Sedimentology and Paleogeography of the Middle Jurassic Qiketai Formation, Turpan-Hami Basin, Northwest China

• Autores: Todd J. Greene, Alan R. Carroll, Marc S. Hendrix, Cheng Keming, Zeng Xiao Ming
• Localización: Lake basins through space and time / coord. por Elizabeth H. Gierlowski-Kordesch, K. Kelts, 2000, ISBN 0891810528, págs. 141-152
• Idioma: inglés
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• Resumen

  • The occurrence and distribution of Early and MiddleJurassic lake systems in northwest China (Figure 1)are poorly represented in the lacustrine literature. This is surprising because lacustrine environments would appear to have flourished in this geologic setting: intracontinental foreland-style, internally drained basins, with rapid, periodic basin floor subsidence,and a thriving humid climate supplying abundant fresh water into the many available basins. Although the Chinese literature reports mostly coaly, swamp/marsh, fluvial/ alluvial, fan delta, deltaic, and marginallacustrine environments for Lower and Middle Jurassic strata, the areal extent and descriptive sedimentology of the lacustrine systems are virtually unknown (Wang et al., 1994; Qiu et al., 1997;Wu and Zhao, 1997;Wu et al., 1997).

    This study will briefly describe one of the many Middle Jurassic lacustrine systems contained within northwest China: the Qiketai Formation (J2q) of the Turpan-Hami basin (Figures 1-3). Based on measured outcrop stratigraphic sections, detailed borehole core descriptions, and well log data, Qiketai Formation141deposits covered an area of nearly 300 km x 40 km along depositional strike and dip, respectively (Figure4). Facies represent littoral to profundal freshwater to saline lacustrine and lake-plain environments and reach a maximum thickness of 250 m in the basin center(Figure 4). The finer grained facies are organic-rich,ranging from 2 to 21% total organic carbon (TOe),with hydrogen indices (HI) reaching 811 mg hydrocarbons/gram rock (Table 1). The data presented here represent the first documentation of this large lake system outside the Chinese literature, and emphasize the importance of future detailed studies of Jurassic lake deposystems throughout northwest China.