Late Paleozoic tectonic amalgamation of northwestern China: Sedimentary record of the northern Tarim, northwestern Turpan, and southern Junggar Basins

A. R. Carroll Exxon Production Research Company, P.O. Box 2189, Houston, Texas 77252-2189 S. A. Graham M. S. Hendrix* Department of Geological and Environmental Sciences, Stanford University, D. Ying Stanford, California 94305-2115 D. Zhou }

ABSTRACT dominantly of lithic volcanic grains similar Ren et al., 1987; Coleman, 1989; Wang et to the rhyolite. al., 1990). The origin and history of these Sedimentary rocks contained in basins In contrast to the Tarim basin, calc-alka- elements, however, and the nature of the adjacent to the Tian Shan provide a long line volcanic rocks and volcanogenic sedi- growth of the Asian continent during this and complex record of the late Paleozoic mentary rocks dominated Carboniferous time remain controversial. In contrast to the continental amalgamation of northwestern and Permian sedimentation in the northern better-understood collisional histories which China, complementing that provided by Turpan and northwestern Junggar basins. mark the closure of the Tethyan oceanic rocks preserved within the range. This Volcanic arcs remained active in the North realm (e.g., the Alpine and Himalayan col- record, which comprises dramatic changes Tian Shan and Bogda Shan through the lisions), the central Asian ‘‘Altaid’’ orogenic in sedimentary facies, sediment dispersal early Late Carboniferous, depositing a ki- belts (cf. S¸engo¨r et al., 1993) generally lack patterns, sandstone provenance, and basin lometers-thick interval of deep marine sed- intact ophiolites or other means of clearly subsidence rates, broadly supports previous iment-gravity flows in the northwestern defining sutures between previously distinct interpretations of a two-part evolution of Junggar basin. Major arc magmatism tectonicblocks.Reactivationofintraplateor- the Tian Shan: Late Devonian to Early Car- ceased in the Late Carboniferous in re- ogenic belts during subsequent interplate in- boniferous collision of the Tarim continen- sponse to closure of the oceanic basin be- teractions (cf. Hendrix et al., 1992) has fur- tal block with the Central Tian Shan, fol- tween the combined Tarim/Central Tian ther obscured these boundaries, making lowed by collision of this combined block Shan block and the North Tian Shan/Bogda interpretation of original Paleozoic struc- with island arcs in the north Tian Shan and Shan arcs. Upper Carboniferous through tures nearly impossible. One approach to Bogda Shan in Late Carboniferous–Early Lower Permian rocks in the northwestern this problem has been to identify magmatic Permian times. The first collision resulted Junggar basin compose the sedimentary fill fronts associated with ancient magmatic arcs in widespread angular unconformities of a bathymetric basin of oceanic depth (on and their associated accretionary com- within the Tarim basin. Continued conver- the northern side of the volcanic arcs), cul- plexes, which might then be used as struc- gence following the collision created a long- minating in a 1000-m-thick marine regres- tural markers to reconstruct plate interac- lived flexural foredeep along the north- sive sequence. Middle to Upper Permian tions prior to final amalgamation (S¸engo¨r et ern margin of the Tarim block, which sandstones were derived from the uplifted al., 1993). This approach, although promis- received at least 2000 m of Lower Carbon- paleo–Tian Shan and bear the distinctive ing, is hampered by the difficulty in distin- iferous through Lower Permian fluvial and provenance imprint of granitic rocks pres- guishing between different subduction-ac- marine sediment derived from the interior ently exposed within the range. Late Per- cretion complexes formed at approximately of Tarim. Subsequent Early Permian conti- mian subsidence of the Junggar basin the same time, and by the structural dislo- nental extension of the northern Tarim ba- accommodated >5 km of nonmarine sedi- cation of these complexes along later strike- sin resulted in the deposition of interbedded ments; however, the cause of this subsidence slip faults. Reconstructions derived from the nonmarine siliciclastic sedimentary rocks and its relationship to regional tectonic present positions of ancient subduction and mafic to felsic volcanic rocks. Sand- events remain controversial. zones are therefore nonunique. stone within this interval was derived from An alternative (and complementary) the paleo–Tian Shan, and is composed pre- INTRODUCTION source of data lies in the sedimentary basin sequences preserved in areas within and ad- Northwestern China and adjacent areas jacent to the Altaid orogenic belts. These of central Asia comprise a collage of dispar- deposits possess the singular advantage that they contain a vertically stacked and rela- *Present address: Department of Geology, ate tectonic elements that amalgamated University of Montana, Missoula, Montana during the late Paleozoic (e.g., Burrett, tively undeformed record of erosion (due to 59812. 1974; Zonenshain and Gorodnitsky, 1977; orogenic uplift) and sedimentation (due to

GSA Bulletin; May 1995; v. 107; no. 5; p. 571–594; 18 figures; 1 table.

571 CARROLL ET AL.

Figure 1. Location map depicting Carboniferous-Permian outcrops and sedimentary basins of northwestern China (modified from Chen et al., 1985). Boxes indicate the approximate locations of Figures 4, 8, and 10.

tectonic subsidence) and therefore avoid employed. As a result, numerous miscon- the evolution of the adjacent orogenic belts. many of the difficulties inherent in unravel- ceptions concerning the geology of the sed- This study is based on fieldwork during the ing complex structural overprints. They of- imentary basins of northwest China have be- summers of 1987, 1988, 1991, and 1992 by ten provide a more continuous and precise come embedded in the literature. As an workers from Stanford University, the Chi- record than that available from deformed example, the Junggar basin has been de- nese Academy of Geological Sciences, and belts. To the extent that such deposits scribed repeatedly as a Late Permian ‘‘back- the Xinjiang Bureau of Geology and Min- record distinctive patterns of regional sub- arc basin’’ (Hsu¨, 1988, 1989) despite the fact eral Resources. Although reconnaissance in sidence or sedimentary provenance, they that its known Upper Permian and younger nature, the data presented here provide a may also aid estimates of the history and sedimentary fill is exclusively nonmarine basis for evaluating alternative hypotheses magnitude of offset on hypothesized strike- (Carroll et al., 1990; Allen et al., 1991; Car- for the evolution of northwestern China and slip faults. Key to the utility of these deposits roll et al., 1992). provide a starting point for more compre- is a detailed understanding of the sedimen- This study focuses on areas adjacent to hensive future studies. tary facies, paleo-sediment dispersal direc- the Tian Shan (shan is Chinese for moun- tions, sandstone provenance, and basin geo- tains) in Xinjiang Uygur Autonomous Re- PALEOZOIC TECTONICS OF history they encompass. Unfortunately, very gion, northwestern China, and provides new NORTHWESTERN CHINA few well-documented, firsthand geologic field data on Carboniferous and Permian field data from northwestern China have outcrop exposures of sedimentary rocks of The Tarim basin (Fig. 1) is underlain by been reported in the western literature. Past the southern Junggar, northwestern Turpan, one of the major cratonal blocks of China, attempts to synthesize such data in a plate and northern Tarim basins (Fig. 1) that bear with Precambrian basement exposed all tectonic framework have relied heavily on directly on the history of late Paleozoic tec- along its periphery (Zhang et al., 1984; Chen (often incomplete) reports from the Chi- tonic amalgamation. We present here a mul- et al., 1985). Paleozoic rocks reach total nese literature, which in many instances tifaceted sedimentary basin analysis, includ- thicknesses of up to 12 km in the northeast- were derived from still earlier studies. Al- ing sedimentary facies, paleocurrent, and ern Tarim basin (Tian et al., 1989), and total though this approach has revealed some of sandstone provenance analyses, and recon- sediment fill may exceed 15 km (Lee, 1985). the principal attributes of the geology of structions of late Paleozoic basin subsid- Published gravity data indicate a subsedi- northwestern China, it has also prevented ence. These data provide a unique record mentary crustal thickness of only 25 km independent evaluation of the primary data not only of the basins themselves, but also of (Lee, 1985), suggesting that Tarim was

572 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA thinned by continental extension, likely dur- Tian Shan and, along with scattered ultra- in the full outcrop. Photographic documen- ing the Late Proterozoic (‘‘Sinian’’). Subse- mafic rocks and radiolarian cherts, are as- tation of selected outcrop facies are in- quent thermal subsidence resulted in the sociated with what is informally known as cluded both here and in Carroll et al. (1990). deposition of shallow marine carbonates to the ‘‘Junggar ocean’’ (Carroll et al., 1990). In addition to describing sedimentary facies, marine shale and sandstone in the Cambrian The Junggar and Turpan basins (Fig. 1) ap- we measured paleocurrent indicators where and Ordovician in the northwestern Tarim pear to be underlain by a basement of struc- possible. Although the numbers of pa- basin, and siliciclastic submarine fans to the turally imbricated Ordovician to Lower Car- leocurrent measurements reported are not northeast (Anonymous, 1991). Similar fa- boniferous accretionary metasedimentary sufficient to establish their statistical signif- cies have been penetrated by boreholes in rocks and oceanic crustal fragments (Zhu, icance, qualitative examination confirmed the northern Tarim basin in the Sha-Can 1984; Coleman, 1989; Feng, 1989; Carroll et that they are representative of larger popu- No. 2 well (Fig. 1; Nishidai and Berry, 1990) al., 1990). The origin of the Turpan basin is lations of indicators (also see Carroll, 1991, and in the central Tarim basin in the Ta- in dispute. Allen and Windley (1993) sug- for additional paleocurrent measurements Zhong No. 1 well (Fig. 1; Anonymous, gested that the Turpan may have already not presented here). Except where noted, 1991), and proprietary seismic reflection been a distinct basin in the Permian, the inferred chemical composition of vol- data suggest that lower Paleozoic cover whereas Hendrix et al. (1992) argued on the canic rocks is based on field characteristics. strata continue relatively unbroken across basis of sediment fill thicknesses and pa- The following discussion proceeds geograph- most of the basin (Yan et al., 1983; Tian et leocurrent directions that the Turpan basin ically from the western Tarim basin to the al., 1989; Graham et al., 1990; Anonymous, did not emerge as a discrete entity until the southeastern Junggar basin. 1991). In the northwestern Tarim basin, Sin- Jurassic. Precambrian rocks are not exposed ian through Devonian rocks are made up of within either the Turpan or Junggar areas, Tarim Basin shallow marine to nonmarine carbonates and isotopic data from Upper Carbonifer- and sandstone, which are unconformably ous through Permian intrusives are consist- Western Tarim Basin. Upper Paleozoic overlain by the Carboniferous and Permian ent with oceanic crustal sources (Feng et al., marine rocks are thrust southward over Cre- deposits described in this study. 1989; Hopson et al., 1989; Kwon et al., taceous red beds north of Kashgar near The Tian Shan (Fig. 1), which exceeds 1989). The North Tian Shan and Junggar Wenguri village (Fig. 1). Lower Permian 2500 km in length and 7400 m in elevation, and Turpan basins also contain voluminous fusulinids (Parafusulina, Rugosofusulina) owes its present physiographic expression to Upper Devonian through Upper Carbonif- have been found in equivalent beds nearby tectonic reactivation through shortening erous arc volcanic rocks and volcanogenic (Liu Xun, personal commun., 1992), but due and uplift during the Himalayan orogeny. deep marine sedimentary rocks deposited in to the structural complexity and lack of However, the Tian Shan also contain two the Junggar ocean (Wang et al., 1986, 1990; study, the precise age of the rocks in the Paleozoic sutures which divide the range Carroll et al., 1990; Windley et al., 1990; study area remains uncertain. Rocks include into three separate tectonic entities: the Allen et al., 1991; Allen and Windley, 1993). silicified carbonate turbidites, lenticular, in- South Tian Shan, Central Tian Shan, and traclastic conglomerate, and thin carbonate/ North Tian Shan (Li et al., 1982; Ji and Co- CARBONIFEROUS-PERMIAN siliciclastic interbeds with bedding-plane ney, 1985; Wang et al., 1986, 1990; Windley STRATIGRAPHY AND SEDIMENTARY trace fossils and possible hummocky cross- et al., 1990; Allen et al., 1991, 1992). The FACIES stratification. Depending on the structural South Tian Shan appear to have originated restoration, this section may record an as an ocean basin during the Late Ordovi- This study relies principally on the avail- evolution from basinal turbidites through cian or Silurian. Fragments of oceanic crust able Chinese literature concerning the age slope and shelf deposits. In any case, Lower are presently in fault contact with thick sec- of upper Paleozoic rocks in the study areas Permian sedimentary facies at Wenguri are tions of turbidite sandstone, shale, pelagic (Fig. 2; Zhang, 1981; Zhang et al., 1983; interpreted to represent deeper-water con- limestone, and chert of Middle Silurian to Chen et al., 1985; Liao et al., 1987; Chang, ditions than those to the northeast at Yin- middle Carboniferous age (Ektova and 1988). On the basis of a limited paleonto- gan-Sishichang (see below). Bel’govskiy, 1980; Vikhter and Sher, 1980; logical sampling from selected strata, these Northwestern Tarim Basin–Bachu Uplift. Kristov and Mikolaychuk, 1983; Zhang, age assignments appear to be reliable. Ex- The Paleozoic section in the Xiaohaizi area 1981; Wang et al., 1990). The Central Tian cept where supported by radiometric dating, of the Bachu uplift consists of a largely con- Shan, which are bounded on the north and the reported ages of mid-Permian and formable succession of Silurian through south by belts of ultramafic rocks sometimes younger rocks are imprecise, however, due Lower Permian shallow-marine to nonma- interpreted as ophiolite fragments, contain to their nonmarine character and faunal en- rine carbonate and siliciclastic sedimentary one or more discrete Precambrian blocks demism. We have attempted to report all rocks. Ordovician shallow-marine limestone (e.g., Zhang et al., 1984). The Central Tian stratigraphic assignments according to the crops out in nearby fault blocks. Lower Car- Shan were episodically intruded throughout time scale of Harland et al. (1990). boniferous through Lower Permian rocks the Paleozoic and during the late Paleozoic We measured detailed sections in the Ta- compose a thin (ϳ600 m) but apparently were the locus of arc magmatism on both its rim, Turpan, and Junggar basins, 15 of conformable sedimentary section inter- northern and southern margins (Chen et al., which are presented here. The measured preted to have been deposited in a shallow- 1985; Hopson et al., 1989; Wang et al., 1990; sections, which present the first detailed marine platform-basin (Liu and Xiong, Allen et al., 1992). documentation of these upper Paleozoic 1991; Wang et al., 1991). The approximate Devonian to Carboniferous calc-alkaline strata in the English-language literature, base of the Carboniferous is marked by a volcanic rocks and deep marine volcano- were carefully chosen to be reasonably rep- thin quartz-pebble conglomerate (30–50 genic sedimentary rocks dominate the North resentative of the sedimentary facies present cm) overlying a scoured surface on cross-

Geological Society of America Bulletin, May 1995 573 CARROLL ET AL.

The Xiaohaizi section is cut by an exten- sive series of gabbroic dikes and by a small composite granitic intrusive; all of these in- trude Devonian sandstone, and most cut the Carboniferous and extend into lower Per- mian rocks (Fig. 3A). The dikes share a common orientation of approximately north-northwest/south-southeast and on av- erage cut normal to the gently dipping host strata. 40Ar/39Ar radiometric dating of two different dikes yielded ages of 274.6 Ϯ 1.5 and 275.6 Ϯ 0.89 Ma (M. McWilliams and B. Hacker, personal commun., 1993–1994). The Carboniferous section also hosts a com- plex of sills related to the dikes; the overall thickness of the silled interval is ϳ50–100 m. Basalt flows such as those at Yingan and Sishichang (see below) are not preserved in the Lower Permian section exposed at Xiao- haizi. We interpret the Xiaohaizi intrusives to indicate at least locally elevated heat flow and limited extension. However, sheeted dikes, pillow lavas, deep marine sedimentary rocks, or any other evidence of oceanic crustal materials are absent. An alkali igne- ous complex exposed immediately south of the Xiaohaizi area includes gabbro, diorite, syenite, and alkali basalt (J. Liou and X. Wang, personal commun., 1994) that in the past has been incorrectly described as a kim- berlite (Du, 1983). 40Ar/39Ar dating of brec- ciated dikes within this complex indicates they were emplaced at about the same time as the gabbroic dikes described above, giv- ing ages of 279.5 Ϯ 0.8 Ma (hornblende) and 278.68 Ϯ 0.82 Ma (phlogopite) (M. McWil- liams and B. Hacker, personal commun., 1993–1994). Northwestern Tarim Basin–Wusi. Excel- lent exposures of Paleozoic sedimentary rocks are afforded by a series of predomi- nantly southeast-directed thrusts that make Figure 2. Carboniferous-Permian chronostratigraphy and partial faunal and floral lists up the Kalpin Uplift (Fig. 1; see McKnight for northwestern China. Radiometric time scale and stratigraphy modified from Harland et al., 1989, and Nishidai and Berry, 1990, et al., 1990. Stratigraphic and paleontological data are modified from Chen et al. (1991), for structural analysis of this area). At least Liao et al. (1987), Liu and Xiong (1991), Wang (1991), Wang et al. (1991), Xiong (1991), 2000 m of Lower and middle Carboniferous and Zhang (1981). rocks are exposed near the town of Wusi, on the northwestern edge of the Kalpin uplift (Fig. 4). Upper Carboniferous and Permian bedded, fluvial Devonian red sandstone and subsurface of the northern Tarim basin, rocks are not present in this area, apparently mudstone. Above the conglomerate, sand- where they include halite and may attain due to erosion resulting from post-Paleozoic stone beds gradually decrease in frequency thickness of 200–300 m (Liu He and uplift. A pronounced angular unconformity and are interbedded with thin carbonate Zhang Zhaixin, personal commun., 1992). separates Cambrian through Silurian shal- grainstones. The upper part of the Lower Similar rocks, punctuated by intertidal to low-marine rocks from mudstone and fluvial Carboniferous section contains thin inter- supratidal deposits and exposure surfaces, conglomerate of the Lower Carboniferous bedded mudstone, micrite, grainstones, and continue upward through the middle Car- Kongtai’aikengou Formation. A sampling of gypsum beds, which are interpreted to have boniferous. Interbedded Lower Permian pebble imbrications and cross-beds in these been deposited in a lagoonal setting (Liu limestone and nonmarine sandstones and conglomerates suggests transport to the and Xiong, 1992; Wang et al., 1991). mudstones lie disconformably over the north (Fig. 5A), although the data are not Evaporites have also been reported in the middle Carboniferous. conclusive. Qualitative examination of sev-

574 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA

covered interval into shelf deposits with hummocky cross-stratification (Fig. 5C) then deepens again into slope olistostrome facies (Fig. 5D). Olistostrome blocks up to 10 m long occur near the top of the expo- sure; these blocks are composed of layered dark gray shale and micrite similar to the enclosing sedimentary rocks. These blocks are interpreted to have been deposited by gravitational collapse of updip slope or car- bonate platform sedimentary rocks. Very few conclusive paleocurrent indicators are present in the shelf and slope facies, but the few that are present are consistent with northward sediment transport (Fig. 5D). This transport direction is paleogeograph- ically consistent with the regional deepening of sedimentary facies from the Yingan- Sishichang area (southeastern Kalpin uplift) to Wusi (northwestern Kalpin uplift), and A with the apparent Tarim basin provenance of underlying Carboniferous conglomerate clasts. Similar gravity flow deposits have been reported elsewhere along strike in the northern Tarim basin (Zhai et al., 1991) and have been observed by us northeast of Baicheng (Fig. 1), confirming that the Car- boniferous foredeep paralleled the present basin margin. The exposures we examined appear to represent only the southern edge of this foredeep, however, and may not be indicative of all of its sedimentary fill. No doubt a substantial portion of this fill came from erosion in the area of the present Tian Shan and was transported longitudinally down the axis of the basin. Unfortunately, the exposures needed to test this hypothesis are difficult to access due to their present location within the southern Tian Shan. Yingan-Sishichang. In contrast to the B Wusi section, Upper Carboniferous rocks Figure 3. Outcrop photographs of Carboniferous and Permian sedimentary rocks in the rest unconformably on Devonian red beds northwestern Tarim basin. A. Dikes cutting Lower Carboniferous lagoonal deposits in the at sections near Sishichang and Yingan Xiaohaizi area (see Fig. 1 for location). The dikes are oriented north-northwest–south- (Figs. 3B and 6A). The Upper Carbonifer- southeast and extend upsection into Lower Permian marine and nonmarine sedimentary ous Sishichang Formation (Fig. 6B) grades rocks. B. Upper Carboniferous sandstone and limestone resting unconformably on Devo- upward from channeled, lenticular con- nian red mudstone and sandstone near the village of Sishichang (see Fig. 4 for location). glomerate and sandstone into interbedded The unconformity is marked by both a color change and slight angularity. sandstone, mudstone, and limestone. Con- glomerate beds near the base of the section range from 5 cm to4minthickness, with eral conglomerate intervals suggests an un- idly upward into interbedded mudstone, maximum clast sizes between 1 cm and 8 cm. roofing sequence of lower and middle Pale- dark gray micrite, and siliciclastic turbidites The lower sandstone beds have scoured ozoic rocks typical of those exposed to the (Fig. 5B), recording a rapid deepening of bases and commonly contain basal pebble southeast; lower conglomerate beds contain depositional environments. Gigantoproduc- lags, lateral accretion surfaces, and trough more red clasts from the Devonian nonma- tid brachiopods (identified as Delepinea cross-beds; paleocurrent measurements rine section, whereas the uppermost con- subcarinata; A. R. Ormiston, personal com- suggest net transport of sediment to the glomerate contains a higher proportion of mun., 1989), support a Visean age assign- north (Fig. 6B). Biomodal transport direc- limestone clasts which bear an affinity to the ment for this facies. Liu and Xiong (1991) tions, soft sediment deformation, and pos- Cambrian-Ordovician carbonate section. report additional Lower Carboniferous fauna. sible tidal bundles in the upper Sishichang The nonmarine conglomerates grade rap- This section continues upward through a Formation suggest deposition in tidal chan-

Geological Society of America Bulletin, May 1995 575 CARROLL ET AL.

tervals within which basalt layers occur. The two basalt units exposed at Sishichang, and a third in the shallow subsurface of the Ta- rim basin, all belong to the lower basalt in- terval (Chang, 1988). Flows in both the up- per and lower intervals thicken, and perhaps coalesce, where they are exposed to the southeast at Yingan. We have also observed dikes cutting the Carboniferous marine and lowest Permian nonmarine sections, which appear to feed flows in the lowest basalt in- terval. Preliminary geochemical analyses in- dicate that the lower series of flows exposed at Sishichang are alkali basalt, and that the upper series of flows have tholeiitic compo- sitions (Liu and Li, 1991; Wang and Liu, 1991). Liu and Li (1991) reported whole- rock K/Ar dates for the two series ranging from 292.4 Ϯ 0.5 to 259.8 Ϯ 0.9 Ma. 40Ar/ 39Ar dating of isolated plagioclase grains contained in the lower series of basalt flows, sampled at a location ϳ20 km southwest of the Sishichang section, indicates an age of 277.53 Ϯ 0.46 Ma (M. McWilliams and P. Gans, personal commun., 1990). This deter- mination fits very closely with the faunal Figure 4. Simplified geology of the eastern Kalpin uplift, modified from unpublished data from the underlying limestone, con- 1:200 000 mapping of the Xinjiang Bureau of Geology and Mineral Resources and Chen et firming the Early Permian age of the basalt- al., 1985 (see Fig. 1 for map boundaries). Line A–B indicates the approximate position of bearing nonmarine sedimentary section. At the schematic cross section in Fig. 17. Numbers on map refer to detailed measured sections locations along strike with the Yingan- shown in Figures 5 and 6. Sishichang sections and in the subsurface of the northwestern Tarim basin, the Early Permian Kupukuziman formation is uncon- nels or adjacent environments in a mixed amites sp., Sphenophyllum, and Sphenopteris formably overlain by nonmarine Upper Per- carbonate/siliciclastic system. Skeletal grain- sp.) are consistent with a Permian age mian mudstone and siliciclastic rocks of the stones of the Lower Permian Kangkelin (Zhang, 1981; H. L. Cousimer, personal Kaipaizileike and Shajinzi formations, Formation sharply overlie the Sishichang commun., 1988; Wu Shaozu, personal com- which together total ϳ2000 m in thickness Formation and contain a normal marine mun., 1992). The coals extend to the west at (Zhang, 1981; Chang et al., 1988). fauna, including tabulate corals preserved in least as far as Yingan, but are thickest and Northern Tarim Basin–Kuqa/Baicheng. growth position. highest in quality near Sishichang. Samples We interpret siliciclastic Carboniferous The Kangkelin Formation limestones of coals mined from two separate seams rocks north and northeast of Baicheng grade upward into variegated nonmarine have mean vitrinite reflectances of 0.53%– (Fig. 1) to be mostly turbidites and slope mudstone, sandstone, conglomerate, coals, 0.59% (Graham et al., 1990), indicating an deposits; these have been overthrust from and basalt of the Kupukuziman Formation original burial depth of several kilometers. the north by a thick series of Lower Permian (Figs. 6C and 7A). Conglomerate and sand- A single sample has a mean vitrinite reflec- intermediate to felsic volcanic rocks (Fig. 7B). stone compose amalgamated, lenticular, up- tance of 1.22% but may have been baked by The volcanic rocks may total several kilo- ward fining units 3–5 m thick and several overlying basalt. meters in thickness, although their base was hundred meters long. We observed one The basalt forms two series of columnar- not observed. The section appears to be a large tree trunk, rooted in situ in clay with jointed, vesicular flows, each totaling ϳ150– mixture of nonmarine pyroclastics and 2 m of upright trunk exposed, which was en- 200 m in thickness. Baked zones extend to flows, with crude columnar jointing visible in gulfed in such a fluvial sandstone body. ϳ1 m beneath the flows. Chang (1988) re- places. Single potassium feldspar grains Trough and planar cross-beds consistently ported that similar basaltic rocks occur be- from rhyolite breccias in this interval yield indicate sediment transport to the southeast neath a relatively wide area of the north- 40Ar/39Ar radiometric ages between 267 and or east (i.e., away from the Tian Shan western Tarim basin and related their 289 Ma, averaging 282 Ϯ 2 Ma (Hendrix et toward the Tarim basin; Fig. 6C). Palyno- distribution to northwest-southeast–trend- al., 1992), making these volcanic rocks morphs collected from coals in this section ing faults. However, the precise age rela- roughly coeval with both the dikes in the (Autonia conferta, Annularia stellata (Schenk), tionships and distribution patterns of these Bachu uplift and the basalt flows at Sishi- Deltoidospora sp., Entyllisa sp., Kraeuselis- basaltic rocks are unclear. Flows were ob- chang and Yingan. The physical relationship porites sp., Latosporites sp., Lepidodendron served to vary in thickness between different between these volcanic rocks and the basalts sp., Pecopteris orientalis (Schenk), Paracal- areas. There are two broad stratigraphic in- mentioned above is unclear, but together

576 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA

Figure 5. Detailed measured sections of Lower Carboniferous Kontai’aikengou Formation sedimentary facies south of the town of Wusi, northwestern Tarim basin (see Fig. 4 for location). Sections are arranged stratigraphically, with the lowest on the left and highest on the right (ϳ1000 m of section represented). A. Fluvial conglomerates near the base of the Kontai’aikengou Formation. Rose diagram indicates sediment transport direction. B. Submarine fan deposits interbedded with micrite and calcareous mudstone. C. Shelf sandstone and shale grading upward into slope olistostrome. D. Slope; clasts are micrite and sandstone, similar in composition to matrix rocks.

they are interpreted to represent a synchro- Turpan Basin Taoshuyuan include shallow-marine lime- nous, bimodal suite. Nonmarine Upper Per- stone and sandstone of the Qijiagou and mian through Triassic sandstone and con- Upper Paleozoic sedimentary rocks crop Aoertu Formations, which are interbedded glomerate overlie the eroded surface of the out near the village of Taoshuyuan in the with intermediate to felsic volcanic rocks Baicheng-Kuqa volcanic rocks; paleocur- northwestern Turpan basin (Fig. 8). Liao et (Liao et al., 1987; Fig. 9A). Nonmarine con- rent measurements made on cross-beds in- al. (1987) reported that ϳ2300 m of Upper glomerate and volcanic rocks dominate the dicate sediment transport from the north to Carboniferous and Permian rocks is ex- sparsely fossiliferous Permian sections. Al- the south, away from the Tian Shan (Hen- posed at this locality. Upper Carboniferous though Liao et al. (1987) differentiated be- drix et al., 1992). to Lower Permian sedimentary rocks at tween Lower and Upper Permian rocks in

Geological Society of America Bulletin, May 1995 577 578 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA

Figure 6. Measured sections through Upper Carboniferous and Lower Permian rocks matrix of ash and plagioclase crystals. Bed exposed near the villages of Sishichang and Yinggan, northwest Tarim basin (see Fig. 4 for thicknesses range from Ͻ1mtoϾ10 m. The locations). A. Simplified measured section through rocks exposed near Sishichang (mod- volcanic flows range from ϳ50 cm to 10 m in ified from unpublished data of the Institute of Geology, Xinjiang Bureau of Geology and thickness, contain medium- to coarsely crys- Mineral Resources). Note overall transgressive-regressive trends. The contact between the talline phenocrysts, and are finely vesicular. Kangkelin and Kupukuziman Formations, not exposed at the location of this section, is Chilled lower contacts are common in the gradational elsewhere along strike. Lettered bars indicate the stratigraphic position of flows, although some bodies also possess detailed measured sections. B. Detailed measured section of the Upper Carboniferous chilled upper contacts and may actually be Sishichang section, ending in the base of the Lower Permian Kangkelin Formation (section sills. The Qijiagou Formation grades up- measured near Yinggan village; see Fig. 4 for location). Note the overall deepening-upward ward into shallow-marine sandstone, con- trend in sedimentary facies, and the north-northwest sediment transport direction. glomerate, and tuffs of the Aoertu Forma- C. Detailed measured section of the Lower Permian Kupukuziman Formation near Sishi- tion (Liao et al., 1987). The sandstone chang village (see Fig. 4 for location). Note southeast-directed paleocurrents. contains a mixture of siliciclastic grains and carbonate skeletal debris (mostly echino- ä derm) up to pebble size. Bed thicknesses range from 10 cm to several meters. Trough and planar cross-beds with amplitudes of 10–80 cm are common, as is plant debris. this area, we were unable to subdivide this crystallized limestone form lenticular, bio- Liao et al. (1987) reported that the non- section (also, the total reported thickness of hermal bodies up to 10 m thick and several marine deposits unconformably overlie ma- Permian deposits is not present in a contin- hundred meters long. Grainstones predom- rine rocks, although the section appeared to uous outcrop section). We therefore limit inate, although Syringopora boundstones be conformable in the areas investigated the following description to a single, contin- also occur locally. Echinoderms contribute during this study. The transition from ma- uous outcrop section and treat the Permian the bulk of the carbonate skeletal debris, rine to nonmarine rocks is relatively abrupt, rocks as undivided. with the remainder including rugose corals however, taking place over a few tens of The Qijiagou Formation at Taoshuyuan is preserved in growth position, and a variety meters at most. Nonmarine Permian depos- made up of interbedded shallow-marine of other corals, brachiopods, bryozoa, and its at Taoshuyuan are composed of inter- limestone, andesitic to dacitic lavas, and la- foraminifera. The lahars include angular to bedded siltstone, sandstone, conglomerate, hars (Fig. 9B). The heavily fractured and re- subround clasts up to 1 cm in diameter in a and intermediate to felsic volcanic rocks.

A Figure 7. Outcrop photographs of Lower Permian rocks in the northwestern and northern Tarim basin. A. Basalt flows interbedded with mudstone and sandstone of the Kukupuziman Formation west of Sishichang (see Fig. 1 for location). Southeast-dipping flatirons of Kangkelin Formation limestone are visible in the background. These basalts contain individual flow units several meters in thickness, and together make up part of the lower series of basalts depicted in Figure 6A. B. Rhyolite breccia along the Kuqa river north of the town of Kuqa (see Fig. 1 for location). B

Geological Society of America Bulletin, May 1995 579 CARROLL ET AL.

ter-lain tuffs and occasional basaltic pillow lavas (Liao et al., 1987). The thickness of this formation appears to be at least several kilometers, although some of this may be the result of suspected (but undocumented) structural repetition. Sandstone predomi- nates and is distinguished from the tuffs chiefly by rounding and sorting of grains and the presence of graded beds and other sed- imentary structures. The sandstone and con- glomerate are both normally and inversely graded. Maximum clast sizes are ϳ3–4 cm, and both clast-supported and matrix-sup- ported conglomerate are present. Carbon- ate megafossils such as rugose corals occa- sionally occur as isolated clasts. Individual flow units of the sandstone and conglomer- ate are generally Ͻ1 m thick, and graded sandstone beds are as thin as 1–2 cm. Sed- imentary structures include ripples, 10-cm- amplitude cross-beds, plane laminations, and possible flame structures. The Qijiagou Formation (Fig. 12B), Figure 8. Simplified geologic map of the Taoshuyuan area (modified after Chen et al., which makes a sharp but apparently con- 1985, and unpublished mapping of the Xinjiang Bureau of Geology and Mineral Resourc- formable contact with the Liushugou For- es). Numbers on map refer to detailed measured sections shown in Figure 9. mation, contains a much larger fraction of carbonate megafossil clasts than the Liu- shugou Formation and does not include The conglomerate forms lenticular, amal- thick (Liao et al., 1987; Fig. 11); the total tuffs or other volcanic rocks. The carbonate gamated beds up to 20–25 m thick with a thickness of this section is not known be- grains represent a diverse normal marine maximum clast size of 20–30 cm (Fig. 9C). cause its base is not exposed in the study faunal assemblage, including corals, echino- Most of the larger conglomerate clasts are area. Upper Devonian and Lower Carbon- derms, brachiopods, mollusks, and bryozoa limestone; Liao et al. (1987) report that iferous rocks are mapped in the Bogdashan (see Liao et al., 1987, and Zhang, 1981, for these clasts contain Middle Carboniferous (Chen et al., 1985), but appear to be largely complete listing of fauna), that apparently fusulinids. Individual conglomerate beds are limited to relatively inaccessible interior ar- led Liao et al. (1987) to describe these de- both normally and inversely graded and are eas of the range. The stratigraphically lowest posits as shallow marine. Pugilis sp. brachio- generally clast supported. Imbricated peb- rocks examined in this study are basinal vol- pods and Gshelia sp. corals were collected bles indicate sediment transport from the caniclastic turbidites and submarine debris during this study from the Qijiagou Forma- southwest to the northeast (Fig. 9C). Plant flows, tuffs, and lavas of the Lower to Upper tion, confirming that these deposits are Up- debris is common throughout the deposits, Carboniferous Liushugou Formation, which per Carboniferous (identifications made by but no fauna was observed. The number of are overlain by interpreted basinal deposits A. R. Ormiston). Most carbonate material interbedded volcanic units increases upsec- (mostly turbidite sandstone, mudstone, and includes relatively robust skeletal material tion, coincident with a rough increase in the shale) of the Upper Carboniferous Qijia- contained in graded beds; more delicate proportion of extrusive relative to intrusive gou, Upper Carboniferous to Lower Per- grain types were not observed. The mixture units. Volcanic rocks low in the sections are mian Aoertu, and Lower Permian Shirenzi- of siliciclastic and carbonate grains ranges mostly sills with chilled margins, whereas gou Formations. Formation boundaries from entirely siliciclastic sandstone to en- the upper volcanic rocks are mostly vesicu- within this interval appear to be based on a crinite, whereas most of the mud present is lar flows. Weathered, dark-colored dikes cut combination of biostratigraphic and litho- silicic. The largest clasts are 4–5 cm rugose the marine deposits and the lower part of stratigraphic criteria. The Lower to Upper corals; conglomerates are both clast sup- the Permian section, terminating roughly at Permian Tashikula Formation contains a re- ported and matrix supported. Individual the level of the upper flows. gressive sequence ϳ1000 m thick, marking beds are generally 10–50 cm thick, although the final retreat of marine waters from the lenticular, carbonate-rich channel-fill de- Junggar Basin region (Carroll et al., 1990). Superjacent posits are commonly amalgamated into beds Upper Permian deposits of the Wulapo, Jin- up to 5 m thick. In one location ϳ15 km Southern Junggar Basin. Upper Carbon- jingzigou, Lucaogou, Hongyanchi, Quanzi- southeast of Urumqi (Fig. 1), the Qijiagou iferous and Permian deposits also crop out jie, and Wutonggou Formations are exclu- Formation is cut by an interpreted subma- along the northwestern flanks of the Bogda sively nonmarine. rine gorge several hundred meters in width Shan, adjacent to the northwestern Junggar The Liushugou Formation (Fig. 12A) and ϳ100 m in stratigraphic thickness, basin (Figs. 1 and 10). These compose a con- constitutes basinal mudstone to conglomer- which is filled with boulder-conglomerate, formable section that is at a minimum 7 km ate, interbedded with andesitic to dacitic wa- coarse-grained sandstone, and basalt flows.

580 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA

Figure 9. Measured sections through Upper Carboniferous and Permian outcrops exposed near the village of Taoshuyuan, northwestern Turpan basin (see Fig. 1 for location). A. Schematic stratigraphy and sedimentary facies of outcrop exposures (modified from Liao et al., intermediate to felsic volcanic rocks). B. Detailed ؍ Bars indicate the approximate position of detailed measured sections (gray .(1987 measured section through mixed shallow-marine limestone and volcanic rocks of the Upper Carboniferous Qijiagou Formation. C. Permian (undivided) fluvial and alluvial conglomerates. Note northwest-directed paleocurrents.

Scoured contacts and meter-scale cross- sandstones deform underlying beds and are These are overlain by turbidites up to 50 cm beds are common within this sequence, topped by megaripples with meter-scale thick, which are often amalgamated into which incises the underlying beds. Marine wavelengths. Flute casts and graded beds units up to 1 m thick. All of the turbidites fauna (mostly bivalves and corals) and bur- are common throughout the sequence; the appear to be tabular at the outcrop scale, rows are common within the sedimentary fill flutes consistently indicate a flow direction and most are normally graded and contain of the submarine gorge. from the east to the west. Wood fragments ripples or wavy laminae. Soft-sediment The Qijiagou Formation grades upward and other carbonaceous material are slumping of the sandstone is common. Mud- into siliciclastic turbidites of the Aoertu For- common. stone and siltstone interbeds are laminated mation (Fig. 12C), which is made up of The Shirenzigou Formation, which con- on a millimeter scale and commonly contain mostly fine- to medium-grained sandstone formably overlies the Aoertu, is marked by plant fragments. Flute casts are rare. interbedded with subequal thicknesses of an increase in the proportion of siliciclastic The Shirenzigou Formation grades up- mudstone and siltstone. Based on the dis- sandstone relative to mudstone and silt- ward into poorly exposed, predominantly tribution of sandstone bodies in outcrop, we stone. The Shirenzigou also includes coarse- muddy and silty facies of the lower Ta- interpret the Aoertu turbidites as submarine grained sandstone containing mud intra- shikula Formation. Burrowed, fine-grained, channel and overbank deposits. Bed thick- clasts up to 15 cm in length. The lower plane-laminated 1- to 2-cm-thick sandstone nesses generally range between 5 cm and 40 Shirenzigou Formation includes several are interbedded with millimeter-scale plane- cm, with occasional lenticular sandstone meter-thick, lenticular submarine debris- laminated mudstone and siltstone. Soft-sed- reaching2minthickness. These lenticular flow deposits with granule-size mud chips. iment slumping is common. The upper part

Geological Society of America Bulletin, May 1995 581 CARROLL ET AL.

(Fig. 13B) and plant debris are common throughout this interval. Nonmarine lime- stone, typically peloidal grainstone mixed with siliciclastic sand, also occurs sporadi- cally throughout the deposits. The Lucaogou and lowermost Hongyan- chi Formations together contain ϳ1000 m of organic-rich lacustrine mudstone (some- times referred to as ‘‘oil shale’’ due to its high organic content), which appears to be the principal source of petroleum in the Junggar basin (Watson et al., 1987; Graham et al., 1990; Carroll et al., 1992). Millimeter- to submillimeter-scale laminae typify these deposits, implying deposition under anoxic conditions (Graham et al., 1990; Carroll et al., 1992). Phosphatic skeletal remains of such fresh-water fish as Chichia sp., Tian- shaniscus longipterus, and Turfania tao- shuyuanensis also occur throughout the oil shale (Liao et al., 1987), however, implying a stratified lake with well-oxygenated sur- face waters. Early diagenetic dolomite con- cretions deform the laminae of the most or- ganic-rich mudstone, and pyrite is common. Total organic carbon (TOC) content aver- ages between 4% and 5%, although TOC Figure 10. Simplified geologic map of the western Bogdashan (modified after Chen et al., commonly exceeds 20%, and values of up to 1985, and unpublished mapping of the Xinjiang Bureau of Geology and Mineral Resourc- 34% have been reported (Graham et al., es). Numbers on map refer to detailed measured sections in Figures 12 and 14. 1990). Dolomite-cemented, rippled siltstone interbedded with the laminated mudstone often contain wood impressions up to 10–20 of this fine-grained sequence includes sev- mations, which are composed of varying cm in length. Palynomorphs from the Lu- eral meter-thick, medium-grained tabular proportions of conglomerate, sandstone, caogou Formation identified during this sandstone with millimeter-scale plane lam- rippled siltstone, and plane-laminated mud- study (Alisporites, Cordaitina, Florinites, inae to hummocky cross-stratification, stone that we interpret to have been depos- Hamiapollenite, Illinites, Kraeuselisporites, which are interpreted to be shelf sandstone. ited in fluvial and lacustrine environments Labiisporites, Leiotriletes, Lycospora, Stria- These mudstone-encased sand bodies grade (Figs. 14A–14C). No reports of fauna in the toabietes, Vittatina) are consistent with a upward into algal limestone of the upper Wulapo Formation were encountered dur- Late Permian age assignment (palyno- Tashikula Formation (Fig. 12D), which rep- ing this investigation, but several genera of morphs identified by G. Barker, H. L. Cousi- resent the first unequivocally shallow-ma- nonmarine ostracodes have been reported mer, and G. Wood). An extensive fauna of rine deposits in the southern Junggar sedi- from the Jingjingzigou Formation (Dar- fresh-water ostracodes and mollusks has mentary section. Silicified stromatolitic winula, Darwinuloides, and Tomiella; Zhang, also been reported from the Lucaogou For- boundstones (Fig. 13A) and pelloidal and 1981). Mudstone and siltstone compose mation (Liao et al., 1987; Zhang, 1981). phylloid algal packstones are interbedded ϳ80% of these deposits, and much of the The Lucaogou Formation grades upward with siliciclastic siltstone and fine-grained coarse-grained material is intraclastic in or- into poorly exposed, nonlaminated mud- sandstone. Bed thicknesses range from 5 cm igin. The sandstone and conglomerate gen- stone, fresh-water limestone, and fluvial to 50 cm. The stromatolites include verti- erally are normally graded and lenticular, conglomerate of the Hongyanchi, Quanzijie, cally stacked hemispheroids and laterally occurring in amalgamated units up to sev- and Wutonggou Formations. Rocks within linked hemispheroids 10–50 cm in wave- eral meters in thickness. Sedimentary struc- this interval are variegated but generally length and 2–20 cm in amplitude. Ripped- tures include plane laminae, low-angle grade in color from gray-green at the base to up horizons are common, suggesting a rel- cross-stratification, ripples, and trough and gray and red at the top. The conglomerates atively energetic intertidal to supratidal planar cross-beds up to 50 cm in amplitude. are generally normally graded and clast sup- environment of deposition. The siliciclastic Paleocurrent directions measured from ported; the largest clasts are pebbles. Amal- siltstone and sandstone also contain wavy cross-beds and parting lineations are highly gamated bed thicknesses reach several laminae that appear to be algal in origin. variable. Root-mottling is common in the meters. Pebble imbrications indicate sedi- Burrowing is common throughout this muddy and silty facies, which generally ap- ment transport from the southwest to the facies. pear to have been deposited under well- northeast (Carroll et al., 1990; Carroll, The Tashikula Formation grades upward oxygenated subaerial and shallow sub- 1991). Interbedded limestone beds are into the Wulapo and Jingjingzigou For- aqueous conditions. Desiccation cracks made up of mixed siliciclastic sandstone and

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carbonate mudstone, peloidal packstone to grainstone, and pelecypod coquinites. Pet- rified wood with traces of coal also occurs in minor amounts. Similar coarse-grained fa- cies characterize Upper Permian deposits adjacent to the northeast Junggar basin, Permian-Triassic (undivided) deposits south of Shihezi, and Upper Permian rocks in the subsurface of northwestern Junggar basin (Chang, 1981; see Fig. 1 for locations). Southeastern Junggar Basin. An upper Paleozoic section similar to that exposed in the western Bogda Shan was examined dur- ing a brief reconnaissance south of the town of Jimsar in the northern foothills of the central Bogda Shan (Fig. 1). Stratigraphic correlation of this area with the western Bogda Shan is based primarily on unpub- lished 1:200 000 and 1:1 000 000 mapping of the Xinjiang Bureau of Geology and Mineral Resources, augmented by the 1:2 000 000 mapping of Chen et al. (1985). Undifferentiated Upper Carboniferous de- posits south of Jimsar are composed of slightly metamorphosed, silicic, fine-grained turbidites and pelagic mudstone. Bed thick- nesses average Ͻ10 cm, and the entire sec- tion is heavily jointed and displays well-de- veloped cleavage. Paleocurrent indicators, including cross-beds and flame structures, are inconclusive but suggest sediment trans- port from east to west. Mafic dikes and other intrusives are common, but no extrusive rocks were observed. Upper Permian rocks crop out in a fault block several kilometers north of the Car- boniferous section, but the contact between Carboniferous and Permian rocks was not observed. The Permian rocks resemble the nonmarine Upper Permian section in the western Bogda Shan. Organic-rich mud- stone similar to the Lucaogou Formation grades upward into coaly shale, then into imbricated conglomerate with paleocurrent directions suggesting sediment transport from the southeast to the northwest. No in- trusive or volcanic rocks were observed.

CARBONIFEROUS-PERMIAN SANDSTONE PROVENANCE

We point-counted thin sections of 61 Up- per Carboniferous and Permian sandstone rocks from the Tarim, Turpan, and Junggar Figure 11. Schematic stratigraphy and sedimentary facies of the southern Junggar basin basins, using a modified Gazzi-Dickinson (modified from Liao et al., 1987; see Fig. 10 for location of detailed measured sections). method (Table 1; see Graham et al., 1993 Error bars indicate approximate range of uncertainty in paleobathymetric/paleo-elevation for detailed techniques). The raw point- estimates. count data were recalculated into detrital modes and plotted on standard ternary di- agrams (Fig. 15) to permit comparison with

Geological Society of America Bulletin, May 1995 583 Figure 12. Detailed measured sections of middle and Upper Carboniferous and Lower Permian sedimentary facies in the western Bogdashan, southern Junggar basin (see Fig. 10 for locations and Fig. 11 for stratigraphic positions of detailed sections). Sections are arranged stratigraphically, with the lowest on the left and highest on the right. A. Debris flows and turbidites of the Lower to Upper Carboniferous Liushugou Formation. Volcanic rocks contained elsewhere in this formation represent the last significant arc magmatism evident in the western Bogdashan. B. Mixed carbonate and siliciclastic turbidites of the Upper Carboniferous Qijiagou Formation. C. Turbidites of the Upper Carboniferous to Lower Permian Aoertu Formation. Flute casts in this formation consistently indicate sediment transport from east to west. D. Lower Permian Tashikula formation. The Tashikula grades from shelf mudstone and sandstone with hummocky cross-stratification to stromatolites interbedded with desiccated mudstones, which represent the oldest shallow-marine and nonmarine deposits in the southern Junggar basin.

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cratonal sandstone with a transitional con- tinental block-recycled orogen provenance (Dickinson and Suczek, 1979; Dickinson, 1985). The composition of these sandstones is consistent with source areas within the Tarim cratonal block with relatively low to- pographic relief and may also reflect recy- cling of previously deposited sedimentary rocks. Sandstone from the nonmarine Kupuku- ziman Formation contains predominantly felsic-volcanic rock fragments that fre- quently display pyroclastic or pumiceous textures. Free monocrystalline quartz and potassium feldspar grains are also common, and many of the monocrystalline quartz grains are angular and may be volcanic in origin. Granitic rock fragments and perthitic potassium feldspars are also common, how- ever, indicating that many of the free quartz A and feldspar grains may in fact have a gra- nitic provenance. Chen et al. (1985) and Wang et al. (1990) reported that Carbonif- erous to Permian ‘‘potassic granites, adam- ellites, and alkali feldspar granites’’ intrude older rocks throughout the Tian Shan. Ero- sion of these bodies and other Tian Shan granites during the Early Permian appears to have shed detritus south into the Yingan- Sishichang area. We interpret the parent vol- canic rocks for these grains to be equivalent to those exposed in the Baicheng-Kuqa area (Fig. 1), which could represent extrusive equivalents of Tian Shan alkalic plutons. Al- though felsic volcanic rocks have not been directly observed near Sishichang, fluvial sandstone above the lower basalt interval are markedly feldspathic and contain abun- dant pebbles of potassium feldspar pheno- cryst-bearing rhyolite. A few of the lithic volcanic grains in the upper nonmarine sand- B stone are either devitrified basaltic glass or Figure 13. Outcrop photographs of Upper Carboniferous and Permian sedimentary fa- possess lathwork textures formed by plagi- cies in the western Bogdashan, southern Junggar basin (see Fig. 10 for location). A. Stro- oclase phenocrysts, and they were probably matolites in the Lower Permian Tashikula Formation, representing the oldest shallow- derived from the basaltic volcanic rocks in- marine deposits in the southern Junggar basin. B. Desiccation cracks in the Upper Permian terbedded with the sedimentary rocks. Jingjingzigou Formation. Junggar-Turpan Sandstones previously recognized provenance types reversal in paleocurrents noted above; the As noted earlier, Lower to Upper Car- (Dickinson and Suczek, 1979; Dickinson, quartzose sandstone of the Sishichang For- boniferous sandstones in both the southern 1985). mation is interpreted to be derived from the Junggar and the northern Turpan study interior of the Tarim craton to the south- areas are intercalated with andesitic to dac- Tarim Sandstones east, whereas the lithic-rich sandstone in the itic volcanic rocks. Not surprisingly, these Kupuzikuziman Formation is derived from sandstones bear the compositional imprint Tarim sandstone samples taken from the the present area of the Tian Shan to the of arc volcanics. Volcanogenic grain types Upper Carboniferous and Lower Permian northwest. The Sishichang Formation is dominate Carboniferous sandstone from outcrops near Sishichang (Fig. 4) display a dominated by monocrystalline quartz (Qm) the southern Junggar and northern Turpan sharp stratigraphically controlled shift in with lesser quantities of polycrystalline basins (Fig. 15), reflecting the ubiquity of modal compositions that coincides with the quartz (Qp) and chert, which is typical of Paleozoic volcanic arcs in the sediment-

Geological Society of America Bulletin, May 1995 585 CARROLL ET AL.

Figure 14. Detailed meas- ured sections of nonmarine Upper Permian sedimentary facies in the western Bogda- shan, southern Junggar basin (see Fig. 10 for location and Fig. 11 for stratigraphic posi- tion). Sections are arranged stratigraphically, with the lowest on the left and highest on the right. A. Fluvial sand- stone and desiccated mud- stone of the Wulapo Forma- tion. B. Fluvial sandstone and siltstone and possible shallow lacustrine mudstone and limestone of the Wulapo For- mation. C. Fluvial sandstone to desiccated lake-marginal mudstone of the Jingjingzi- gou Formation.

source terranes that surrounded these areas pseudomatrix (deformed lithic grains that ance of granitic rock fragments in Permian (Junggar and Turpan results are plotted to- resemble matrix material) is common. For Junggar and Turpan sandstone parallel that gether due to their compositional similari- these reasons, no attempt has been made to seen in Tarim sandstones and may mark the ty). Volcanic rock fragments of intermediate quantify the relative proportions of felsic, first erosional exposure of Tian Shan gra- to felsic composition and plagioclase feld- intermediate, and mafic grains counted as nitic intrusives. Some Upper Permian sand- spar make up the vast majority of these volcanic rock fragments. Chert grains and stones contain an increased proportion of grains (Table 1). Due to the chemically la- polycrystalline quartz occur only in very low lithic framework grains relative to Lower bile nature of these grain types, nearly all of quantities in the Junggar and Turpan samples. Permian samples, suggesting recycling of the Junggar and Turpan sandstone have been The relative proportions of quartz and previously deposited arc volcanic rocks and subjected to extensive cementation and potassium feldspar grains both increase volcaniclastic sedimentary rocks. The appar- postdepositional alteration. Cements gener- slightly in overlying Permian sandstones, ent bimodality of Upper Permian sandstone ally represent a complex paragenesis of zeo- suggesting extinction of volcanic arcs and compositions may result in part from the rel- lites, clays, carbonates, and silica; in most partial erosional unroofing of some of their atively small number of sandstone samples cases, any original porosity has been com- associated volcanic strata. Granitic rock counted; more extensive sampling would pletely occluded. Albitization, sericitization, fragments, although rare, are also found in likely reveal a gradation across a large range and carbonatization of the grains in some the Permian sandstones. The increase in of lithic contents, rather than a grouping of cases make grain identification difficult, and quartz and potassium feldspar and appear- compositions into distinct modes.

586 Geological Society of America Bulletin, May 1995 TABLE 1. COMPOSITION OF CARBONIFEROUS-PERMIAN SANDSTONE FROM THE TARIM, TURPAN, AND JUNGGAR BASINS

Note:C1ϭLower Carboniferous; C2 ϭ Upper Carboniferous; P1 ϭ Lower Permian; P2 ϭ Upper Permian; K ϭ potassium feldspar; P ϭ plagioclase; Qm ϭ monocrystalline quartz; Qt ϭ monocrystalline quartz ϩ polycrystalline quartz ϩ chert; Qp ϭ polycrystalline quartz ϩ chert; F ϭ total feldspar; Lt ϭ Qp ϩ total lithic fragments; L ϭ sedimentary ϩ volcanic ϩ metamorphic lithic fragments; Lv ϭ volcanic lithic fragments; Lsm ϭ sedimentary ϩ metamorphic lithic fragments; %PMC ϭ porosity, matrix, and cement.

Geological Society of America Bulletin, May 1995 587 CARROLL ET AL.

Figure 15. Ternary plots of modal sandstone grain compositions in the Tarim, Turpan, and Junggar basins (See Table 1 for data employed). Provenance associations proposed by Dickinson and Suczek (1979) are provided for comparison. Polygons indicate one ;Lower Permian ؍ Carboniferous; P1 ؍ standard deviation about the average value for each group (average indicated by an open square; C .Upper Carboniferous ؍ Lower Carboniferous; C2 ؍ Upper Permian); C1 ؍ P2

LATE PALEOZOIC BASIN vertical width of the profiles in Figure 16 The northwestern Junggar basin ap- SUBSIDENCE approximates the uncertainty in these pears to have experienced relatively little estimates. tectonic subsidence during the Carbonif- Geohistory analyses of selected outcrop Total and tectonic subsidence rates in- erous through Early Permian, although the sections were utilized to compare patterns creased sharply in the northwestern Tarim uncertainties in paleobathymetry for this pe- of Paleozoic basin subsidence in the north- basin during the Late Devonian as a thick riod are large (tentatively estimated at 2 km, western Tarim basin and northwestern series of predominantly nonmarine, red-col- Fig. 16). An overall shoaling of this section Junggar areas (Fig. 16), using standard ored siliciclastic rocks were deposited. The is interpreted because of the apparent lack backstripping techniques (see Hendrix et al., significance of this acceleration of subsid- of any significant unconformities, and the 1992, for further discussion of the modeling ence is unknown; it apparently records an systematic progression of sedimentary facies techniques employed). These sections were from submarine fans through shelf deposits undocumented tectonic event within the selected because they offer continuous ex- and algal stromatolites. Because of the large Tarim block. Erosion or nondeposition posures and, on the basis of field reconnais- degree of error in paleobathymetric esti- characterized the Sishichang area through- sance, appear to be representative of Pale- mates prior to the deposition of the shallow- ozoic basin fill in each area. Stratigraphic out most of the Carboniferous. As noted water stromatolites, Figure 16 appears to thicknesses for the Tarim basin correspond above, however, ϳ2000 m of Carboniferous depict a slowing (or even reversal) of sub- approximately to the Sishichang section (see clastic and carbonate rocks are preserved in sidence during the Early Permian. We in- above description of the lower portion of the Wusi foredeep to the northwest (see terpret this apparent reversal of subsidence this section) and were taken from Zhang Fig. 4 for location). Net subsidence acceler- as an artifact of the methodology used to (1981). Thicknesses for the Junggar basin ated again in the Sishichang area during the construct the geohistory diagram, rather were based on Liao et al. (1987) and corre- Early Permian, coincident with the onset of than a real feature of basin evolution. Total spond approximately to those in Figure 11. the bimodal volcanism described above, and and tectonic subsidence accelerated sharply Estimates of paleobathymetry and paleoel- transport of sediment from the paleo–Tian in the Late Permian, coincident with the on- evation are based on sedimentary facies; the Shan. set of nonmarine sedimentation. Note that

588 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA

this increased subsidence appears to post- date Early Permian subsidence in the north- western Tarim basin by up to 30 m.y., sug- gesting that the two arose from different causes.

DISCUSSION

Tarim/Central Tian Shan Collision

Paleomagnetic studies indicate that dur- ing most of the Paleozoic the northern Ta- rim basin occupied lower latitudes than at present (Bai et al., 1987; Li, 1990). Devo- nian red beds of the Subasi Formation in the Kalpin uplift document 9Њ of northward transport (Bai et al., 1987; Li, 1990). Watson et al. (1987) and Wang et al. (1990) pro- posed that during this time, an ocean basin north of the Tarim block was being actively subducted beneath a Central Tian Shan magmatic arc. On the basis of studies in the Tian Shan, several workers have postulated that the Tarim block collided with the Cen- tral Tian Shan block during the Late Devo- nian or Early Carboniferous (Wang et al., 1986; Hopson et al., 1989; Wang et al., 1990; Windley et al., 1990; Allen et al., 1991, 1992). Zeng et al. (1983) reported the pres- ence of widespread Lower Carboniferous angular unconformities within the Central Tian Shan, which may record deformation resulting from the collision with Tarim. Sim- ilar deformation occurred in the northwest Tarim basin, where angular unconformities near Yinggan-Sishichang and Wusi (Fig. 4) place Upper Carboniferous on Devonian and Lower Carboniferous on Silurian, re- spectively. A regional sub-Carboniferous angular unconformity has also been re- ported in the subsurface of the Tarim basin at the Tazhong oil field (see Tazhong No. 1 well location in Fig. 1) and in the northern Tarim (Anonymous, 1991; Zhou and Jia, 1991). Paleomagnetic studies document 18Њ northward movement and ϳ46Њ clockwise rotation of the northwestern Tarim block between the Late Devonian and Late Car- boniferous (Sharps et al., 1989; Li, 1990). Although the paleolatitude and orientation of the Central Tian Shan during this time are uncertain, we interpret the thick Car- boniferous section near Wusi to have been deposited in a flexural foredeep created by the continued convergence of Tarim and the Central Tian Shan (Fig. 17). Alternating Figure 16. Geohistory diagrams for the (A) northwestern Tarim basin, and (B) southern shallow and deep depositional environ- Junggar basin. ments in the Carboniferous document a long and complex interplay between tec-

Geological Society of America Bulletin, May 1995 589 CARROLL ET AL.

Figure 17. Schematic cross section of Carbonifer- ous–Lower Permian north- western Tarim basin fore- deep (see Fig. 4 for line of section and locations of Wusi, Yinggan, and Sishi- -Lower Per ؍ chang). P1 -Lower to Up ؍ mian; C1–2 per Carboniferous.

tonic subsidence of the foredeep, sediment North Tian Shan/Junggar Collision Terminal collision of the combined Ta- supply, and sea-level fluctuation that may rim/Central Tian Shan block with the North have spanned as much as 70 m.y. Diachro- Following the interpreted collision of the Tian Shan/Bogda Shan arc complex oc- nous closure of the suture between the two Tarim and Central Tian Shan blocks in Late curred in the Late Carboniferous to Early continental blocks (cf. Graham et al., 1975) Devonian to Early Carboniferous times, arc Permian (Wang et al., 1986, 1990; Hopson may account for some of this time span, al- magmatism continued along the northern et al., 1989; Carroll et al., 1990; Windley et though probably not all of it. Wang (1985) edge of the Central Tian Shan at least until al., 1990; Allen et al., 1991, 1992). During and Lai and Wang (1988) indicated that the the early Late Carboniferous (Zhou, 1987; this period the southern Junggar basin re- South Tian Shan sea (which filled the North Wang et al., 1990). During the intervening ceived a thick series of sedimentary rocks Tarim foredeep; Fig. 18) gradually retreated period, an unknown width of oceanic crust recording an overall retreat of marine wa- from the east to the west between the Early (termed the North Tian Shan Sea in Fig. 18) ters. The thickness of this section, which Carboniferous and the Early Permian, con- separated the Central Tian Shan block from rests conformably on earlier-deposited vol- sistent with the paleomagnetic record of volcanic arcs in the North Tian Shan and caniclastic rocks, is more than adequate to clockwise rotation of the Tarim block. Bogda Shan; Windley et al. (1990) suggested account for the sedimentary infill of a basin Paleocurrent measurements and sand- on the basis of metamorphic fabrics near of oceanic depth. Alternatively, Windley et stone provenance indicate that during this the Central Tian Shan/North Tian Shan al. (1990), Allen et al. (1991), and Allen et period most of the sediment input into the boundary (Fig. 1) that this ocean basin was al. (1992) suggested that the thickness of this southern flank of the Tarim foredeep was being subducted southward beneath the interval may have been partially accommo- derived from the southeast. As noted above, Central Tian Shan. The exact temporal and dated by flexural subsidence of the southern however, central and northern portions of areal distribution of arc activity and polarity Junggar. Sediment transport directions the foredeep are not well represented in this of subduction represented by the North within this interval, recorded by flute casts, study due to their geographic inaccessibility. Tian Shan and Bogda Shan volcanic rocks is are interpreted from this study and that of It is likely that a substantial volume of sed- unclear. These areas may record synchro- Carroll et al. (1990) to have been predom- iment was shed into the basin from uplifts to nous magmatism above two different sub- inantly from east to west, parallel to the the north and transported longitudinally ducting plates, may have formed diachro- present structural grain of the area. along the basin axis. Alternatively, the nously above a common subducting plate, or northern Tarim basin may have been the lo- may represent elements of a single mag- Permian Subsidence of the Northern cus of north-directed passive margin sedi- matic arc. Intra-arc extension or later strike- Tarim and Southern Junggar Basins mentation in an extensional basin formed slip faulting may have modified the original after the collision of Tarim (Zhou et al., geometry of these areas; unfortunately, the Relatively widespread Early Permian 1994). Further sedimentological, structural, evidence needed to resolve this problem magmatism is recorded by interbedded ba- and paleomagnetic studies in the Tian Shan fully lies concealed beneath the Mesozoic- salt, felsic volcanic rocks, and volcanogenic will be required to test these hypotheses. Cenozoic cover of the Turpan basin. sandstone in the northern Tarim basin,

590 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA

within an otherwise compressive setting may result from collisions involving irregular continental margins. Alternatively, the vol- canic rocks might represent back-arc mag- matism arising from subduction of oceanic lithosphere beneath the southern margin of Tarim (ϳ400–600 km away in present co- ordinates). Evidence for extensive arc activ- ity during this period is lacking, however, as are back-arc volcanic rocks in the Triassic (when magmatic arcs are known to have been active to the south in the western Kun- lun; Hendrix et al., 1992). It is clear from the foregoing observations that back-arc oce- anic spreading, as proposed by Hsu¨ (1988, 1989), did not occur at this time. Also, no major normal faults related to Early Per- mian volcanism have been documented. Rapid Early Permian subsidence of the northern Tarim basin may have also re- sulted from diffuse extension of the basin due to the relaxation of stresses related to the earlier collision of Tarim with the Cen- tral Tian Shan block. Upper Permian rocks in the northwestern Tarim basin were not observed during this study but are reported to be composed of exclusively nonmarine facies lacking significant volcanic units (Zhang, 1981; Chang et al., 1988). During the Late Permian, ϳ5 km of non- marine mudstone, sandstone, and conglom- erate was deposited in the southern Junggar basin. Several workers have suggested that these nonmarine rocks were accommodated by thermal subsidence following regional ex- tension, based on half-graben structures in- terpreted from proprietary seismic reflec- tion data in the northern Junggar (Bally et al., 1986), the southeast-northwest axial dis- tribution of Upper Permian lacustrine mud- stone beneath the basin (Zhao, 1982), and the occurrence of various mafic to felsic in- trusive and volcanic rocks on the basin mar- gins (Windley et al., 1990; Allen et al., 1991, 1992, 1995; Allen and Windley, 1993). An intriguing variation on this theme is the pro- posal, based in part on larger regional con- siderations, that the Junggar was one of sev- Figure 18. Schematic paleogeography of western China during the late Paleozoic (dia- eral basins created by Late Permian tectonic gram not drawn to scale). shear between postulated sinistral shear zones (Allen et al., 1995). Although Late Permian extension of the Junggar basin can- which is approximately coeval with the in- (Fig. 1; Wang and Liu, 1991). Dikes in the not be discounted on the basis of presently trusives in the Xiaohaizi uplift. Together, Xiaohaizi area trend parallel to this zone available evidence, the above observations these rocks are interpreted to record limited and normal to the presumed late Paleozoic are not entirely convincing. For example, continental extension. Basaltic eruptions, al- collisional zone between Tarim and the published seismic data from the northern though widespread in the northern and cen- Central Tian Shan. S¸engo¨r et al. (1978) doc- Junggar basin (Liu, 1986; Peng and Zhang, tral Tarim basin subsurface, appear to be umented a similar geometry for basalt 1989) do not resolve the fault plane bound- greatest along a zone trending northwest- eruptions in the upper Rhine Graben of ing the interpreted half graben and, in fact, southeast through the Bachu-Xiaohaizi area central Europe and proposed that extension provide no evidence that it actually contains

Geological Society of America Bulletin, May 1995 591 CARROLL ET AL.

Upper Permian sedimentary fill. Further- resent late-stage arc or back-arc magmatic Tarim that eventually filled from the east to more, although thick Upper Permian differentiates. Finally, it has been suggested the west. This combined Tarim/Central Tian lacustrine mudstones do indeed appear to that central Asia was subjected to wide- Shan block then collided with magmatic arcs be confined to an axial ‘‘trough’’ beneath the spread intrusion by A-type anorogenic gran- in the North Tian Shan and Bogdashan in center of the basin (cf. Carroll et al., 1992), ites following regional tectonic consolida- the Late Carboniferous–Early Permian, al- there is no evidence that the total thickness tion (Coleman, 1989). If this is the case, then though the details of these events are poorly of Upper Permian nonmarine sedimentary much of the felsic magmatism in and around understood. During the same interval the rocks follows the same trend. Several studies the Junggar basin may be related not to lo- remnants of the Junggar/Turpan ocean ba- have documented the presence of coarse- calized extension, but instead to much sin filled with marine sediments derived grained Upper Permian deposits approxi- broader (and poorly understood) regional from partial dissection of the inactive vol- mately equivalent to the lacustrine mud- thermal events. Clearly, more work is canic edifices surrounding the basin. stone in the southern margin of the Junggar needed to fully unravel the complex origins In the northern Tarim basin Early Per- basin (e.g., Zhao, 1982; Carroll et al., 1990; and timing of late Paleozoic magmatism in mian subsidence was accompanied by Graham et al., 1990). These rocks may have western China. eruption of a bimodal volcanic suite, sug- gone undetected in the subsurface of the An alternative to Permian extension of gesting that basin subsidence at this time southern Junggar basin due to the great Junggar is north-vergent thrusting brought was related to continental extension. Simi- thickness (up to 11 km) of Mesozoic-Ceno- about by continued crustal shortening, as larly prominent volcanic rocks do not occur zoic foreland cover in this area. It is there- suggested by Watson et al. (1987), Graham within the thick Upper Permian sedimen- fore possible that the total Upper Permian et al. (1990), and Carroll et al. (1992). Qual- tary fill of the Junggar basin, however, where interval thickness continues to increase itative examination and limited meas- subsidence may have resulted from a re- southward of the principal lacustrine mud- urements of north-directed paleocurrents newed phase of tectonic compression and stone interval, and that the apparent thick- and a continued increase in the proportion flexural loading of the basin. Alternatively, ness maximum of these rocks in the center of quartz ϩ potassium feldspar grains in the Junggar basin may have experienced ex- of the basin is an artifact of the facies change these rocks evince the continued topo- tension during the Late Permian related to from fine-grained to coarse-grained deposits. graphic expression of the paleo–Tian Shan relaxation of earlier compressional stresses, Although late Paleozoic magmatism is in- to the south, which may have been uplifted or transtension resulting from regional sin- dicated by a variety of intrusive and volcanic on thrust faults. This interpretation is also istral shear. It is noteworthy that if regional rocks exposed on the margins of the Junggar consistent with the low apparent heat flows extension did occur at any time during the basin, the genesis of these rocks and their evident from modeling of the thermal ma- Permian, it was not sufficient in magnitude precise age relationships with Late Permian turity of organic matter contained in Upper to reverse the overall trend from marine to basin subsidence are suspect. For example, Permian lacustrine mudstone (Graham et nonmarine depositional environments that gabbro intrusions in the Bogdashan, cited by al., 1990; Carroll et al., 1992), and with occurred in both the Tarim and Junggar ba- Windley et al. (1990) and Allen et al. (1991) structural and stratigraphic evidence for sins. The loss of marine environments may as evidence for Permian magmatism, actu- Late Permian compression of the north- reflect either regional elevation due to com- ally predate the deposition of Upper Per- western margin of the Junggar basin during pressional thickening of the crust, thermal mian lacustrine mudstone by 40–60 m.y. the same time interval (cf. Lin, 1984; Xie et doming and uplift, or an oversupply of clas- These gabbros, which intrude Carbonifer- al., 1984). The hypothesis of flexural loading tic sediments relative to basin subsidence. ous volcanics and volcanogenic sediments, of the basin as a result of compression also Eustatic sea-level changes may also have in- have yielded a U-Pb radiometric age of 328 may not be entirely incompatible with minor fluenced the transition from marine to non- Ϯ 10 Ma (Hopson, 1989), placing them well normal faulting within basin; such faulting marine sedimentation, particularly during within the Carboniferous and suggesting may occur in foreland basins as a result of the Late Permian drop in global sea level. that they are more likely related to arc mag- flexure. Sandstone compositions and limited pa- matism rather than Permian extension. Sim- leocurrent measurements provide evidence ilar crosscutting relationships with de- CONCLUSIONS for the uplift of a paleo–Tian Shan range formed turbidites are the only constraint on during the middle to Late Permian, the ero- the age of mafic dikes in the southern Bog- The net convergence of the Tarim block sional products of which could have filled in dashan reported by Allen et al. (1991) and with Asia during the late Paleozoic is re- adjacent marine basins. Allen and Windley (1993), leaving open the corded by a long-term shift in the Tarim, Finally, it should be noted that what may possibility that they too predate (or post- Turpan, and Junggar basins from mixed ma- prove to be the single most revealing data date) Late Permian basin subsidence. The rine and nonmarine sedimentation to exclu- source for the evolution of the northwestern eastern Bogdashan pillow lavas reported by sively nonmarine conditions. The sedimen- China sedimentary basins has yet to be em- Carroll et al. (1990) occur within the Car- tary sections examined in this study also ployed: seismic reflection surveys and bore- boniferous Liushugou or Qijiagou Forma- reinforce previous models, based on inter- hole data from the subsurface of the basins tions, significantly predating Late Permian pretations from the Tian Shan, that this ad- themselves. The recent opening of portions deposition. We postulate that these lavas dition of Tarim to Asia took place in two of these basins for exploration by western oil and the southern Bogdashan dikes may be stages. The collision of Tarim with the Cen- companies will eventually result in an explo- roughly coeval and are unrelated to Late tral Tian Shan block began in the Late De- sion in our understanding of the Tarim, Tur- Permian extension. Allen et al. (1991) argue vonian and continued into the Carbonifer- pan, and Junggar basins. Until the data from that the geochemistry of the dikes is atypical ous, resulting in the creation of a flexural these investigations are available for public of mature volcanic arcs; perhaps they rep- foredeep along the northern margin of examination, the true nature of the conti-

592 Geological Society of America Bulletin, May 1995 LATE PALEOZOIC TECTONIC AMALGAMATION, CHINA nental growth of vast tracts of central Asia petroleum potential of the Junggar and Tarim basins, north- Li, Y. P., 1990, An apparent polar wander path from the Tarim west China [Ph.D. dissert.]: Stanford, California, Stanford Block, China: Tectonophysics, v. 181, p. 31–41. will remain concealed beneath its deserts. University, 405 p. Liao, Z., Lu, L., Jiang, N., Xia, F., Sung, F., Zhou, Y., Li, S., and Carroll, A. R., Liang, Y., Graham, S. A., Xiao, X., Hendrix, M. S., Zhang, Z., 1987, Carboniferous and Permian in the western Chu, J., and McKnight, C. L., 1990, Junggar basin, northwest part of the east Tianshan Mountains: Beijing, Eleventh Con- ACKNOWLEDGMENTS China: Trapped late Paleozoic ocean: Tectonophysics, gress of Carboniferous Stratigraphy and Geology, Guide v. 181, p. 1–14. Book Excursion 4, 50 p. Carroll, A. R., Brassell, S. C., and Graham, S. A., 1992, Upper Lin, L., 1984, The discovery of nappe-screened oil pool and the Permian lacustrine oil shale of the southern Junggar basin, prospects of Karamay oilfield: Oil and Gas Geology, v. 5, X. Xiao, Z. Wang, and X. Liu arranged northwest China: American Association of Petroleum Ge- p. 1–10. access to and logistical support in western ologists Bulletin, v. 76, p. 1874–1902. Liu, C., and Xiong, J., 1991, New understanding of Carboniferous Chang, C., 1981, Alluvial-fan coarse clastic reservoirs in Karamay, and Permian stratigraphy in the northern region of Tarim China. Y. Liang, Y. Li, and S. Wu provided in Mason, J. F., ed., Petroleum geology in China: Tulsa, basin, in Jia, R., ed., Research of petroleum geology of the Oklahoma, Penwell Co., p. 154–170. northern Tarim basin in China: Wuhan, China University of invaluable assistance in interpreting the Chang, J., 1988, Correlation of Lower Permian series of terrestrial Geoscience Press, v. 1, p. 64–73 (in Chinese with English stratigraphy of Xinjiang. C. L. McKnight, X. facies in west part of Tarim platform: Xinjiang Geology, v. 6, abstract). p. 2–14 (in Chinese with English abstract). Liu, H., 1986, Geodynamic scenario and structural styles of Mes- Wang, J. Zhu, Z. Min, and Y. Tang provided Chen, M., Wang, J., Wang, X., and Ma, Y., 1991, Biostratigraphic ozoic and Cenozoic basins in China: American Association boundary between Carboniferous and Permian in Kalpin of Petroleum Geologists Bulletin, v. 70, p. 377–395. field assistance. M. McWilliams and P. Gans region, Xinjiang, in Jia, R., ed., Research of petroleum ge- Liu, J., and Li, W., 1991, Petrologic characteristics and ages of (Stanford University) provided unpublished ology of the northern Tarim basin in China: Wuhan, China basalt in north Tarim, in Jia, R., ed., Research of petroleum University of Geoscience Press, v. 1, p. 86–93 (in Chinese geology of northern Tarim basin in China: Wuhan, China 40 39 Ar/ Ar radiometric age determinations. with English abstract). University of Geoscience Press, v. 1, p. 194–201 (in Chinese Chen, Z., Wu, N., Zhang, D., Hu, J., Huang, H., Shen, G., Wu, G., with English abstract). N. Carroll, M. Smith, and R. Byrd (Texaco Tang, H., and Hu, Y., 1985, Geologic map of Xinjiang McKnight, C. L., Carroll, A. R., Chu, J., Hendrix, M. S., Graham, Overseas Holdings Inc.) assisted in obtain- Uygur autonomous region: Beijing, Geologic Publishing S. A., and Lyon, R. J. P., 1989, Stratigraphy and structure of House, scale 1:2 000 000. the Kalpin uplift, Tarim basin, northwest China, in Proceed- ing biostratigraphic ages from the Sishi- Coleman, R. G., 1989, Continental growth of northwest China: ings, Seventh Thematic Conference on Remote Sensing for Tectonics, v. 8, p. 621–635. Exploration Geology, Calgary, Alberta: Ann Arbor, Envi- chang section; H. Cousimer identified paly- Dickinson, W. R., 1985, Interpreting provenance relations from ronmental Research Institute of Michigan, p. 1085–1096. nomorphs and D. Wells and L. Taylor detrital modes of sandstone, in Zuffa, G. G., ed., Provenance Nishidai, T., and Berry, J. L., 1990, Structure and hydrocarbon of arenites: Hingham, Massachusetts, D. Reidel Publishing potential of the Tarim basin (NW China) from satellite identified fusulinids. A. R. Ormiston (Amoco) Company, p. 333–361. imagery: Journal of Petroleum Technology, v. 13, p. 35–58. Dickinson, W. R., and Suczek, C. A., 1979, Plate tectonics and Peng, X., and Zhang, G., 1989, Tectonic features of the Junggar identified the Junggar megafossils. Vitrinite sandstone compositions: American Association of Petrole- basin and their relationship with oil and gas distribution, in reflectances were measured by W. G. Dow, um Geologists Bulletin, v. 63, p. 2164–2182. Hsu¨, K. J., and Zhu, X., eds., Chinese sedimentary basins: Du, P. L., 1983, Brief introduction of geological characters of kim- Amsterdam, Elsevier, p. 17–31. D. I. O’Connor, and J. H. Ruffin. Discus- berlite body at Wajelitag in Bachu county, Xinjiang: Xin- Ren, J., Jiang, C., Zhang, Z., and Qin, D., 1987, Geotectonic evo- jiang Geology, v. 1, p. 55–63 (in Chinese with English lution of China: Berlin, Springer-Verlag, 203 p. sions with R. Coleman, E. D. Goodman, abstract). S¸engo¨r, A. M. C., Burke, K., and Dewey, J. F., 1978, Rifts at high angles to orogenic belts: Tests for their origin and the upper Y. Li, W. L. Lindemann, K. Marsaglia, C. A. Ektova, L. A., and Bel’govskiy, G. L., 1980, Main features of Pa- leozoic structure of southeastern Tien Shan: Geotectonics, Rhine graben as an example: American Journal of Science, Ross, S. Nie, R. Sharps, Z. Wang, and L. P. v. 14, p. 459–464. v. 278, p. 24–40. Feng, Y., Coleman, R. G., Tilton, G., and Xiao, X., 1989, Tectonic S¸engo¨r, A. M. C., Natal’in, B. A., and Burtman, V. S., 1993, Evo- Zonenshain all improved this manuscript, as evolution of the west Junggar region, Xinjiang, China: Tec- lution of the Altaid tectonic collage and Paleozoic crustal growth in Eurasia: Nature, v. 364, p. 299–307. tonics, v. 8, p. 729–752. did comments by G. Ulmishek, K. J. Hsu¨, Sharps, R., McWilliams, M., Li, Y. P., Cox, A., Zhang, Z., Zhai, Z., Graham, S. A., Dickinson, W. R., and Ingersoll, R., 1975, Hima- Gao,Z.,Li,Y.A.,andLi,Q.,1989,LowerPermianpaleomag- layan-Bengal model for flysch dispersal in the Appalachi- K. Biddle, and P. Molnar. We are grateful to netism of the Tarim Block, northwestern China: Earth and an-Ouachita system: Geological Society of America Bulle- Planetary Science Letters, v. 92, p. 275–291. D. B. Rowley and D. Burbank for their con- tin, v. 86, p. 273–286. Tian, Z., Chai, G., and Kang, Y., 1989, Tectonic evolution of the Graham, S. A., Brassell, S., Carroll, A. R., Xiao, X., Demaison, G., Tarim basin, in Hsu¨, K. J., and Zhu, X., eds., Chinese sed- structive reviews. Financial support was pro- McKnight, C. L., Liang, Y., Chu, J., and Hendrix, M. S., imentary basins: Amsterdam, Elsevier, p. 33–43. vided by the Stanford-China Industrial 1990, Characteristics of selected petroleum-source rocks, Vikhter, B. Y., and Sher, S. D., 1980, The geological evolution of Affiliates, an industrial consortium that Xinjiang Uygur Autonomous Region, northwest China: the southern Tien Shan fold system: Geotectonics, v. 14, American Association of Petroleum Geologists Bulletin, p. 213–221. has included Agip, Amoco, Anschutz, BHP v. 74, p. 493–512. Wang, G., Liu, C., and Xiong, J., 1991, Permo-Carboniferous sed- Graham, S. A., Hendrix, M. S., Wang, L. B., and Carroll, A. R., imentary facies in northeastern Tarim basin, in Jia, R., ed., Petroleum, Chevron, Conoco, Elf-Aquit- 1993, Collisional successor basins of western China: Impact Research of petroleum geology of northern Tarim basin in aine, Enterprise Oil, Exxon, Mobil, Occi- of tectonic inheritance on sand composition: Geological So- China: Wuhan, China University of Geoscience Press, v. 1, ciety of America Bulletin, v. 105, p. 323–344. p. 160–168 (in Chinese with English abstract). dental, Pecten, Phillips, Sun, Texaco, Trans- Harland, W. B., Armstrong, R. L., Cox, A. V., Craig, L. E., Smith, Wang, H. Z., chief compiler, 1985, Atlas of paleogeography of A. G., and Smith, D. G., 1990, A geologic time scale 1989: China with explanatory text: Beijing, Cartographic Publish- world Energy International, and Unocal. Cambridge, England, Cambridge University Press, 263 p. ing House, 85 p. Hendrix, M. S., Graham, S. A., Carroll, A. R., Sobel, E. R., Mc- Wang, S., 1991, Sporopollen assemblage of Lower Permian Radiometric dating at Stanford is supported Knight, C. L., Schulein, B. J., and Wang, Z., 1992, Sedi- Kaipaizileike formation, north Tarim, in Jia, R., ed., Re- by Department of Energy Grant mentary record and climatic implications of recurrent de- search of petroleum geology of northern Tarim basin in formation in the Tian Shan: Evidence from Mesozoic strata China: Wuhan, China University of Geoscience Press, v. 1, DE-FG05-88ER75499. of the north Tarim, south Junggar, and Turpan basins, p. 94–99 (in Chinese with English abstract). northwest China: Geological Society of America Bulletin, Wang, T., and Liu, J., 1991, A preliminary investigation on for- v. 104, p. 53–79. mative phase and rifting of Tarim basin, in Jia, R., ed., Re- Hopson, C., Wen, J., Tilton, G., Tang, Y., Zhu, B., and Zhao, M., search of petroleum geology of northern Tarim basin in REFERENCES CITED 1989, Paleozoic plutonism in east Junggar, Bogdashan, and China: Wuhan, China University of Geoscience Press, v. 2, eastern Tianshan, northwest China: Eos, v. 70, p. 1403–1404. p. 115–124 (in Chinese with English abstract). Allen, M. B., and Windley, B. F., 1993, Evolution of the Turfan Hsu¨, K. J., 1988, Relict back-arc basins: Principles of recognition Wang, Z., Wu, J., Lu, X., Zhang, J., and Liu, C., 1986, An outline basin, Chinese central Asia: Tectonics, v. 12, p. 889–896. and possible new examples from China, in Kleinspehn, on the tectonic evolution of the Tian Shan of China: Bulletin Allen, M. B., Windley, B. F., Zhang, C., Zhao, Z. Y., and Wang, K. L., and Paola, C., eds., New perspectives in basin analysis: of the Institute of Geology, Chinese Academy of Geological G. R., 1991, Basin evolution within and adjacent to the Tien New York, Springer-Verlag, p. 245–263. Sciences, v. 15, p. 81–92 (in Chinese with English abstract). Shan range, NW China: Journal of the Geological Society of Hsu¨, K. J., 1989, Origin of sedimentary basins in China, in Hsu¨, Wang, Z., Wu, J., Lu, X., Liu, C., and Zhang, J., 1990, Polycyclic London, v. 148, p. 369–378. K. J., and Zhu, X., eds., Chinese sedimentary basins: Am- tectonic evolution and metallogeny of the Tian Shan moun- Allen, M. B., Windley, B. F., and Zhang, C., 1992, Paleozoic col- sterdam, Elsevier, p. 207–227. tains: Beijing, Science Press, 217 p. lisional tectonics and magmatism of the Chinese Tien Shan, Ji, X., and Coney, P. J., 1985, Accreted terranes of China, in How- Watson, M. P., Hayward, A. B., Parkinson, D. N., and Zhang, central Asia: Tectonophysics, v. 220, p. 89–115. ell, D. G., ed., Tectonostratigraphic terranes of the circum- Z. M., 1987, Plate tectonic history, basin development and Allen, M. B., S¸engo¨r, A. M. C., and Natalin, B. A., 1995, Junggar, Pacific region: Houston, Circum-Pacific Council for Energy petroleum source rock deposition onshore China: Marine Turfan, and Alakol basins as Late Permian to ?Early Tria- and Mineral Resources, p. 349–361. and Petroleum Geology, v. 4, p. 205–225. ssic extensional structures in a sinistral shear zone in the Kristov, Ye. V., and Mikolaychuk, A. V., 1983, Geosynclinal base- Windley, B. F., Allen, M. B., Zhang, C., Zhao, Z. Y., and Wang, Altaid orogenic collage, Central Asia: Journal of the Geo- ment of the crust of the Fergana-Kokshaal Hercynides: G. R., 1990, Paleozoic accretion and Cenozoic redeforma- logical Society of London, v. 152, p. 327–338. Geotectonics, v. 17, p. 233–241. tion of the Chinese Tien Shan range, central Asia: Geology, Anonymous, 1991, Petroleum geology of the Tarim basin: Beijing, Kwon, S. T., Tilton, G. R., Coleman, R. G., and Feng, Y., 1989, v. 18, p. 128–131. Science Press (seven volumes). Isotopic studies bearing on the tectonics of the west Junggar Xie, Hong, Zhao, B., Lin, L. D., and You, Q. M., 1984, Oil-bearing Bai, Y., Chen, Q., Sun, Q., Li, Y. A., Dong, Y., and Sun, D., 1987, region, Xinjiang, China: Tectonics, v. 8, p. 719–727. features along the Karamay overthrust belt, northwestern Late Paleozoic polar wander path for the Tarim platform Lai, J., and Wang, J., 1988, Atlas of the paleogeography of Xin- Junggar basin, China, in Wagner, H. C., Wagner, L. C., and its tectonic significance: Tectonophysics, v. 139, jiang: Urumqi, China, Xinjiang People’s Publishing House, Wang, F. F. H., and Wong, F. L., eds., Petroleum resources p. 145–153. 92 p. (in Chinese with English abstract). of China and related subjects: Houston, Texas, Circum- Bally, A. W., and eight others, 1986, Notes on sedimentary basins Lee, K. Y., 1985, Geology of the Tarim basin with special emphasis Pacific Council for Energy and Mineral Resources Earth in China—Report of the American Sedimentary Basins Del- on petroleum deposits, Xinjiang Uygur Zizhiqu, northwest Science Series, v. 10, p. 387–402. egation to the Peoples Republic of China: U.S. Geological China: U.S. Geological Survey Open-File Report 85-616, Xiong, J., 1991, Permo-Carboniferous conodont sequence in Survey Open-File Report 86-327, 108 p. 55 p. northeastern Tarim basin, in Jia, R., ed., Research of pe- Burrett, C. F., 1974, Plate tectonics and the fusion of Asia: Earth Li, C., Wang, Q., Liu, X., and Tang, Y., 1982, Explanatory notes troleum geology of northern Tarim basin in China: Wuhan, and Planetary Science Letters, v. 21, p. 181–189. to the tectonic map of Asia: Beijing, Cartographic Publish- China University of Geoscience Press, v. 1, p. 74–85 (in Carroll, A. R., 1991, Late Paleozoic tectonics, sedimentation, and ing House, 44 p. Chinese with English abstract).

Geological Society of America Bulletin, May 1995 593 CARROLL ET AL.

Yan, Y., Yang, S., Hu, B., Wen, C., and Jin, H., 1983, Some prob- Zhang, Z., Liou, J. G., and Coleman, R. G., 1984, An outline of the Zhu, B., 1984, Ancient ocean crust and plate tectonics in south- lems concerning petroleum geology of the Tarim basin: Sci- plate tectonics of China: Geological Society of America Bul- western section of western Junggar: Bulletin of the Chinese entia Sinica, v. 26, p. 500–514. letin, v. 95, p. 295–312. Academy of Geological Sciences, v. 10, p. 137–148 (in Chi- Zeng, Y., Zhu, X., and Wang, G., 1983, On the relative problems Zhao, B., 1982, The prospects of petroleum exploration of Permo- nese with English abstract). of Tianshan cycle: Xinjiang Geology, v. 1, p. 67–73 (in Chi- Carboniferous in the Junggar Basin: Oil and Gas Geology, Zonenshain, L. P., and Gorodnitsky, A. M., 1977, Paleo-Mesozoic nese with English abstract). v. 3, p. 1–14 (in Chinese with English abstract). and Mesozoic reconstructions of the continents and oceans: Zhai, X., and Wang, G., 1991, Characteristics of Carboniferous Zhou, D., Chang, E. Z., and Carroll, A. R., 1994, Carboniferous– Geotectonics, v. 11, p. 159–172. gravity flow deposits in southern margin of Tianshan moun- Early Permian post-collisional extension of Tian Shan and tains, in Jia, R., ed., Research of petroleum geology of northern Tarim, northwestern China: American Association northern Tarim basin in China: Wuhan, China University of of Petroleum Geologists Annual Convention Program, v. 3, Geoscience Press, v. 1, p. 169–174 (in Chinese with English p. 289–290. abstract). Zhou, R., 1987, The advance on isotope geochronology of Xin- Zhang, X., 1981, Regional stratigraphic chart of northwestern jiang: Xinjiang Geology, v. 5, p. 15–105 (in Chinese with China, branch of Xinjiang Uygur autonomous region: Bei- English abstract). jing, Geological Publishing House, 496 p. (in Chinese). Zhou, Y., and Jia, R., 1991, Geological conditions for formation of Zhang, Z., Wu, S., Gao, Z., and Ziao, S. B., 1983, Research on large oil and gas fields in north Tarim basin, in Jia, R., ed., sedimentary model from Late Carboniferous to Early Per- Research of petroleum geology of northern Tarim basin in MANUSCRIPT RECEIVED BY THE SOCIETY NOVEMBER 29, 1993 mian epoch in Kalpin region, Xinjiang: Xinjiang Geology, China: Wuhan, China University of Geoscience Press, v. 2, REVISED MANUSCRIPT RECEIVED AUGUST 31, 1994 v. 1, p. 9–20 (in Chinese with English abstract). p. 1–10. MANUSCRIPT ACCEPTED OCTOBER 3, 1994

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594 Geological Society of America Bulletin, May 1995