云南昭通中新世晚期生物地层化学元素的组合特征及古埋藏环境分析

The Characteristics of the Biostratigraphic Chemical Elemental Combinations and Taphonomic Environmental Analyses of theLatest Miocene Deposits in Zhaotong, Yunnan

摘要: 文中对云南昭通市昭阳区水塘坝中新世晚期湖沼相沉积地层昭通组剖面11层含化石层逐层共采集16件分析样品，并采用电感耦合等离子体原子发射光谱法对样品中与生物体生存关系密切的19种元素进行了测试。根据分析数据同时结合生物地球化学理论推断得出：昭通地区中新世晚期沉积盆地大量不同种类动物化石丰富埋藏极有可能是因这些动物长期通过食物、饮水等途径，将铬、锶元素摄入动物体内并不断累积，从而造成生物体内铬、锶元素的高异常含量，长期作用导致动物正常的生理机能发生紊乱，故而在此大规模的埋藏保存。此外，依据元素的化学组成特征和化石层沉积环境的分析，认为该地区中新世晚期应该属于流水较弱的湖泊沼泽地带，以及滨湖相环境，气候条件曾经历了由较温暖潮湿向逐渐干燥转变的过程。

Abstract: We collected 16 samples from the 11 fossiliferous layers respectively within Zhaotong Formation in Shuitangba, representing the late Miocene lacustrine deposits of Shaoyang District, Zhaotong Yunnan. 19 biogenic elements were analyzed from these samples using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry). Based on the biogeochemical theory, the results indicate the potential reason of the abundant vertebrate fossil assemblages preserved in the basin during latest Miocene. Chromium and strontium were ingested through food and water by the animals inhabited around; the two elements reached in a high abnormal level in organism by long term accumulation, caused the physiological function disorder of these animals and finally led to the regional faunal extinction. In addition, according to the characteristics of the chemical compo- sition and the sedimentary features of the fossiliferous beds, the paleoenvironment of the region was considered as lakes, swamps or off-shore lake with low hydrodynamic condition; climate also experienced the gradual shift from humid and warm to dry condition during latest Miocene.