Cretaceous OAE₂ Anoxic Event In Western Tarim Basin

Cretaceous is a special time in history,when has played a major geological events occurred, Such as the global oceanic anoxic events(OAEs), Oxygen-rich events, Significant radiation and biological communities change, the emergence of super-static tape, bio-mass extinction events, etc. oceanic anoxic events and oxygen events is closely related to extinction events and the formation of mineral resources.Therefore, the OAEs has been well received by the concern raised has been one of the hot topics up for the study. The study of Cretaceous ocean at Aptian-Albian, Cenomanian-Turonian, and Coniacian-Santonian oceanic anoxic events occurred many times during the period, were called OAE1, OAE2, and OAE3, which OAE2 reached a global scale. The previous large-scale oceanic anoxic events produced organic carbon burial, the atmosphere-ocean system to produce a profound effect, its main role is to lead to decreased CO2 atmosphere-ocean system, O2 increased, and the attendant global cooling and enhanced oxidative capacity of the marine. Cretaceous oceanic anoxic events abroad research has extremely broad, and its relatively weak in China (China's Progress in Cretaceous oceanic anoxic events mainly from southern Tibet). Tarim Basin in the western region is the continuous development of our marine Cretaceous and a few well-exposed areas. Based on the western margin of the Tarim Basin region Kuzigongsu section Wuqia Cretaceous sedimentary characteristics and indicators of sediment color and organic matter research, combined with previous research results, obtained the following conclusions:1. Tarim Basin where is the process of the second transgression in late Cretaceous western. Kizilsu group in the early Cretaceous alluvial next cycle-based on fluvial clastic rocks, Late Cretaceous, Tethys seawater intrusion through Central Asia, . Southwest Depression of the Tarim Basin area, the deposition cycles of the coastal Kizilsu Groups clastic rocks, thanks to the Kukebai Formation to normal sea water intertidal-subtidal mudstone and carbonate deposits, black shale, and in particular the period of the emergence of planktonic foraminifera that Ariake Sea transgression reached its maximum size. Wuytak Fm regression phase, the formation of variegated mudstone, siltstone sandstone and mudstone of tidal cream-supratidal sedimentary. Dental group in the area to Yigeziya Fm second transgression, forming intertidal algae sandy marl and limestone deposition.2. Study of the Late Cretaceous Cenomanian-Turonian, Kukebai Fm exist oceanic anoxic events of sedimentary records. Of sediment color a value lower profile and higher total organic carbon and black shales with marine planktonic environment for the emergence of direction was the reduction of marine hypoxia conditions. Combined with the group of carbon and oxygen isotope anomalies and bivalves negative organisms, like porcelain shells and calcareous foraminifera not developed porous shell type characteristics (Guoxian Pu,1995), confirmed that the western Tarim Basin Cretaceous Kukebai Fm prayer group Cenomanian-Turonian oceanic anoxic event of the existence (OAE2); Kukebai Fm, black mudstone and shale in the folder as well as four biological limestone sediment color and total organic carbon content showed a value of abnormal changes in volatility, which total The organic carbon content values corresponding to black mudstone and shale, while the lower corresponds to the biogenic limestone, suggesting that oceanic anoxic events in the area of hypoxia is not a continuous process, and the intermittent four oceanic anoxic events, namely OAE2a, OAE2b, OAE2c OAE2d.3. Research on Cretaceous Cenomanian-Turonian Kukebai Fm of oceanic anoxic event deposition record is Tethys sea toward the concrete manifestation of China's northern branch, the branch of Tethys sea toward the south in the Tibet region of China there OAE2 oceanic anoxic events, and further shows that the presence of Tethys sea toward the north and south China's two branches.There is OAE2 events in western Tarim Basin, which is rich in events of the Cretaceous of China, the global Cretaceous oceanic anoxic events OAE2 and formation mechanism of contrast, to identify the environment and the Tarim Basin of Cretaceous source rocks in the formation of large-scale Ancient climate control factors and the evolution of the Cretaceous marine biota, and its replacement with the major geological events of the links was very important.