The Study On Environmental Proxies From The Marine Cretaceou-Paleogene Boundary In Wuqia Region, Tarim Basin In Western

As is known to all, the catastrophe and extinctions occurred in late Cretaceous is one of the most severe events during the geological history, causing a reduction of genera from 2866 to 1502, which means nearly half of the genera extincted and the extinction of the species as high as 79%, especially remarked by the mass extinction of dinosaurs once dominated on the earth. Corresponding to this catastrophe, a thin clay was worldwildly deposited in the earth (i.e. K-T boundary), indicating a significant change of global paleoclimate, thus it is particularly important to study it(K-T boundary) as a record of the paleoevironmen and paleoclimate.Compared to the international researches on K/T boundary, Chinese researchers did a little work in this field, therefore, the enhancement on this studies not only enriches the studies on the events happened during Cretaceous-Paleogene Period and plays a important role in the comparison of the global climate change, but has great significance in the studies on the relationship between the catastrophe and subsequence recovery, the influence of natural environment on the biosphere, the adaption of the biosphere to the natural environment, and how to gain the enlightenment safeguarding the survive and the sustainable development.The western Tarim Basin is an ideal experimental field preserving continuous Late Cretaceous-Paleogene marine stratum and good outcrops in China apart from Tibet. Previous researchers (Hao Yichun, Guo xianpu etc.)did a lot of work and made a series of important achievements, however, the research and discussion on the paleoenvrionmen and paleoclimate from Late Cretaceous to Early Paleogene was seldom involved.Based on substantial field surveys, we selected an intact Kuzigongsu section spaning from Late Cretaceous to Paleogene where is 8 km northeast from Wuqia new-town and 110 km northwest from Kashi City, margining of Tianshan. On the basis of previous research, samples were collected from late Cretaceous Yigeziya Fm to early Paleogene Tuyiluoke Fm, especially at the transition of two Fms-gray-green clay we made a high dense sampling for following experimental analysis. Based on the analysis of the color, organic carbon content, carbon and oxygen isotope and geochemical indicators of calcium carbonate in the sediments, we can obtain the results as follows:1) Although the Yigeziya-Tuyiluoke Fm of the Late Cretaceous-Paleogene is mainly formed by marine deposit, the change from large-scale transgression inYigeziya Fm to dramatic regression in Tuyiluoke Fm shows that the sedimentary environments of the Late Cretaceous-Paleogene had experienced great changes.2) The reduction of the red value between the Tuyiluoke Fm and Yigeziya fm is inevitably relevant to the decrease of the oxidation. This sudden decrease of the red value and a decline of the oxidation indirectly reflects that the environment in this area have changed greatly.3) Organic carbon content shows a steady trend in the middle Yigeziya fm(the value reduced near the upper clay layer), the lowest value 0.04% was detected in the gray-green clay between two Fms, the content recovered after entering the Yigeziya Fm, this result is well consistent with the biological extinction under the K/T boundary and the recovery after the catastrophe above the K/T boundary.4) Sudden reduction of Carbon and oxygen isotopes in the clay layer supplied objective evidence that the gray-grey clay between the two fm is the K/T boundary.5) The sharply decline of the CaCO3 content is coincided with that in many other parts of the world in Cretaceous and Paleogene boundary. These phenomena are probably resulted from poor nourishment in the ocean, extinction or dropping of biology, short-time decrease of the temperature.