sedimentology, organic geochemistry, and petroleum ...carroll/publications/pdf/hendrix et al.,...

ABSTRACT

Lower and Middle Jurassic coal-bearing strataoccur widely throughout central Asia and are welldeveloped in northwestern China, where theirthicknesses in the southern Junggar, northernTarim, and Turpan basins exceed 2500, 2300, and1500 m, respectively. Examination of these strataalong 13 transects across basin margin outcrop

belts indicates that they are entirely nonmarinemeandering f luvial deposits with local develop-ment of braided fluvial and lacustrine deltaic facies.Chinese subsurface data suggest that regionalJurassic lacustrine facies are present down deposi-tional dip, consistent with predictions from globalcirculation modeling of Early and Middle Jurassicmonsoonal precipitation.

Laboratory analyses of coals and organic-richshales show a dominance of terrestrial, higherplant components. Visual kerogen analysis indi-cates that vitrinite, inertinite, and exinite are thedominant macerals, and elemental analysis charac-terizes most kerogens as type III. Rock-Eval analy-ses yield moderate hydrogen index values (50–300)and very low oxygen index values (<20). Jurassicsource rock extracts are characterized by odd-over-even normal alkane distributions, high pristane/phytane and high hopane/sterane ratios, domi-nance of C29 sterane homologs, local abundance ofditerpenoid compounds, and low abundance of tri-cyclic terpanes.

Geochemical correlation with four petroleumsfrom the Junggar, Tarim, and Turpan basins stronglysuggests that the Jurassic coaly deposits and theirlacustrine equivalents downdip are petroleumsource rocks. Sterane and hopane distributions ofpetroleums and extracts of their putative Jurassicsource rock are similar and can be easily distin-guished from published distributions of these com-pounds in other source rock layers. Additional cor-relation parameters include high pristane/phytane;low abundance or lack of tricyclic terpanes, butsimilar distributions where present; and lack ofgammacerane (with one exception) and carotanes,compounds that characterize Permian andOrdovician source rocks and their respectivepetroleums. Pyrolysis–gas chromatography ofselected Jurassic samples suggests that they possesspotential for liquid hydrocarbon generation.Expulsion of C15+ hydrocarbons from Jurassicsource rocks appears likely, despite the traditionalview that bituminous coals are incapable ofexpelling long-chain hydrocarbons.

929AAPG Bulletin, V. 79, No. 7 (July 1995), P. 929–959.

©Copyright 1995. The American Association of Petroleum Geologists. Allrights reserved.

1Manuscript received June 15, 1994; revised manuscript receivedFebruary 2, 1995; final acceptance February 28, 1995.

2Department of Geological and Environmental Sciences, MitchellBuilding, Room 138, Stanford University, Stanford, California 94305-2115.Current address: Department of Geology, University of Montana, Missoula,Montana 59812.

3Biogeochemistry Laboratories, Departments of Chemistry and Geology,Geology Building, 1005 East 10th Street, University of Indiana, Bloomington,Indiana 47405-5101.

4Exxon Production Research Company, P.O. Box 2189, Houston, Texas77252-2189.

5Department of Geological and Environmental Sciences, MitchellBuilding, Room 138, Stanford University, Stanford, California 94305-2115.

Field work for this study was conducted in cooperation with the ChineseAcademy of Geological Sciences and the Xinjiang Bureau of Geology andMineral Resources during the summers of 1987, 1988, and 1989. Specialthanks are due to Xiao Xuchang, Liang Yunhai, and Wang Zuoxun. We arealso grateful for the field assistance of Benjamin Schulein, Ed Sobel, CleavyMcKnight, and Chu Jinchi. Stanford research was supported by the Stanford-China Geosciences Industrial Affiliates, a group that has included Agip,Amoco, Anadarko Petroleum, Anschutz, ARCO, BHP, BP, Canadian-Hunter,Chevron, Conoco, Elf-Aquitaine, Enterprise, Exxon, Fletcher-Challenge,Japan National, Mobil, Occidental, Pecten, Phillips, Statoil, Sun, Texaco,Transworld Energy International, Union Texas, and Unocal. Additionalfunding was provided by the David and Lucile Packard Fellowship forScience and Engineering (granted to S. C. Brassell to support biomarkerresearch at Stanford). G. Barker and G. Wood (Amoco) and U. Biffi (Agip)identified palynoflora in conjunction with this study. Rock-Eval pyrolysis,vitrinite reflectance, TOC, and elemental analysis data were provided in partby R. A. Hutton and L. J. Lipke (Amoco), G. J. Demaison (formerly withChevron), R. J. Moiola, J. M. Armentrout, and C. P. Lacerda (Mobil), R. W.Blake, C. R. Robison, and N. P. Carroll (Texaco). L. Lipke and R. Hutton(Amoco) provided extractions and HPLC separations of selected samples.Exxon Production Research Company provided pyrolysis-GC, HPLCseparations, and whole-oil and saturate GC and GC-MS analyses of selectedsamples, and permission to publish these results. C. L. Thompson-Rizer(Conoco) supplied visual kerogen data. J. Clayton (U.S. Geological Survey,Denver) provided the Junggar petroleum sample 94-HU-1. F. J. Fago(Stanford) assisted in selected GC-MS analyses. We thank M. Golan-Bac, G. B. Hieshima, J. A. Kennedy, and L. A. F. Trindade for helpful discussion ofthese data, and we are especially grateful for constructive reviews of themanuscript by D. D. Miller, J. M. Moldowan, K. E. Peters, D. Waples, and oneanonymous reviewer.

Sedimentology, Organic Geochemistry, and PetroleumPotential of Jurassic Coal Measures: Tarim, Junggar, andTurpan Basins, Northwest China1

Marc S. Hendrix,2 Simon C. Brassell,3 Alan R. Carroll,4 and Stephan A. Graham5

INTRODUCTION

Organic-rich Jurassic strata are widespreadthroughout central Asia and have been reportedfrom northwestern China, western and southernMongolia, and adjacent parts of the former SovietUnion (Vakhrameyev and Doludenko, 1977;Ulmishek, 1984; Hendrix et al., 1992, 1994b;Hendrix and Graham, 1993). Throughout theXinjiang Uygur Autonomous Region of northwest-ern China (Figure 1), Lower through MiddleJurassic coal provides the principal energy sourcefor everything from electrical power plants to localhousehold ovens. Lee (1985a) estimated that thesouth Junggar basin alone contains in excess of 270 × 109 t of high-quality bituminous coal.Comparisons of estimated total and recoverabletonnages for other coal-bearing basins indicate thatthe tonnages of high-quality coal in the Junggarbasin are comparable to those of other prolificbasins of the world (Table 1).

These coals and their associated organic-richmudstones likely act as a source rock for petroleumand gas accumulations of the southern Junggar,northern Tarim, and Turpan basins within Xinjiang(Lee, 1985a, b; Graham et al., 1990; Huang et al.,1991; Zhou et al., 1993). Petroleum in the Junggar,Turpan, and Tarim basins has been known for cen-turies. Natural seeps were exploited from each ofthese basins along the ancient Silk Road. Morerecently, large commercial accumulations of

petroleum have been discovered in the Junggar andTarim basins, and moderate-size accumulationshave been discovered in the Turpan basin (Nishidaiand Berry, 1991; Oil & Gas Journal, 1993; Zhou etal., 1993).

Source rock considerations have rapidly assumedconsiderable importance, given China’s recentdecision to open many of its onshore basins,including the Tarim basin, to international biddingfor exploration. No unequivocal geochemical cor-relation between Jurassic strata and petroleumrecovered from Xinjiang’s oil fields has been pub-lished. The source potential of these strata remainsuncertain, although various Chinese studies havereported similarities between sterane and hopanedistributions of Lower and Middle Jurassic sourcerocks and certain crude oils in the East Junggar andTurpan basins (Wang and Chen, 1990; Huang et al.,1991; Zhou et al., 1993). Complicating the picture,however, are other strata, such as the Permianlacustrine oil shales, which provide a source forpetroleum in the Junggar basin (Carroll et al.,1992). Similarly, the Tarim basin has several poten-tial petroleum source rocks, including Cambrian–Ordovician, Carboniferous, and possibly Creta-ceous marine rocks, as well as Permian and Jurassicnonmarine rocks (Fan et al., 1990; Graham et al.,1990).

The lack of published analyses of potentialsource rocks for each of Xinjiang’s basins has beena barrier to comprehensive correlation studies with

930 Jurassic Coal Measures, Northwest China

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Transect through Jurassic strata

Jurassic isopach (km)

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(see caption for locality abbr.)

0 100 km

T I A N S H A N

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42°00'

80°00' 82°00' 84°00' 86°00' 88°00'76°00' 78°00'

Xinjiang Uygur

TURPAN BASIN

AutonomousRegion

Figure 1—Location ofstudy area, transectsacross Jurassic strata,and collection sites ofselected oil samples forthis study. Jurassicisopachs in Junggar andTarim basins from Lee(1985a, b). M = Manas, X = Xishanyao, B = Badaowan, HL = Heavenly Lake, J = Jimsar, D = Dabanchang,T = Taoshuyuan, Kr = Korla,Y = Yengisar, K = Kuqa,Bc = Baicheng, Q = Qiugetale, Aw = Awate, Kz = Kuzigongsu.

petroleum from all three basins. In particular, fewdetails have been reported on the sedimentologicand organic geochemical attributes of Jurassic coalystrata. Although several organic geochemical stud-ies of Mesozoic strata and/or allegedly Mesozoicoils exist in the Chinese literature (Lu, 1981; Li andJiang, 1987; Fan et al., 1990; Wang and Chen, 1990;Huang et al., 1991; Zhou et al., 1993), they areeither limited in scope or difficult to evaluate criti-cally because they provide little data. Geochemicalanalyses of organic-rich Jurassic strata reported inthe Western literature (e.g., Graham et al., 1990)are too sparse to adequately assess Jurassic sourcepotential.

This study provides a detailed organic geochemi-cal database for organic-rich Lower and MiddleJurassic strata throughout central Xinjiang, therebypermitting a more comprehensive interpretation ofthe area’s petroleum potential. Because our sam-pling was limited to outcrops on deformed basinmargins whose palinspastic origins lay far from pro-ducing areas, our goals are not to match specificbeds to specific oils, but rather to look for kindredaffinities that point to likely source sequences. Bulkand molecular organic geochemical data wereacquired from a sample suite collected along 13transects of Mesozoic strata in the southernJunggar, northern Tarim, and western Turpanbasins (Figure 1). Field and laboratory evidence ispresented that demonstrates that organic-richLower and Middle Jurassic strata are dominated byterrestrial-derived type III kerogens. Molecular geo-chemical techniques strongly suggest a correlationbetween these kerogens and four petroleum sam-ples collected from the northern Tarim, southernJunggar, and Turpan basins.

GEOLOGIC SETTING

Sedimentary, Tectonic, and PaleoclimaticFramework

Thick organic-rich strata of Early through MiddleJurassic age occur throughout the southernJunggar, northern Tarim, and Turpan basins ofnorthwest China (Figures 1, 2). Jurassic sedimenta-ry accumulations in all three basins exhibit fore-land-style isopach configurations (Lee, 1985a, b;Huang et al., 1991; Allen et al., 1993), suggestingthat each basin was an asymmetric, flexurally sub-siding trough adjacent to active fold and thrustbelts that bounded the Tian Shan (Hendrix et al.,1992). Mesozoic facies and thickness trends, aswell as paleocurrent, provenance, and subsidenceanalysis, indicate that the Tarim and Junggar basinswere physiographically partitioned by the TianShan throughout the Mesozoic, as the Tian Shan

Hendrix et al. 931

Tab

le 1

. E

stim

ated

To

tal

To

nn

ages

fo

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vera

l C

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rin

g B

asin

s an

d C

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par

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ith

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on

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e fr

om

th

e Ju

ngg

ar B

asin

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To

tal E

stim

ated

Rec

ove

rab

leN

um

ber

of

Th

icke

st S

eam

Rec

ove

rab

leB

asin

Age

of

Co

al(G

t)(G

t)Se

ams

Min

ed(m

)(%

)R

efer

ence

s

Sou

ther

n J

un

ggar

Earl

y–M

idd

le J

ura

ssic

270

18~

4225

7Le

e, 1

985a

No

rth

ern

Tar

imEa

rly–

Mid

dle

Ju

rass

icN

AN

A23

>20

NA

Lee,

198

5bA

pp

alac

hia

nP

enn

sylv

ania

n-P

erm

ian

455

NA

NA

5Sc

hm

idt,

197

9C

rato

nic

(U

.S.)

Pen

nsy

lvan

ian

0.5

0.07

NA

NA

14Sc

hm

idt,

197

9R

ocky

Mou

ntai

n (U

.S.)

Cre

tace

ou

s–Eo

cen

e20

522

>15

3811

Gla

ss, 1

975;

Sch

mid

t, 1

979

Alb

erta

(C

anad

a)Ea

rly

Cre

tace

ou

s–T

erti

ary

127

3N

AN

A2

Can

ada

Min

istr

y Su

pp

ly &

Se

rvic

es, 1

977

Gip

psl

and

(A

ust

ralia

)T

erti

ary

107

40>

7>

6037

Glo

e, 1

984

Syd

ney

(A

ust

ralia

)T

erti

ary

<10

2<

16N

AN

A16

Fett

wei

s, 1

979

Tu

ngu

sska

(R

uss

ia)

Cre

tace

ou

s17

443.

9N

AN

A<

1Fe

ttw

eis,

197

9Le

na

(Ru

ssia

)C

reta

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us

2647

3.4

NA

NA

<1

Fett

wei

s, 1

979

*NA

= d

ata

not a

vaila

ble.


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19

L a t e T r i a s s i cZhang, 1983 (palynoflora)

e. Middle JurassicZ. Liu, 1990 (palynoflora)

E a r l y J u r a s s i cM i d d l e J u r a s s i cYang and Sun, 1986 (palynoflora)

E a r l y J u r a s s i cM i d d l e J u r a s s i cGu, 1982

(nonmarine bivalves) Late Triassic

Early JurassicHuang, 1993 (sporopollen)

late Early Jur. early Early Jurassicearly Mid. Jur.late Middle JurassicLiu, 1993(sporo-pollen)

E a r l y J u r a s s i cWu, 1990 (plant remains)

Late TrEarly JurassicEarly to Middle JurassicWu and Zhou, 1986

Early JurassicWu, 1990 (plant remains)

Early LiasLate LiasMiddle Jur.Sun, 1989 (sporo-pollen)

Taliqik

01

0.5

E a r l y J u r a s s i c Late TriassicE. JurassicWu, 1990 (plant remains)

Early TriassicMiddle JurassicS. Liu, 1990

L a t e T r i a s s i cEarly JurassicMiddle JurassicZhang and Li, 1990 (sporo-pollen)

Kuzigongsu Section Callovian AalenianU.Biffi (1993, pers. comm.)

(palynoflora)

bp

d

bp

d

(plant remains)

(conchostracans)

NO

RT

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was repeatedly deformed in response to varioustectonic accretion events at the southern Asiancontinental margin (Hendrix, 1992; Hendrix et al.,1992). Paleocurrent, organic facies, and isopachconfigurations indicate that the Turpan basinevolved as a discrete physiographic entity by theEarly Jurassic (Huang et al., 1991; Hendrix et al.,1992). Flexurally driven Early and Middle Jurassicsubsidence rates for basin depocenters in centralXinjiang were in excess of 55 m/m.y. (>30 m/m.y.for the Turpan basin), leading to the accumulationof 2600 m of sediment in the south Junggar, 2500m in the north Tarim, and 1500 m in the westTurpan depocenters (Figure 2) (Hendrix et al.,1992).

Lower and Middle Jurassic organic-rich stratadeposited in basins of central Xinjiang are entirelynonmarine, based on their floral and faunal assem-blages (Figure 2) (Zhang, 1981; Lai and Wang,1988). During this period, abundant, probablymonsoonal, rainfall led to the development ofextensive meander-belt fluvial systems transverseto the ancestral Tian Shan range, as suggested byfacies assemblages in basin margin outcrops and bypaleocurrent measurements (Hendrix et al., 1992).Regionally extensive, occasionally anoxic, lakes orbogs probably occupied interior foredeep regionsof these basins (Lai and Wang, 1988; Huang et al.,1991). In some outcrops we examined, Jurassicstrata appear to be lacustrine deltaic, as along theManas transect (southern Junggar basin; Figure 1),where coal-bearing strata are laterally continuous.

Coal-bearing strata in central Xinjiang are divid-ed into several formations by Chinese stratigra-phers (Figure 2). According to Zhang (1981), mostcoal is mined from the Badaowan and Xishanyaoformations in the southern Junggar and Turpanbasins and from the Ahe and Kezilenuer formationsin the northern Tarim basin (Figure 2). Our obser-vations of the stratigraphy of central Xinjiang basinssuggest that, although most coal is mined fromthese formations, abundant organic-rich strata arepresent throughout Lower and Middle Jurassicdeposits in each basin (Figure 2).

Chronostratigraphic Control

Precise dating of Mesozoic nonmarine coal-bear-ing strata in central Xinjiang is difficult due to a

lack of interbedded, datable volcanic units and lit-tle reported magnetostratigraphic work (although,see McFadden et al., 1988a, b). The strata are highlyfossiliferous, however, and many floral and faunalstudies have been conducted to constrain the ageof these rocks. As a result, there is general agree-ment that the organic-rich sequences are as old asTriassic and as young as Middle Jurassic. However,more detailed assignments differ from study tostudy due to the highly endemic nature (e.g., Li,1993) and moderate to poor preservation ofMesozoic nonmarine flora and fauna in the Xinjiangbasins (Figure 2). In addition, the Chinese practiceof extensive taxonomic subdivision hampers corre-lation of Chinese flora and fauna with areas outsideChina (Zhang and Li, 1989).

Biostratigraphic age assignments have been pub-lished based on vertebrate (Wu, 1987), molluskan(Gu, 1982), conchostracan (S. Liu, 1990), and high-er plant remains (Wu, 1990) (Figure 2), but palyno-logic studies appear to be the most successful.Published age estimates of Mesozoic organic-richstrata based on palynology fall into two broad cate-gories. The first group of studies maintains that thedeposits are largely or entirely Triassic in age (e.g.,Zhang, 1983; Zhang and Li, 1990; Figure 2). Thesecond and larger group of studies contends thatthe coal-bearing deposits are of Early throughMiddle Jurassic age (He and Wu, 1986; Wu andZhou, 1986; Yang and Sun, 1986; Sun, 1989; Z. Liu,1990, 1993; U. Biffi, 1993, personal communica-tion) (Figure 2).

Exact placement of the Triassic–Jurassic bound-ary remains controversial. Various studies havenoted the presence of Triassic survivor species inJurassic coal-bearing strata (e.g., Yang and Sun,1986; Liu and Sun, 1992). Wu (1990) further addedto the uncertainty by reporting Early Jurassic florasfrom the Taliqik Formation, which is usuallyassigned a Late Triassic age. More biostratigraphicstudies are needed to clarify the age of centralXinjiang organic-rich Mesozoic deposits, particular-ly in terms of correlation with well-constrained flo-ral assemblages outside China (e.g., Sarjeant et al.,1993). In this paper, we provisionally refer to thecoaly deposits as Lower through Middle Jurassic,because the literature and the palynology of oursamples (U. Biffi, 1993, personal communication)favor such a conclusion. Given uncertainties, it ispossible that parts of these deposits may be Triassic.

Hendrix et al. 933

Figure 2—Complete Jurassic sections for the Kuqa and Manas localities (northern Tarim and southern Junggarbasin depocenter sections), and Jurassic section for Taican-1 well, reported by Huang et al. (1991) on the basis ofcore. Age interpretations and formation names, derived from Chinese literature, are plotted adjacent to each sec-tion. Note that significant controversy exists, particularly with regard to the exact placement of the Triassic–Juras-sic boundary. Also shown are the locations of sections in Figure 3.

In the following discussion, we do not attempt todifferentiate or correlate samples from specific for-mations, because of the lack of sufficient age con-trol and the difficulty in correlating specific forma-tions or organic-rich intervals between localities.

FIELD METHODS AND SAMPLING STRATEGY

At the 13 locations where Jurassic strata wereexamined, recent exposures were suitable to permitdetailed inspection of facies. Most natural outcropsof the organic-rich facies were too weathered forreliable analysis. Where possible, stratigraphic sec-tions were measured to document the style of sedi-mentation (Figure 3) (Hendrix et al., 1992).Unweathered samples were collected from subsur-face coal mines at each locality. With the exceptionof samples 87-D-5A, 89-K-112, and 89-Bc-6A, collect-ed from natural outcrops, all geochemical work wasperformed on unweathered subsurface samples.Our access to subsurface workings was restricted,so exact stratigraphic placement of individual sam-ples within the mined interval is unknown.

Jurassic sediments are thickest in the southernJunggar and northern Tarim depocenters near theManas and Kuqa localities, respectively (Figures 1,2). These two localities also contain the largestnumber of operating coal mines. Samples were alsocollected from localities away from the basindepocenters (Figure 1). Currently, more than onecoal seam is being mined at most locations.Individual seams in the northern Tarim and south-ern Junggar Mesozoic foredeeps are reported inexcess of 25 m thick, and as many as 42 separatecoal seams are being mined in the subsurface at theBadaowan locality (Figure 1) (Hendrix, 1992).

To better assess the petroleum potential ofJurassic rocks, we investigated the organic geo-chemistry of four petroleum samples likely to havebeen generated from these rocks in Xinjiang basins,based on geologic relations. These samples includea produced oil from the southern Junggar basin(94-HU-1), a seep oil collected from the northernTarim basin (92-Bc-101), and one seep oil and oneproduced oil from the north central Turpan basin(93-QK-6 and 93-QK-101, respectively; Figure 1).

SEDIMENTARY FACIES

In all three basins, Lower Jurassic strata overlieallegedly uppermost Triassic alluvial and braided


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(northern Tarim) (southern Junggar)

rhyzoids

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L E G E N D

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Figure 3—Detailed measured sections of the meanderingfluvial lithofacies from Kuqa and Manas. Exact place-ment of these sections in the complete Jurassic sectionsmeasured for each locality is shown in Figure 2.

fluvial conglomerate, sandstone, and siltstone ofthe Haojiagou Formation (south Junggar and northTarim basins) and the Taliqik Formation (Turpanbasin; Figure 2). This transition appears to be grada-tional in all three basins and is interpreted as gener-ally conformable. Organic-rich Jurassic strata ineach basin consist of interbedded sandstone, silt-stone, and shale (Figures 2; 3; 4A, B). Conglomerateis minor and, where present, typically occurs as alag at the base of sandstones. Plant debris is highlyvariable in form and state of preservation through-out organic-rich strata of all three basins. Plantdebris ranges from log jams (Figure 3B) to whollyarticulated plant fossils (Figure 4C), and includesin-situ rhyzoids at the top of many thin sandstonesand siltstones (Figure 3) (Hendrix, 1992).

Three major sedimentary environments are rep-resented by Lower and Middle Jurassic strata alonguplifted margins of Xinjiang basins. In each basin,most Jurassic deposits are characterized by mean-dering fluvial facies. Local braided fluvial depositscharacterize parts of the Turpan and northernTarim basins. Within parts of the Junggar basin,lacustrine deltaic facies are present.

Meandering Fluvial Facies

Most Lower and Middle Jurassic strata in centralXinjiang basins consist of interbedded sandstone,siltstone, shale, and coal interpreted as meanderingfluvial sequences. Sandstone beds associated withthis facies are lenticular on a lateral scale of tens tohundreds of meters, and many contain minor con-glomeratic lags at their base with associated toolmarks or rare gutter casts (Figure 4D). Lateral accre-tion surfaces are common, and shallow-water trac-tion-transport structures, such as trough cross-bed-ding, planar lamination, and ripples, are alsocommon. Detailed outcrop sections were measuredin this facies at both the Manas and Kuqa localities(Figure 3). Each detailed section contains at leastone approximately 10-m-thick major sandstone con-sisting of an overall upward-fining sequence (Figure4E) with a scoured and tool-marked base (Figure4D), several amalgamation surfaces, an abundanceof shallow-water traction-transport structures (suchas trough cross-beds and planar lamination), and arippled top. These thick sandstones are interpretedas major meandering fluvial channel complexes.The finer grained parts of each section contain silt-stone layers, commonly with rhyzoids, coaly shale,abundant plant impressions on bedding planes(Figure 4C), and a series of thin interbedded (≤1 mthick) fine-grained sandstones. These thinner sand-stones are not characterized by substantial upwardfining, but are typically uniformly fine grained. Theyare commonly planar laminated near the base, but

display climbing ripples toward the top and areinterpreted as crevasse splay deposits (Figure 3).One such approximately 70-cm-thick sandstone atthe Manas site has casts of therapod(?) dinosaurfootprints on its base (Hendrix, 1992).

These meandering f luvial organic-rich stratagrade upward into monotonous fine-grained redbeds of the Qigu Formation (northern Tarim andsouthern Junggar basins) or Qiketai Formation(Turpan basin; Figure 2).

Braided Fluvial Facies

Lower Jurassic strata of the Badaowan Formationin the western Turpan basin are considerably coars-er than equivalent rocks from the Junggar andTarim basins and lack organic-r ich layers. InTurpan, they comprise well-organized, braided flu-vial pebbly sandstone and siltstone, typified by ver-tically stacked sandy bar deposits and lenticulargeometries on a scale of tens of meters (Hendrix etal., 1992). Within the Lower Jurassic YengisarFormation along the Kuqa and Yengisar transects(Tarim basin), over 300 m of sand-rich braided flu-vial deposits were observed (Figure 2) (Hendrix etal., 1992).

Lacustrine Deltaic Facies

In the southern Junggar basin depocenter(Manas), the main coal-bearing portions of the sec-tion contain sandstone, siltstone, and shale hori-zons, which are commonly tabular for hundreds ofmeters and probably represent a lacustrine delta(Figure 4B). Low-angle lateral accretion surfaces areobserved in many of the thicker sandstones, sug-gesting either a very large meandering fluvial sys-tem or perhaps distributary mouth bar prograda-tion (Figure 4F). The richest Jurassic coal layersassociated with this facies contain abundant “clink-er” rock formed by in-situ burning of subbitumi-nous and bituminous coal as a result of sponta-neous combustion of outgassed methane (Coates,1988). Lack of any marine flora or fauna in thesestrata is consistent with a lacustrine deltaic inter-pretation. For additional sedimentologic informa-tion on each of these facies, refer to Hendrix(1992) and Hendrix et al. (1992).

BULK GEOCHEMICAL ANALYSES

Visual Kerogen Analysis

Relative proportions of organic macerals arequantified for eight Jurassic coal samples, each from

Hendrix et al. 935


Figure 4—Photographs of outcrops and sedimentary structures typical of organic-rich Jurassic strata from Xinjiangbasins. (A) Organic-rich, meandering fluvial facies (Kezilenuer Formation), Kuqa, northern Tarim basin. Trees inforeground are about 5 m high. Note lenticular sandstone geometries and thin, outcropping coal bed. (B) Laterallycontinuous Middle Jurassic coal-bearing lacustrine facies, Manas, southern Junggar basin. One-story building forscale (circled). Note the tabular geometry of sandstone beds (light-colored), and the thick coal seam (>10 m) at thestratigraphic level of the building. (C) Plant impressions (Baiera sp.?) typical of bedding surfaces in fine-grainedLower and Middle Jurassic strata from Xinjiang basins. (D) Gutter casts on sole of conglomerate bed in meanderingfluvial lithofacies, Badaowan Formation, Heavenly Lake. (E) Middle Jurassic fining-upward channel sandstone com-plex overlying overbank mudstone, Kezilenuer Formation, Kuqa. (F) Large lateral accretion surfaces (>20 m relief)in the meandering fluvial lithofacies of the Sangonghe Formation, Manas, southern Junggar basin.

A B

DC

E F

a different locality in the Junggar or Tarim basin(Table 2). Vitrinite is commonly the dominant com-ponent, as expected for terrestrially derived coal(Figure 5). Four of the five analyzed samples fromthe Junggar basin contain significant abundances(up to 38%) of exinite. Exinite (also termed “lipti-nite”) comprises a class of lipid-rich macerals thatinclude waxes, resins, spores, cuticles, and algalbodies (Tissot and Welte, 1984) that may provide asource of oil (Püttman et al., 1986) (Figure 5). Theapparently lower percentages of exinite in Tarimsamples is likely an artifact of the small sample size(n =3). The percentage of inertinite (fusinitic orcharcoal-like material) present in each sample variesfrom a few percent to over 60%, suggesting that sub-stantial proportions of Jurassic organic matter maybe reworked or charcoal. Much of the vitrinite ismoderately f luorescent, suggesting that it con-tains bitumen or exudatinite (nonreflective, fluo-rescent bitumen, filling apophyses, pores, etc.),which is indistinguishable from the vitrinite itself(C. Thompson-Rizer, 1992, personal communica-tion). Most of the samples yield vitrinite reflectancevalues (Ro average = 0.76%) above that associatedwith the threshold of oil generation (Ro = ∼0.6%),suggesting that the observed fluorescence resultsfrom liberated or thermally generated bitumen.

Vitrinite Reflectance

Vitrinite reflectance data indicate that most sam-ples are slightly immature to mature with respectto oil and gas generation (Table 3; Figure 6), withone important exception discussed in the follow-ing sections. Samples collected within the south-ern Junggar and northern Tarim depocenter sec-tions average slightly higher Ro values than thosefrom areas outside the foredeeps, consistent with

regional post-Jurassic sediment thickness trends.However, a substantial number of analyses fromTarim localities away from the depocenter yieldreflectances markedly higher than depocenter val-ues. The Awate, Qiugetale, and Baicheng samples(Figure 1) account for the high reflectance values(Figure 6). All three sites occur basinward of majorthrust faults in the northwestern Tarim basin, sug-gesting that high Ro values are the result of burialdue to stacking of thrust sheets.

Ref lectance values for the Turpan basin areslightly immature to mature with respect to oil andgas generation (Figure 6) (see also Graham et al.,1990). Since post-Jurassic stratal thicknesses for thewestern Turpan basin are similar to those of thesouthern Junggar and northern Tarim basin flanks(Hendrix et al., 1992), these Ro data suggest thatpost-Jurassic thermal history of these three areaswas comparable. Hendrix (1992) and Hendrix et al.(1992) performed geohistory analysis (backstrip-ping) of the Manas and Kuqa measured sections, aswell as a composite section for the Turpan basin.Because the Manas and Kuqa sections were bothcompiled from outcrops spanning more than 10km perpendicular to structural and depositionalstrike, and involved correlation across severalbroad folds at Kuqa, the degree to which these sec-tions represent generative areas within each basinis uncertain. Nevertheless, the results suggest thatJurassic strata in basinal areas proximal to each sec-tion are currently within the oil window.

Elemental Analyses and Rock-Eval Pyrolysis

Interpretation of kerogens in coaly Jurassic sam-ples relies more heavily on elemental analysis (Table4; Figure 7) than Rock-Eval pyrolysis results (Table3; Figure 8). Most of the variation in composition of

Hendrix et al. 937

Table 2. Visual Kerogen Analysis of Selected Jurassic Samples, Southern Junggar and Northern Tarim Basins*

Ro Vt Ex In Am Mn PySample Basin or Location Formation (%) (%) (%) (%) (%) (%) (%)

Southern Junggar Basin88-M-115A Manas Xishanyao 0.71 87 11 2 0 0 088-B-2 Badaowan Badaowan 0.64 35 4 60 0 1 088-HL-102 Heavenly Lake Badaowan 0.5 25 15 28 0 32 088-J-3 Jimsar Badaowan 0.45 43 38 7 0 12 088-X-1 Xishanyao Xishanyao 0.52 26 26 63 0 2 0

Northern Tarim Basin87-K-54 Kuqa Kezilenuer 0.75 84 6 10 0 0 087-Y-11 Yengisar Yengisar 0.54 22 0 0 0 77 188-Aw-38A Awate Kezilenuer 1.77 75 0 0 25 0 0

*Formation = stratigraphic formation; Ro = vitrinite reflectance; Vt = vitrinite macerals; Ex = exinite macerals; In = inertinite macerals; Am = amorphousmacerals; Mn = mineral matrix; Py = pyrite.

the samples on an atomic hydrogen-to-carbon (H/C)vs. oxygen-to-carbon (O/C) van Krevelen diagram(Figure 7) appears to be caused by the wide rangeof thermal maturity, consistent with the wide rangeof vitrinite reflectance values (Figure 6; Table 3).The least mature samples from the Junggar basinflank positions and the Turpan basin provide thebest indication of kerogen type and suggest a domi-nance of hydrogen-poor type III kerogens, consis-tent with visual kerogen analyses indicating domi-nance of vitrinitic and inertinitic macerals (Figure 5;Table 2). However, two samples lie in the regionbetween type II and type III kerogens (Figure 7).Visual kerogen analysis of one of these samples (88-J-3) indicates that it contains 38% exinite (liptinite),which is responsible for the high H/C ratio.

Hydrogen index (HI) vs. oxygen index (OI) dia-grams constructed from Rock-Eval pyrolysis data(Espitalié et al., 1977) suggest that the predominance

of hydrogen-poor type III kerogens indicated by ele-mental analysis is not supported by the Rock-Evaldata (Figure 8; Table 3). Rather, most samples fromboth the Tarim and Junggar basins plot along the typeI or type II thermal evolution pathways on an HI vs.OI diagram. A subordinate number of samples fromthe Tarim and Junggar basins, as well as most samplesfrom the Turpan basin, appear to follow the thermalevolution pathway for type III kerogens. Reasons forthis apparent discrepancy in kerogen characteriza-tion between the two techniques are not entirelyclear, although this phenomenon has been noted byother workers during analysis of coal (Teichmüllerand Durand, 1983; Kagya et al., 1991; Mpanju et al.,1991; D. J. Curry, 1995, personal communication).Peters (1986) discussed the tendency of Rock-Evalpyrolysis to overestimate the liquid hydrocarbonpotential of coaly samples. Thus, it is likely that thehigh HI/low OI signature of most Jurassic samples is


Figure 5—Thin-section photomicrographs of coal sample 88-J-3 (Jimsar transect, southern Junggar basin). (A)Reflected light; (B) ultraviolet light. Scale bar = 50 mm. Note the relative degrees of fluorescence between inertinite(I), vitrinite (V), and exinite (E) macerals.

A B

an artifact of Rock-Eval analysis, rather than an indica-tion of hydrogen-rich type I or type II kerogens.

Pyrolysis–Gas Chromatography

Pyrolysis–gas chromatography was conductedon 41 samples to determine the tendency ofJurassic rocks to generate liquid hydrocarbons. Thehigh temperatures of pyrolysis–gas chromatogra-phy produce compounds rarely observed inpetroleum (e.g., abundant n-alkenes) and compli-cate correlation of source rocks with oils (Gormlyand Mukhopadhyay, 1983). Nevertheless, pyroly-sis–gas chromatography can provide evidence ofkerogen structure and, by inference, the liquidhydrocarbon generation potential of a source rock(Dembicki et al., 1983). Gas-prone kerogens andsource rocks tend to liberate abundant low-molecu-lar-weight aromatic compounds, whereas oil-pronekerogens and source rocks liberate a larger propor-tion of nonaromatic compounds, such as n-alkanesand n-alkenes (Dembicki et al., 1983; Solli andLeplat, 1986; Tegelaar et al., 1989).

Pyrolysis–gas chromatography results suggestthat many Jurassic coal samples are capable of gen-erating liquid hydrocarbons. Compound distribu-tions for most samples lie between two end-mem-ber compositions (Figure 9). In samples dominatedby inertinitic or vitrinitic macerals, chromatogramsare characterized by an abundance of aromaticcompounds and a lack of alkene/alkane doublets(e.g., Figure 9H; see Hendrix, 1992, for additionalpyrograms). Although small quantities of high-molecular-weight (> ∼n-C25) alkanes are present inthe pyrolyzate, the most dominant compounds arelow-molecular-weight aromatic compounds typicalof woody tissues (e.g., phenols). Jurassic samplescontaining abundant exinitic macerals (resins, cuti-cles, spores) tend to be dominated by alkene/al-kane doublets and show low quantities of low-molecular-weight aromatic compounds (e.g.,Figures 9C, 9E) (Hendrix, 1992). This second endmember is more representative of oil-prone kero-gens (Dembicki et al., 1983; Solli and Leplat, 1986).Katz et al. (1991) also noted prominent alkane/alkene doublets in a Jurassic sample fromXishanyao (southern Junggar basin). Many Jurassicsamples (e.g., Figures 9A, B, D, F, G) yieldpyrolyzates with characteristics of both end mem-bers: prominent alkene/alkane doublets with sub-stantial low-molecular-weight aromatic com-pounds, suggesting mixed organic matter types.

The prominence of alkene/alkane doublets sug-gests that these strata are capable of liquid hydro-carbon generation, given sufficient thermal stress.Geochemical correlation of Jurassic organic-richstrata with samples of Xinjiang petroleum offers

the possibility to establish independent evidencefor expulsion of some hydrocarbons from theserock sequences.

BIOLOGICAL MARKER COMPOUNDS

Biological markers (biomarkers) are geologicallyoccurring organic compounds that possess evi-dence, either direct or inferred, of their biologicalorigin (e.g., Peters and Moldowan, 1993, and refer-ences therein). They have been described asmolecular fossils, although changes in chemicalstructure during diagenesis and evolutionarychanges in the chemistry of living organisms makeit difficult or impossible to establish the direct bio-logical precursor molecule for many biologicalmarker compounds. Nevertheless, biological mark-ers characterize the organic matter contributed to asediment and, by extension, aid description of itsdepositional environment. Distr ibutions ofbiomarkers provide the best means for direct corre-lation between petroleums and their suspectedsource rocks. In addition, maturity-inducedchanges in many biomarkers can provide informa-tion on the thermal history of organic-rich rocks.

We investigated biomarker distributions in thealiphatic hydrocarbon fraction of 35 organic-richLower through Middle Jurassic samples from thesouthern Junggar, northern Tarim, and Turpanbasins, and four petroleum samples collected fromXinjiang sedimentary basins (Figure 1, Appendix1). Biomarkers are the primary tools used to inter-pret the types of organic matter from which eachoil sample was generated and from which we infertheir maturity. Most importantly, we comparebiomarker distributions in the four oils with thosein the Jurassic rocks to explore possible geneticrelationships.

Acyclic Alkanes

Normal alkanes are the most abundant com-pounds for all samples in this study, although vari-ous distributions of n-alkanes and different abun-dances of n-alkanes relative to other componentscharacterize individual samples (Table 5; Figures10, 11). In nearly all rock samples, the dominant n-alkane is either n-C21, n-C23, or n-C25, and a slightto pronounced odd-over-even preference (OEP) ispresent (Figure 10). (Carbon preference index iscalculated for n-C19 to n-C29.) Due to increasedmaturity, the OEP for Tarim extracts tends to besomewhat less than that of Junggar samples (Table5; Figure 10). Whole oil–GC (gas chromatogram)traces of the four petroleum samples (Figure 11)indicate that three of the oils are also dominated by

Hendrix et al. 939

n-alkanes. The lower carbon preference index (i.e.,closer to 1.0) for these petroleums is attributed tohigher thermal maturity, relative to rock samples(Table 5; see Maturity section). Sample 92-Bc-101

(northern Tarim seep) is highly biodegraded, andconsequently n-alkanes were not detected.

Pristane (Pr) and phytane (Ph) are by far the dom-inant acyclic isoprenoids in all Jurassic rock extracts


Table 3. Vitrinite Reflectance, Rock-Eval Pyrolysis, and TOC Data, Jurassic Coal and Shale, Xinjiang Basins*

Lat. Long. Ro Ro Tmax S1Sample** (° - ′) (° - ′) (%) (n) (°C) (mg HC/g)

Southern Junggar Basin89-M-3D 43-49 86-06 0.71 50 435 2.989-M-3H 43-49 86-06 0.55 43 431 3.089-M-17A 43-54 85-51 0.75 97 435 2.289-M-17F 43-54 85-51 0.73 96 435 6.089-M-20 43-55 85-51 0.58 54 433 1.889-M-22A 43-55 85-50 0.82 82 435 2.489-M-27 43-55 85-52 0.70 50 434 2.288-M-115A 43-54 85-51 0.71 95 433 4.488-J-3 43-52 89-06 0.45 50 424 2.888-HL-102 44-03 88-04 0.50 50 435 1.988-HL-105 44-03 88-04 0.60 50 431 1.588-HL-106 44-03 88-04 0.54 90 432 2.388-B-1 43-54 87-43 0.54 98 437 0.788-B-2 43-54 87-43 0.64 50 434 3.288-X-1 43-44 87-15 0.52 50 426 0.3

Junggar Average 0.62 433 2.5Standard Deviation 0.10 3 1.3

Western Turpan Basin88-T-5 43-11 89-18 0.42 98 429 0.687-D-5A 43-22 88-24 0.75 47 419 0.4

Turpan Average 0.59 424 0.5Standard Deviation 0.23 7 0.1

Northern Tarim Basin89-K-19A 42-13 83-12 0.66 93 431 4.489-K-20B 42-13 83-11 0.72 75 444 6.289-K-20D 42-13 83-11 0.64 76 441 2.889-K-21F 42-13 83-11 0.75 96 442 1.589-K-22D 42-13 83-10 1.27 50 443 3.689-K-112 42-10 83-06 0.82 50 448 0.689-Kr-1A 41-53 86-08 0.66 50 433 0.289-Kr-1C 41-53 86-08 0.62 50 425 1.389-Y-205A 42-05 84-33 0.91 50 438 0.989-Q-64 42-11 81-40 0.83 50 444 4.289-Q-67 42-11 81-40 0.91 69 445 5.789-Q-71 42-11 81-40 0.60 95 442 3.389-BC-6A 42-00 81-31 1.16 50 468 0.789-Bc-9 42-01 81-32 1.20 31 466 0.889-Bc-10C 42-01 81-32 1.03 30 459 2.288-Aw-38C 41-42 80-45 2.18 50 529 0.290-Kz-35 39-43 75-02 0.70 50 450 0.490-Kz-36 39-43 75-02 0.77 50 444 1.6

Tarim Average 0.92 450 2.3Standard Deviation 0.39 23 1.9

*HI and OI values calculated using Leco TOC measurements; nc = not calculated.**M = Manas, X = Xishanyao, B = Badaowan, HL = Heavenly Lake, J = Jimsar, D = Dabanchang, T = Taoshuyuan, Kr = Korla, Y = Yengisar, K = Kuqa,

Bc = Baicheng, Q = Qiugetale, Aw = Awate, Kz = Kuzigongsu, PI = production index.

and in each of the petroleums. Pr/Ph ratios forJurassic shales and coals range from 1.3 to 8.0, aver-aging 4.5 (2σ = 1.7), whereas Pr/Ph ratios of thefour petroleum samples range from 4.3 to 5.0, aver-aging 4.7 (2σ = 0.4). Neither Pr nor Ph were detect-ed in sample 92-Bc-101 (northern Tarim oil seep)

due to biodegradation. With this exception, thehigh Pr/Ph ratios for most extract and oil samples(generally greater than 2.5) are consistent with ahigher plant-dominated nonmarine environment(Powell and McKirdy, 1973). Given the many poten-tial biological sources and diagenetic pathways for

Hendrix et al. 941

Table 3—Continued.

S2 S3 TOC (Leco)(mg HC/g) (mg CO2/g) PI S2/S3 (%) HI OI

91.4 4.2 0.03 21.9 65.7 124 5178.0 4.3 0.02 41.2 80.6 221 5130.6 2.8 0.02 46.8 75.5 170 3117.5 4.1 0.05 28.9 75.6 155 5

41.6 0.8 0.04 51.4 26.2 151 295.7 2.8 0.02 34.3 73.6 129 393.2 14.6 0.02 6.4 74.2 126 19

167.7 4.4 0.03 38.0 72.1 210 5183.8 7.6 0.02 24.2 53.0 232 9

80.0 2.5 0.02 31.7 42.4 184 5105.4 3.5 0.01 29.7 74.4 141 4124.2 5.8 0.02 21.5 77.3 163 7106.3 8.3 0.01 12.8 70.5 150 11133.8 1.9 0.02 71.1 78.1 173 2

66.5 12.6 0.00 5.3 74.4 93 17

114.4 5.3 0.02 31.0 67.6 161 738.9 3.8 0.01 16.9 14.8 37 5

81.5 18.5 0.01 4.4 63.0 112 253.2 30.9 nc 0.1 55.0 4 47

42.4 24.7 nc 2.3 59.0 58 3655.3 8.7 nc 3.0 5.7 76 16

182.5 5.5 0.02 33.2 74.4 225 6185.4 2.9 0.03 63.1 73.5 227 3

68.1 1.1 0.04 61.3 32.2 189 334.6 14.6 0.04 2.4 nc 50 2174.0 0.8 0.05 88.1 72.5 102 12.9 0.3 0.16 8.9 4.7 53 6

88.8 6.6 0.00 13.6 42.8 121 8151.8 7.0 0.01 21.8 81.7 194 8

59.9 4.0 0.02 15.0 72.3 84 5169.3 1.3 0.02 135.4 72.4 228 1119.9 2.3 0.05 52.6 67.5 166 3

82.2 1.3 0.04 65.7 51.4 194 214.9 9.4 0.05 1.6 77.7 22 1470.8 0.1 0.01 589.8 57.7 102 036.8 2.0 0.06 18.4 75.3 53 29.9 1.6 0.02 6.3 69.9 15 2

60.6 2.4 0.01 25.3 62.7 98 390.9 2.7 0.02 34.0 49.9 167 4

83.5 3.7 0.04 68.7 61.1 127 557.6 3.7 0.04 134.6 19.9 73 5

these compounds (e.g., Goossens et al., 1984; tenHaven et al., 1992), Pr/Ph ratios are used here onlyas supporting evidence for contributions of terres-trial organic matter and as a correlation tool.

Steroidal Hydrocarbons

In the Jurassic shales and coals and in the fourpetroleum samples, steranes were detected in

GC-MS (gas chromatography–mass spectrometry)analyses of saturate fractions, but their concentra-tions were typically too low to permit quantifica-tion except from m/z 217 traces acquired in mul-t iple ion detection (MID) mode. Withoutexception, the sterane distributions for rock andpetroleum samples are dominated by C29homologs, forming a cluster near the C29 apex ofa sterane ternary plot (Table 5; Figure 12). Eachof the petroleum samples is also dominated byC29 regular [i.e., 5α(H), 14αH), 17α(H); hereafterαα, and 5α(H), 14β(H), 17β(H); hereafter ββ]steranes, although petroleum samples 94-HU-1(Junggar) and 92-Bc-101 (Tar im) containmarginally higher proportions of C27 and C28 ster-ane homologs. Many rock extracts are sufficientlymature to exhibit complete isomerization of C29αα steranes at the C-20 position [i.e., S/(S+R) per-cent ratios of 52–55%; Seifert and Moldowan,1986], although some are incompletely isomer-ized (average = 34.3%; 2σ = 13.1%; Table 5).Percentages of C29 ββ 20S+20R relative to C29 αα20S+20R also indicate a spread of maturities with-in rock extract samples (average = 42.1%; 2σ =13.2%; Table 5), although none of the samplesappear to have reached peak maturity (maximum= 65.5%; peak = 67–71%; Seifert and Moldowan,1986). All four petroleum samples exhibit com-plete or nearly complete C29 αα 20S/S+R steraneisomerization (average = 49.8%; 2σ = 6.1%; Table5), but somewhat immature C29 ββ/(αα + ββ)ratios (average = 46.1%; 2σ = 5.8%; Table 5), sug-gesting that the oils were not derived from peakoil window conditions. The greater relative matu-rity of the petroleum results in higher abun-dances of C29 diasteranes compared to the abun-dance of these compounds in most source rocks(Figure 12).

Hopanoid Compounds

A prominent suite of hopanes was detected inevery rock extract except 89-K-112 (Figure 13;Table 5). Hopane distributions in each of thepetroleum samples are notably similar to those ofthe rock extracts, irrespective of basin. C29 and C3017α(H), 21β(H) hopanes (hereafter αβ) are typicallythe most abundant hopane in rock extracts andpetroleum (Figures 10, 13). Maturity levels of mostextracts and all four petroleums are sufficiently highto result in nearly full isomerization of C31 17α(H),21β(H) hopanes at the C-22 position (average =51.9%; 2σ = 11.5% for extracts, average = 59.7%; 2σ= 1.2% for oils; “peak” isomerization approximately57–62%; Seifert and Moldowan, 1986). Higherhopane homologs show progressively lower con-centrations, commonly up to C33 or C34 hopanes.


0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1

Junggar Depocenter

Junggar non-depocenter

Tarim Depocenter

Tarim basin flank

Awate (Aw); Baicheng (Bc); Qiugetale (Q)lower plate structural position?

Ro (%)

Gas WindowOil Window

Kuqa (K)

Xishanyao (X); Jimsar (J)Badaowan (B); Heavenly Lake (HL)

Kuzigongsu (Kz); Korla (Kr)

northwestern Tarim

Manas (M)

# ofsamples

5

10

0

5

10

0

5

10

0

5

10

0

5

10

0

Turpan Basin5

10

Taoshuyuan (T); Dabanchang (D);Flaming Mountain (42° 48′N 89° 5′E)

0

GasOil

Figure 6—Frequency plots of mean vitrinite reflectancevalues for Jurassic samples of central Xinjiang basins.Refer to Figure 1 for sample locations and Hendrix (1992)for Ro point-count histograms for individual samples.

C35αβ hopanes are detectable in many samples, butare not anomalously high with respect to C34αβhopanes. This stepwise decrease in hopane abun-dance from C31αβ to C35αβ homologs is consistentwith the presence of free oxygen in the diageneticenvironment which has oxidized the precursormolecule bacteriohopanetetraol (C35) to a C32 acid,possibly followed by loss of the carboxyl group toC31 if sufficient oxygen is present (Peters andMoldowan, 1993).

High concentrations of 28,30-bisnorhopane, com-monly regarded as an indicator of high-productivity

marine upwelling conditions (e.g., Curiale et al.,1985; Curiale and Odermatt, 1989), were detectedin samples 89-M-3D and 89-M-3H from the southJunggar basin depocenter. Identification was con-firmed by analysis of spectra. We believe this to bethe first report of the occurrence of this marker innonmarine strata.

In addition to homohopanes, distributions ofother pentacyclic terpanes are broadly similarbetween the rock extracts and petroleum, but alsoreflect the greater maturity of the petroleum. Tsand Tm [C27 18α(H), 22,29,30-trisnorneohopane

Hendrix et al. 943

Table 4. Elemental Analysis of Selected Jurassic Samples, Junggar, Turpan, and Tarim Basins

H C N O S Atomic AtomicSample Locality (%) (%) (%) (%) (%) H/C O/C

Southern Junggar Basin88-M-113A Manas 3.58 52.39 0.06 21.15 0.30 0.82 0.3088-M-114 Manas 4.34 70.36 0.51 13.87 0.93 0.74 0.1588-M-115A Manas 4.53 73.65 1.25 7.84 1.35 0.74 0.08 89-M-3H Manas 5.73 82.13 1.09 7.11 0.30 0.84 0.0689-M17A Manas 4.45 80.84 0.45 6.68 0.09 0.66 0.06 89-M17F Manas 4.07 84.99 0.41 5.68 0.06 0.57 0.0589-M-20 Manas 2.07 29.28 0.15 4.63 0.18 0.85 0.1289-M22A Manas 3.76 82.22 0.97 6.35 0.49 0.55 0.0688-J-3 Jimsar 4.53 48.23 0.17 15.78 0.29 1.13 0.2588-J-4 Jimsar 3.41 36.31 0.20 21.97 0.14 1.13 0.45 88-HL-102 Heavenly Lake 2.86 47.95 0.06 21.71 0.44 0.72 0.3488-HL-106 Heavenly Lake 4.99 73.78 0.11 20.38 0.24 0.81 0.2188-B-1 Badaowan 4.68 66.73 0.93 16.58 2.48 0.84 0.1988-X-1 Xishanyao 4.31 71.11 0.20 24.30 0.21 0.73 0.2688-X-3 Xishanyao 3.22 41.42 0.92 35.07 0.59 0.93 0.64

Junggar Average 4.04 62.76 0.50 15.27 0.54 0.80 0.21Standard Deviation 0.91 18.46 0.42 8.88 0.64 0.17 0.17

Western Turpan Basin88-T-4 Taoshuyuan 2.54 48.27 0.77 32.09 0.23 0.63 0.5088-T-5 Taoshuyuan 3.65 47.71 3.97 17.20 1.02 0.92 0.27

Turpan Average 3.10 47.99 2.37 24.65 0.63 0.77 0.38Standard Deviation 0.78 0.40 2.26 10.53 0.56 0.20 0.16

Northern Tarim Basin87-K-46 Kuqa 4.78 76.65 0.65 17.69 0.23 0.75 0.1789-K-19A Kuqa 5.32 81.21 0.43 8.99 0.47 0.79 0.0889-K-20B Kuqa 5.72 81.96 1.18 5.42 1.65 0.84 0.0589-K-20D Kuqa 2.24 38.35 0.18 4.16 0.38 0.70 0.0889-K-21F Kuqa 4.00 74.12 1.30 13.51 0.45 0.65 0.1488-Aw-38D Awate 3.75 90.75 0.39 4.66 0.32 0.50 0.0489-Bc-9 Baicheng 4.02 77.70 1.00 4.10 1.09 0.62 0.0489-Bc-10C Baicheng 5.23 79.35 0.39 7.59 0.26 0.79 0.0789-Q-67 Qiugetale 2.70 68.46 0.38 5.27 0.10 0.47 0.0689-Q-71 Qiugetale 2.74 40.87 0.44 3.33 0.25 0.80 0.0689-Y-201C Yengisar 5.45 77.37 0.78 8.50 0.41 0.85 0.0889-Y-205A Yengisar 2.98 80.31 0.33 7.96 0.20 0.45 0.07

Tarim Average 4.08 72.26 0.62 7.60 0.48 0.68 0.08Standard Deviation 1.22 16.12 0.36 4.27 0.44 0.15 0.04

and C27 17α(H), 22,29,30-trisnorhopane, respec-tively] were detected in most rock extracts and allfour petroleums (Table 5). Ts/(Ts+Tm) ratios(expressed as a percentage) in the rock extractsare generally low (average = 8.6%; 2σ = 12.9%),ref lecting the comparative immaturity of thesesamples (Seifert and Moldowan, 1986; Curiale,1992). The higher Ts/(Ts+Tm) ratios in thepetroleums (average = 37.7%; 2σ = 10.3%) supporttheir higher maturity, although the values are sta-tistically indistinguishable from those of high-maturity rock extracts from within and nearby theKalpin uplift (i.e., Baicheng, Qiugetale, Awate local-ities; average = 27.4%; 2σ = 16.9%). Gammacerane,commonly viewed as an indicator of abnormalsalinity (Brassell et al., 1988), is below detectionlimits in all Jurassic extracts and three of the fourpetroleums (Figure 13). Petroleum sample 92-Bc-101 contains detectable gammacerane (gammac-erane/C30 hopane = 0.097) and slightly lowerabundance of C31 hopanes than other petroleumand rock extract samples. Fan et al. (1990) hasreported gammacerane in four of ten Jurassic core

samples recovered from within the Tarim basin.Thus, it is likely that the gammacerane in sample92-Bc-101 reflects derivation from more basinalJurassic source rocks than the extracts from basinmargins reported here.

Tricyclic Terpanes

C19 through C29 tricyclic terpanes were detectedin low abundance in many of the rock extracts,although appreciable quantities of these com-pounds were present in the more mature rockextracts, particularly those from the northwesternTarim margin (Bc, Q, and Aw in Figure 1; Hendrix,1992; Figure 13). Small but significant quantities ofthese compounds were also detected in petroleumsamples 94-HU-1 and 92-Bc-101, which exhibit ahigher thermal maturity than most of the rockextracts. Aquino Neto et al. (1983) noted that thetricyclic/17α(H) hopane ratio increases for relatedoils of increasing thermal maturity. Comparisons ofthe distribution of tricyclic terpanes betweenpetroleum and rock extracts are similar, and areconsistent with a correlation between the two(Figure 13). Low C25/C26 ratios (<1) in rockextracts and the two oil samples suggest a lacus-trine source rather than a marine source (Figure13) (Zumberge, 1987; Peters et al. 1994).

Diterpenoid Compounds

A series of bi-, tri-, and tetracyclic diterpenoidswas detected in many of the rock extract samples.The compounds included phyllocladane, nor-lab-dane, nor-isopimarane, isopimarane, 4β(H) nor-isopimarane, and 8β(H) labdane, among others(Noble et al., 1985, 1986; Hendrix, 1992). In somecases, individual diterpenoid compounds were con-centrated enough to produce a detectable RIC(reconstituted ion chromatogram) peak (Figure 10;Hendrix, 1992). Comparison of the abundance anddiversity of diterpenoids indicates higher abun-dances of diterpenoid compounds, relative to n-alkanes, in Junggar rather than Tarim samples(Table 5). It is unclear whether these differencesare a function of diagenetic preservation orwhether they represent diversity of diterpenoidsources from one side of the Tian Shan to the other.Diterpenoids were not detected in any of thepetroleum samples.

Diterpenoids are generally interpreted as beingderived from conifers (Simoneit, 1977; Barrickand Hedges, 1981; Noble et al., 1985, 1986). Theprominent suites of diterpenoids in the rockextracts therefore suggest land-derived organicmatter associated with deposition of the coals and


1.8

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Junggar "Flank"Tarim "Flank"

Junggar Depocenter

Tarim DepocenterTurpan basin

LOCALITY

Lithologic Classification(inset into locality symbol)

SHALE (≤ 50% TOC) COAL (> 50% TOC) unknown TOC (not meas.)

Figure 7—Van Krevelen diagram for selected Jurassicsamples from Xinjiang basins. Thermal maturity path-ways from Tissot and Welte (1984). Refer to Table 3 forTOC values and Table 2 for specific compositional infor-mation. Junggar depocenter = Manas locality; Junggar“flank” = Jimsar, Heavenly Lake, Badaowan, Xishanyaosections; Tarim depocenter = Kuqa section; Tarim “flank”= Awate, Baicheng, Qiugetale, and Yengisar localities.

organic-rich shales. It is unclear whether theabsence of diterpenoids in the petroleum samplesis a function of their greater maturity, comparedto the source rock samples, or their derivationfrom source rocks without diterpenoid com-pounds. Although diterpenoids were prevalent inmany of the rock extracts, not all of the samplescontained detectable diterpenoids (Table 5).Thus, lack of diterpenoid compounds in thesepetroleum samples does not exclude a Jurassicsource.

Other Biomarkers

Carotenoids, such as β-carotane and γ-carotane,were not detected in any of the rock extracts or thefour petroleum samples. This consistent absence ofcarotanes is particularly significant because of theiruse in the correlation of Permian-sourcedpetroleum in the Junggar basin (Carroll et al.,1992).

Pentacyclic triterpanes (e.g., oleanane andlupane), significant components of many Tertiarycoal deposits (Ekweozor et al., 1979; Hoffman et al.,1984), are absent from rock extracts and petroleumexamined here. These compounds are derived fromangiosperms, which did not radiate significantlyuntil the Early Cretaceous. Their absence is consis-tent with the Jurassic age of these deposits.

THERMAL MATURITY

Sterane isomerization values are consistent withvitrinite reflectance measurements, which suggeststhat most of the rock samples either have notentered the oil window (Ro <0.6%) or are mature(Ro ∼0.6–0.9%) with respect to petroleum genera-tion. The greater thermal maturity of the northwest-ern Tarim basin, based on vitrinite reflectance data,is not evident in sterane and hopane isomerizationratios because these processes are complete atlower levels of thermal maturity. Similarly, diaster-ane/sterane percentage ratios of rock extracts (aver-age = 30.0%; 2σ = 10.1%) do not exhibit maturitytrends from basin flanks to depocenters. In con-trast, Ts/(Ts+Tm) ratios (Table 5) (Seifert andMoldowan, 1986; Curiale, 1992) vary widely, withthe most mature rock samples from northwestTarim yielding the highest Ts/(Ts+Tm) ratios (Table5). For a complete discussion of stereochemicalmaturity parameters measured in Jurassic rockextract samples from Xinjiang see Hendrix (1992).Given that rock samples analyzed in this study werecollected from uplifted basin margins and are farfrom producing areas, there is considerable uncer-tainty regarding the degree to which maturity ofthese samples are representative of subsurfaceJurassic rocks that may be currently expelling oil.For this reason, we have restricted our discussion ofJurassic strata to depositional issues and character of

Hendrix et al. 945

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OXYGEN INDEX (S3/TOC)*100

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JUNGGAR AND TURPAN BASINS TARIM BASIN

Other Junggar samples

Junggar samples described in this study

(Hendrix, 1992)

Other Turpan samples

Turpan samples described in this study

(Hendrix, 1992)

Other Tarim samples

Tarim samples described in this study

(Hendrix, 1992)Ty

pe

II

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II

Type IIIType III

Figure 8—Hydrogen index (HI) vs. oxygen index (OI) plots for all Jurassic samples collected from Xinjiang basinsin this study. HI and OI values derived from Rock-Eval pyrolysis and Leco TOC data. Refer to Table 3 and Hendrix(1992) for Rock-Eval and TOC data for each sample plotted here.

source sequences, rather than generative issues. Fordetailed discussions of the thermal history of basinmargins based on apatite fission-track data and

indexed to Ro data, see Hendrix et al. (1994a) andSobel and Dumitru (in press). Constraints on burialhistory and geologic evolution for these basins are


Figure 9—Pyrolysis–gas chromatograms (using techniques in Colling et al., 1986) for selected Jurassic samples fromthe (A–D) southern Junggar, (E–G) northern Tarim, and (H) western Turpan basins. The abundance of n-alkene/n-alkane doublets, relative to low-molecular-weight aromatic compounds, is typical of samples with oil generativepotential. Note the diversity of traces for this suite of samples, suggesting that a significant number of samples areoil prone, whereas several others are likely gas prone. The suggestion that some of these samples are oil prone isconsistent with the abundance of exinitic macerals observed in Jurassic rock samples (Table 2; Figure 5) and a posi-tive biomarker correlation between rock extracts and four petroleums from the Junggar, Turpan, and Tarim basins.

discussed in Graham et al. (1990), Hendrix et al.(1992), and Carroll et al. (1993).

DISCUSSION

Early and Middle Jurassic Lake Development

The widespread distribution of exclusively non-marine Lower and Middle Jurassic organic-rich stra-ta across the study area and adjacent regions(Vakhrameyev and Doludenko, 1977; Lai and Wang,1988; Hendrix et al., 1994b) led Huang et al. (1991)and Hendrix et al. (1992) to postulate regionallyextensive lakes in the southern Junggar, northernTarim, and Turpan basins. Indeed, all three basinshave had a protracted history of lacustrine develop-ment. Extensive Late Permian lakes (Carroll et al.,1992) and Late Cretaceous lakes (Shen and Mateer,1992) have been inferred from the Junggar sedi-mentary record. Regional lacustrine depositioncharacterized the Turpan basin in the Jurassic andin the Pleistocene (Huang et al., 1991; Nishidai andBerry, 1991), and large ephemeral lakes continue tooccupy significant portions of central Asia (e.g.,Lop Nur in the eastern Tarim basin, Manas andEbinur Lakes in the Junggar basin).

Most of the Lower and Middle Jurassic strataexposed on the f lanks of the three basins bearmeandering fluvial rather than lacustrine affinities.Nevertheless, the ubiquity of organic-rich strata,their considerable thickness, and the likelihood thatthe present basin edges expose only proximal litho-facies strongly suggest that regional lacustrine faciesoccupy basin depocenters in the subsurface.Additional circumstantial evidence supports thisconclusion. The fossil remains of a large aquaticdinosaur in Jurassic outcrops near Baicheng (Bc inFigure 1) (Wu, 1987) attests to the existence of adeep water body. Huang et al. (1991) reportedwidespread Jurassic lacustrine deposits from thesubsurface of the Turpan basin. Zhou et al. (1993)analyzed a series of produced oils from the Turpanbasin and cited their low sulfur content (0.03–0.06%), pristane predominance (average ∼2.3), highparaffinic content relative to conventional oil, andlow asphaltene content as consistent with a lacus-trine source. Zhou et al. (1993) also reported similarsterane and hopane distributions between these oilsand a series of Jurassic lacustrine mudstones collect-ed from core. Regional facies distributions and pale-ocurrent measurements along uplifted basin mar-gins (Hendrix et al., 1992) suggest that meanderingfluvial/deltaic strata trend into regional lacustrinestrata down depositional dip.

Global paleoclimatic modeling predictions(Kutzbach and Gallimore, 1989) and regional paleo-climate syntheses (Parrish, 1993) suggest that the

Jurassic organic-rich deposits across much of cen-tral Asia are the result of monsoonal circulationinduced by the configuration of the large Pangeanlandmass. According to Parrish (1993), during theLate Triassic–Early Jurassic, seasonally alternatinghigh and low pressure cells formed over proto-Laurasia and proto-Gondwana (Hendrix et al.,1992). These pressure cells forced seasonal airmasses to flow across the warm, equatorial TethysOcean, accumulating moisture and depositing itonshore in the form of monsoonal rainfall. Theexistence of widespread organic-rich facies is con-sistent with such a monsoonal climate. Hendrix etal. (1992) suggested that the Early and MiddleJurassic Tian Shan apparently did not possess suffi-cient relief to produce a rain shadow. Given thethick, widespread nature of organic-rich meander-ing fluvial sediments and the apparent duration oftheir deposition, any basinward lacustrine systemwas probably a long-lived feature existing, albeitperhaps intermittently, for millions of years.Cessation of the monsoon by the Late Jurassic ispredicted by global atmospheric circulation models(e.g., Kutzbach and Gallimore, 1989), and is consis-tent with regional development of Upper Jurassicred beds (e.g., Qigu Formation, Figure 2) and rela-tive increases in Classopollis pollen, derived fromdrought-tolerant, probably opportunistic Cheiral-ipidiaceae conifers (Vakhrameyev and Doludenko,1977; Vakhrameyev, 1982).

Sources of Organic Matter

Many lines of evidence suggest that higher plantswere the principal source of organic matter forLower through Middle Jurassic rock samples.Abundant higher plant detritus, ranging from logjams to well-preserved leaf impressions and rhy-zoids, is common throughout the deposits in allthree basins. Vitrinite is a major, if not dominant,maceral for all organic-rich Jurassic samples exam-ined (Table 2). Atomic H/C and O/C ratios suggest ahigher plant source (Table 4). Moderate to strongodd-over-even carbon preference indices and a dom-inance of medium- to high-molecular-weight n-al-kanes, typical for higher plant-derived organic mat-ter (Gagosian et al., 1981; Tegelaar et al., 1989),characterize most samples. C29 steranes are the dom-inant homolog, consistent with higher plant-derivedbitumens and oils (Huang and Meinschein, 1979; Ra-manampisoa et al., 1989). Diterpenoids, recognizedbiomarkers from conifers (Simoneit, 1977; Barrickand Hedges, 1981; Noble et al., 1985, 1986), weredetected in over 85% of the rock extracts. ClearlyEarly and Middle Jurassic rainfall patterns permittedvast coniferous forests to develop on both sides ofthe Tian Shan and also within the intermontane

Hendrix et al. 947

Table 5. Summary Biomarker Parameters for Jurassic Rock Extracts and Selected Petroleums, Xinjiang Basins

C29 StDominant C27 St C28 St C29 St (S/S+R αα)

Sample n-Alkane CPI Pr/ Ph (%) (%) (%) (%)

Junggar Basin89-M-3D 21 1.0 6.6 5.0 17.8 77.2 30.389-M-3H ** 23 1.8 4.4 3.0 14.8 82.3 33.289-M-17A nc nc nc 1.3 22.0 76.7 44.189-M-17F ** 23 1.1 5.4 3.8 23.1 73.1 41.389-M-20 ** 20 1.1 5.4 9.7 14.9 75.4 37.389-M-22A 23 1.1 3.4 2.1 22.6 75.3 40.789-M-27 25 1.3 2.1 2.9 6.2 90.9 39.688-M-115A 23 1.1 3.4 2.3 17.1 80.6 50.088-J-3 23 2.1 6.9 4.0 14.8 81.2 5.088-HL-102 23 1.3 3.4 6.1 20.5 73.4 33.288-HL-105 23 1.3 4.5 2.0 15.8 82.2 22.988-HL-106 23 1.5 5.5 1.2 18.7 80.1 21.688-B-1 21 1.3 2.6 3.7 4.6 91.8 32.688-B-2 23 1.3 8.0 1.5 20.3 78.3 41.088-X-1 23 1.7 3.8 2.6 17.3 80.2 2.3

Junggar Average 22.8 1.4 4.5 3.4 16.7 79.9 31.7Standard Deviation 1.2 0.3 1.8 2.2 5.4 5.5 13.6

Turpan Basin88-T-5 23 2.0 4.6 4.4 12.8 82.9 nd87-D-5A 22 nc nc 2.1 22.9 74.9 32.4

Turpan Average 22.5 nc nc 3.3 17.8 78.9 ncStandard Deviation 0.7 nc nc 1.6 7.2 5.6 nc

Tarim Basin89-K-19A 23 1.2 6.6 3.0 11.2 85.8 33.989-K-20B ** 23 1.1 4.3 22.5 9.1 68.3 38.389-K-20D ** 23 1.0 3.4 15.0 14.6 70.5 41.189-K-21F 21 1.1 nc 6.3 10.4 83.3 45.189-K-22D 18 0.9 1.3 1.4 18.8 79.8 44.889-K-112 17 0.9 5.3 nd nd nd nd89-Kr-1A ** 25 1.7 4.9 1.7 21.1 77.2 9.189-Kr-1C 25 1.6 6.9 1.7 15.6 82.6 10.389-Y-205A 21 1.1 5.7 3.2 16.8 80.0 12.789-Q-64 nc nc nc 3.5 18.1 78.4 44.889-Q-67 ** 20 1.0 nc 9.4 17.9 72.6 42.589-Q-71 17 0.9 2.4 3.5 0.9 95.6 45.489-Bc-6A 17 nc 2.6 16.2 18.0 65.8 41.289-Bc-9 ** 20 1.0 nd 14.7 15.6 69.7 35.789-Bc-10C 25 1.0 nd 14.8 20.1 65.1 43.888-Aw-38C 22 nc nc 38.7 17.4 43.9 44.690-K-35 23 1.1 3.8 3.2 19.1 77.7 46.590-K-36 25 1.0 4.9 5.1 12.4 82.4 46.3

Tarim Average 21.3 1.1 4.3 9.6 15.1 75.2 36.8Standard Deviation 2.9 0.2 1.7 9.9 5.0 11.3 13.0

Selected Xinjiang Petroleum Samples94-HU-1 (Junggar) nc 1.0 4.3 3.8 32.9 63.2 45.693-QK-6 (Turpan) nc 0.9 5.0 16.4 14.9 68.7 44.393-QK-101 (Turpan) nc 0.9 5.0 12.7 18.9 68.4 51.992-Bc-101 (Tarim) nc biodegr. biodegr. 19.1 19.9 60.9 57.6

Petroleum Average nc 0.9 4.7 13.0 21.7 65.3 49.8Standard Deviation nc 0.0 0.4 6.7 7.8 3.8 6.1

*nc = not calculated; nd = not detected. CPI (carbon preference index) = (n-C19 + n-C21 + n-C23 + n-C25 + n-C27 + n-C29)/(n-C20 + n-C22 + n-C24 + n-C26 + n-C28); quantified using RIC (where possible) or m/z 85. Pr/Ph = pristane/phytane; quantified using RIC. Percent C27 St = 100 × (C27/C27 + C28 + C29 20S + 20R5α(H),14α(H),17α(H) steranes; quantified using m/z 217. Percent C28 and C29 steranes were calculated in a similar fashion. Percent C29 St S/(S + R) = 100 ×C29 5α(H), 14α(H), 17α(H) sterane 20S/(20S + 20R); quantified using m/z = 217. Percent C29 St ββ/αα + ββ = 100 × C29 5α(H), 14β(H), 17β(H) 20S + 20Rsterane/(C29 5α(H), 14α(H), 17α(H) 20S + 20R sterane + C29 5α(H), 14β(H), 17β(H) 20S + 20R sterane); quantified using m/z = 217. Percent C29 DSt/(DSt +St) = 100 × (C29 13β(H), 17α(H) 20S + 20R diasterane)/(C29 13β(H),17α(H) 20S + 20R diasterane + C29 5α(H), 14α(H), 17α(H) 20S + 20R sterane); quantifiedusing m/z 217. Percent Ts/(Ts+Tm) = 100 × 18α(H)-22,29,30-trisnorneohopane/(18α(H)-22,29,30-trisnorneohopane + 17α(H)-22,29,30-trisnorhopane);quantified using m/z 191. Percent C31 Hop 22S/(S + R) = 100 × C31 17α(H), 21β(H) hopane 22S/(C31 17α(H), 21β(H) hopane 22S + 22R); quantified using m/z191. Hop/St = C30 17α(H), 21β(H) hopane/C29 20S + 20R 5α(H), 14α(H), 17α(H) steranes; quantified using m/z 217 and m/z 191. Diterpenoid diversity values= number of compounds. Diterpenoid abundance: t = trace, l = low, mod = moderate, maj = major component; quantified using m/z 123.

**Fractionated by liquid chromatography. All ratios are based on integrated peak areas.

portions of the range such as the Turpan basin.Vakhrameyev and Doludenko (1977) studied Jurassicfloras of central Asia, and concluded that a robustand varied coniferous flora inhabited the presentstudy area during the Early and Middle Jurassic.

Abundant hopanes in most of the rock extractsindicate significant contributions of organic matterfrom bacteria (Ourisson et al., 1979). Hopane/ster-ane ratios are a measure of the relative contribu-tions from bacteria and algae (Table 5) (Hoffman et

Table 5—Continued.

C29 St C29 (DSt/ (Ts/ C31 Hop(ββ/αα+ββ) DSt+St) Ts+Tm) (22S/S+R) Diterp. Diterp.

(%) (%) (%) (%) Hop/St Diversity Abundance

38.0 44.1 2.5 58.1 4.1 6–10 mod29.7 22.1 1.7 54.3 3.9 >10 majnc 22.9 2.0 58.6 5.3 nc ncnc 29.0 1.6 53.1 nc 1–2 t21.1 19.5 0.9 56.0 8.5 6–10 t18.4 25.4 1.9 57.7 nc 3–6 mod20.9 13.6 1.2 58.3 10.0 6–10 t27.8 20.1 1.8 59.1 9.6 6–10 l51.4 15.0 0.4 29.0 5.8 3–6 majnc 29.9 3.0 57.2 nc >10 majnc 28.2 0.9 53.2 4.8 1–2 majnc 16.5 0.7 55.8 1.9 1–2 majnc 22.7 0.3 57.7 19.6 1–2 modnc 28.0 1.8 58.1 3.2 1–2 modnc 41.0 2.0 23.0 6.5 nd nd

29.6 25.2 1.5 52.6 6.911.7 8.7 0.8 11.0 4.7

nc 42.2 1.3 15.7 4.9 6–10 mod65.5 27.4 13.6 23.9 nc 3–6 t

nc 34.8 7.4 19.8 nc nc ncnc 10.5 8.7 5.8 nc nc nc

nc 27.7 1.0 58.5 nc 1–2? t?50.5 44.3 11.5 54.9 nc 3–6 t47.5 38.2 11.5 57.8 36.5 1–2? t?43.6 41.5 7.8 56.0 13.1 1–2 t28.3 27.4 2.5 59.5 3.7 1–2? t?nc nd nd nd nc nd ndnc 22.2 nd 54.8 nc 1–2 lnc 23.1 0.6 46.2 10.8 1–2 modnc 38.0 1.5 49.5 5.1 6–10 l48.2 40.8 19.1 59.8 nc nc nc45.4 38.6 15.9 55.4 nc 3–6 t44.8 29.8 2.8 58.8 17.8 3–6 t58.3 32.8 45.1 50.4 nc 6–10 mod52.8 28.7 21.1 51.2 nc 3–6 t55.5 27.9 44.4 44.6 nc nd nd53.1 60.5 43.7 60.2 nc 3–6 t39.1 19.3 2.8 58.0 2.4 6–10 maj45.3 29.8 2.3 59.2 22.1 >10 l

47.1 33.6 15.4 55.0 13.9 nc nc7.7 10.1 16.2 4.9 11.4 nc nc

51.2 33.8 39.4 61.5 11.6 nd nd48.5 37.8 31.1 59.2 3.8 nd nd46.8 37.1 28.8 58.9 4.4 nd nd37.8 34.7 51.6 59.4 15.3 nd nd

46.1 35.8 37.7 59.7 8.8 nc nc5.8 1.9 10.3 1.2 5.6 nc nc

al., 1984; Duncan and Hamilton, 1988). Hopane/sterane ratios in rock extracts (average = 9.5; 2σ =8.5) and petroleum (average = 8.8; 2σ = 5.6) sug-gest that the terrestrially derived organic matter iscomplemented by contributions from bacteria. Thesimilarities in this ratio also link these petroleumsto a Jurassic source.

The marginally higher proportion of C27 and C28steranes in petroleum samples 94-HU-1 (Junggar)and 92-Bc-101 (Tarim), relative to rock extracts(Figure 12), is probably due to derivation of theseoils from basinal strata with slightly more lacustrinecharacter than the largely fluvial, coaly sections fromthe basin margins. The presence of diterpenoids in

85% of the rock extracts, all derived from basin mar-gins, and the corresponding lack of diterpenoids inall four petroleum samples is consistent with thishypothesis, although high maturity may also explainthe absence of these compounds in the oils.

Jurassic Strata as a Petroleum Source inXinjiang Basins

Both Chinese and Western studies report multi-ple source rocks in Xinjiang basins (Fan et al.,1990; Graham et al., 1990). Most investigations ofJunggar basin petroleum suggest that the extremely


89-Bc-6A

40003000200010000

89-K-20B

89-M-20

89-Q-67

4000300020001000040003000200010000

100% 100%

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17

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2319

29

17Pr

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19

27

Hopanes

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D

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27

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19

27

40003000200010000

17

Pr

23

19

29

27

(northern Tarim)

(northern Tarim)

(southern Junggar)

(northern Tarim)Ro = 0.72

Ro = 0.58

Ro = 1.16

Ro = 0.91

S2 = 41.62

S2 = 119.87

S2 = 14.93

S2 = 185.41

time (sec.)

time (sec.)time (sec.)

time (sec.)

Hop

-29

Hop

-30 Hop

-31

Figure 10—Reconstituted ion chromatograms (RIC) for saturate hydrocarbon fractions for selected Jurassic rockextracts, southern Junggar and northern Tarim basins. Labels on peaks refer to carbon number of n-alkanes. Pr =pristane. Hop-29, Hop-30, and Hop-31 = hopanes with 29, 30, and 31 carbon numbers, respectively. Evaporative lossof low molecular weight (<n-C16) probably occurred during sample handling. Note the slight to pronounced n-al-kane odd-over-even preference (n-C19 to n-C31); the predominance of hopanes, particularly in sample 89-M-20; andthe abundance of diterpenoid compounds (D for samples 89-M-20 and 89-Q-67).

organic-rich Upper Permian lacustrine facies is thedominant petroleum source for the basin (Grahamet al., 1990; Carroll et al., 1992). In addition, Jiangand Fowler (1986) suggested Carboniferous marinemudstones as a significant source for the giantKaramay field, although no evidence was presentedto document the age of the analyzed source rocks.The northern Tarim basin lacks the organic-richUpper Permian lacustrine facies of the Junggarbasin, but contains Ordovician marine black shalesgenerally regarded as the basin’s most significantsource rock (e.g., Graham et al., 1990); these shaleshave been geochemically correlated with variousTarim oils (Fan et al., 1990; Yang, 1991). Fan et al.(1990) also suggested that Cambrian dolomites andCarboniferous–Permian organic-rich shales andcoals from the northern Tarim basin are additionallocal sources of petroleum, although Graham et al.(1990) found the source rock quality of these stratato be poor.

Our geochemical results from four selectedcrude oils from all three basins suggest a geochemi-cal correlation with Jurassic organic-rich rocks.Pristane/phytane ratios are high in each petroleumand the Jurassic rock extracts, typical of terrestrialoils (e.g., Powell and McKirdy, 1973). Sterane andhopane distributions are similar to those of therock extracts (Figures 12, 13) and are notably differ-ent from distributions reported for Ordovician orPermian source rocks or oils from the Tarim andJunggar basins, respectively. For example, a strongpredominance of C29 steranes in all four oils is con-sistent with sterane distributions in Jurassic rockextracts and different from Cambrian–Ordoviciansource rocks and oils in Tarim, which have consid-erably larger relative abundances of C27 and C28steranes (Yang, 1991) (Figure 12), or Permian lacus-trine source rocks from Junggar, which have sube-qual amounts of C28 and C29 steranes (Carroll et al.,1992) (Figure 12). The abundance of tricyclic ter-panes relative to pentacyclic terpanes (Figure 13) isconsiderably lower for the rock extracts andpetroleum reported here than for Cambrian–Ordovician or Carboniferous–Permian sources andtheir corresponding oils reported from the Tarimbasin (Fan et al., 1990).

The presence of minor gammacerane in oil sam-ple 92-Bc-101 (northern Tarim basin) is an anomalyin the correlation with Jurassic source rocks.Gammacerane is absent from all of the Jurassic rockextracts and all petroleums except this sample(Figure 13). Results from Zhou et al. (1993) suggest-ed that basinal lacustrine mudstones, which locallycontain gammacerane, and basin margin f luvialcoaly strata, which lack gammacerane, both providesignificant petroleum source rock contributions tothe Turpan basin. A similar change in source rockfacies may also characterize the northern Tarim

Hendrix et al. 951

Figure 11—Whole-oil gas chromatogram traces for fourpetroleums from Xinjiang basins. Numbers above peaksrefer to number of carbons in n-alkanes. Pr = pristane,Ph = phytane. Paraffins and isoprenoids are biodegrad-ed in sample 92-Bc-101 (northern Tarim basin). On thebasis of biomarker correlations, each of thesepetroleums is consistent with derivation from Jurassicstrata.

basin because other geochemical parameters sug-gest that the sample was derived from lacustrineJurassic source rocks down depositional dip ratherthan f luvial coaly strata observed along upliftedbasin margins. Hopane and sterane biomarkerparameters are consistent with a correlationbetween oil sample 89-Bc-101 and Jurassic rockextracts (Figures 12, 13). The relative distribution ofC27, C28, and C29 steranes for this oil are notably dif-ferent from those values reported for northernTarim well Shacan 2 oil, considered to be derivedfrom Ordovician source rocks in the northern Tarimbasin (Figure 12). Oil sample 92-Bc-101 contains0.14% sulfur, consistent with a nonmarine source,especially considering the highly biodegraded char-acter of the oil. This value is lower than the sulfurcontent of 0.3% reported for the Shacan 2 oil (Yang,1991). Yang (1991) also reports that Carbon-iferous–Lower Permian source rocks from northTarim contain β− and γ-carotane, both of which arelacking in oil sample 92-Bc-101.

Increasing evidence suggests that coals and asso-ciated type III kerogen can yield not only gas orcondensate (e.g., Tissot and Welte, 1984), but alsosignificant quantities of oil (Murchison, 1987;Curry et al., 1994). According to Hunt (1991), thetwo main relevant criteria are the liptinite contentof the coal and the importance of adsorptioneffects during primary migration, which are relatedto seam thickness. In part, the traditional view thatcoals are largely gas prone may be the result of his-torical bias in the study of North American andEuropean Paleozoic coals, prior to the study ofMesozoic–Cenozoic coals containing contributionsfrom resinous conifers and angiosperms (Thomas,1982). Coals and related continental strata withtype III kerogen provide the source for commercialoil accumulations in sedimentary basins of NewZealand (Collier and Johnston, 1991; Johnston etal., 1991; Curry et al., 1994), Australia (Philp andGilbert, 1986; Curry et al., 1994), Indonesia(Hoffman et al., 1984; Bjorøy et al., 1988), Tanzania(Kagya et al., 1991; Mpanju et al., 1991), and China(Fu et al., 1991; Luo et al., 1991). Reports of lipti-nite-rich coals as oil source rocks (e.g., Püttman etal., 1986) are generally accepted, and recent TEM(transmission electron microscopy) observations oftype III kerogens (Liu and Taylor, 1991) have sug-gested that vitrinite-rich and even inertinite-richcoals may constitute important oil source rocks (cf.

Saxby and Shibaoka, 1986). In addition, composi-tional studies of bitumens and kerogens from coalsuggest that cracking to gas or condensate is not aprerequisite for expulsion of liquid hydrocarbonsfrom coals (Huc et al., 1986; Horsfield et al., 1988).

The oil-generative character of Jurassic coals andshales of Xinjiang basins (Figure 9) is almost cer-tainly due to the locally high percentages of hydro-gen-rich macerals, such as exinite, as noted forother oil-generative coals (Curry et al., 1994). Thegeochemical parameters that support the ability ofthese strata to generate oil and their biomarker cor-relation with petroleum from each of the threebasins examined are consistent with this idea. Thiswork indicates that Jurassic coaly deposits are acritical component of exploration risk reduction innorthwestern China.

CONCLUSIONS

(1) Lower and Middle Jurassic coal-bearing strataare widespread across much of central Asia and arewell developed in the southern Junggar, northernTarim, and western Turpan basins of northwesternChina. Thicknesses and estimated volumes ofJurassic coal in these basins make these among theworld’s largest coal deposits. Jurassic coaly strataexposed along uplifted basin margins in northwestChina were deposited in meandering fluvial and,locally, in lacustrine deltaic systems. Regionallyextensive Jurassic lakes probably developed basin-ward from present-day outcrop belts. High runoffconditions and possible regional lake developmentare consistent with global circulation modeling pre-dictions of Early and Middle Jurassic monsoons inthe study area (Kutzbach and Gallimore, 1989;Hendrix et al., 1992; Parrish, 1993).

(2) Field and laboratory data indicate a domi-nance of terrestrial organic matter in the Jurassicdeposits. Preserved plant remains, ranging from logjams to leaf impressions and in-situ rhyzoids, arecommon in Jurassic deposits. Maceral composi-tions are dominated by vitrinite and inertinite, butsubstantial exinitic material also occurs. Elementalanalysis indicates that the kerogens are dominantlytype III. Mean vitrinite ref lectance values rangefrom 0.42 to 2.18%, but indicate that Jurassic stratafrom most sample locations are slightly immatureto mature with respect to petroleum generation.


Figure 12—m/z 217 fragmentograms and sterane distributions for Jurassic rock extracts and petroleums. Ternarydiagram shows relative percentages of C27, C28, and C29 14α(H), 17α(H) steranes for all rock extracts, compared topetroleums. The similarity in m/z 217 traces and distribution of C27, C28, and C29 sterane components between rockextracts and petroleums suggests that the petroleums are derived from Jurassic strata. Shown also are comparativevalues for selected other oils and source rocks from Xinjiang basins.

Hendrix et al. 953

Turpan

Tarim

Junggar

C29

C28

C27

(60%)

60%

60%C27C29

C28

(60%) (100%)

Jurassic Rock Extracts Petroleums

93-QK-6, 93-QK-101 (Turpan)

92-Bc-101 (Tarim)

94-HU-1 (Junggar) (southern Junggar basin)Rock Extract 89-M-17F

(southern Junggar basin)Petroleum 94-HU-1

(Turpan basin seep)Petroleum 93-QK-6

(Turpan basin)

Petroleum 93-QK-101

(northern Tarim basin seep)Petroleum 92-Bc-101

(northern Tarim basin)

Rock Extract 89-Q-67

1. C27 5α(Η)14α(Η)17α(Η) 20S

6. C29 5α(Η)14α(Η)17α(Η) 20S sterane

2. C29 13β(Η)17α(Η) 20S diasterane

4. C29 13β(Η)17α(Η) 20R diasterane

STERANE IDENTIFICATION KEY

1

2

34 5

6

6

7

9

8

1

2

3

4

5

m/z 217

m/z 217

m/z 217

m/z 217

m/z 217

m/z 217

7

89

6

1

2

3

4

5

78

9

6

1

2

3

4

5

7

89

6

1

2

3

3

4

5

7 89

6

1

2

4

5

7

8 9

3. C27 5α(Η)14α(Η)17α(Η) 20R

7. C29 5α(Η)14β(Η)17β(Η) 20R sterane

8. C29 5α(Η)14β(Η)17β(Η) 20S sterane

9. C29 5α(Η)14α(Η)17α(Η) 20R

5. C28 5α(Η)14α(Η)17α(Η) 20R

T I M E

I N

T E

N S

I T

Y

Sha-2 oil (Yang, 1991)

Permian oil shale & Karamay oils

(Carroll et al., 1992; Jiang et al., 1988; Philp et al., 1989)


(southern Junggar basin)Rock Extract 89-M-17F

(southern Junggar)Petroleum 94-HU-1

(Turpan basin)Petroleum 93-QK-6

(Turpan basin)Petroleum 93-QK-101

(northern Tarim basin)Petroleum 92-Bc-101

(northern Tarim basin)Rock Extract 89-Q-67

m/z 191

m/z 191

m/z 191

m/z 191

m/z 191

m/z 191

23

4

5

6

7

9 1011 12

2

1

1

3

4

5

6

2

1

3

4

5

6

9

TERPANE IDENTIFICATION KEY

2

1

2

1

3

4

5

65

6

21C19

C20

C21

C23

C24

C26

C28

C29 (22R)

C29 (22S)

3

4

5

6

2

2

2

1

1

1

3

4

5

6

R

2. Tm = 17α(H)-22,29,30-trisnorhopane

1. Ts = 18α(H)-22,29,30-trisnorneohopane

C2917α(H)21ß(H)-norhopane C2917ß(H)21α(H)-norhopane

5. C3017α(H)21ß(H)-hopane 6. C3017ß(H)21α(H)-hopane

4. C3017α(H)21ß(H)-diahopane

9. C3117β(H)21α(H)-homohopanes

BNH. 28,30-Bisnorhopane

8. Gammacerane

10. C3217α(H)21ß(H)-homohopanes 11. C3317α(H)21ß(H)-homohopanes 12. C3417α(H)21ß(H)-homohopanes

7

9

10

11 12

7

10

11 12

9

7

10

1112

3

9

7

1011 12

8

7 10

911 12

9

7

1011

12

T I M E

I N

T E

N S

I T

Y

3.

(Moldowan et al., 1991)

BNH

(samples 89-M-3D and 89-M-3H only)

(southern Junggar basin)

(northern Tarim basin)

Presence of 28,30-Bisnorhopane

Tricyclic Terpanes

Rock Extract 89-M-3H

m/z 191

m/z 191

m/z 191

Rock Extract 89-Q64

(southern Junggar basin)Tricyclic Terpanes

Petroleum sample 94-HU-1

C19, C20, C21, C23, C24, C25, C26 (22R), C28 (22R), C29 (22R), C29 (22S) Tricyclic Terpane(labeled separately on trace)

C19C20

C21

C23

C24

C26

C25

C25

C28

T I M E

7. C3117α(H)21ß(H)-homohopanes (22S+22R isomers)

R

(confirmed by mass spectra)

C29 (22R)

C29 (22S)

Samples from the northwestern Tarim basin aremature to overmature. Biomarker distributions sup-port the conclusion that higher land plant organiccontributions are dominant, but also indicate sub-stantial bacterial contributions.

(3) Jurassic coaly strata have significant potentialas petroleum source rocks. Pyrolysis–gas chro-matography of selected samples in this study(Figure 9) yields prominent alkene-alkane doublets,typical of petroleum source rocks (Dembicki et al.,1983). Positive correlations with oils from thesouthern Junggar, northern Tarim, and Turpanbasins have been established for Jurassic coals.Biomarker parameters, indicating a positive correla-tion between rock extracts and petroleum, includesimilar sterane and hopane distributions, low abun-dance to absence of tricyclic terpanes with similardistributions where present, lack of gammaceranein all but one oil, lack of carotanes, and high pris-tane/phytane ratios typical of terrestrially derivedorganic matter and petroleum. Anomalies in the oil-source correlation include marginally higher C27and C28 steranes in the Junggar and Tarim oils, pres-ence of gammacerane in the Tarim oil, and lack ofditerpenoids in all four oils. Each of these anoma-lies can be attributed to derivation of petroleumfrom more distal, Jurassic lacustrine facies ratherthan the proximal coal-bearing facies describedhere. Recent advances in assessing coal as apetroleum source rock suggest that certain coalsmay be significant sources of oil, consistent withthe oil source potential interpreted for Jurassic coalmeasures from northwestern Chinese basins.

APPENDIX 1

Bulk Geochemical Analyses

A total of 159 organic-rich samples were collected for this study.A Delsi Instruments® Rock-Eval II was used to pyrolyze 144 samplesto provide bulk geochemical information prior to more detailedorganic geochemical analysis (Table 3) [see Hendrix (1992) for addi-tional data]. Total organic carbon (TOC) was determined using aLeco® instrument after crushing the samples and treating with HClto remove carbonates. These TOC values were used to calculate HI(hydrogen index) and OI (oxygen index) values.

Because Xinjiang Jurassic coals and organic-rich shales haveextremely high TOC values (average 67%), 8–10-mg samples wereused for Rock-Eval analysis. Test analyses conducted with varioussample sizes indicated that this procedure provides the most reli-able results (Hendrix, 1992). Larger sample sizes tended to satu-rate the FID (flame ionization detector). [See Espitalié et al.

(1977), Katz (1983), and Peters (1986) for more detailed discus-sions of the Rock-Eval pyrolysis technique and its limitations.] Inaddition to Rock-Eval and TOC analyses, bulk organic geochemicaltechniques employed in this study included visual kerogen (Table2), elemental analysis (Table 4), and vitrinite reflectance (Table 3).

Hydrocarbon Extraction, Fractionation, and Analysis

Detailed organic geochemical analyses were performed onselected samples to address issues of organic matter source, matu-ration, hydrocarbon generation potential, and comparison withknown petroleum. Selected samples were trimmed (approximate-ly 10 g), rinsed in CH2Cl2 to remove organic contaminants, andpulverized to approximately100 µm. Approximately 2 to 9 g ofeach sample were solvent-extracted via Soxhlet (3:1;CH2Cl2:CH3OH). Extraction typically proceeded for over 72 hr (3days) before negligible coloration of solvent was observed. Theresulting extract/solvent mixture was roto-evaporated and dried ina nitrogen stream at or less than 40°C.

Because iron sulfide (FeS2) is commonly observed on fresh frac-ture surfaces, especially in the coals, two methods were used toremove sulfur. For all but eight samples (Table 5), extracted bitumenwas percolated through Cu powder, reduced by cleaning with HCl,and rinsed with deionized H2O, acetone, CH3OH, and CH2Cl2. Inaddition, sample extracts with excessive elemental sulfur were driedand exposed to direct contact with CH2Cl2-rinsed Hg. Desulfurizedextracts were fractionated into aliphatic, aromatic, and NSO-com-pound fractions using thin-layer chromatography (glass plates coatedwith 0.25 mm silica gel, eluted for 24 hr with ethyl acetate and acti-vated at 300°C for 1 hr prior to use) and hexane eluant.

Eight samples (Table 5) were extracted and fractionated as fol-lows. Powdered samples were Soxhlet extracted (100% CH2Cl2).Extracts were dissolved in methylene chloride and concentratedto 1 mL volume; 25 mL pentane was added to precipitateasphaltenes (precipitation accelerated by refrigeration for 4 hr at1–2°C). Asphaltenes were removed by centrifuging. Deasphaltedextracts were fractionated using a gravity-fed, silica-gel liquid chro-matography column (100–200 µm silica gel supports activated at400°C prior to use). Saturates, aromatics, and NSO-compoundswere eluted with 100% CH2Cl2, 50:50 CH2Cl2:CH3OH, and 100%CH3OH, respectively. Fractions were removed under a 40°C waterbath in a nitrogen stream. Fractionation of all four petroleums ana-lyzed in this study was performed using this method.

Gas chromatography–mass spectrometry (GC–MS) of aliphaticcompounds was performed using a Varian Model 3400® gas chro-matograph (on-column and split-splitless injectors used; 30 m ×0.25 mm i.d., fused silica capillary column with a 0.25 µm DB-5coating). The GC was directly interfaced with a Finnigan-Mat TSQ-70® mass spectrometer. Full data acquisition GC-MS and multipleion detection GC-MS (m/z 156, 217, 231, 253, 400, 191) were per-formed for 39 total samples (19 samples plus 16 from Junggar and4 from Turpan, including petroleum).

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ABOUT THE AUTHORS

Marc S. Hendrix

Marc S. Hendrix received hisB.A. degree in geology fromWittenberg University (Springfield,Ohio) in 1985 and his M.S. degreein geology at the University ofWisconsin–Madison in 1987. Hebegan his studies of Mesozoicbasins in western China as a Ph.D.candidate at Stanford University.He received his degree in 1992 andhas since conducted sedimentarybasin analysis and petroleum potential assessment stud-ies of Mongolian sedimentary basins. In 1994, he joinedthe faculty at the University of Montana as an assistantprofessor.

Simon C. Brassell

Simon C. Brassell graduatedfrom the University of Bristol,United Kingdom, with a B.Sc.degree in chemistry and geology(1976) and a Ph.D. in organic geo-chemistry (1980). He was therecipient of a Royal Society 1983University Research Fellowship atBristol, then moved to the U.S. asan associate professor at StanfordUniversity (1987–1991). Since1991, he has been professor of geological sciences atIndiana University. His research interests lie in biogeo-chemistry, focused on the use of the molecular and iso-topic characteristics of organic matter to assess andinterpret stratigraphic, environmental, and climatic vari-ations in the sedimentary record.

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Alan Carroll

Alan Carroll is a research special-ist in the integrated basin analysisdivision for Exxon ProductionResearch Company. Between 1983and 1986, he worked as an explo-ration and production geologist forSohio. He received geology degreesfrom Carleton College (B.A., 1980),the University of Michigan (M.S.,1983), and Stanford University(Ph.D., 1991). His research inter-ests include sedimentary basin analysis, lacustrine sedi-mentology and sequence stratigraphy, organic geochem-istry, and the tectonic evolution or northwestern China.

S. A. Graham

Stephan A. Graham holds threedegrees in geology (B.A., 1972,Indiana; M.S., 1974, and Ph.D.,1976, Stanford), and spent 1976–1980 with Exxon ProductionResearch and Chevron. Since 1980,Graham has been a professor atStanford University, specializing inbasin studies, particularly in theUnited States, Mongolia, andChina. He received AAPG’s SprouleAward (1985) and was an associate editor of the AAPGBulletin from 1983 to 1989.

sedimentology, organic geochemistry, and petroleum ...carroll/publications/pdf/hendrix et al.,...

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