward of ex-

isting highstand shelf edges (Figures 2, 3). Lowstand incised-valley

systems transported sediment to shelf margins, where the entrenched

rivers eroded notches (not to be confused with major submarine

canyons) in the shelf edge. Small ephemeral deltas were developed

associate. Her main research focus is in clastic andcarbonate sequence stratigraphy, depositional sys-tems, and image analysis.

ACKNOWLEDGEMENTS

The State of Texas Advanced Resource Recovery Pro-gram supported this research. Patricia Montoya andRandy Remington, geophysical associates at the Bu-reau of Economic Geology, contributed to the workon this project. Mike Pawelek of IBC Petroleum, Inc.,Gary Biesiedecki and Gary Miller of SABCO Oil andGas Corporation, and Matt Hammer of Royal Explo-ration Company, Inc., provided industrial support.We especially extend our gratitude to WesternGecofor use of seismic data. We thank David Jennette,Susann Doenges, and David Stephens, respectively,for critical reviews, technical editing, and graphicssupport during manuscript preparation.Major credit for ideas expressed in this paper aredue to Robert M. Mitchum Jr., John Sangree, andJohn C. Van Wagoner and their former Exxonassociates, including Peter R. Vail and Henry W.Posamentier, for their original pioneering researchin the field of siliciclastic sequence stratigraphy.These workers all contributed significantly not onlyto the entire field, but also to the valid, originalstatic sequence model.In addition, although conceptual differences exist be-tween our sequence ideas and inferred processes pro-posed earlier by William E. Galloway and his associatesand students, we are deeply indebted to them for pro-viding a regional perspective of the character anddistribution of Frio depositional systems. Our differ-ing views are based on data and concepts unavailableto them and other prior workers who concentratedon the Tertiary systems of the Texas Gulf Coast Basin.To all of the numerous earlier contributors to this vitalpetroleum region, we extend our professional grati-tude for their research efforts. For example, early workby both Merle C. Israelsky beginning in 1935 andS. W. Loman in 1949 contributed documentation of thecyclicity and deltaic facies characterizing the Tertiaryrocks of the Gulf of Mexico Basin. These two geolo-gists, among many others, such as pioneer micropa-leontologists Helen Jean Plummer (Bureau of EconomicGeology), Julia A. Gardner, Alva C. Ellisor, and EsterR. Applin (former University of Texas students of J. A.Udden, director, Bureau of Economic Geology, 1915–1932), who first established most benthic foraminiferalzones, are true giants in Gulf Coast Tertiary stratigraphyand micropaleontology and therefore deserve to becredited even long after their contributions. Likewise,William L. Fisher and J. H. McGowen contributed orig-inal concepts of siliciclastic depositional systems anal-ysis applied to the Paleocene and Eocene Wilcox Group.We thank the Geology Foundation of the John A.and Katherine G. Jackson School of Geosciencesat the University of Texas at Austin for funding thecolor figures and the partial page charges.

1502 Growth-Faulted, Intraslope Subbasin Analysis by Applying Sequence-Stratigraphic Principles

at the mouths of entrenched valleys. The deltas, which

are shallow-water depositional systems, were incapable

of prograding into deep water on the continental slope

of the Gulf of Mexico Basin. Oversteepened deltaic sed-

iments repeatedly slumped from the distal delta front

and flowed down the slope surface by gravity (turbidity

and debris) flow. Density-flow sediments in basin-floor

depressions or channels (Figure 3) accumulated wher-

ever the gradient of the slope surface diminished and

hydraulic jumps occurred. Therefore, reservoirs in low-

stand systems tracts are fundamentally different from

those in highstand and transgressive systems tracts.

Lowstand depositional systems also were subjected

to contemporaneous structural activity that progres-

sively modified the configuration of slope and basin

floors. Growth-fault subsidence and uplift rates of dis-

placed shale or salt ridges resulted in highly variable

subbasin accommodation rates. These variations im-

posed characteristic parasequence stacking patterns and

areal distribution on lowstand delta systems. Likewise,

density-transported sediments were distributed to areas

of maximum accommodation. Consequently, poten-

tially deeply buried sandstone reservoir facies that were

deposited basinward of shelf edges lack the continuity

and predictability that characterized shallower reser-

voirs deposited on relatively stable shelves during high-

stands and transgressions. Lowstand sandstone reservoir

discontinuity and pinch-out potential onto syndeposi-

tional structures (Figures 2, 3) require rethinking of ex-

ploration strategies from dominantly postdepositional

domal and superimposed fault closures to combination

trapping by updip and lateral reservoir pinch-outs re-

lated to syndepositional structural movement.

Models of growth-faulted lowstand depositional sys-

tems were proposed more than a decade ago by Vail

(1987), Sangree et al. (1990), and Mitchum et al. (1994),

among others, but our study expands their models to

focus on depositional processes that occurred during

relative lowstands of sea level, which played a major

role in initiating growth faulting and filling of resulting

intraslope subbasins (Figures 2, 3). A chronostratigraph-

ic sequence framework permits precise correlation and

prediction of timing and distribution of reservoir dep-

osition and structural development. Understanding

both of these factors complements the use of three-

dimensional seismic data.

CONVENTIONAL CONCEPTS APPLIED TOPAST EXPLORATION

In growth-faulted areas, some stratigraphers constructed

correlation frameworks based on marine-condensed sec-

tions or their contained maximum flooding surfaces

while ignoring or denying relative changes in sea level

that induced subaerial and submarine erosion and

Figure 1. Location map of the detailed study area along thesouth Texas Coast. Intraslope, growth-faulted subbasins dis-cussed in this paper are noted by numbers: (1) lower NuecesValley subbasin; (2) upper Nueces Bay subbasin; (3) CorpusChristi Bay: Encinal Channel subbasin (west 3A) and CorpusChristi Channel subbasin (east 3B); (4) Red Fish Bay subbasin;(5) Mustang Island (nearshore) subbasin; and (6) MustangIsland (offshore) subbasin. Fault traces are generalized and onFrio horizons. Seaward, each subbasin corresponds to a pro-gressively younger Frio third-order sequence. The center of themap is at lat. 27.78jN, long. 97.26jW. Faults are generalizedfrom 3-D seismic and well-data analyses.

Brown et al. 1503

type 1 unconformities (Edwards, 1980; Galloway et al.,

1982; Galloway 1989a; Tyler and Ambrose, 1985,

among many authors; see Galloway et al., 1982, and

references therein). This framework led to the view

that onshelf and basinal sandstone facies that were

deposited between successive marine-condensed sec-

tions are time equivalent. Several workers incorrectly

consider deep-water slope-fan facies to be time equiv-

alent to shallow-marine, onshelf, wave-dominated, del-

taic facies by extending their time lines coincident with

maximum flooding surfaces through many successive

intraslope subbasins, some of which had not yet been

created (Edwards, 1984, among other publications).

Marine-condensed facies containing maximum flooding

surfaces were deposited from pelagic suspension and

by in-situ seafloor deposition under biogenic and authi-

genic processes on shelves as well as in deep water. It is

correct that marine-condensed sections are operational

time lines, but that does not mean that all sandstone

facies deposited between successive marine-condensed

sections are time equivalent.

Onshelf current- and wave-dominated deposition

in shallow-marine deltas and coastal strike systems oc-

curred by totally different processes than those of slope

fans and basin-floor fans. Furthermore, onshelf and off-

shelf depositional episodes are not only depositionally

and environmentally different, but they were deposited

during temporally discrete time intervals. To consider

them time equivalent leads to serious miscorrelations.

The fact that similar microfauna and microflora

characterize marine-condensed sections, whether depos-

ited in shallow or deep water, further encourages some

workers to infer that all sediments between the same

marine-condensed sections are time equivalent (Ed-

wards, 1984). This idea pervaded stratigraphy for dec-

ades, when paleontologists inferred that thick coastal

Figure 2. Highly schematic block diagram illustrating depositional systems tracts operative during relative lowstands of sea level,middle and late Oligocene epoch. Distribution of fluvial systems and coastal systems are modified after Galloway et al. (1982) andGalloway (1986). Sketch infers paleogeography during the slope-fan deposition soon after activation of growth-fault movement. Theshelf is subaerially exposed, and sediment is bypassing the shelf through incised river systems. See legend on Figure 3 for symbol definitions.


deltaic and fluvial systems existing stratigraphically be-

tween marine-condensed sections were deposited under

similar neritic environments because their paleobathy-

metric maps used the abundant neritic fossils in deeper

water bounding marine-condensed sections. Their maps

were valid for water depths during maximum flooding

but not for the intervening deltaic deposition.

More recently (Brown et al., 2003a), research has

begun to address the repetitive and dynamic stratigraph-

ic history of growth-faulted subbasins and their inferred

stages of structural instability and depositional and ero-

sional episodes. For decades, many published papers,

principally about the Gulf of Mexico Basin, have de-

scribed and offered interpretations and models address-

ing the geologic history of unstable continental margins

that are characterized by syndepositional, down-to-the-

coast normal faults (i.e., Galloway et al., 1982; Winker

and Edwards, 1983; Galloway, 1989b; Ewing, 2002).

None of the studies of growth-faulted continental mar-

gins include results based on a thorough test of the ap-

plicability of sequence-stratigraphic processes to provide

a model that addresses all seismic and wire-line-log

observations. Such a test is the principal goal of the

research discussed herein.

NEW APPROACHES TOUNDERSTAND DEVELOPMENT OFGROWTH-FAULTED SUBBASINS

Sequence-Stratigraphic Methods

A valuable key stratigraphic approach or tool that evolved

from our studies (Brown et al., 2003b) is a composite

wire-line log that places the lithostratigraphy of a sub-

basin into a chronostratigraphic sequence framework.

The tool, named a ‘‘site-specific sequence-stratigraphic

section (S5) benchmark chart’’ (Figure 4), is a stratigraph-

ic product for summarizing all available sedimentary-

and time-related information into a single, integrated

display. For example, systems tracts, stratigraphic sur-

faces, relative sea level cycles, petrophysics, and age

data can be placed in chronostratigraphic context and

correlated basinwide. S5 benchmark charts are based

on composites of wire-line-log sections of several key

wells spliced to avoid faulted-out sections and to dis-

play the most complete stratigraphic succession. Conse-

quently, the S5 benchmark chart captures the record of

maximum depositional history and cycles recorded in

the subbasin strata. For example, sequence-bounding

unconformities and parasequence maximum flooding

surfaces of various frequencies are chronostratigraphic

surfaces. Except for diachronous ravinement surfaces

at the base of transgressive systems tracts, systems tracts

are bounded by chronostratigraphic unconformities

and maximum flooding surfaces. Internally, systems

tracts comprise diachronous lithofacies successions. Fur-

thermore, systems tracts link depositional processes and

systems to relative changes of sea level.

A sequence model by Vail (1987) and Mitchum et al.

(1994) clearly illustrates sequence-stratigraphic architec-

ture of growth-faulted successions and the relationship

to initiation and evolution of faulting. We fully agree

with the static architectural model of Mitchum et al.

(1994) but have added a dynamic scenario (Figures 3, 5)

to it.

Application of Sequence Concepts and Ideas

Serving as examples, the Corpus Christi Bay and Red

Fish Bay subbasins (Figure 1, subbasins 3A, 3B, and 4,

respectively) in the greater Corpus Christi Bay area,

Texas, are genetically similar to many growth-faulted

subbasins that were filled during half a dozen second-

order (�10-m.y.) Tertiary cycles along the northwest-

ern margin of the Gulf of Mexico Basin. We under-

took detailed studies of the subbasins in Figure 1 to

document their sequential (cyclic) erosional, deposi-

tional, and tectonic history to create a dynamic model

that can be applied elsewhere in Tertiary strata of the

Gulf of Mexico Basin and in other basins worldwide

(Figures 3, 5). Our studies indicate that analyzed sub-

basins were filled during third-order lowstand depo-

sitional events of the Oligocene Frio Formation, a major,

petroleum-producing lithostratigraphic unit along the

Texas and Louisiana coasts. Each subbasin was the fo-

cus of lowstand deposition, serving as a depocenter

during one third-order, sparsely fourth-order (Trevino

et al., 2003), relative lowstand of sea level. Slope sys-

tems compose most of the sedimentary volume of each

depocenter (Figures 6–9).

Structurally, the subbasins are located on the basin-

ward, downthrown, hanging-wall side of regional growth-

fault systems that, in plan view, comprise many typical-

ly connected and aligned, basinward-concave (arcuate)

fault segments (Figures 1, 2), which are collectively

called ‘‘flexures.’’ Evidence suggests that fault timing

and approximate age of specific sedimentary fill are

similar in the hanging-wall blocks of each regional fault

system. Consequently, the factor(s) activating faults

is (are) assumed to have existed simultaneously for

tens of miles along the Oligocene shelf margin. Seismic

Brown et al. 1505

data (Figures 6, 10) document arcuate fault segments

on the basinward flank of a shale ridge (salt ridges in

other areas) mobilized during fault subsidence of an

older, landward, growth-faulted intraslope subbasin.

Chronostratigraphic Correlation

Tracing seismic reflections, as proposed by Vail et al.

(1977), best carries out chronostratigraphic correlation.

Except for major erosional unconformities and second-

ary impedance boundaries (e.g., multiples, fluid inter-

faces, and diagenetic horizons), reflections represent

impedance contrasts that mark the change above and

below condensed shale drapes at tops of parasequences

or parasequence sets. Generally, these widespread and

thin shale beds parallel stratal surfaces and may persist

laterally through facies changes.

Correlation of seismic reflections generally pro-

vides greater precision than correlation of microfossils.

First or last occurrences of taxa marking the boundaries

of a biozone are sparsely found at stratigraphic positions

where the fossil-designated marker can be applied to a

traceable log or seismic event, and suppression of bio-

zone boundaries by high sedimentation rates locally

introduces significant limitations in establishing valid

chronostratigraphic faunal zone boundaries. When re-

flections are calibrated with conformable surfaces on

wire-line logs, accurate tracing of the surfaces in a sin-

gle sequence or systems tract using wire-line logs is

another means of chronostratigraphic correlation.

Seismic reflections from onshelf strata are relatively

parallel and continuous, reflecting the shallow-marine,

laterally continuous coastal strata. The high-continuity

seismic reflections and equivalent wire-line-log correla-

tions exhibited by onshelf strata are commonly referred

to as ‘‘railroad tracks.’’ The only major onshelf discon-

tinuities are lowstand incised valleys that eroded into

highstand systems during falling relative sea level and

display orders-of-magnitude-deeper erosion than com-

ponent distributary or other highstand-aggradational

Figure 3. Diagrammatic dip cross section showing formation of successive growth-faulted subbasins. Note that each subbasin is filledwith genetically similar but diachronous depositional systems. Note: this figure’s legend also applies to Figures 2, 4, 5, 7, 8, 12, and 14.Based on Vail (1987) and Mitchum et al. (1994). Note that 3 and 4 equal third- and fourth-order sequence events throughout this report.


fluvial-channel fills deposited during relative sea level

rise (i.e., transgression or highstand) (Van Wagoner

et al., 1990; personal observation, senior author).

In contrast, lowstand gravity-flow facies are highly

discontinuous in a subbasin because they typically are

transported into areas of irregular seafloor topography.

Consequently, correlation of individual basin-floor fans

or slope fans is highly challenging (Figures 7–9). Basin-

floor fans may rest on the same unconformity and yet

not represent contemporaneous deposition.

Sandstones in slope fans are the most discontinuous

systems in a subbasin because of autocyclic shifting of

depositional sites. Proximal parts of slope fans are typ-

ically thin but thicken toward the axes of basins, where

the fans may undergo compaction and tend to amal-

gamate into very thick, highly contorted, sandstone

bodies comprising the basinward parts of several high-

frequency fan lobes. Continuity and, hence, approxi-

mate correlation of sandy facies in individual fans is

poor, but general correlation of sand-rich facies bundles

is fair in dip sections (Figures 6, 7). In strike profile

(Figure 8), the fans exhibit lenticular geometry with

abrupt facies terminations, making any correlation ques-

tionable. In dip sections, some workers incorrectly cor-

relate proximal, updip-fan sandstones with deeper sand-

stone units by equating shallower sandstones with deeper

ones simply in the order of downward well penetration

or occurrence (Figure 9). This practice results in mis-

correlations because a single, thick, deep, basinal, amal-

gamated sandstone package may be equivalent to several

individual, thin, updip, fan sandstones (Figure 9). Sand-

prone packages or zones may be delineated and cor-

related, but the individual sandstones in the packages

display neither continuity nor time equivalence.

Stages in Development of Growth-Faulted Subbasins

Intraslope subbasin development history can be divided

into several genetic stages (Figure 5). We infer that

the stages were synchronized with relative cycles of sea

level, during which depositional systems and systems

tracts were deposited. Sequences are the products of the

Figure 3. Continued.

Brown et al. 1507

Figure 4. S5 bench-mark chart for EncinalChannel subbasin 3A,Corpus Christi Bay, Texas.Composite log exhibitscolor-coded sequenceboundaries, flooding sur-faces, and systems tracts,among other stratigraphicdata. Type 1 unconformi-ties and flooding surfacesconstitute chronostrati-graphic surfaces that maybe used to construct atime-stratigraphic frame-work for the subbasin.The 27.49-Ma unconform-ity represents a majorrelative fall of sea level(Hackberry age of Curtisand Echols, 1985) accom-panied by fluvial entrench-ment and submarinecanyon erosion. Comparewith Figures 12 and 14.


Figure 5. Inferred stages in the tectonic and depositional history of Frio intraslope subbasins along the basinward side of a regionalgrowth-fault system, middle and lower Texas Coast. Stages 1–7 are described in the text. Red arrows indicate change in relative sealevel.

Brown et al. 1509

interplay of sediment supply, erosion, gravity tectonics,

relative cycles of sea level, and changing accommodation

rates. Process stages were repetitive, and we propose that

they were driven principally by third-order (�1–2 m.y.)

composite eustatic sea level cycles (Van Wagoner et al.,

1990) that successively produced and filled resulting

subbasins. However, as our studies in subbasins 4 and 5

(Figure 1) suggest, fourth-order sequences can also

initiate these processes (Trevino et al., 2003; Hammes

et al., in press).

Stage 1

During late relative sea level highstand, deltaic deposi-

tional systems prograded across the continental shelf to,

or near, the shelf edge (Figure 5A). The low-gradient,

highstand fluvial systems stored the sand-rich coarser

fraction of their sediment load in channel fill and point

bars. The relatively muddy sediment load of highstand

deltaic depositional systems initially accumulated on

the upper slope. Oversteepening of the muddy delta-

front facies resulted in slumping of the upper slope and

redeposition on the lower slope.

Stage 2

During a later relative lowstand of sea level, lowstand

incised-valley systems transported their entire sediment

loads (including coarser stored component) to shelf mar-

gins, where these entrenched rivers eroded notches in

their respective shelf edges (Figure 5B). Small ephemeral

deltas developed at the mouths of entrenched valleys.

Shelf-edge deltas were shallow-water lowstand deposi-

tional systems that were incapable of prograding into

deeper water on the continental slope. Oversteepened

deltaic sediments slumped from the distal delta front and

flowed down the slope surface by gravity flow. Density-

flow sediments stacked in depocenters to form basin-

floor fans (Figure 5B).

Stage 3

Lowstand deposition continued on the continental slope

while the rate of relative fall of sea level decreased

(Figure 5D, E). This deposition continued until leveed

slope channels constructed aggradational slope fans that

onlapped the upper slope and downlapped the type 1

surface or any basin-floor fan. Continued deposition

Figure 6. Three-dimensional seismicprofile aligned parallel to the paleoslopein the Encinal Channel subbasin (3A;Figure 1). Profile displays the growth faultresponsible for generating the subbasin.Increased accommodation rates near thegrowth fault produced proximal expansion.Uplift of a shale ridge produced sufficientbathymetric relief to cause thinning of bothslope-fan and deltaic systems onto thestructural and seafloor uplift. Seismic datacourtesy of WesternGeco.


Figu

re7

.Dip

-alig

ned

wir

e-lin

e-lo

gse

quen

ce-s

trat

igra

phic

cros

sse

ctio

nA

A0 ,R

edFi

shBa

ysu

bbas

in.I

ndiv

idua

lhig

h-fr

eque

ncy

delta

icsy

stem

s(c

ompo

site

sequ

ence

sof

Mitc

hum

etal

.,19

94),

com

pose

this

thir

d-or

der

Frio

delta

icsy

stem

(seq

uenc

e4

ofFi

gure

1).S

ands

tone

cont

ent

inon

eof

the

high

-fre

quen

cyde

ltaic

syst

ems

isdi

spla

yed

inFi

gure

11.F

aults

are

base

don

3-D

seis

mic

and

wel

l-log

anal

yses

.Se

eFi

gure

3fo

rle

gend

.

Brown et al. 1511

Figu

re8

.Str

ike-

alig

ned

wir

e-lin

e-lo

gse

quen

cest

ratig

raph

iccr

oss

sect

ion

BB0 ,R

edFi

shBa

ysu

bbas

in,e

xhib

itsla

tera

lrel

atio

nshi

psam

ong

low

stan

dle

veed

slop

efa

ns,a

ndde

ltaic

syst

ems

(seq

uenc

e4,

Figu

re1)

wer

ede

posi

ted

byau

tocy

clic

ally

shift

ing

slop

ech

anne

ls.

See

Figu

re3

for

lege

nd.


of thick slope fans created substantial depocenters

(Figures 2, 5E) basinward of entrenched river mouths.

Several fourth- and fifth-order fans typically composed

a third-order slope fan (Figures 7, 8).

In dip profile, slope fans are typically lenticular to

wedge shaped, but strike sections exhibit mounded seis-

mic geometry. The geologic record shows that major

blocks of outer shelf and upper slope have failed and

shifted basinward, producing a major evacuation em-

bayment in the shelf margin. An example is the Hack-

berry embayment of southeastern Texas and south-

western Louisiana (Halbouty and Barber, 1961; Ewing

and Reed, 1984). The slump-generated embayment oc-

curred during a relative fall in sea level at about 27.49 Ma

(Figure 4). Rapid subaerial exposure of about 600 ft

(200 m) of outer shelf and upper slope eliminated sub-

merged buoyancy support (per Archimedes’ principle).

We agree with Winker and Edwards (1983) that de-

watering of coastal aquifers along the failure zone per-

haps lubricated the rupture zone, exacerbating the

basinward slide of the large block. We do not, however,

invoke this process of slumping to explain most low-

stand systems tracts.

Stage 4

The occurrence of major lowstand depocenters basin-

ward of arcuate growth-fault segments indicates that

stress created by the intraslope depocenters overloaded

the previously deposited unstable, mud-rich slopes. Even-

tually, the loading stress produced failure of large sec-

tions of the outer shelf and upper slope that slowly

slipped downward along curved (fault) failure surfaces

(Figure 5D). Dip of fault surfaces eventually flattened

downward to produce rotational movement of the

hanging-wall block (Figure 3). Slope-fan deposition con-

tinued to displace and mobilize the underlying, high,

pore-pressured muds, thus rotating the more cohesive

hanging-wall block. Resulting greater accommodation

rates (Figure 5D) near the growth fault accommodat-

ed deposition of thicker proximal facies. Eventually,

subsidence-generated accommodation rates diminished,

and fans thinned basinward onto uplifted shale ridges,

producing a landward dip of slope-fan sandstone bodies.

Mobilized older mud-rich units near the base of the

hanging-wall block were slowly pushed basinward and

upward into a ridge (Figures 2, 3, 5D) that eventually

became the basinward margin of the growth-faulted

Figure 9. Schematic dip representation of amalgamation of high-frequency, autocyclic slope fans (subbasin 2, Figure 1) along theaxis of upper Nueces Bay faulted intraslope subbasin. Incorrect correlations of sands are illustrated in red. Correct correlation ofsandstones deposited during higher order cycles is illustrated in green (abandonment surfaces), which meld into several fourth-orderslope fans. Attempts to correlate each proximal slope-fan sandstone unit with a single amalgamated axial basinal slope fan (e.g., SS1proximal to SS1 axial) lead to major miscorrelations. Slope fans in strike section (see Figure 8) are discontinuous and make correlationhighly questionable.

Brown et al. 1513

graben. With downslope uplift, the faulted hanging-

wall block attained complete closure of the intraslope

subbasin (Figures 3, 5, 6).

Stage 5

Shale-ridge growth and fault-surface friction decreased

the rate of hanging-wall subsidence, permitting slope-

fan deposition to elevate the floor of the subbasin (by

continued deposition) until water depth was suffi-

ciently shallow to permit the small, entrenched, river-

mouth delta system to prograde over the slope deposits

(Figure 5E). These deltas extended the shelf edge basin-

ward. Because subsidence (accommodation) rates are

initially high at the onset of lowstand delta pro-

gradation, deltaic facies also thicken (expand) toward

the fault (Figures 3, 10). High-frequency sequences,

if deposited, are typically components of third-order

lowstand-prograding systems (Van Wagoner et al.,

1990; Brink et al., 1993; Brown et al., 1995).

The high-frequency deltaic systems are highstand

tracts of fourth- or fifth-order lowstand-prograding

systems (Van Wagoner et al., 1990). Therefore, high-

frequency type 1 unconformities may erode the com-

ponent highstand tracts, and high-frequency basin-

floor fans are then deposited basinward at the toe of the

deltaic slope (Figure 3). The high-frequency fans are

components of the third-order lowstand-prograding

wedges and have been called ‘‘shingled toe-of-slope’’

fans (Vail, 1987, p. 10). Some workers consider these

shingled fans to represent random slumping from shelf-

edge deltas (Galloway, 1986, p. 10), but they always rest

on fourth- or fifth-order type 1 surfaces (observation of

senior author). The higher frequency deltas typically

thin onto the sea bottom, which is being progressively

uplifted over salt or, in the case of the current study

area, shale ridges.

Because of higher subsidence rates next to growth

faults and uplift of the seafloor basinward of the fault

(Figures 2, 6), the lowstand slope fan and deltaic sys-

tems dip and expand in thickness toward the principal

growth fault and thin onto a domal structural configu-

ration commonly called a ‘‘rollover anticline’’ (Figures 3,

5, 10, 11). These structures are primary petroleum

traps in growth-faulted subbasins. Sand-rich, deltaic,

lowstand-prograding wedges are reservoirs on rollover

anticlines (Figure 6). The distal parts of some lowstand

depositional systems were deposited basinward of shale

or salt ridges (Figure 3); hence, these distal segments

Figure 10. Isopach map of Frio (sub-basin 4, Figure 1), third-order lowstanddeltaic wedge (pw) deposited in Red FishBay subbasin. Cool colors indicate thickervalues. Greatest thickness = 2640 ft (804 m).Map illustrates thickening (expansion) to-ward growth faults, documenting faultmovement during deposition of the deltasystems. Expansion is best exhibited indip-aligned sections, such as Figure 7.Arrows indicate approximate location ofsediment input via incised valleys. Thecenter of the map is at lat. 27.86jN,long. 97.11jW. Faults are based on 3-Dseismic and well-log analyses.


of the systems tracts display only regional depositional

thickness variations and were not expanded across con-

temporaneous faults (Figure 3).

Stage 6

Note that until this point in time, the only deposition

on the previous highstand delta plain (Figure 5A, E)

occurred in the incised valley(s), whereas interfluves

were subaerially exposed. When the relative sea level

began to rise at a rate greater than sediment was sup-

plied to the lowstand deltas, retrogradation of shore-

lines marked the onset of regional transgression or

retrogradation. The delta plain of the third-order low-

stand delta system was flooded and became a shallow

submerged ramp or shelf between the shale ridge and

the growth fault (Figure 5F). The shale ridge served as

a buttress that defined the location of a new shelf edge.

Lowstand deltas onlapped and downlapped uplifted

shale-ridge structures (Figures 5F, 6).

Following active deposition, marine-condensed en-

vironments expanded out of isolated parts of the basin

and contemporaneously blanketed both shelf and deep

basin. However, as stages 1–5 illustrate (Figure 5A–E),

facies deposited between successive maximum floods

are not necessarily time equivalent, and correlation using

this concept may introduce chronostratigraphic errors.

Stage 7

During the latter part of the third-order relative cycle

of sea level, highstand delta systems prograded across

the submerged ramp to the new shelf-edge location

(Figure 5G), and during a subsequent relative fall of

sea level, the highstand river again became entrenched,

and its sediments initiated another lowstand depocenter

that eventually resulted in another growth-faulted sub-

basin (Figures 2, 3). Other previous highstand rivers

along the coast similarly became entrenched, and col-

lectively, the faulted depocenters defined another re-

gional flexure or growth-fault system with subbasin

hanging-wall blocks buried by younger lowstand sedi-

ments (Figure 2).

Control on the Location of Incised-Valley-Fill Systems

The areal intersection of growth faults (Figure 2) may

have produced minor strike-slip accommodation faults

normal to the average regional trend of the faults be-

cause rates of movement along normal faults were

not necessarily the same in adjacent fault segments.

After maximum flooding, onshelf rivers avulsed from

previous fluvial axes, which exhibited paleotopographic

relief caused by differential sand and mud compac-

tion. The positive paleotopographic axes deflected

river flow laterally during the next cycle. When the

next highstand rivers incised because of falling rel-

ative sea level, their entrenched mouths notched the

shelf edge at positions lateral to the previous point

sources. Entrenched rivers commonly followed paths

that crossed previous growth faults at fractured and

faulted intersections of two adjacent arcuate fault seg-

ments (Figure 2).

Figure 11. Net sandstone mapof high-frequency deltaic systemscomposing the Frio sequence 4(Figures 1, 3, 12) third-orderdelta system in Red Fish Baysubbasin. Note increasing thick-ness of section with proximityto growth fault. The center ofthe map is at lat. 27.80jN, long.97.17jW. Faults are based on 3-Dseismic and well-log analyses.

Brown et al. 1515

SIGNIFICANCE IN PETROLEUM EXPLORATION

Sequence Perspective

Understanding the tectonic and depositional factors gen-

erating intraslope subbasins improves understanding

of reservoir architecture and trapping potential in

their hydrocarbon systems (Figures 12, 13). Predicting

reservoir discontinuity and lateral facies changes in the

lowstand systems tracts depends on the understanding

of the interplay of depositional processes and syndepo-

sitional tectonics (Figures 12–14) that are temporally

related to relative changes in sea level (i.e., sequence

stratigraphy). Routine geologic tasks in production

Figure 12. Chronostratigraphic diagram (Wheeler, 1958) of Frio depositional sequences 2–6 and their relationship to geologic age,microfossil biozones, and other time-related factors. Note that benthic zone ages (Berggren et al., 1985) have been converted to new ages(Berggren et al., 1995) using a timescale program (GEOMAR, 2002) located at http://www.odsn.de/odsn/services/conv_ts/conv_ts.html onthe basis of more recent unstable isotope and oxygen stable isotope ratios (Abreu and Haddad, 1998), and that ages of T1 unconform-ities have been adjusted from Haq et al. (1987) to those of Hardenbol et al. (1998). Marine condensed sections (i.e., maximum floodingsurfaces) have been readjusted from Haq et al. (1987) to Wornardt et al. (2001). See Hardenbol et al. (1998) for further credits andinformation. Polarity chronozones from Cande and Kent (1992, 1995).


operations, such as reservoir correlations and accu-

rate structural mapping, benefit from using a reliable

sequence-stratigraphic framework (Figures 4, 12) that

provides chronostratigraphic map envelopes and seis-

mic reflections that are generated by essentially chrono-

stratigraphic impedance boundaries.

Commonly, lithofacies inferred to be correlative are

incorrectly correlated by assuming that genetically simi-

lar wire-line-log facies patterns were deposited con-

temporaneously. Placing the stratigraphy and structure

of a field into a sequence-stratigraphic context pre-

cludes miscorrelation of reservoirs and incorrect struc-

tural assumptions based on traditional log-facies cor-

relations (Figure 12). Log-facies maps are useful only

if facies are time equivalent, not simply because they

look alike. Similarly, detailed structural contour maps

of a diachronous stratigraphic surface introduce false

assumptions into information required for production

and field-development decisions. Correlating field pro-

duction and engineering information in a sequence

framework is the only method to ensure large-scale

comparison of similar temporal events or age-equivalent

data needed to record, compare, and interpret signif-

icance of field data.

Figure 12. Continued.

Brown et al. 1517


Petroleum Geology

Intraslope subbasins contain traps, reservoirs, and seals

that are typical of river-dominated deltaic systems.

Intraslope subbasins (Figures 1, 3, 14), however, are

bounded by major fault systems that are migration path-

ways linking reservoirs and source beds comprising deep-

marine mudstones from within the overpressured parent

basin. Magara in Galloway et al. (1982, p. 24) discussed

the elements of the Frio hydrocarbon system, including

source beds, maturity, expulsion, and migration infor-

mation. Deeply buried, hot, overpressured strata trapped

below the shelf by regional second-order transgressive

surfaces and marine-condensed facies provide a re-

gional seal (Figures 4, 6, 14). Petroleum-bearing fluids

move from a deep geopressured environment upward

to permeable fault gouge (fault rock) along fault planes

until the fluids reach potential sandstone reservoirs.

This is the only mechanism for hydrocarbons to reach

onshelf reservoirs above the regional seal. Consequent-

ly, most hydrocarbons are trapped in lowstand reser-

voirs below the regional seal.

Trapping in prograding-wedge deltaic sandstones oc-

curred on hanging-wall rollover anticlinal or crestal fault

closures or by updip pinch-out of reservoir facies against

sealed growth faults in the footwall block (Figures 3,

14). Deltaic sandstones are base sealed by mud-rich

prodelta and top sealed by delta-plain facies. The po-

tential for updip pinch-out of sandstone facies adds ex-

cellent combination structural-stratigraphic trapping po-

tential. These elements make this petroleum system

one of the best encountered in siliciclastic provinces.

Basin-floor fans that are typically blocky and mas-

sive provide the maximum potential for stratigraphic

trapping because most of them pinch out in all direc-

tions and are overlain and underlain by basinal shale

facies (Figures 5B, 12, 14). Fans may be both sealed and

sourced by adjacent deep-basin condensed sections.

Third-order fans rest on surfaces that are concordant

basin equivalents of sequence-bounding unconformi-

ties (Figures 12, 14). Early lowstand and density flows

that occurred before shale-ridge uplift provided a basin-

ward barrier, permitting bypass of the local hanging wall

and deposition much farther into the basin. In contrast,

although shingled fans at the toes of high-frequency

lowstand deltaic systems (Figures 12, 14) remained in

the hanging-wall subbasin, they exhibit poor updip seals

because of feeder channels.

Slope fans are composed dominantly of shale and

siltstone. Potential reservoir facies are thin, blocky,

channel-fill, and digitate levee-splay facies. Slope-fan

facies are highly discontinuous and limited in volume,

lacking lateral continuity. Levee facies are characteris-

tically tight because of high silt and mud content. Slope-

fan channels exhibit limited updip trapping and seal,

because they are conduits for fluids to exit into incised-

valley fill (Figure 3). Hanging-wall block rollover clo-

sures and extensional (crestal) faults are the only viable

traps. In this area, exploration for slope channel-fill

facies with adequate trapping requires random drilling

that might intersect a structurally trapped channel.

SUMMARY AND CONCLUSIONS

Our depositional model of progressively younger low-

stand depositional systems in successively younger and

basinward-stepping subbasins (Figures 12, 14) pro-

vides a mechanism to explain (1) growth-fault genesis,

(2) occurrence of lowstand systems in subbasins, and

(3) diachroneity of successive subbasin strata that ex-

hibit similar facies and lithostratigraphy (Figures 3,

12, 14). These observations are consistent with the

idea that lowstand depocenters exerted load stress on

upper slope sediments, triggering growth-fault move-

ment that was coincident with late Oligocene third-

order relative lowstands. These data-based observa-

tions support the inferences discussed below.

Figure 13. Eustatic sea level, subsidence, and relative sea level and accommodation rates (A–C: x meters per x time per interval)and actual estimated changes (D–H: x meters) in evolution of growth-faulted hypothetical subbasins 1 and 2. Note that red verticaldashed lines connect all sketches at equivalent times. (A) Eustatic sea level change rates. (B) Anomalous growth-fault subsidencerates superimposed on regional subsidence curve. (C) Relative sea level change (eustatic change � subsidence rate = relative sealevel rate). Note that the anomalous subsidence rate in the subbasin produces an anomalous positive accommodation rate, but thatsubsidence negates some of the eustatic fall. (D) Anomalous growth-fault subsidence is in x meters superimposed on regionalsubsidence curve. Note initial growth of shale ridges. (E) Absolute sea level at times of maximum depositional rates. (F) Eustatic(absolute) sea level changes in x meters. Note the relationship of the eustatic curve with depositional systems tracts. Relative (actual)change in sea level is in x meters (accommodation envelope) outside of growth-faulted subbasin. (H) Relative (actual) change in sealevel in x meters (accommodation envelope) in growth-faulted subbasins. Note the anomalous added lowstand of relative sea level inx meters in subbasins. Based on Posamentier and Vail (1988). No value for x is intended.

Brown et al. 1519

Figu

re1

4.S

impl

ified

chro

nost

ratig

raph

icdi

agra

m(s

ubba

sins

inFi

gure

1)of

Olig

ocen

eFr

ioFo

rmat

ion

(32

Ma

–25

.38

Ma)

inC

orpu

sC

hris

tiar

ea,T

exas

.Thi

sdi

spla

yex

hibi

tssh

elf,

slop

e,an

dba

sina

ldep

ositi

onal

syst

ems

trac

tsan

dth

eir

geol

ogic

time

rela

tions

hips

inea

chse

quen

ceth

atco

mpr

ises

the

Frio

litho

stra

tigra

phic

unit.

Cha

rtdo

cum

ents

appr

oxim

ate

age

and

basi

nwar

dsh

iftof

subb

asin

s1

–6

duri

ngFr

iode

posi

tion

and

impl

ies

tem

pora

lind

epen

denc

eof

low

stan

dde

posi

tiona

lsys

tem

sam

ong

the

subb

asin

s.A

vera

gedu

ratio

nof

thir

d-or

der

Frio

sequ

ence

sis

abou

t1.

4m

.y.


Activation of each fault system correlates tem-

porally with a third-order fall of relative sea level

(Figures 3, 12, 14), terminating highstand prograda-

tion. Because of falling relative sea level, subsequent

highstand rivers were entrenched and shifted basinward

to shelf edges. The avulsing rivers typically relocated

from previous highstand river axes and occupied a neg-

ative paleotopographic pathway, where two arcuate

growth-fault system segments intersected (Figure 2).

Although marine-condensed sections (containing a

maximum flooding surface) and unique concentrated

fossil taxa may correlate from shelf to intraslope sub-

basins, sandstone facies deposited on shelves and in

intraslope subbasins between successive flooding events

are not necessarily contemporaneous and should not be

correlated (Figure 12). Onshelf highstand and trans-

gressive deposition was temporally distinct from off-

shelf lowstand slope-fan, basin-floor fan, and prograding-

wedge deltaic deposition (Figures 12, 14).

Shelves were subaerially exposed during lowstands.

Simply because condensed sections comprise the same

microfossils throughout the basin does not imply that

all intermediate facies are time equivalent. In fact, the

zone fossils also accumulated basinward in areas where

future subbasin subsidence and lowstand sedimenta-

tion had not yet occurred. Successive condensed sec-

tions obviously do not necessarily enclose equivalent

sandstone facies.

Entrenched river mouths that eroded shelf-edge

notches served as point sources that focused the total

lowstand fluvial-sediment load onto specific localized

sites on the upper slope and consequently produced

depocenters that can be interpreted to have exerted

sufficient load stress to trigger slumping and normal

faulting that created intraslope subbasins. This trigger

may also have released stored stress related to re-

gional basin subsidence and tectonics. Conclusions indi-

cate that relative sea level and sedimentary processes

may generate and combine with tectonic subsidence

(Figures 5, 13) and compactional stress to generate im-

portant structural events (Figure 6).

Sequence-stratigraphic analysis is an appropriate

method for identifying subtle variations exhibited in

a stratigraphic succession (Figure 8). Application of

sequence stratigraphy provides the potential for chrono-

stratigraphic correlation within and among growth-

faulted subbasins, thus improving prediction of strati-

graphic and areal distribution of deeply buried lowstand

reservoirs; providing a guide to potential combination

traps; opening a window on exploration for deep, un-

expanded subfault reservoirs and traps; placing the sub-

basin into a petroleum system framework; and focusing

on improper correlation of genetically similar wire-

line-log patterns of temporally lithostratigraphic units.

REFERENCES CITED

Abreu, V. S., and G. A. Haddad, 1998, Glacioeustatic fluctuations:The mechanism linking stable isotope events and sequencestratigraphy from the early Oligocene to middle Miocene:SEPM Special Publication 60, p. 245–259.

Berggren, W. A., D. V. Kent, and J. A. Van Couvering, 1985, Neo-gene chronology and chronostratigraphy, in N. J. Snelling, ed.,The chronology of the geologic record: Geologic SocietyMemoir 10, p. 211–260.

Berggren, W. A., D. V. Kent, C. C. Swisher III, and M. P. Aubry, 1995,A revised Cenozoic geochronology and chronostratigraphy, inW. A. Berggren, D. V. Kent, M. P. Aubry, and J. Hardenbol,eds., Geochronology, time scales and global stratigraphic cor-relation: SEPM Special Publication 54, p.129–212.

Brink, G. J., J. H. G. Keenan, and L. F. Brown Jr., 1993, Depositionof fourth-order, post-rift sequences and sequence sets, LowerCretaceous ( lower Valanginian to lower Aptian), Pletmos Basin,southern offshore, South Africa, in P. Weimer and H. Posa-mentier, eds., Siliciclastic sequence stratigraphy— Recent de-velopments and applications: AAPG Memoir 58, p. 43–69.

Brown Jr., L. F., J. M. Benson, G. J. Brink, S. Doherty, A. Jollands,E. H. G. Jungslager, A. Mutingh, and N. J. S. van Wyk, 1995,Sequence stratigraphy in offshore South African divergent ba-sins: An atlas on exploration for Cretaceous lowstand traps bySoekor (Pty) Ltd.: AAPG Studies in Geology 41, 184 p.

Brown Jr., L. F., R. G. Loucks, and R. H. Trevino, 2003a, Revisitingmature fields with modern technology and geologic concepts:Examples from the Frio of south Texas (ext. abs.), in Structureand stratigraphy of south Texas and northeast Mexico: Appli-cations to exploration: Gulf Coast Section SEPM Foundationand South Texas Geological Society, p. 289–291.

Brown Jr., L. F., R. G. Loucks, and R. H. Trevino, 2003b, Using S5

benchmark wire-line logs to characterize the sequence stratig-raphy of depositional systems in growth-faulted intraslopebasins (abs.): AAPG Annual Meeting Program, v. 12, p. A20.

Cande, S. C., and D. V. Kent, 1992, Ultrahigh resolution marinemagnetic anomaly profiles: A record of continuous paleoin-tensity variations?: Journal of Geophysical Research, B, SolidEarth and Planets, v. 97, no. 11, p. 15,075–15,083.

Cande, S. C., and D. V. Kent, 1995, Revised calibration of thegeomagnetic polarity timescale for the Late Cretaceous andCenozoic: Journal of Geophysical Research, B, Solid Earth andPlanets, v. 100, no. 4, p. 6093–6095.

Curtis, D. M., and D. J. Echols, 1985, Habitat of oil and gas in themiddle Frio (Oligocene) Hackberry: Gulf Coast Section SEPMFoundation Fourth Annual Research Conference Proceedings,p. 263–274.

Edwards, M. B., 1980, The Live Oak delta complex: An unstableshelf-edge delta in the deep Wilcox trend of south Texas: GulfCoast Association of Geological Societies Transactions, v. 30,p. 611–622.

Edwards, M. B., 1984, Electric log correlation in growth-faultedregions— A workshop: Course Notes, 28 p.

Ewing, T. E., 2002, Practical sequence stratigraphy in onshoreexploration and development with examples from the Yeguaand Cotton Valley trends: Gulf Coast Association of Geo-logical Societies and Gulf Coast Section SEPM Transactions,v. 52, p. 257–266.

Brown et al. 1521

Ewing, T. E. and R. S. Reed, 1984, Depositional systems andstructural controls of Hackberry sandstone reservoirs in south-east Texas: University of Texas at Austin, Bureau of EconomicGeology Geological Circular 84-7, 48 p.

Galloway, W. E., 1986, Depositional and structural framework ofthe distal Frio Formation, Texas coastal zone and shelf: Uni-versity of Texas at Austin, Bureau of Economic GeologyGeological Circular 86-8, 16 p.

Galloway, W. E., 1989a, Genetic depositional sequences in basinalanalysis I: Architecture and genesis of flooding surface-boundeddepositional units: AAPG Bulletin, v. 73, p. 125–142.

Galloway, W. E., 1989b, Genetic stratigraphic sequences in basinanalysis: II. Application to northwest Gulf of Mexico Cenozoicbasin: AAPG Bulletin, v. 73, p. 153–154.

Galloway, W. E., D. K. Hobday, and K. Magara, 1982, Frio For-mation of the Texas Gulf Coast Basin— Depositional systems,structural framework, and hydrocarbon origin, migration dis-tribution, and exploration potential: University of Texas atAustin, Bureau of Economic Geology Report of Investigation,v. 122, 78 p.

GEOMAR, 2002, Zone age conversion program: http://www.odsn.de/odsn/services/conv_ts/conv_ts.html: Ocean DrillingStratigraphic Network, Research Center for Marine Geosciences,Kiel and the Geological Institute of the University Bremen.

Halbouty, M. T., and T. D. Barber, 1961, Port Acres and PortArthur fields, Jefferson County, Texas: Gulf Coast Associationof Geological Societies Transactions, v. 11, p. 225–234.

Hammes, U., R. G. Loucks, L. F. Brown, R. H. Trevino, R. L.Remington, and P. Montoya, in press, Structural setting andsequence architecture of a growth-faulted lowstand subbasin,Frio Formation, south Texas: Gulf Coast Association of Geo-logical Societies Transactions.

Haq, B. U., J. Hardenbol, and P. R. Vail, 1987, Timing and depo-sitional history of eustatic sequences: Constraints on seismicstratigraphy: Science, v. 235, no. 4793, p. 1156–1167.

Hardenbol, J., J. Thierry, M. B. Farley, P. C. de Graciansky, and P. R.Vail, 1998, Mesozoic and Cenozoic sequence chronostrati-graphic framework of European basins, in P. C. de Graciansky,J. Hardenbol, J. Thierry, and P. R. Vail, eds., Mesozoic andCenozoic sequence stratigraphy of European basins: SEPMSpecial Publication 60, p. 3–13.

Lawless, P. N., R. H. Fillon, and R. G. Lytton III, 1997, Gulf ofMexico Cenozoic biostratigraphic, lithostratigraphic, and se-quence stratigraphic event chronology: Gulf Coast Associationof Geological Societies Transactions, v. 47, p. 271–282.

Mitchum Jr., R. M., J. B. Sangree, P. R. Vail, and W. W. Wornardt,1994, Recognizing sequences and systems tracts from well

logs, seismic data, and biostratigraphy: Examples from thelate Cenozoic, in P. Weimer and H. W. Posamentier, eds.,Siliciclastic sequence stratigraphy: Recent developments andapplications: AAPG Memoir 58, p. 163–198.

Posamentier, H. W., and P. R. Vail, 1988, Eustatic controls onclastic deposition: II. Sequence and systems tract models, inC. K. Wilgus, B. S. Hastings, C. G. St. C. Kendall, H. W.Posamentier, C. A. Ross, and J. C. Van Wagoner, eds., Sea-levelchanges: An integrated approach: SEPM Special Publication 42,p. 125–154.

Sangree, J. B., P. R. Vail, and R. M. Mitchum Jr., 1990, A summaryof exploration applications of sequence stratigraphy, in J. M.Armentrout and B. F. Perkins, eds., Sequence stratigraphy asan exploration tool— Concepts and practices in the Gulf Coast(abs.): Gulf Coast Section SEPM 11th Annual Research Con-ference, Houston, Texas, Program and Abstracts, p. 321–327.

Trevino, R. H., R. G. Loucks, L. F. Brown Jr., and R. L. Remington,2003, General geology of the mid-Tertiary Block 889 fieldarea, offshore Mustang Island, Texas: Gulf Coast Associationof Geological Societies Transactions, v. 53, p. 802–814.

Tyler, N., and W. A. Ambrose, 1985, Facies architecture andproduction characteristics of strandplain reservoirs in the FrioFormation, Texas: University of Texas at Austin, Bureau ofEconomic Geology Report of Investigations, v. 146, 42 p.

Vail, P. R., 1987, Seismic stratigraphy interpretation using sequencestratigraphy: Part 1. Seismic stratigraphy interpretation pro-cedure, in A. W. Bally, ed., Atlas of seismic stratigraphy:AAPG Studies in Geology 27, p. 2–14.

Vail, P. R., R. M. Mitchum, and S. Thompson III, 1977, Seismicstratigraphy and global changes of sea level: Part 3. Relativechanges of sea level from coastal onlap, in C. W. Payton, ed.,Seismic stratigraphy applications to hydrocarbon exploration:AAPG Memoir 26, p. 63–97.

Van Wagoner, J. C., R. M. Mitchum Jr., K. M. Campion, and V. D.Rahmanian, 1990, Siliciclastic sequence stratigraphy in welllogs, cores, and outcrops: AAPG Methods in ExplorationSeries 7, 55 p.

Wheeler, H. E., 1958, Time-stratigraphy: AAPG Bulletin, v. 42,no. 5, p. 1045–1063.

Winker, C. D., and M. B. Edwards, 1983, Unstable progradationalclastic shelf margins, in D. J. Stanley and G. T. Moore, eds.,The shelfbreak— Critical interface on continental margins:SEPM Special Publication 33, p. 139–157.

Wornardt Jr., W. W., B. Shaffer, and P. R. Vail, 2001, Revision ofthe late Miocene, Pliocene, and Pleistocene sequences cycles:Gulf Coast Association of Geological Societies Transactions,v. 51, p. 477–481.


Documents

Understanding growth-faulted, intraslope subbasins by