JURASSIC CLASTIC COMPOSITION IN THE SOUTHERN JUNGGAR BASIN, NORTHWEST CHINA: IMPLICATIONS FOR BASIN-RANGE PATTERN AND TECTONIC ATTRIBUTES

Abstract

It is important method to understand provenance types, basin-range evlution and tectonic attributes through detrital composition of sandstones. The sandstone framework grains and detrital heavy minerals of Jurassic in Tianshan and southern Junggar basin generally show low detrital maturity, which mainly resulted from tectonic activities and orogenesis the provenance area-the (ancestral) Tianshan. To the Jurassic of three field sections in Tianshan Mountains, the ancestral Tianshan supplied provenance mainly consisting of metamorphic rocks and acidic volcanic rocks and characterized by recycled orogen and mixed orogenic sandstones types, but the characteristics of detrital composition show different provenances of the three sections. The Jurassic of southern Junggar basin consist of provenances of metamorphic, acidic volcanic and sedimentary rocks attributed to recycled orogen, magmatic-arc and arc orogenic sandstones types. The detrital compositions suggesting some differences in provenance between the western and eastern section of southern Junggar basin, but the characteristics of Houxia and Toutunhe section show that they have similar sandstones types and tectonic attributes. The integrated research on clastic deposition of Jurassic filed sections and well cores shows that the main sediment sources of Jurassic southern Junggar basin include the Kelamaili, west Junggar Mountain and (ancestral) Tianshan. The Junggar Basin and Tarim Basin were not physiographically separated throughout the Early-Middle Jurassic by an ancestral version of the Tianshan Mountains. From the Late Jurassic to the terminal Jurassic, the changes in sedimentary facies, unstable heavy minerals and sandstone composition show tectonically active setting and obvious uplift of Tianshan during the Late Jurassic to the early age of early Cretaceous, led to the widely different sedimentary succession of Tarim Basin and southern Junggar Basin.