松辽盆地晚中生代生物演化与环境变化

The Late Mesozoic bio evolution and environmental changes in Songliao basin.

松辽盆地晚中生代经历了热隆张、裂陷、坳陷和萎缩４ 个地质演化阶段，后３ 个阶段相应发育了三大生物群，即热河生物群、松花江生物群和明水生物群。通过对三大生物群中介形类和叶肢介的演化史研究，认为环境的变化影响和控制着生物的发生、发展和繁盛。构造活动期，生物组合具有低分异度、低丰富度的特点，化石的纹饰结构也相对简单；构造平稳期，湖生生物迅速发展并繁盛，生物组合具有高分异度、高丰富度的特点，化石壳面纹饰结构趋于复杂化、多样化。从单一超层序的沉积体系域演变来看，随着古湖盆水体的进侵和加深，生物组合特征也表现为由低分异度、低丰富度逐渐向高分异度、高丰富度发展，并且化石壳面纹饰结构有由简单逐渐向复杂化、多样化方向演化发展的趋势；从化石的横向分布来看，滨浅湖相暗色泥岩中化石含量最丰富，其次是三角洲前缘相和三角洲分流平原相，深湖相、山前平原淤积相和泛滥平原相中少见化石。生物在其地史演化进程中，记载了环境变迁信息，因此，可以通过分析沉积盆地中产出的化石组合特征，再现古地理、古环境。

In Late Mesozoic, the evolution of the Songliao basin progressed through 4 stages: thermal doming, rifting, depression and shrinkage. Corresponding to the late three stages: it developed three biotas, Jehol biota, Sungari biota and Mingsui biota. According to the evolutionary study of Ostracoda and Conchostraca, a conclusion can be obtained, that environment changes affected and controlled the origination, development and prosperity of the organisms. In the active tectonic period, biogenic assembly has characteristics of low differentiation, and low abundance and the lamella structures of fossil groups are relatively simple. In the stable tectonic period lake biota developed rapidly and were very prosperous, and the biogenic assembly has characteristics of high differentiation and high abundance; the lamellar structures of fossil structures become complicated and multiplicated. Viewed from the evolution of a simple super stratigraphic sedimentary system, as the water body of the paleo lake transgressed and deepened, the biogenic assembly became highly differential and highly abundant from low differential and low abundant, and the lamellar structure of fossil groups had a tendency of more compellation and multiplication from simplification. Viewed from a lateral distribution, fossil groups are mostly abundant in the shore and shallow lake phase dark mud stones, and the next in the predelta phases and deltaic distributary plain phases; while fossil groups are very seldom occurred in deep lake phases, piedmont plain depositional phases and flood plain phases. In the history of bio evolution, fossil can record the information of the environmental changes. So that, paleogeography and paleoenvironment can be rebuild which based on the information of the fossil assemblage in the sedimentary basin.