三水盆地SB-01孔微体古生物群的组合特征及古新统—始新统界线探讨

本文分析了三水盆地SB-01孔微体古生物群的组合特征,结合全岩碳酸盐碳、氧同位素数据探讨了古新统-始新统界线在该孔中的具体层位．介形类化石分为两个组合,即Eucypris sanshuiensis组合（89．0—73．38m）和Sinocypris nitela-Cyprois buxinensis—Limnocythere honggangensis组合（73．38—0m）．前者属种单调,丰度低,后者前期和中期属种单调,丰度低,而后期属种相对较为丰富,丰度快速上升;轮藻化石也可分为两个组合,即Peckicharasubspherica．Rhabdocharafiangduensis组合（89．0—73．38m）和cyrogona qianjiangica-Obtusochara brevicylindrica组合（73．38—53．75m）．前者属种丰富,丰度高,化石个体较大,后者属种单调,丰度很低,化石个体较小．在孔深73．38m处,微体古生物群发生重大更替,且全岩碳酸盐碳同位素（下降幅度大于3．0％。）、氧同位素值均在此处发生突变,这与古新世一始新世最热事件（PETM）时期的地质记录相一致,因而认为三水盆地古新统-始新统界线在孔深73．38m处．     

New material of microfossils from the Ediacaran Doushantuo Formation in the Zhangcunping area, Yichang, Hubei Province and its zircon SHRIMP U-Pb age

The Zhangcunping area is located at the north limb of the Huangling anticline in Yichang, Hubei Province. Here, the sedimentary succession of the Ediacaran Doushantuo Formation is similar with that in the Weng’an area, Guizhou Province. A large number of new microfossils (mainly acanthoacritarchs) from the Doushantuo Formation in this area are reported in this paper. The fossil assemblage shows similarity as the phosphatized biota of the Doushantuo Formation at Weng’an, Guizhou Province and the silicified biota of the Doushantuo Formation at the Yangtze Gorges, which suggests that the Zhangcunping area is a key for correlation of the Doushantuo Formation between the Weng’an area, Guizhou Province and the Yangtze Gorges. Besides, a new zircon SHRIMP U-Pb age (614.0±7.6 Ma) is first obtained from a horizon underneath the exposed surface in the middle of the Doushantuo Formation in the Zhangcunping area. This age not only provides a new datum for subdivision of the Ediacaran Doushantuo Formation, but also indicates that the age of the exposed surface in the middle of the Doushantuo Formation in the Yangtze Platform should be posterior to 614.0±7.6 Ma. Due to the horizon of the Weng’an biota situated above the exposed surface, the age of the Weng’an biota should be posterior to 614.0±7.6 Ma as well. Supported jointly by the Basic Foundation of scientific research work from Ministry of Science and Technology of the People’s Republic of China (Grant No. J0716), Science and Technology of China for fundamental work (Grant No. 2006FY120300-2), National Natural Science Foundation of China (Grant Nos. 40772013 and 40672022) and China Geological Survey (1212010611801-3)     

The potential of vertebrate microfossils for marine to non-marine correlation in the Late Jurassic

Fish (cartilaginous: elasmobranch and bony: osteichthyan actinopterygian) and reptile (crocodile) microfossils comprising scales and teeth have been examined from a series of limestone samples in the Upper Jurassic of France and Germany to gauge the possibilities of using them for correlation between fully marine and hypo-or hyper-saline (non-marine) deposits.     

A simulation experiment on phosphatized spherical microfossils

The identification and characterization of the phosphate preservation of the spherical microfossils in the Ediacaran Doushantuo time and the Early Cambrian has long been controversial.Modern artificial simulation experiments of phosphate animal eggs can provide scientific evidence to settle the aforementioned disputes.This experiment simulated environmental changes to observe the early morphological changes of the Bluntnose black bream eggs(Megalobrama amblycephala).It was found that the eggs can show a different morphology in the phosphate environment and that these eggs exhibited considerable morphological variations under different conditions.Thus,those eggs cannot be ascribed to the same species based only on the features.The experimental results are expected to provide a useful reference for the identification of phosphatized microfossils and provide a more empirical basis for their genesis.     

The potential of vertebrate microfossils for marine to non-marine correlation in the Late Jurassic

Fish (cartilaginous: elasmobranch and bony: osteichthyan actinopterygian) and reptile (crocodile) microfossils comprising scales and teeth have been examined from a series of limestone samples in the Upper Jurassic of France and Germany to gauge the possibilities of using them for correlation between fully marine and hypo-or hyper-saline (non-marine) deposits.     

Climate and environment reconstruction during the Medieval Warm Period in Lop Nur of Xinjiang,China

We made multi-proxy analysis of ^14C, grain size, microfossils, plant seeds, and geochemical elements on samples from a profile in the central West Lake of Lop Nur. The grain size suggests relatively stable sedimentary environment around the Medieval Warm Period （MWP） with weak storm effect, which is followed by frequent strong storm events. Abundant microfossils and plant seeds in this stage indicate a warm and humid fresh to brackish lake environment. C, N, and stable elements are high in content in the sediments while Rb/Sr, Ba/Sr, and Ti/Sr are in a steady low level. In addition, plenty of red willows lived here prior to about 700 a B.P., indicating a favorable environmental condition. The results indicate that the environment in Lop Nur and its west bank turned to be favorable at about 2200 a B.P., where the Loulan Culture began to thrive. Then the climate and environment came to be in the good condition in the Tang and Song Dynasties, when the storm effect became weaker, rainfall increased and the salty lake water turned to be brackish to fresh lake water. Hence, limnic biomass increased with higher species diversity.