Science in China Series D: Earth Sciences

© 2007 SCIENCE IN CHINA PRESS Springer

Cenozoic basin development and its indication of plateau growth in the Xunhua-Guide district

LIU ShaoFeng1,2,3†, ZHANG GuoWei4 & P. L. HELLER5

1 State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China; 2 College of Geosciences and Resources, China University of Geosciences, Beijing 100083, China; 3 Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education, China University of Geosciences, Beijing 100083, China; 4 Department of Geology, Northwest University, Xi’an 710069, China; 5 Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA The Xunhua, Guide and Tongren Basins are linked with the Laji Mountain and the northern West Qinling thrust belts in the Xunhua-Guide district. Basin depositional stratigraphy consists of the Oligocene Xining Group, the uppermost Oligocene-Pliocene Guide Group and the Lower Pleistocene. They are divided into three basin phases by unconformities. Basin phase 1 is composed of the Xining Group, and Basin phase 2 of the Zharang, Xiadongshan, Herjia and Ganjia Conglomerate Formations in the Guide Group, and Basin phase 3 of the Gonghe Formation and the Lower Pleistocene. Three basin phases all develop lacustrine deposits at their lower parts, and alluvial-braided channel plain deposi- tional systems at upper parts, which constitute a coarsening-upward and progradational sequence. Basin deposition, paleocurrent and provenance analyses represent that large lacustrine basin across the Laji Mountain was developed and sourced from the West Qinling thrust belt during the stage of the Xining Group (Basin phase 1), and point-dispersed alluvial fan-braided channel plain deposition sys- tems were developed beside the thrust and uplifted Laji Mountain and sourced from it, as thrusting migrated northwards during the stage of the Guide Group (Basin phase 2). Evolution of basin-mountain system in the study area significantly indicates the growth process of the distal Tibetan Plateau. The result shows that the Tibetan Plateau expanded to the northern West-Qinling at Oligocene (29―21.4 Ma) by means of northward folded-and-thrust thickening and uplifting and frontal foreland basin filling, and across the study area to North Qilian and Liupan Mountain at the Miocene-Pliocene (20.8―2.6 Ma) by means of two-sided basement-involved-thrust thickening and uplifting and broken foreland basin filling, and the distant end of Tibetan Plateau behaved as regional erosion and intermontane basin aggrada- tional filling during the Pliocene and early Pleistocene (2.6―1.7 Ma).

Xunhua-Guide district, Cenozoic basins, provenance analysis, basin-mountain evolution, plateau growth

Growth of intracontinental plateau orogenic belt, that is, developed within the intracontinental plateau is essential outward expanding and uplifting process from the colli- to the interpreting plateau growth mechanism. The sci- sional belt, and its geodynamics are a frontier topic of entific significance of unraveling tectonism and climate world attention[1―3]. The detailed growth process of in- change, especially Cenozoic uplift and growth of plateau, tracontinental plateau involves in not only quite complex through the analysis of surficial process of uplift, ero- patterns of distributed deformation and deep lithospheric Received January 10, 2007; accepted May 10, 2007 architecture but also erosional redistribution of load, and doi: 10.1007/s11430-007-6012-3 †Corresponding author (email: [email protected]) sediment accumulation within intermontane basins. The Supported by the National Natural Science Foundation of China (Grant Nos. study of coupling relation between basin and mountain 40234041 and 40672135) and the 111 Project (B07011) www.scichina.com www.springerlink.com Sci China Ser D-Earth Sci | Nov. 2007 | vol. 50 | Supp.II | 277-291

sion, subsidence and accumulation happening within paper gave a preliminary understanding of the Cenozoic basin and mountain system has been gradually realized, structural evolution of the studied area, and supplied and some important research results have been achieved some basin evidence and data for wholly probing into in worldwide plateaus and orogenic belts[4―6]. Therefore the growth mechanism of the northeastern Tibetan Pla- the study of structural and depositional process and their teau. feedback relationship, which are related with plateau growth, in basin and mountain (or structural deformation 1 Basin structural framework belt) system of a young active plateau is essential to un- The Guide, Tongren and Xunhua Basins are distributed derstanding the history of plateau development and the along the two belts of southern Laji Mountain and West mechanism of plateau growth. Qinling, respectively (Figure 1). The Xunhua Basin, the The Xunhua-Guide is located at the southeast part of West Qinling thrust belt to the south and the Lajishan northeastern Tibetan Plateau, a connection place be- thrust belt to the north form a rhombus shape, and rep- tween the northern West Qinling and Qilian. The results resent a typical characteristics of structure in the north- show that the late stage of northeastward growth of Ti- eastern Tibetan Plateau. The NWW-striked northern betan Plateau happened at late Cenozoic[2,7,8]. Some im- West Qinling thrust belt, is connected with the Shangdan portant results have been reached about structural geol- fault in the East Qinling across the southern Linxia Ba- ogy[9―14], basin sedimentation[14―16], magnetic stratigra- sin eastwards, and with northern Caidam fault belt [17―19] phy and the relationship between basin develop- across the Riyue Mountain and the southern Qinghai [17,19] ment and thrust of the northern West Qinling , etc. in Lake westwards. The Lajishan thrust belt, distributed the Xunhua-Guide area, but several key scientific ques- along the northern Xunhua Basin in an arc-shape, joins tions of structural control of basin marginal structural together with the West Qinling thrust belt westwards and belts on Cenozoic basin development, basin and moun- eastwards, respectively, and forms Riyueshan thrust belt tain evolution and its response to plateau growth need to at the western part. be further studied. Through systematic study of the Ce- The frontal fault of the northern West Qinling thrust nozoic basin sedimentation, paleocurrent and prove- belt at the southern margin of the Xunhua Basin repre- nance, and the analysis of basin margin thrusting, this sents as the Middle Triassic thrust on Lower Cretaceous

Figure 1 Geological structural sketch of Xunhua-Guide. a, b, c and d represent the location of stratigraphic sections. 1, Archean-Proterozoic; 2, Protero- zoic; 3, Lower Paleozoic; 4, Ordovician granite; 5, Upper Paleozoic-Triassic; 6, Jurassic granite; 7, Cretaceous; 8, Xining Group; 9, Guide Group; 10, Pleistocene; 11, Holocene; 12, fault.

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and the Xining Group of the Lower Tertiary[19]. A lot of chean and Lower Proterozoic gneiss, quartzschist, quart- tight folds, small thrust faults with attitude of 182<30, zite and various granites are distributed between the we- and cleavages are developed with the northern West stren Laji Mountain and the northern West Qinling thrust Qinling thrust belt. Southernward-vergence Gangcha belts[21]. These middle-high grade metamorphic rocks thrust, with E-W strike along the northern Tongren Basin, and granite rocks could be the sources of the sediments is characterized by the thrust of Middle and Lower Tri- in the Guide or western Xunhua Basins. assic over the Xining and Guide Groups. The northern West Qinling thrust converges at the west with the Laji- 2 Basin filling sequences shan thrust to form a southward-vergence, Riyueshan The Cenozoic stratigraphy in the Xunhua and Guide thrust belt in which Archean and Ordovician granites, Basins is composed of the Oligocene Xining Group, the Middle and Upper Triassic thrust on the Xining and Neogene Guide Group, Pleistocene and Holocene. The Guide Formations[19]. The northern West Qinling thrust Xining Group, mostly distributed in the Xunhua Basin, belt is composed mainly of the Lower-Middle Long- Laji Mountain and its northern area besides the Guide wuhe Group, and part of the Upper Carboniferous- and Tongren areas, is composed of three parts, and its Permian Ganjia Formation, the Carboniferous-Lower lower part is mainly found in the local parts of the Permian Gahai Group and the Middle Permian Daguan- southern Xunhua Basin, outcrop of Archean basement shan Formation, the Upper Triassic Huari, Rinaore For- rock of the middle Xunhua Basin and the top of Laji mations and the Late Triassic-Jurassic granites[20,21]. The Mountain. The Guide Group is divided into the Zharang, composed rocks of the stratigraphic formations are Xiadongshan, Herjia, Ganjia Conglomerate and Gonghe flysch clastic rock, chert, a few carbonate and volcanic Formations upwards. Fang et al.[19] recently divided the rock which supply a main depositional source for the Guide Group into Guidemen, Garang, Ashigong, Herjia, northern Cenozoic basin. Ganjia and Amigang Formations (Table 1). The research The Lajishan thrust belt shows itself as a two-sided on paleogeomagnetism of the Xining and Guide Groups thrust shape, that is, northward thrust at its northern side shows the ages of the Xining and Guide Groups and and southward thrust at its southern side[20]. The eastern their equivalent strata[22,17,19]. The Xining Group is aged part of Laji Mountain at the northern and eastern Xun- ― hua Basin is characterized by Lower Paleozoic, Upper as 29.0 21.4 Ma, comparative to the Tala Formation in Devonian and a few Archean and Lower Proterozoic the Linxia Basin, and the Guide Group as 20.8―1.8 Ma thrust on the Lower Cretaceous, the Xining and Guide (Table 1). The former is the upper Oligocene and the Groups. The deformed Upper Cambrian chert slate, at lowest Miocene, and the latter is the Miocene and Plio- the frontal Laji Mountain of the northern Hualong Town, cene. southward thrust on the Guide Group conglomerate, and 2.1 Xining Group the thrust fault dips in a direction of NE30 with an angle The Xining Group, the lowest part of the Cenozoic of 60°. The Guide Group in front of the thrust was de- above the Cretaceous, is widely distributed in the dif- formed to form a syncline with a steeper northern limb ferent basins of the study area, and unconformably cov- (the stratigraphic attitude, 221°∠68°) and a gentle ers on the Archean-Lower Proterozoic basement or Cre- southern limb (348°∠12°). At the western Laji Moun- taceous conglomerate in the Xunhua Basin, the Triassic tain, the north-western Xunhua Basin, the Lower Paleo- strata in the Guide and Tongren Basins, the Lower Pa- zoic pinches out, and the Middle Proterozoic thrust on leozoic or the Archean-Lower Proterozoic metamorphic the Cretaceous or Paleozoic. The eastern part of Laji rocks in the Laji Mountain. The Xining Group of the Mountain is composed mainly of the intermediate-basic measured sections along Kashida village about 15 km volcanic rock, pyroclastic rock, chert, and a little clastic rock and Ordovician granite and Upper Devonian strati- from the south-southeast of Xunhua Town and Laxiong graphy[21] which could be the main provenance of the village about 8 km from the southwest of Xunhua Town Xunhua Basin. The western part of the Laji Mountain is is composed of chocolatebrown, nacarat sandy con- composed mainly of quartzite, slate and phyllite of glomerate and silty mudstone (Figure 2), and is divided Changcheng System, dolomite limestone, dolomite, into three parts. The first part in the Kashida village sec- limestone and phyllite of Jixian System, etc. The Ar- tion, 170 m in thickness, consists of maroon interbedded

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Table 1 Cenozoic stratigraphic correlation, ages and basin phase division in Xunhua-Guide and its adjacent areas

conglomerate and pebbly fine sandstone or mudstone, fine sandstone and gypsum layers with 10―20 cm and unconformably overlies on the Archean-Lower Pro- thickness. Apparently these layers could be interpreted terozoic. The conglomerate layers, 1.5―2.0 m in thick- to be lacustrine or shallow lacustrine deposits, and be- ness, laterally extend with clear scour surfaces at their come fluvial plain deposits at the upper part, and the bases, and are composed of grain-supported, rounded or gypsum layers could be the products of shallowing intermediate-rounded gravels with about 1―5 cm, or 10 lacustrine deposits. The third part of the Xining Group in cm at most in diameter. The gravels mostly with flat the Laxiong Village section, more than 500 m in thick- shape are imbricated orientally. The pebbly fine sand- ness, is composed of interbedded sandstone and con- stone and mudstone, with massive bedding, between the glomerate, and conglomerate from lower to upper parts. gravel layers are 1―2 m in thickness. The gravel layers The lower intervals of lenticular sandstone and con- are interpreted to be gravel braided channel deposits, glomerate are laterally amalgamated within which fine and their upper parts to be flood plain or muddy flow or very fine sandstone are developed. Cross or lateral deposits. The gravel layers are thinned and become accretional beddings are developed in the lenticular lens-shaped, but the fine sandstone and mudstone layers sandstone and conglomerate, and gravels within them are thickening, and gravels are fining upwards in the are rounded, and about 2―5 cm (0.5 cm at least and whole sequence. The depositional environment becomes 10―15 cm at most) in diameter. Massive or ripple bed- meandering channel plain at the upper part. The second dings are developed in the fine sandstone. These strati- part of the Xining Group in the Laxiong Village section, graphic composites are interpreted as meandering chan- 150―200 m in thickness, is composed of nacarat mud- nel plain deposits, and the conglomerate and sandstone stone with horizontal beddings, partly interbedded very as channel deposits and the fine sandstone as flood plain

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gravels are slightly orientated, and about 5―10 cm (10―20 cm at most) in diameter, which is interpreted to be gravel braided channel deposits. At the uppermost the conglomerate layers are lenticular and develop lateral accretional bedding and some massive bedding, which could be the deposits of meandering channels. The lower Pleistocene fluvial or debris flow conglomerate uncon- formably overlies the Xining Group, and the Guide Group is absent. The base of the Xining Group is kept on the western Laji Mountain, and is composed of nacarat conglomer- ate with more than 100 m in thickness. The gravels are slightly orientated and partly no sorted at the base, and mostly no rounded. The sizes of the gravels are graded into about 8―10 cm (20 cm at most), 5 cm, 1―2 cm in diameter. The directionality and stratification of gravels are increased upwards, and the gravels are in the shape of flat. The each of stratigraphic sequence is about 10― 30 cm in thickness. This conglomerate is interpreted as gravel braided channel deposits and partly debris flow deposits at the base. The Xining Group was also found to the south of Hualong Town in the middle of the Xun- hua Basin, and unconformably covers on Archean- Lower Proterozoic. The residual base of the stratigraphy has similar characteristics to the section of Kadashi vil- lage, and represents gravel (2―5 cm in diameter) braid- ed channel and flood plain fine sandstone deposits. 2.2 Guide Group The Guide Group mostly overlies the Xining Group, but the Triassic in the Guide and Tongren Basins. Fang et al.[19] represent that there was hiatus and unconformity between the Xining and Guide Groups in the Guide Basin[19,24]. The Guide Group consists mainly of granule gravel conglomerate, mudstone, siltstone, interbedded sandstone and conglomerate, and bowlder conglomerate, and is divided into the Zharang, Xiadongshan, Herjia, Figure 2 Stratigraphic sequences, lithic or gravel composition of the Ganjia Conglomerate and Gonghe Formations. Here we Xining Group in Kashida Village (a) and Laxiong Village (b) in the Xun- hua Basin. 1, Meta-sandstone; 2, phyllite; 3, slate; 4, volcanic; 5, granite; take the sections from the Zharang to the base of 6, dolomite; 7, limestone; 8, chert; 9, sandstone; 10, medium and Xiadongshan Formations in the Guidemen area and from Coarse-grained sandstone; 11, fine-grained sandstone; 12, mudstone. Mud, the upper Xiadongshan to Gonghe Formations in the mudstone; VF, very fine sandstone; F, fine sandstone; M, middle sandstine; C, coarse sandstone; G, gravel. Square black points beside lithologic col- Ganjia area as examples to introduce the stratigraphic umn represent location of gravel counting or lithic test. Location of sec- characteristics of the Guide Group (Figure 3). tions (a) and (b) is shown in Figure 1. A good outcrop of the base of the Zharang Formation is developed in the Guidemen and Ashigong, and con- deposits. The upper third part mostly consists of con- sists of a set of gray yellow conglomerate, about 100 m glomerate and a few interlayers of thin sandstone. The thickness (Figure 3c). This formation is stratified and

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develops large scour surfaces. The gravels, 5―25 cm in tal deposits, and gravel or sandy braided channel, cre- diameter, are slightly orientated, but mostly neither vasse channel or spray, plain lake deposits. sorted nor rounded. The interbedded granule conglom- The base of Xiadongshan Formation in the Guidemen erate and sandstone or sandy mudstone are developed area consists of brown yellow, fuschia mudstone, with upwards. The conglomerate layers with cross and roug- horizontal bedding, interbedded with green gray or gray hly parallel beddings laterally and stably extend and are calcareous claystone, muddy limestone, brown yellow 2 m to 20 cm in thickness and thinning upwards. The gravel sandstone and granule conglomerate (Figure 3c). sandy mudstone or mudstone, 30 cm to 2 m thick or The calcareous claystone is associated with muddy thickening upwards, within the conglomerate developing limestone, and both laterally extend and are about 1m massive and horizontal beddings. The Zharang Forma- thick. The coarse sandstone and granule conglomerate, tion is interpreted to be alluvial fan-braided channel with cross or roughly parallel beddings and about 0.5―1 plain deposits, consisting of gravel braided channel, de- cm diameter gravels, are usually developed on limestone bris flow facies, upwards changed from proximal to dis- or mudstone with sharp contacts. These rocks constitute

Figure 3 Stratigraphic sequence, lithic or gravel composition of Guide Group in Guidemen (c) and Ganjia (d) in Guide Basin. Round and square black points beside lithologic column represent location of lithic or gravel counting. Location of measured sections d and d is shown in Figure 1. Upper part of lithologic column of section d was modified from Song Chunhui et al.[15]. 1, Meta-sandstone; 2, slate; 3, schist and phyllite; 4, gneiss; 5, quartzite; 6, vol- canic; 7, granite; 8, shallow intrusive rock; 9, intermediate-basic volcanic; 10, sandstone; 11, mudstone; 12, claystone; 13, others (red sandstone); 14, lime- stone. The other explanations are shown in Figure 2.

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coarsening-upward sequences, at the tops of which ex- in general, 8―15 cm at most in diameter. The Herjia posure marks are usually developed. The mudstone is Formation is interpreted to be gravel braided channel interpreted to be a kind of lacustrine deposits, and sand- plain deposits, and aged as 7.8―36 Ma[19]. stone and conglomerate to be lakeshore or distal alluvial The 300-m-thick Ganjia Conglomerate Formation is plain deposits. The paleogeomagnetic research results of composed of gray bowlder conglomerate interbedded [19] Fang et al. represent that the Zharang Formation is with lenticular gravel sandstone and very fine sandstone aged as 20.8―19 (?) Ma, the base of Xiadongshan For- (Figure 3d). The gravels in the conglomerate are orien- mation as 19―17 (?) Ma. The stratigraphy from the up- tated, sub-rounded, and about 5―30 cm (100 cm at per Xiadongshan through Gonghe Formations is well most) in diameter. The formation is interpreted to be developed in the Ganjia area (Figure 3d). The upper Xia- alluvial fan-braided channel plain deposits, aged as dongshan Formation in the Ganjia area consists of 3.6―2.6 Ma[19]. The about 200 m thick, Gonghe Form- thickening, redbrown and mostly massive mudstone and ation, unconformably overlied on the Ganjia Formation, sandy mudstone, interbedded with granule conglomerate, consists of light gray mudstone containing yellow thin gray calcareous mudstone and muddy limestone. The sandstone and unsorted granule conglomerate, and its lower part of the formation contains more very thin (0.5 top misses as erosion. It is interpreted to be shallow lake m thick) gray calcareous mudstones, within which short and subaqueous debris flow deposits, aged as 2.6―1.8 extended lenticular or long extended laminarization [19,15,24] Ma . According to Fang Xiaomin’s research on the granule conglomerate or gravel sandstone with sharp Linxia Basin to the east of the study area in Gansu base scour surfaces are developed. Some lenticular con- Province, the conglomerate of the Jinggoutou Formation glomerate and coarse sandstone, with cross bedding and (1.76―1.72 Ma), above the Dongshan Formation comp- orientated gravels, are interpreted to be channel deposits. arative to the Gonghe Formation in the Guide Basin, is Some other stratified or lenticular conglomerates, with developed, and defined as the Lower Pleistocene, which massive bendding and no sorted gravels, are interpreted is also largely distributed in the Xunhua Basin and un- to be debris flow or channel-like debris flow deposits. conformably overlies the Xining Group. Parts of thin granule conglomerate or gravel coarse sandstone, with parallel or roughly parallel beddings, to 2.3 Division of stratigraphic sequence be sheet flow deposits. The 0.5―8 m-thick conglomer- The unconformities are developed above the Xining ates or gravel coarse sandstones are thickened and coar- Group and the Ganjia Conglomerate Formation of the sened upwards, and conglomerate layers are increased. Guide Group respectively in the Xunhua-Guide [15,19,24] The gravels are graded as 2―3 mm, 2―3 cm, 3―5 cm, area . The Cenozoic stratigraphy is divided into 3 and 8―10 cm. The whole upper Xiadongshan Forma- basin phases bordered by the unconformities. Basin tion is interpreted as very shallow lacustrine and flood phase 1 includes the Xining Group, and Basin phase 2 plain deposits on the distal alluvial fan-braided plain, includes the Zharang, Xiadongshan, Herjia and Ganjia and aged as 17 (?)―7.8 (?) Ma[19]. As a whole, the Conglomerate Formations of the Guide Group, and Ba- sin phase 3 includes the Gonghe and Lower Pleistocene. Xiadongshan Formation is a sequence of lacustrine, dis- Each basin phase represents the whole depositional fill- tal alluvial fan-braided channel plain deposits upwards. ing of a prototype basin[25]. Lacustrine deposits at the The Herjia Formation, 700 m thick, in the Ganjia area lower or lowest parts of the three basin phases, and delta consists mainly of dark red, brown, yellow and gray co- and alluvial fan-braided channel plain depositional sys- nglomerate, sandy conglomerate, mudstone, sandy mud- tems at the upper part are developed. Basin phases are stone, etc. (Figure 3d). Massive and cross stratified con- characterized by a sequence of progradation and coars- glomerate or sandy conglomerate, mediate-coarse sand- ening upwards. The thicknesses and ages of the strati- stone are characterized by lateral extension and thicken- graphy represent that the depositional and subsidence ing upwards. The conglomerate or sandstone and mud- rates are increased upwards[19]. stone, silty mudstone at the lower part are interbedded. Mudstone is thinned and gradually disappear upwards, 3 Analysis of sediment provenance and thickened conglomerate is interbedded with coarse or gravel sandstone, and contains gravels with 5―10 cm The basin sediments are a kind of “linkage” of basin and

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mountain. The analysis of sediment provenance can help of higher southward and westward, and lower northward us to probe into unroofing process of the provenance and and eastward. Although some of the Xining Group was tectonic uplift events in mountains[26]. The provenance deposited on the West Qinling thrust belt, it is the south- analysis on sediments of the Xining and Guide Groups ern margin of the basin, and the Laji Mountain has no in different strata or different districts in the Xunhua and influence on the deposition of the Xining Group as it did Guide Basins effectively reveals the uplift events and not emerge to the base level of deposition at the synde- tectonic process in the West Qinling and the Lajishan positional stage. So a large basin, not including the Ton- thrust belts. Besides test of fragment composition in gren Basin, existed, which is the composition of the sedimentary rocks and its comparison with provenance Longxi Basin and is linked with the Linxia Basin. stratigraphy, we will fully probe into uplift and unroof- The distribution of the Guide Group is different from ing process of provenance thrust belt linking with that of the Xining Group. Except a lacustrine basin ex- analyses of prototype basins and paleocurrents. isting in the Guide Basin, point-source drainage disper- 3.1 Prototype basin recovery and paleocurrent sal alluvial fan-braided channel plain systems were de- analysis veloped along the northern Xunhua Basin and the north- ern and eastern margins of the Laji Mountain (Figure 5). The recovery of remanent basin of the Xining Group The gravel alluvial fan-braided channel plain progra- through removing the overlying Guide Group, Pleisto- dated southward at the northern margin of the Guide cene and Holocene in the study area represents that the lake basin, with the northern Lajishan thrust belt thrust- Xining Group is mainly distributed to the north of the ing southward. The conglomerate of the Ganjia Con- West Qinling thrust belt, and only some of it is located glomerate Formation of the top of Basin phase 2 pro- upon the thrust belts in the Guide and Tongren Basins gradated to the front of the thrust belt. The paleocurrent (Figure 4). The Xunhua Basin is mostly covered by the of the Guide Group in the Guide Basin was mainly south, Xining Group. The lacustrine and meandering channel south-south-westward, but was westward at the north- plain deposits of the middle part of the Xining Group are eastern part of the basin controlled by the thrust fault at mainly distributed in the central basin and the braided the eastern margin of the basin. So the Guide Basin is an channel conglomerate deposits of the upper part of the independent lake basin isolated from the marginal Xun- Xining Group mainly remain in the southern margin of hua Basin. It gets across the West Qinling thrust belt, the basin. Owing to the basement uplift, the lower part and extends to the southern Laji Mountain (Riyue of the Xining Group, the conglomerate, overlying the Mountain), and the sediments dispersed southward from Archean-Proterozoic outcrops. There is no outcrop of the southern Laji Mountain, and formed a large alluvial the Xininig Group in the eastern part of the Laji Moun- fan-braided channel plain at the late stage. Different tain, but there remains a block of the conglomerate of from the Guide Basin, the Tongren Basin is located on the basal Xining Group in the western part. Paleocurrent the northern West Qinling thrust belt. The northern mar- analysis obtained from clast imbrication and cross-bed- gin of the basin was modified by the southern vergence ding shows that the river systems in the southern Xun- thrusts, and southern part extended to the outside of the hua Basin mainly flowed south-east-eastward, north- study area. The granule conglomerate at the northern east-eastward and northeastward, which are parallel or basin is well stratified with flat and stable scour surfaces perpendicular to the northern West Qinling thrust belt, at its base, and each layer, about 1.5 m thick, develops and in the northern Xunhua Basin, the front of the cross and roughly parallel beddings, within which grav- southern Laji Mountain (to the northwest of Hualong els are about 5 cm in diameter. This part of the Guide Town), flowed northeastward, pointing to the Laji Group is interpreted to be braided channel plain deposits. Mountain, and in the northwestern Xunhua Basin the Thickening bowlder conglomerate developed in the river systems flowed south-east-eastward. Although the southern basin is stratified, and gravels within it are paleocurrent directions vary, they are mostly concen- about 5―15 cm, 20―150 cm at most in diameter and trated in north-north-east or north-east-east (Figure 4). unsorted and unrounded, which is interpreted to be Paleocurrent data represent that the sediments mainly proximal gravel alluvial fan deposits. Paleocurrent data flowed northward and eastward at the syndepositional indicate that the fans were built by runoff that flowed stage of the Xining Group, which show the paleo-relief toward the north-north-west, parallel to the extend of

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Figure 4 Basin distribution, paleocurrent and lithic or gravel composition of Xining Group in Xunhua-Guide area. Distribution of Xining Group is shown in figure, and other pre-Cenozoic stratigraphy is shown as white color; Piegraphs show lithic or gravel composition and percentages in different areas; Rose graphs show paleocurrent. No. shows serial numbers of lithic or gravel accounting; n. shows numbers of paleocurrent measurement. 1, Sandstone; 2, fine sandstone and mudstone; 3, mudstone; 4, limestone; 5, chert; 6, granite; 7, volcanic rock; 8, marble; 9, phyllite; 10, meta-quartzite sanstone; 11, paleocur- rent. The other explanations are shown in Figure 1. the basin. The Guide Group is distributed in shape of fan from the Laji Mountain. No lacustrine and delta systems, along the northern margin of the Xunhua Basin, and is correspond to the middle and lower parts of the Guide bordered by southward-vergent thrust in the southern Group in the Guide Basin, are found in the Tongren and front of the Laji Mountain. No Guide Group is devel- Xunhua Basins. The deposits in the Tongren and Xunhua oped at the southern margin of the basin. The Guide Basins probably mostly correspond to those of Herjia Group in the Xunhua Basin is composed mostly of and Ganjia Conglomerate Formations in the upper Guide stratified conglomerate with flat and stable basal scour Group (Basin phase 2) in the Guide Basin. So the depos- surfaces. Gravels in the group are graded as 2―5 cm, its of the Guide Group in the Xunhua Basin were mainly 5―8 cm, 8―10 cm and even about 25 cm in diameter. controlled by the Lajishan thrust, but no deposit was controlled by the frontal thrust of the northern West Parts of them are poorly sorted and unrounded and are Qinling thrust belt. The Guide Group in the Tongren interpreted to be debris flow deposits, and parts of them Basin overlain on the thrust belt belongs to the wedge- are stratified with roughly parallel beddings and are in- top deposits, and was sourced from the south and the terpreted to be gravel braided channel deposits. Pa- alluvial fans were dispersed northward. leocurrent data obtained from gravel imbrication and a few of cross beddings indicate that runoff and rivers 3.2 Analysis of fragment composition of sediments flowed toward the south, south-south-west and south- The gravel and lithic composition of sedimentary rocks west. So the Guide Group in the northern Xunhua Basin supplies important evidence for revealing provenance of formed three alluvial fans and their frontal braided sediments and uplift and unroofing process of prove- channel plains, and was sourced from the Laji Mountain nance[27]. As the Xining and Guide Groups consist of to the north. The alluvial fans were also developed at the conglomerate and sandstone, we apply different methods northern and eastern sides of the Laji Mountain, sourced to study fragment composition of sedimentary rocks.

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Thin sections were made for sandstone (mainly medium large lake existed except for the Guide Basin. As the and coarse-grained sandstone) and about 500 ― 550 point-source drainage dispersal alluvial fan-braided framework grains were counted per slide and percent- channel plain systems were developed in the Guide ages of different fragments were calculated. In areas Group, their provenance data much easily represent up- where gravels are abundant, we collected gravel clast lift and unroofing process in sediment source areas. data in the field. In each case nearly every grain in an Systematic analysis of lithic or gravel composition in area of 2 m2 was identified, typically more than 100 different segments of the Guide Group in the Guide Ba- clasts. Here we analyze distribution of fragment compo- sin represents that the composition of the Zharang, sition in the vertical sections and planes in the Xining Xiadongshan and Herjia Formations is composed of (Basin Phase 1) and Guide (Basin Phase 2) Groups, re- sandstone, meta-sandstone, slate, limestone, granite, spectively. As the sources of the basins in the Xun- chert, etc. and Ganjia Conglomerate and Gonghe For- hua-Guide area were mainly from the northern West mations changed to schist, phyllite, quartzite, limestone [19] Qinling and the Lajishan thrust belts that have clearly and gneiss, etc. (Figure 3). The source areas of the different rock compositions, the accounting analysis of former stratigraphy were from the Mesozoic and Paleo- lithic and gravel composition is an important symbol to zoic in the Riyue Mountain, and those of the latter from judge the provenances of sediments and uplift of prove- the Archean-Lower Proterozoic metamorphic rocks were nances. distributed between the Laji Mountain and the West The Xining Group in the study area is mainly distrib- Qinling, which represent an uplift and unroofing process uted to the north of the northern West Qinling thrust belt. from surface to depth and unroofing age of the basement Lithic composition in the Kashida and Laxiong sections rocks was after Pliocene. Regional analysis (Figure 5) in the southern Xunhua Basin has no clear change in the also shows the two kinds of provenances which were whole sections, and is composed of sandstone, limestone, eroded from the Riyue Mountain and Laji Mountain to granite and chert, and less meta-quartzite sandstone, the north. The bowlders in the Guide Group conglomer- slate, phyllite, volcanic rocks and mudstone (Figure 2), ate in the Tongren Basin are composed of fine-grained which were sourced from the Triassic and Carbonifer- sandstone, mudstone, meta-sandstone, limestone, granite ous-Permian developed in the northern West Qinling and chert, besides some reworked red sandstone and thrust belt to the south. The lithic or gravel composition volcanic rocks (Figure 5). The former were sourced of the Xining Group in different areas of the southern, from the Mesozoic and Paleozoic stratigraphy, and the middle and northern Xunhua Basin is also composed of letter probably from the underlied Xining Group or the sandstone, very fine sandstone, mudstone, meta-sand- Lower Cretaceous sandstone and the volcanic rocks of stone, limestone, granite, chert, mudstone and a few Upper Triassic Huari and Rinaore Formations in the volcanic rocks. Gravels in the basal conglomerate of the West Qinling. The Guide Group in the northern Xunhua Xining Group remaining on the western Laji Mountain Basin is linked with the Laji Mountain thrust belt. The are composed of limestone, sandstone, mudstone and composition of lithic fragments and gravels is clearly meta-sandstone, and a few quartzite, marble and vein changed. A lot of basic and intermediate volcanic grav- quartz (Figure 4). Analysis of lithic or gravel composi- els appear, and schist, quartzite and gneiss gravels are tion represents that the lithic or gravel composition of increased, but some of chert, granite (including shallow the Xining Group in the Xunhua Basin and above the intrusive), dolomite, limestone, sandstone and mudstone Laji Mountain is similar to the stratigraphic lithology in remain in the Guide Group conglomerate (Figure 5). The the northern West Qinling thrust belt, and the prove- lithology of gravels is consistent with stratigraphic rocks nance of the Xining Group was the thrust belt to the in the Lajishan thrust belt and its adjacent regions. The south. But there is no lithic fragment and gravel in the gravels of basic and intermediate volcanic rocks were northern Xunhua Basin which came from the stratigra- erosed from the Cambrian or Ordovician stratigraphy, phy in the Laji Mountain, so the Laji Mountain did not and the schist and gneiss gravels from the Archean- emerge to the surface at the syndepositional stage of the Lower Proterozoic basement, and the dolomite and Xining Group. limestone probably from the middle Proterozoic in the The depositional framework of the Guide Group is Lajishan thrust belt and its adjacent regions. The frag- quite different from that of the Xining Group, and no ment composition of Guide Group in the northern and

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Figure 5 Basin distribution, paleocurrent and lithic or gravel composition of Guide Group in Xunhua-Guide area. Distribution of Xining and Guide Groups is shown in the figure, and other pre-Cenozoic stratigraphy is shown as white color; piegraphs in the figure show lithic or gravel composition and percentages in different areas; Rose graphs show paleocurrent in different area. No. shows serial numbers of lithic or gravel accounting; n shows numbers of paleocurrent measurement. 1, Sandstone; 2, fine sandstone and mudstone; 3, mudstone; 4, reworked sandstone; 5, dolomite or limestone; 6, chert; 7, granite; 8, volcanic rock; 9, meta-quartzite sandstone; 10, quartzite; 11, schist and gneiss; 12, feldspar; 13, quartzite; 14, paleocurrent. The other explana- tions are shown in Figure 1. northeastern sides of the Laiji Mountain has the same Mountain and the Qaidam Basin, and a SE region that characters as the above. Owing to absent exact age con- extends from Qinghai Lake eastward to the Liupan trol over the Guide Group, the deposits along the mar- Mountain. The NW region is characterized by WNW- gins of the Laji Mountain probably correspond to the trending folds and thrust faults, separated by parallel Herjia and Ganjia Conglomerate Formations in the up- basins, which appear to transfer left-lateral motion on per Guide Group according to lithologic correlation. So the Altyn Tagh fault into NE-directed shortening. Sig- the uplift and unroofing age of the Laji Mountain is moidal strike-slip faults and thrust faults that bound from the Late Miocene to Pliocene, but the frontal thrust rhomb-shaped late Miocene-Quaternary basins charac- of the West Qinling thrust belt probably stopped activity terize the SE region. Pattern of left-lateral strike-slip during the stage of the Guide Group so that the Guide along the Haiyuan fault and shortening along the N-S Group in the Guide Basin dispersed southward across trending folds and thrust faults in the Liupan Mountain [28,29] the northern West Qinling thrust fault and in the Tongren suggests eastward extrusion . The topography of the Basin dispersed northward over the top of the West northeastern margin of the Tibetan Plateau is marked by Qinling thrust belt. elevations between ~2500 and 4000 m, which is much lower than the typical ~4000 to 5000 m of the central 4 Discussion on basin and mountain and southern Tibetan Plateau. When and how this part of the Tibetan Plateau grew outward and upward has re- evolution and plateau growth mechanism cently received increasing attention[1―3,7,8,17,19,28―35] due The northeastern young and active Tibetan Plateau is a to its relevance for Tibetan uplift models. Based largely typical area to study plateau growth. The northeastern on neotectonic, stratigraphic, and geomorphological in- Tibetan Plateau is divided into two regions, a NW region formation, Tapponnier et al.[3] concluded that the Tibetan that includes Altyn Tagh fault, the western Qilian Plateau grew northward in Cenozoic, which started with

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Eocene uplift of the southern plateau, followed by the focused. Evolution of basin and mountain and growing central plateau in the Qligocene-Miocene and the north- mechanism of the distal plateau at the different stage are eastern part in the most recently (Pliocene-Pleistocene). introduced below. Within the northeastern plateau, deformation and uplift (1) The stage of Oligocene unidirectional thrust uplift was driven by northeast-directed left-lateral slip along and large-scale foreland basin filling. The structure, the Altyn Tagh fault, progressing from southwest to nor- deposition and provenance analysis in the Xunhua- theast and ending with today’s growth in the Liupan Guide area represents that the northern West Qinling Mountain. Much of the convergence has been absorbed thrust belt bordered the south of the sedimentary basin by shortening along major WNW sinistral and NNW de- of the Xining Group, named a foreland basin, in which xtral transpressional faults[1―3,7,8,26,30,31]. To deeply study the sediments were mainly sourced from the thrust belt. evolution of Cenozoic basin and mountain system in the The local Xining Group deposits in the Guide and Ton- Xunhua-Guide area is very important for thorough re- gren Basins were probably filled in piggyback basins on vealing the growing process of the Tibetan Plateau, es- the thrust belt, which were connected with the northern pecially the northeastern plateau. Systematically sum- foreland basin. The whole foreland basin was linked [17] marizing the structural framework, basin filling se- with the Linxia Basin , and extended to the Qinghai quence and provenance characteristics, we divided basin Lake across the northern Riyue Mountain and the south- and mountain evolution into 4 stages (Figure 6), in ern side of the northern Qilian Mountain, which consti- which the former 2 stages are the main ones this paper tuted a large-scale, eastward open, foreland basin across

Figure 6 Evolution model of Cenozoic in the Xunhua-Guide area. Different grades of grey filled in the figure represent different ages of basin stratigra- phy; horizontal and vertical lines represent the West Qinling and Lajishan thrust belts, respectively; full curving arrows represent transportation directions of erosed sediments; upward vertical arrows represent crust uplift; circle with a central point represents the Yellow River.

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the Liupan Mountain, named Longzhong Basin. The to thrust of this stage[19]. So northward growth of the paleocurrent data show that the river systems in the Tibetan Plateau was mainly characterized by the north- study area mainly flowed northward and eastward, ward thrust expanding from the northern West Qinling transverse to and parallel to the thrust belt, respectively. thrust belt to the Lajishan thrust belt and even to the The lithic composition of the sediments represents that northern Qilian and Liupan Mountain at the Miocene the Laji Mountain was not exhumed to base level of and Pliocene. The former basin stratigraphy was de- deposition at the syndepositional stage. So the Tibetan formed and the newly small-scale broken basins beside Plateau expanded northward to the study area at the the thrust belt were filled up during the thrust expanding Oligocene (29―21.4 Ma)[17,19,34―39] by way of unidirec- stage as an example of the Laji Mountain. The growth tional fold and thrust thickening uplift and its frontal mechanism of the thrust belts is similar to the process of foreland basin filling. Laramide basement-involved thrust and broken foreland (2) The stage of Miocene to Pliocene (20.8―2.6 Ma) basin development in Rocky Mountains in western [40―42] two-sided thrust uplift and broken foreland basin filling. USA , which drove further uplifting of plateau and The basin framework was clearly changed during the thickening of basin depositional stratigraphy and was stage of the Guide Group (Basin phase 2) (20.8―2.6 characterized by a backward thrust, but predominantly northward thrust. The backward thrust was probably Ma) in the study area, and was characterized by the for- related with southward intracontinental subduction and mer large-scale basin broken into many small basins, the barrier of the North China Block during Late Mesozoic northern Xunhua Basin, Xining Basin, Guide Basin and and Cenozoic. Tongren Basin, in which alluvial fan-braided channel (3) The stage of Pliocene-Early Pleistocene (2.6―1.7 plain systems were developed except for the Guide Ba- sin. Provenance analysis shows that the Lajishan thrust Ma) regional erosion and planation and intermontane backward and uplifted, which partitioned the former basin aggradational filling. The geological process in large-scale basin of the Xining Group stage and con- Pliocene and Early Pleistocene in the study area was characterized by planation of former-formed mountains trolled the deposits of gravel fans along the two sides of and aggradational filling of intermontane basins (Basin the Laji Mountain. As the thrust front migrated north- phase 3). The Lower Pleistocene river or debris flow ward, the northern West Qinling belt stopped thrusting, deposits in the study area, but Upper Pliocene Gonghe and the Tongren Basin, controlled by southward uplift, Formation lacustrine deposits in the Guide Group, un- acted as an isolated, piggyback basin. Fang et al.[19] in- conformably overlay the Xining, Guide Groups, etc. The dicated the deposition of Guide Group in the Guide Ba- depositional stratigraphy was not controlled by the pre- sin was controlled by 6 southward-vergence thrust faults, sent river, especially the Yellow River, and was mainly mainly 3 faults to the north, developed in the northern distributed upon the basin strata of the former stages or Riyue Mountain and Laji Mountain (see Figure 3 of the front of mountains (Figure 1). This stage was not Fang et al.[19]), and had no relationship with the northern only an important stage of erosion and planation, but West Qinling thrust belt, through the study of paleo- also a stage of lake atrophy or prophase of early forma- geomagnetism, sedimentology and thrust structure. tion of the Yellow River. Thrust uplift at the northern (Laji Mountain) and eastern (4) The stage of Middle Pleistocene-nowadays verti- (Lijiaxia) sides of the Guide Basin jammed the eastward cal uplift and erosion and incision. The study area un- and northward flow of rivers and formed a closed lake derwent a change from lateral thrust thickening and ba- basin, which was fast filled up with fluvial plain systems. sin aggradation of the former stage to a new regional Regional analysis shows that the Longzhong Basin, lo- vertical uplift and fluvial incision since the Middle cated between the southern North Qilian and the north- Pleistocene, and developed deeply incision of the Yellow ern West Qinling, was partitioned into several broken River and multilevel river terraces or planation[43]. foreland basins by Corridor Nanshan thrust, Haiyuan thrust and Qingtongxia-Guyuan thrust at the Miocene 5 Conclusions and Pliocene. The Pliocene bowlder conglomerate in the northern Tibetan Plateau was the depositional response (1) The Xunhua, Guide and Tongren Basins, linked

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with the Laji Mountain and the northern West Qinling Qinling thrust belt to the south but the Laji Mountain thrust belts, respectively, constitute a unified basin and was below the base level of deposition. The Laji Moun- mountain system. The Laji Mountain formed a two- tain thrust and uplifted, and the former formed basin was sided thrust belt. The eastern part of West Qinling thrust partitioned at the stage of the Guide Group (Basin phase belt mainly thrust northwards, and its western part was 2). The point-source drainage dispersal alluvial fan- converged with the Laji Mountain, which constructed a braided channel plain depositional systems were devel- backward thrust belt. oped over the northern West Qinling thrust belt and be- (2) The basin stratigraphy mainly consists of Oligo- side the Laji Mountain. cene Xining Group, uppermost Oligocene-Pliocene (4) Basin and mountain evolution of the study area Guide Group and Lower Pleistocene that are separated has an important indication to the growth of the distal by unconformities, and is divided into 3 Basin phases, Tibetan Plateau. Results show that the Tibetan Plateau that is, Basin phase 1 as the Xining Group, Basin phase grew northward during the Cenozoic and expanded to 2 as the Zharang, Xiadongshan, Herjia and Ganjia Con- the northern West Qinling at the Oligocene (29―21.4 glomerate Formations, and Basin phase 3 as the Gonghe Ma) by way of unidirectional fold-thrust thickening and Formation and the Lower Pleistocene. The lower two uplifting and frontal foreland basin filling, and to the basin phases are composed of lower lacustrine and upper Laji Mountain, northern Qilian and Liupan Mountain at alluvial fan-braided channel plain deposits that form the Miocene-Pliocene by way of two-sided basement coarsening-upward progradation sequences, and Basin involved thrut thickening and uplifting and broken fore- phase 3 is composed of lower lacustrine and upper land basin filling. The distal Plateau mainly behaved as gravel channel or debris flow deposits. regional erosion and planation and intermontane basin (3) Analyses of basin deposition, paleocurrent and aggradation during the Pliocene and Early Pleistocene. fragment composition represent that a large-scale lacus- The authors would like to thank Drs. Sun Yangui, Dong Yunpeng, Cheng trine basin was developed at the stage of the Xining Shunyou, Zhang Huiping, Margaret E. McMillan for their helpful works in Group (Basin phase 1), and the source area was the West the field.

1 Meyer B, Tapponnier P, Bourjot L, et al. Crustal thickening in mantle in northeastern Tibet. Earth Planet Sci Lett, 1990, 97: Gansu-Qinghai, lithospheric mantle subduction, and oblique, strike- 382―403 [DOI] slip controlled growth of the Tibet Plateau. Geophys J Int, 1998, 135: 9 Wang E Q, Zhang Q, Burchfiel C B. The Lajishan fault belt in Qinghai 1―47 [DOI] Province: A multi-staged uplifting structural window. Sci Geol Sin (in 2 Métivier F, Gaudemer Y, Tapponnier P, et al. Northeastern growth of Chinese), 2000, 35(4): 493―500 the Tibetan Plateau deduced from balanced reconstruction of two 10 Zheng D W, Zhang P Z, Wan J L, et al. Late Cenozoic deformation depositional areas: The Qaidam and Hexi Corridor basins, China. subsequence in northeastern margin of Tibet―Detrital AFT records Tectonics, 1998, 17(6): 823―842 [DOI] from Linxia Basin. Sci China Ser D-Earth Sci, 2003, 46(Supp.): 3 Tapponnier P, Xu Z, Roger F, et al. Oblique stepwise rise and growth 266―275 of the Tibet Plateau. Science, 2001, 294: 1671―1677 [DOI] 11 Dupont-Nivet G, Horton B K, Butler R F, et al. Paleogene clockwise 4 Gillespie J M, Heller P. Beginning of foreland subsidence in the Co- tectonic rotation of the Xining-Lanshou region, northeastern Tibetan Pl- lumbian-Sevier belts, Southern Canada and northwest Montana. Ge- ateau. J Geophys Res, 2004, 109(B04401): doi:10.1029/2003JP002620 ology, 1995, 23(8): 723―726 [DOI] 12 Yu Q W, Li C A, et al. Cenozoic Uplift-Deposition-Climate Evolution 5 DeCelles P G. Late Jurassic to Eocene evolution of the Cordilleran and Their Coupling Relationship (in Chinese). Wuhan: China Uni- thrust belt and foreland basin system, western U.S.A. Am J Sci, 2004, versity of Geosciences Press, 2001. 1―123 304: 105―168 [DOI] 13 Shi Y F, Li J J, Li B Y, et al. Uplift and environment evolution of 6 DeCelles P G, Gehrels G E, Quade J, et al. Neogene foreland basin plateau. In: Sun H, Zheng D, eds. Formation, Evolution and Devel- deposits, erosional unroofing, and the kinematic history of the Hi- opment of Tibetan Plateau. Guangzhou: Guangdong Science & malayan fold-thrust belt, western Nepal. Bull Am Ass Petrol Geol, Technology Press, 1998. 73―138 1998, 110: 2―21 14 Fothergill P A. Late Tertiary and Quaternary intermontane basin 7 Burchfiel B C, Deng Q, Molnar P, et al. Intracrustal detachment evolution in North-East Tibet: The Guide Basin. PhD thesis thesis. within zones of continental deformation. Geology, 1989, 17(8): University of London, 1998. 1―228 748―752 [DOI] 15 Song C H, Fang X M, Li J J, et al. Late Cenozoic depositional evolu- 8 Tapponnier P, Meyer B, Avouac J P, et al. Active thrusting and tion in Guide Basin, Qinghai Province and uplift of the northern Ti- folding in the Qilian Shan, and decoupling between upper crust and betan Plateau. Geol Rev (in Chinese), 2003, 49(4): 337―346

290 LIU ShaoFeng et al. Sci China Ser D-Earth Sci | Nov. 2007 | vol. 50 | Supp.II | 277-291

16 Horton B K, Dupont-Nivet G, Zhou J, et al. Mesozoic-Cenozoic 1989, 99: 123―153 [DOI] evolution of the Xining-Minhe and Dangchang basins, northeastern 31 Gaudemer Y, Tapponnier P, Meyer B, et al. Partitioning of crustal slip Tibetan Plateau: Magnetostratigraphic and biostratigraphic results. J between linked, active faults in the eastern Qilian Shan, and evidence Geophy Res, 2004, 109(B04402): doi:10.1029/2003JB002913 for a major seismic gap, the ‘Tianzhu gap’, on the western Haiyuan 17 Fang X, Garzione C, Van der Voo R, et al. Initial flexural subsidence fault, Gansu (China). Geophys J Int, 1995, 120: 599―645 [DOI] by 29 Ma on the NE edge of Tibet: Magnetostratigraphy of the Linxia 32 Chen Z, Burchfiel B. C, Liu Y, et al. Global Positioning System Basin, China. Earth Planet Sci Lett, 2003, 210: 545―560 measurements from eastern Tibet and their implications for In- 18 Parés J M, Van der Voo R, Downs W R, et al. Northeastward growth dia/Eurasia intercontinental deformation. J Geophys Res, 2000, 105: and uplift of the Tibetan Plateau: Magnetostratigraphic insights from 16,215―16,227 [DOI] the Guide Basin. J Geophys Res, 2003, 108(B1), 2017, 33 Ritts B, Biffi U. Magnitude of post (in Chinese)Middle Jurassic (Ba- doi:10.1029/2001JB001349 jocian) displacement on the central Altyn Tagh fault system. Geol Soc 19 Fang X, Yan M, Van der Voo R, et al. Late Cenozoic deformation and Am Bull, 2000, 112: 61―74 [DOI] uplift of the NE Tibetan Plateau: evidence from high-resolution 34 Yin A, Rumelhart P E, Butler R, et al. Tectonic history of the Altyn magnetostratigraphy of the Guide Basin, Qinghai Province, China. Tagh fault system in northern Tibet inferred from Cenozoic sedi- Geol Soc Am Bull, 2005, 117(9/10): 1208―1225 [DOI] mentation. Geol Soc Am Bull, 2002, 114: 1257―1295 [DOI] 20 Qinghai Provincial Bureau of Geology and Minerals. Regional Ge- 35 Wang X, Wang B, Qiu Z. Danghe area (western Gansu, China) bio- ology of Qinghai Province (in Chinese). Beijing: Geological Pub- stratigraphy and implications for depositional history and tectonics of lishing House, 1991. 1―217 northern Tibetan Plateau. Earth Plane Sci Lett, 2003, 208: 253―269 21 Sun C R, Chen G L, Li Z R, et al. Stratigraphy (Lithostratic) of [DOI] Qinghai Province (in Chinese). Wuhan: China University of Geo- 36 Gilder S, Chen Y, Sen S. Oligo-Miocene magnetostratigraphy and sciences Press, 1997. 1―340 rock magnetism of the Xishuigou section, Subei (Gansu Province, 22 Fang X M, Li J J, Zhu J J, et al. Absolute age determination and di- western China) and implications for shallow inclinations in central vision of the Cenozoic stratigraphy in the Linxia Basin, Gansu Prov- Asia. J Geophy Res, 2001, 106: 30,505―30,521 [DOI] ince, China. Chin Sci Bull (in Chinese), 1997, 42(14): 1457―1471 37 George A D, Marshallsea S J, Wyrwoll K, et al. Miocene cooling in 23 Li J J, Fang X M, Van der Voo R, et al. Late Cenozoic magneto- the northern Qilian Shan, northeastern margin of the Tibetan Plateau, stratigraphy (11–0 Ma) of the Dongshanding and Wangjiashan sec- revealed by apatite fission-track and vitrinite-reflectance analysis. tions in Longzhong Basin, western China. Geologie en Mijnbouw, Geology, 2001, 9: 939―942 [DOI] 1997, 76: 121―134 38 Jolivet M, Brunel M, Seward D, et al. Mesozoic and Cenozoic tec- 24 Song C H, Fang X M, Gao J P, et al. Tectonic uplift and sedimentary tonics of the northern edge of the Tibetan Plateau: Fission track con- evolution of the Guide Basin in the northeast margin of Tibetan Pla- straints. Tectonophysics, 2001, 343: 111―134 [DOI] teau in Cenozoic era. Acta Sediment Sin (in Chinese), 2001, 19(4): 39 Sobel E, Arnaud N, Jolivet M, et al. Jurassic to Cenozoic exhumation 493―500 history of the Altyn Tagh range, northwest China, constrained by 25 Liu S, Yang S. Upper Triassic-Jurassic sequence stratigraphy and its 40Ar/39Ar and apatite fission track thermochronology. In Hendrix M S, structural controls in the western Ordos Basin, China. Basin Res, 2000, Davis G A, eds. Paleozoic and Mesozoic Tectonic Evolution of Cen- 12: 1―18 [DOI] tral Asia: From Continental Assembly to Intracontinental Deforma- 26 Liu S, Zhang G. Fundamental ideas, contents and methods in study of tion. Boulder, Colorado: Geological Society of America Memoir 194, basin and mountain relationships. Earth Sci Front (in Chinese), 2005, 2001. 247―267 12(3): 101―111 40 Snoke A. Geological history of Wyoming within the tectonic frame- 27 Hendrix M S, Graham S A, Amory J Y, et al. Noyon Uul (King work of the North American Cordillera. Wyoming State Geological Mountain) Syncline, southern Mongolia: Lower Mesozoic sedimen- Survey Public Information Circular 38, 1997. 1―52 tary record of the tectonic amalgamation of central Asia. Geol Soc Am 41 Tikoff B, Maxson J. Lithospheric buckling of the Laramide foreland Bull, 1996, 108: 1256―1274 [DOI] during Late Cretaceous and Paleogene, western United States. Rocky 28 Burchfiel B. C, Zhang P, Wang Y, et al. Geology of the Haiyuan Fault Mountain Geology, 2001, 36(1): 13―35 [DOI] zone, Ningxia-Hui autonomous region, China, and its relation to the 42 Dickinson W R, Klute M A, Hayes M J, et al. Paleogeographic and evolution of the northeastern margin of the Tibetan Plateau. Tectonics, paleotectonic setting of Laramide sedimentary basins in central Rocky 1991, 10(6): 1091―1110 Mountain region. Geol Soc Am Bull, 1988, 100: 1023―1039 [DOI] 29 Zhang P, Burchfiel B C, Molnar P, et al. Amount and style of late 43 Li J, Fang X, Van der Voo R, et al. Magnetostratigraphic dating of Cenozoic deformation in the Liupan Shan area, Ningxia Hui river terraces: Rapid and intermittent incision by the Yellow River of Autonomous Region, China. Tectonics, 1991, 10(6): 1111―1129 the northeastern margin of the Tibetan Plateau during the Quaternary. 30 Molnar P, Lyon-Caen H. Fault plane solutions of earthquakes and ac- J Geophy Res, 1997, 102: 10,121―10,132 [DOI] tive tectonics of the Tibetan Plateau and its margins. Geophys J Int,

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