Northeastward growth of the Tibet plateau deduced from balanced reconstruction of two depositional areas: The Qaidam and Hexi Corridor basins, China

We address the problem of late Cenozoic uplift, erosion, and growth of northeastern Tibet by reconstructing, from isopach maps and drill holes, the volumes and masses of sediments deposited in the Qaidam and Hexi Corridor basins since ∼35 Myr ago. The mass budget is based on simple geometrical assumptions such as regional similarity of the thickness ratios between strata of different ages. In the Qaidam, where our record extends back to the Oligocene, the budget shows a huge rise of the accumulation rates after the beginning of the Pliocene (5.3 Ma). The early Pliocene seems to be the period of maximum deposition with accumulation rates in excess of 1 mm yr−1 (∼ 2.7 kg m−2 yr−1) of compacted rocks throughout the basin. There also seems to be a southeastward shift of the largest depocenters between the upper Pliocene (3.4–1.6 Ma) and the Quaternary. In the Hexi Corridor, sedimentation is confined to small foreland flexural depressions associated with the frontal thrusts of the Qilian Shan and occurs at an average rate one order of magnitude smaller than in the Qaidam basin. The accumulation rate is maximum in the Quaternary. The sedimentation history appears to support a plateau‐building mechanism resulting from the combination of two geologicallly common processes: crustal‐scale thrusting and sedimentary basin infilling. The time needed to completely fill the Qaidam basin and make its catchment a plateau closely resembling that of the highest part of Tibet (Qangtang) is of the order of 9 Myr. The mechanism now at work north of the Kunlun, which involves rapid infilling of broad, flat areas separated by relatively narrow mountain ranges, has thus probably been important in producing the high, smooth topography that characterizes much of central Tibet.

[1]  J. Curray.  Sediment volume and mass beneath the Bay of Bengal , 1994 .

[2]  F. Masson,et al.  Seismic tomography of northern Tibet and Kunlun: Evidence for crustal blocks and mantle velocity contrasts , 1996 .

[3]  G. Peltzer,et al.  Magnitude of Late Quaternary Left-Lateral Displacements Along the North Edge of Tibet , 1989, Science.

[4]  K. Gallagher.  An examination of some uncertainties associated with estimates of sedimentation rates and tectonic subsidence , 1989 .

[5]  THE JIUXI BASIN, HEXI CORRIDOR, NW CHINA: FORELAND STRUCTURAL FEATURES AND HYDROCARBON POTENTIAL , 1993 .

[6]  P. Molnar,et al.  Active tectonics of Tibet , 1978 .

[7]  P. Pinet,et al.  Continental erosion and large‐scale relief , 1988 .

[8]  G. Peltzer,et al.  On the mechanics of the collision between India and Asia , 1986, Geological Society, London, Special Publications.

[9]  Eric J. Fielding,et al.  How flat is Tibet , 1994 .

[10]  F. Ahnert.  Functional relationships between denudation, relief, and uplift in large, mid-latitude drainage basins , 1970 .

[11]  B. Meyer.  Mécanismes des grands tremblements de terre et du raccourcissement crustal oblique au bord Nord-Est du Tibet , 1991 .

[12]  J. V. D. Woerd.  Couplage cinématique entre décrochements et chevauchements actifs dans le Nord du Tibet : croissance du plateau Tibétain , 1998 .

[13]  Kevin P. Furlong,et al.  Simulating Clastic Sedimentary Basins: Physical Fundamentals And Computer Programs For Creating Dynamic Systems , 1994 .

[14]  P. England,et al.  A thin viscous sheet model for continental deformation , 1982 .

[15]  M. Barazangi,et al.  High-frequency seismic wave propagation beneath the Indian Shield, Himalayan Arc, Tibetan Plateau and surrounding regions: high uppermost mantle velocities and efficient Sn propagation beneath Tibet , 1983 .

[16]  Peter Molnar,et al.  Mantle dynamics, uplift of the Tibetan Plateau, and the Indian Monsoon , 1993 .

[17]  A. Hirn,et al.  Crustal structure and variability of the Himalayan border of Tibet , 1984, Nature.

[18]  J. Bowler,et al.  Late pleistocene evolution of salt lakes in the Qaidam basin, Qinghai province, China , 1986 .

[19]  W. J. Morgan,et al.  Uplift of Tibetan Plateau , 1985 .

[20]  P. Davy,et al.  Shortening of analogue models of the continental lithosphere: New hypothesis for the formation of the Tibetan plateau , 1994 .

[21]  P. Conaghan,et al.  Plate tectonics and the Himalayas , 1973 .

[22]  Bertrand Meyer,et al.  Crustal thickening in Gansu‐Qinghai, lithospheric mantle subduction, and oblique, strike‐slip controlled growth of the Tibet plateau , 1998 .

[23]  R. Kidd,et al.  A time-slice approach to the history of Cenozoic sedimentation in the Indian Ocean , 1995 .

[24]  R. Clayton,et al.  Notes on Sedimentary Basins in China Report of the American Sedimentary Basins Delegation to the People's Republic of China , 1986 .

[25]  M. McNutt,et al.  Evidence from gravity and topography data for folding of Tibet , 1994, Nature.

[26]  M. Zhao,et al.  Source process of the 1990 Gonghe, China, earthquake and tectonic stress field in the northeastern Qinghai-Xizang (Tibetan) plateau , 1996 .

[27]  M. Mattauer.  Intracontinental subduction, crust-mantle décollement and crustal-stacking wedge in the Himalayas and other collision belts , 1986, Geological Society, London, Special Publications.

[28]  F. Métivier.  Volumes sédimentaires et bilans de masses en Asie pendant le Cénozoïque , 1996 .

[29]  M. Coward,et al.  THE CHAIDAM BASIN (NW CHINA): FORMATION AND HYDROCARBON POTENTIAL , 1990 .

[30]  Qing-liang Wang,et al.  Study of dislocation model and evolution characteristics of vertical deformation field of gongheMS=6.9 earthquake , 1993 .

[31]  P. Bird.  Initiation of intracontinental subduction in the Himalaya , 1978 .

[32]  M. Caffee,et al.  Holocene left-slip rate determined by cosmogenic surface dating on the Xidatan segment of the Kunlun fault (Qinghai, China) , 1998 .

[33]  F. Métivier,et al.  Mass transfer between eastern Tien Shan and adjacent basins (central Asia): constraints on regional tectonics and topography , 1997 .

[34]  Philip England,et al.  FINITE STRAIN CALCULATIONS OF CONTINENTAL DEFORMATION .2. COMPARISON WITH THE INDIA-ASIA COLLISION ZONE , 1986 .

[35]  Bertrand Meyer,et al.  Active thrusting and folding in the Qilian Shan, and decoupling between upper crust and mantle in northeastern Tibet , 1990 .