4期陈杰等 : 中国西南天山西域砾岩的磁性地层年代与地质意义 577 图 1 西南天山喀什 - 阿图什褶皱带构造位置及剖面位置 ( a) GTOPO30 DEM 地形示研究区位置 ( b) Landsat TM 卫星影像 (喀什 - 阿图什褶皱带包括明尧勒喀什阿图什木吐勒 - 八盘水磨等背

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1 QUATERNARY SC IENCES Vol. 27, No. 4 July, (2007) R. V. Heermance D. W. Burbank K. M. Scharer (, ; Department of Earth Science, University of California, Santa Barbara, CA 93106, USA; Department of Geology, Appalachian State University, Boone, NC 28608, USA), - 5 6,,,,( )( ) 1515Ma [ 1 ], 816Ma [ 1 ],119Ma, Ma( KBT),, 1515Ma 410Ma mm /a, 410Ma > 10mm /a, 210Ma P539. 3, P546 A 1, ( ), == ( Ma), ( [ 2 5 ] [ 6 10 ] ), : 1) [ 3 5, 11 ] 2), [ 9, 10, 12, 13 ] 3) [ ] 4) [ 18, ], [ 22 ], [ 2, 3, 6 10, ],, Ma,4Ma,,, ( time lag) [ 20 ], [ 28 30, 34 ],,, - ( 815km, 5Ma 2 3 ), : 41 E2mail: chenjie@eq2igl. ac. cn 3 (: ) (: EAR ) ,

4期陈杰等 : 中国西南天山西域砾岩的磁性地层年代与地质意义 577 图 1 西南天山喀什 - 阿图什褶皱带构造位置及剖面位置 ( a) GTOPO30 DEM 地形示研究区位置 ( b) Landsat TM 卫星影像 (喀什 - 阿图什褶皱带包括明尧勒喀什阿图什木吐勒 - 八盘水磨等背斜 ; 图中浅色的新近纪乌恰群阿图什组泥岩粉砂及砂岩互层组成背斜的核部, 背斜周缘

2 4期陈杰等 : 中国西南天山西域砾岩的磁性地层年代与地质意义 577 图 1 西南天山喀什 - 阿图什褶皱带构造位置及剖面位置 ( a) GTOPO30 DEM 地形示研究区位置 ( b) Landsat TM 卫星影像 (喀什 - 阿图什褶皱带包括明尧勒喀什阿图什木吐勒 - 八盘水磨等背斜 ; 图中浅色的新近纪乌恰群阿图什组泥岩粉砂及砂岩互层组成背斜的核部, 背斜周缘的不连续黑灰色条带为胶结致密坚硬的西域砾岩 ) Fig. 1 Landsat TM im age of the southwestern Tian Shan show ing location of sections 2 阿图什组西域砾岩的地层特征地层剖面 (见图 1b和图 2 )进行了的大比例尺实测, 开展了详细的 2 维 3 维空间沉积学研究, 喀什 - 阿图什褶皱带位于塔里木与南天山的过渡带 (图 1a ),是喀什前陆盆地逆断裂 - 褶皱带的最获得古水流向测量数据 80 个,并对其中 3 个剖面的 7 个层位开展了砾石碎屑成分统计 (见图 2 ) 其前缘和最新构造变形带, 吸收了吉尔吉斯天山以南现今 GPS 观测地形变 ( 7 10mm / a ) 的大部中,明尧勒背斜南翼的明尧勒剖面 (M YL ) 实测地层厚 1147m,喀什背斜南翼的喀什西剖面 ( KSW ) 实测分 [ 30, ] 地表由数排北东东向左阶雁列展布的褶皱带组成,长约 150km,宽约 30km (图 1b ) 包括地层厚 1249m, 喀什城剖面 ( KST ) 实测地层厚 939m,阿图什背斜南翼的博古孜河剖面 ( BGZ) 实测明尧勒喀什阿图什木吐勒 - 八盘水磨等背斜这些背斜地表主要由上新统阿图什组粉砂砂岩和地层厚 3440m, 干旱沟剖面 ( GHG ) 实测地层厚 815m,中阿图什剖面 (AM )实测地层厚 973m 更新统西域砾岩组成, 其中阿图什背斜西段和明尧阿图什组在博古孜河剖面出露最全 (见图 2 ), 勒背斜核部出露中新统乌恰群砂泥岩我们在喀什远源盆地选择出露较好的分布在总厚度约为 2830m,以苍棕色为主,是一套巨厚的黄褐土黄色泥岩砂质泥岩和黄灰黄绿色泥质砂岩褶皱带不同构造部位有代表性的博古孜河干旱沟粉砂岩砂岩砂砾岩之互层, 上部出现块状砂岩和中阿图什明尧勒喀什西喀什城等 6 条晚新生代砾岩夹层,属河流洪泛沉积总体具下细上粗的反

3 第 578 四纪研究 2007 年图 2 喀什 - 阿图什褶皱带 6 个典型剖面地层柱状图 ( a) 博古孜河干旱沟和中阿图什剖面 ( b) 明尧勒剖面 ( c) 喀什西喀什城剖面 ( d) 砾石成分统计 (古流向资料主要来自对地层交错层理波痕古河道轴向叠瓦状排列砾石的测量 ) Fig. 2 Stratigraphy of six sections ( a, b, c ) and the clast composition data ( d) 韵律,下部以泛滥平原相砂质泥岩粉砂岩为主, 常见水平层理各种类型小波痕层理及生物潜穴等,具交错层理的河道砂质沉积与泛滥平原相泥质沉积交砂泥岩与砾岩之比大于 4 1, 属于典型的砂质辨状河流相沉积西域砾岩与下伏的阿图什组呈整合连续沉积, 互出现,向上砂岩渐多,由下而上,颜色由深变浅,粒径由细变粗,砂岩中常含粗砂或细砾石条,两者常互成透镜体或相变 ; 上部出现砾岩夹层, 愈向上砾岩夹层增多增厚 ; 砾石粒径变粗,但仍以细粒相为主, 底部为 1 5m 厚的砾岩层夹砂岩粉砂层, 向上在数十米至近百米的范围内,砾岩层迅速增多增厚,砂岩粉砂层等细粒层减少减薄,很快过渡为巨厚块状砾岩偶夹砂岩粉砂透镜体在博古孜河剖面出露

4 4 : 579 ( 2a), 1000m,,,,,,, 2 8cm,,,, -, [ 28 30, 33, 34 ],,, ;,,, 4 1,,,,,,,,, ;, 6,,,, [ 28 30, 33, 34, 36 ] 3, , [ 15, 37, 38 ], -, ( 1b),- [ 30, 34 ] (BGZ), 116Ma, 10km ( GHG),, [ 30 ], 311, 5, 105 ( ) 315, , ,314 ( )950, ,, 64 [ 30 ] [ 30, 33, 34 ] , 2G ( [ 34 ] ) [ 30, 34 ],,, 3 ( 5mT 10mT), , (, 2005, ) ( ) 1

5 , 2 3, A /m, Jones [ 39 ] N. R. Nowaczyk (, 2004), Kirschvink [ 40 ] 4 ( 5 8 ) ( 990 Candon iella a lbicans, Eucypris sp., D a rw inu la sp., ), (MAD ) 6, 10 McFadden McElhinny [ 41 ] 5 A [ 30 ], B [ 33 ] C [ 30, 34 ], 3 8 9,, [ 32, 34 ] McElhinny [ 42 ] McFadden Jones [ 43 ] 5 [ 30, 33, 34 ], 95% 99%,, 5, 312 (MAD 10 ) ( virtual geomagnetic pole, VGP), VGP, 5 ( 3) 5, Cande Kent [ 44 ], (BGZ) A11n C3n. 4n,( KST) T1n C1n ( 3) : 1) [ 45 ], 5 < < 20Ma 2) [ 45 ] ( Ilyocypris errabund is, Candona com presaform is, C. spp., Ilyocypris m anasensis) 3) 20Ma Cande Kent [ 44 ], 5Ma ( 3) 4 ) (MYL),,( KST) ( 1b[ 34 ] 2),, 5) 5, ( KSW ) ( KST)( [ 34 ] 2a ) (BGZ) ( GHG)([ 30 ] 2) 3 ( 4), mm /a, :,,, -,,/,4, (AH ) [ 1 ] ( 1b),, 2 [ 1 ] [ 10, 46 ]

4 : 581 3 (MYL) ( KSW ) ( KST) (BGZ) ( GHG) VGP [ 44 ] 1, 5 Cande Kent [ 44 ] C3n. 4n ( 5123Ma) Fig.

6 4 : (MYL) ( KSW ) ( KST) (BGZ) ( GHG) VGP [ 44 ] 1, 5 Cande Kent [ 44 ] C3n. 4n ( 5123Ma) Fig. 3 L ithologic and magnetostratigraphic results from M ingyaole, Kashi W est, Kashi Town, Boguzihe, and Ganhangou sections with VGP latitude p lotted against stratigraphic height and correlation to the GPTS of Cande and Kent [ 44 ], [ 9, 10 ], N2m [ 47 ], ( forebulge) 200km [ 48 ] 60km,- 100km, ( foredeep), Talling Burbank [ 49 ], : 1) ; 2)

7 Fig. 4 Age versus stratigraphic thickness p lot of five sections using data and correlations from Fig. 3, 10% 50% ; 3) 5% ; 4) ; 5) GPTS,5 ( 1) 4 411,,, 1 5m,,,,, 60% 70%, 50% ( 2d) ( 75%, 25% [ 1 ] ),,,, ( KBT),, 2500m, 2000m [ 1 ], 1000m, 4200m < 300m,,, ( 1b),,,, [ 36 ] KBT/km KBT/km /Ma 1 ( KBT) (AY) Table 1 Initiation of deformation and the Xiyu conglomerates, and the p re2 and post2deformation distances of the sections and the accumulation rates (AH) (BGZ) ( GHG) (MYL) ( KSW ) ( KST) [ 1 ] [ 1 ] /m Ma - 1 /Ma ( <4. 0Ma) ( <1. 2Ma) (> 4. 0Ma) ( <1. 07Ma) [ 1 ] 8. 6 [ 1 ] < /Ma [ 1, 50 ] [ 1 ] 4 [ 1 ]

8 4 : 583 ( KBT),,,,> 15cm, 1 2m,, (, [ 1 ] ) ( KBT),,,,, - [ 1 ], - ( ) 4 5km ( 1b),,,,, -,,, [ 30, 34 ] ( 1b),, ( 1b) 1000m,,500m, ( 1b 2) 2,,,,, (A lai) ( 1b),,,,,,,,, 412, [ 24 ] 3Ma, Charreau [ 32 ] Sun [ 31, 51 ] 418Ma 217Ma 3158Ma [ 25 ], 315Ma [ 27 ] 3Ma [ 52 ] 1 2, [ 2, 3, 6 10, 26 ],,,, 1, 119Ma 017Ma,, 1515Ma 816Ma [ 1 ],,,,,, TA9402 ( 1b H2H ) ( 13 21km) [ 1, 30, 34, 36 ],, 1515Ma 119Ma mm /a, 119Ma 10 11mm /a ( 1 5), 1515Ma,56 63km,, 116Ma

9 , ( 10 11mm /a) 2Ma Fig. 5 Plot of m igration rates of the deformation front and the gravel front over time 14mm /a 413 ( ) (, [ 9 ] ) [ 21 ] [ 4 ], [ 9, 10, 13 ], [ 18 ],,,, ; /, 4100Ma, 1120Ma 1107Ma ( 4 1), 112Ma1107Ma ( 1), [ 30, 34 ] 4Ma,, 15km, ; [ 1 ] 414, [ 50 ] [ 29, 30, 34, 36 ] [ 1 ] ( 1), ( ) ( ), [ 1, 30, 34, 36 ], ( KBT), 1b H2H ( TA9402), ( 1), 5 ( KBT) 1613Ma [ 1, 50 ], 1315Ma, mm /a [ 1 ], 4Ma mm /a 114Ma, > 10 mm /a 119Ma,, mm /a ( 5) 119Ma 10 11mm /a,

10 4 : 585 ( ) [ 4, 9, 10, 12 21, 38 ],, 1515Ma 410Ma mm /a, mm /a ( 5), 2Ma > 10mm /a, 4Ma, 4 2Ma [ 9, 10 ],,,,,, 4Ma, 114Ma 4Ma, 14km 119Ma( 1b 3), 2Ma( 5) [ 15, 20 ], Siwalik (35 45mm /a) [ 4 ] Sevier (20mm /a) [53 ], 5Ma, ( 017mm /a), 2Ma ( 10mm /a),-, 2Ma, 1515Ma,, Patricia Ruano J. L. Kirschvink N. R. Nowaczyk, ( References) 1 Heermance R V, Chen J, Burbank D W et al. Chronology and tectonic controls of Late Tertiary deposition in the southwestern Tian Shan foreland, NW China. B asin Research ( accep ted), ,,.. ( ), 1947, (21) : Huang T K, Young C C, W eng W B et al. Report on geological investigations of some oil fields in Sinkiang. Geological M em oris ( Series A), 1947, (21) : , :. ( ). :, Huang Jiqing, Chen B ingwei. On the formation of Pliocene2 Quaternarymolasses in the Tethys2H imalayan tectonic domain and its relation with the Indian plate motion. In: Book Newsroom in M inistry of Geology ed. Scientific Papers on Geology for International Exchange, No. 1. Structural Geology, Geomech Anics. Beijing: Geological Publishing House, Burbank D W, Beck R A, Raynolds R G H et al. Thrusting and gravel progradation in foreland basins: A test of post2thrusting gravel dispersal. Geology, 1988, 16 (12) : ,,.., 1979, (6) : L i Jijun, W en Shixuan, Zhang Q ingsong et al. A discussion on the period, amplitude and type of the uplift of the Q inghai2xizang Plateau. Scientia S inica, 1979, 22 (11) : Avouac J P, Tapponnier P, Bai M et al. Active thrusting and folding along the northern Tien Shan and Late Cenozoic rotation of the Tarim relative to Dzungaria and Kazakhstan. Journal of Geophysical R esearch, 1993, 98: ,,.. :, Deng Q idong, Feng Xianyue, Zhang Peizhen et al. Active Tectonics in Tian Shan. Beijing: Seismological Press, Burchfiel B C, B rown E T, Deng Q D et al. Crustal shortening on the margins of the Tianshan, Xinjiang, China. International Geology Review, 1999, 41 (8) : Molnar P. Late Cenozoic increase in accumulation rates of terrestrial sediment: How m ight climate change have affected erosion rates? Annual R eview of Earth and Planetary Sciences, 2004, 32: Zhang P Z, Molnar P, Downs W R. Increased sedimentation rates and grain sizes 2 4Myr ago due to the influence of climate change on erosion rates. N ature, 2001, 410: ,,.

11 (D ), 2004, 34 ( 2 ) : Fang Xiaom in, Zhao Zhijun, L i Jijun et al. Magnetostratigraphy of the Late Cenozoic Laojunm iao anticline in the northern Q ilian Mountains and its implications for the northern Tibetan Plateau up lift. Science in China ( Series D), 2005, 48 (7) : Molnar P T, England P. Late Cenozoic uplift of mountain ranges and global climate change: Chicken or egg? N ature, 1990, 346: Molnar P. Climate change, flooding in arid environments, and erosion rates. Geology, 2001, 29 (12) : Heller P L, Angevine C L, W inslow N S et al. Two2phase stratigraphic model of foreland2basin sequences. Geology, 1988, 16: Jordan T E, Flem ings P B, Beers J A. Dating thrust2fault activity by use of foreland2basin strata. In: Kleinspehn K L, Paola C eds. New Perspective in Basin Analysis. New York: Springer2Verlag, Flem ings P B, Jordan T E. Stratigraphic modeling of foreland basins: Interp reting thrust deformation and lithospheric rheology. Geology, 1990, 18: Burbank D W. 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12 4 : 587 ). :, Jia Chengzao, Zhang Shiben, W u Shaozu et al. Stratigraphy of the Tarim Basin and Adjacent A reas (Volume ). Beijing: Science Press, M tivier F, Gaudemer Y, Tapponnier P et al. Mass accumulation rates in A sia during the Cenozoic. Geophysical Journal Interna2 tional, 1999, 137: Burov E B, D iament M. The effective elastic thickness of continental lithosphere: W hat does it really mean? J ourua l of Geophysica l R esea rch, 1995, 100 (B5) : Beaumont C. Foreland Basins. Geophysical Journal of the Royal Astronom ical Society, 1981, 65: Talling P J, Burbank D W. A ssessment of uncertainties in magnetostratigraphic dating of sedimentary strata. In: A sissaoiu A, McNeil D F, Hurley N F eds. Applications of Paleomagnetism to Sedimentary Geology 49. SEPM Special Publication, Sobel E R, Chen J, Heermance R V. Late O ligocene EarlyM iocene initiation of shortening in the Southwestern Chinese Tian Shan: Imp lications for Neogene shortening rate variations. Earth and Planetary Science Letters, 2006, 47 (1 2) : Sun J, Xu Q, Huang B. Late Cenozoic magnetochronology and paleoenvironmental changes in the northern foreland basin of the Tian Shan Mountains. Journal of Geophysical Research, 2007, 112, B04107, doi: /2006JB Sun J, L iu T. The age of the Taklimakan Desert. Science, 2006, 312: Horton B K, Constenius K N, Decelles P G. Tectonic control on coarse2grained foreland2basin sequences: An examp le from the Cordilleran foreland basin, U tah. Geology, 2004, 32: M AGNETOCHRO NOLO GY AND ITS IM PL ICAT IO NS O F THE X IY U CO NGLOM ERATE IN THE SO UTHW ESTERN CH INESE T IAN SHAN FO RELAND Chen J ie R. V. Heermance D. W. Burbank K. M. Scharer W ang Changsheng ( S tate Key Laboratory of Earthquake D ynam ics, Institute of Geology, China Earthquake Adm inistration, B eijing ; D epartm ent of Earth Science, U niversity of California, Santa B arbara, CA USA; D epartm ent of Geology, A ppalachian S tate U niversity, B oone, NC USA ) Abstract M agnetostratigraphy of the Kashi foreland basin along the southern margin of the Tian Shan in western China defines the chronology of both sedimentation and the structural evolution of this collisional mountain belt. Five magnetostratigraphic sections rep resenting ca. 815km of distal basin strata p rovide a 22 and 32dim ensional record of continuous deposition since ca. 5M a. The distinctive Xiyu conglomerate makes up the uppermost strata in 4 of 5 magnetostratigraphic sections w ithin the foreland and form s a wedge that thins southward. Age of the basal Xiyu conglomerate varies from 1515Ma at the northernmost part of the foreland [ 1 ], to 816Ma in the central (medial) part of the foreland [ 1 ] , and to Ma, Ma, and Ma along the southern deformation front of the foreland basin. These data indicate that the Xiyu conglom erate is highly time2 transgressive and has p rograded southward immediately after the initial up lift of the Kashi B asin Thrust ( KBT). This finding contrasts w ith p revious studies which assumed that the Xiyu conglom erate is either Plio2Pleistocene in age or rep resents a chronostratigraphic unit. The southward gravel p rogradation occurred at an average rate of mm /a between 1515Ma and 119Ma, before accelerating to ca mm /a. Results indicate a stepped m igration of deformation into the Kashi foreland at least at 1613Ma [ 1 ], 1315Ma [ 1 ], 410M a, and 114M a. Progressive reconstruction of a seism ically controlled cross section through the foreland p roduces total shortening of 13 21km and m igration of the deformation front at mm /a between Ma, mm /a between Ma, and > 10mm /a since 410Ma. Since 5Ma, increased sediment accumulation ( ca. 017mm / a) and gravel p rogradation rates ( ca. 10mm / a) appear linked to higher deformation rates on the Keketamu, A tushi, and Kashi anticlines and increased subsidence due to loading from both the Tian Shan and Pam ir ranges. The accelerated erosion was possibly caused by climate change. W hereas the rap id ( ca. 10mm /a) p rogradation of the Xiyu conglomerate after 2Ma may be p romoted by global climate change, its overall p rogradation since 1515M a is due to the p rogressive encroachm ent of deform ation into the foreland. The tight temporal and spatial linkage between the m igration of both the gravel front and the deformation front suggest a causal linkage between southward gravel p rogradation and pulsed m igration of deformation. Tectonics is the fundamental control on conglomerate distribution within the Kashi foreland, although climate likely p lays a role at shorter time scales. Key words Tian Shan, foreland basin, Xiyu conglomerate, magnetostratigraphy, Tectonics, climate gravel p rogradation,

3 : 3 285, ( 1) 2 1 Fig11 CD cover of the Electronic Version of the National Physical A tlas of China 211 ( 2), ;, ;, ; 2 Fig12 System structure of th

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