摘要
The Tarim basin experienced a complex tectonic evolutionary history from Sinian to Ceno zoic. Eight largescale and more than 20 subordinate unconformities defining tectonosequences of dif ferent protobasins formed in various tectonic settings have been identified within the Phanerozoic in the Tarim basin, their distribution determining the general characteristics of sequence stratigraphic framework of the basin. Tectonostratigraphic unit I （magasequence） consists mainly of the Sinian Sys tem, which formed in a rift or aulacogen setting and can been subdivided into two subordinate strati graphic units （supersequences）. Unconformity （Tgg） between Sinian and Cambrian with surface karsti fication is regarded as a postrift unconformity. Tectonostratigraphic unit II comprises the Cambrian and the Ordovician and can be divided into six subordinate tectonostratigraphic units, recording the tectonogeographic evolution of the prototype basins from Cambrian to Early Ordovician passive car bonate continental margin or cratonic depression and the Late Ordovician submarine to neritic ret roarc foreland and cratonic depressions. The tectonic uplift related to the formation of the unconformity Tg5-2 resulted in the remarkable change in basin tectonic setting from a passive divergent to an active convergent, with the development of the Tazhong （塔中） uplift, the Tangguzibasi （塘古孜巴斯）, and the northern depression at the end of the Middle to the early Late Ordovician. The widespread angular unconformity Tg5 formed by a relatively strong compressive deformation, which caused an abrupt tec tonogeographic change of the basin from abyssal to a neritic setting in response to the collision andassociated tectonic deformation of the North Kunlun （昆仑） orogenesis during the Late Ordovician to the Early Silurian. Tectono stratigraphic unit III is composed of the Silurian and the Lower to Middle Devonian and character ized by the development of fluvial or deltaic and clastic littoral and neritic deposits. Largescale terrigenous clastic depositional wedges progra dated from the north to south in the southeast ern slope of the basin indicate the continuously shallowing and uplifting along the northern basin margin. Tectonostratigraphicunit IV includes the Upper Devonian, Carboniferous, and Permian and can be classified into two sub ordinate tcctonostratigraphic sequences. The angular unconformity （Tg3） at the base of the unit is the most widespread unconformity and the strong compression and uplift of the basin during this period has been suggested to be related to the collision of the Tianshan （天山） orogenesis and resulted in fun damental change in tectonic geomorphology with higher to the northeast and lower to the southwest. Tectonostratigraphic unit IV records another tectonic cycle from weak extension to compression in ba sin setting and is composed mainly of nearshore elastic deposits of embayment basin f＇flls. From the Triassic, the Tarim basin evolved into a period characteristic of development of intracontinental de pressions and marginal foreland basins and experienced several cycles from rapid subsidence to strong uplift and deformation, resulting in superimposition and reformation of differently orientated proto basins filled with a series of regional depositional cycles bounded by major unconformities and consist ing of extremely thick alluvial and lacustrine deposits. The Kuqa foreland depression in the northwest ern basin margin developed since the Triassic and deposited a elastic wedge of the Mesozoic to Cenozoic more than I00 000 m in thickness, which progradated and thin towards the southern Tabei （塔北） forebulge. The largescale sedimentary cycles from alluvial, fluvial to lacustrine, and finally fluvial deposits are attributed to the results of foreland tectonisim from active to relatively quiet stages. The foreland tectonisim was active during the Triassic, relatively quiet during the Jurassic, and active again from the Late Jurassic to the Cretaceous. To the Eogene, the depression subsided again and the com pression intermittently increased, resulting in a series of faulted and folded structural belts.
The Tarim basin experienced a complex tectonic evolutionary history from Sinian to Ceno zoic. Eight largescale and more than 20 subordinate unconformities defining tectonosequences of dif ferent protobasins formed in various tectonic settings have been identified within the Phanerozoic in the Tarim basin, their distribution determining the general characteristics of sequence stratigraphic framework of the basin. Tectonostratigraphic unit I （magasequence） consists mainly of the Sinian Sys tem, which formed in a rift or aulacogen setting and can been subdivided into two subordinate strati graphic units （supersequences）. Unconformity （Tgg） between Sinian and Cambrian with surface karsti fication is regarded as a postrift unconformity. Tectonostratigraphic unit II comprises the Cambrian and the Ordovician and can be divided into six subordinate tectonostratigraphic units, recording the tectonogeographic evolution of the prototype basins from Cambrian to Early Ordovician passive car bonate continental margin or cratonic depression and the Late Ordovician submarine to neritic ret roarc foreland and cratonic depressions. The tectonic uplift related to the formation of the unconformity Tg5-2 resulted in the remarkable change in basin tectonic setting from a passive divergent to an active convergent, with the development of the Tazhong （塔中） uplift, the Tangguzibasi （塘古孜巴斯）, and the northern depression at the end of the Middle to the early Late Ordovician. The widespread angular unconformity Tg5 formed by a relatively strong compressive deformation, which caused an abrupt tec tonogeographic change of the basin from abyssal to a neritic setting in response to the collision andassociated tectonic deformation of the North Kunlun （昆仑） orogenesis during the Late Ordovician to the Early Silurian. Tectono stratigraphic unit III is composed of the Silurian and the Lower to Middle Devonian and character ized by the development of fluvial or deltaic and clastic littoral and neritic deposits. Largescale terrigenous clastic depositional wedges progra dated from the north to south in the southeast ern slope of the basin indicate the continuously shallowing and uplifting along the northern basin margin. Tectonostratigraphicunit IV includes the Upper Devonian, Carboniferous, and Permian and can be classified into two sub ordinate tcctonostratigraphic sequences. The angular unconformity （Tg3） at the base of the unit is the most widespread unconformity and the strong compression and uplift of the basin during this period has been suggested to be related to the collision of the Tianshan （天山） orogenesis and resulted in fun damental change in tectonic geomorphology with higher to the northeast and lower to the southwest. Tectonostratigraphic unit IV records another tectonic cycle from weak extension to compression in ba sin setting and is composed mainly of nearshore elastic deposits of embayment basin f＇flls. From the Triassic, the Tarim basin evolved into a period characteristic of development of intracontinental de pressions and marginal foreland basins and experienced several cycles from rapid subsidence to strong uplift and deformation, resulting in superimposition and reformation of differently orientated proto basins filled with a series of regional depositional cycles bounded by major unconformities and consist ing of extremely thick alluvial and lacustrine deposits. The Kuqa foreland depression in the northwest ern basin margin developed since the Triassic and deposited a elastic wedge of the Mesozoic to Cenozoic more than I00 000 m in thickness, which progradated and thin towards the southern Tabei （塔北） forebulge. The largescale sedimentary cycles from alluvial, fluvial to lacustrine, and finally fluvial deposits are attributed to the results of foreland tectonisim from active to relatively quiet stages. The foreland tectonisim was active during the Triassic, relatively quiet during the Jurassic, and active again from the Late Jurassic to the Cretaceous. To the Eogene, the depression subsided again and the com pression intermittently increased, resulting in a series of faulted and folded structural belts.
基金
supported by the National Natural Science Foundation of China(No.41130422)
the National Basic Research Program of China(Nos.2011CB201100-03 and 2006CB202302)
the Frontier Research Project of Marine Facies of the Oil Industry in China
