撞击地层学及其研究进展

地质历史中的地外物体撞击地球事件可在撞击点、近源区和远源区分别形成撞击坑熔融岩体、近源溅射岩席及海啸沉积和远源溅射层等一系列撞击地层层序。撞击地层有其独特的物理学和化学特征，与正常沉积作用、火山喷发和板块碰撞等成因的地层显然有别。通过对撞击地层层序的时空变化、所包含的撞击成因矿物、撞击微球粒和微玻璃陨石以及古生物和地球化学异常等的研究，可以了解撞击事件的发生频率、幅度和撞击天体的性质等，也为探索生物和地球环境的灾难性变化及其起因提供了新的思路。

IMPACT STRATIGRAPHY-AN INTRODUCTION

Extraterrestrial impact events can produce an impact stratigraphical sequence consisting of impact melt-sheet in crater, proximal ejecta-blankct and tsunami nearby crater, and distal ejecta layer in distal sites. Physical and chemical features of impact-generated strata are different from those of sedimentary and wolcanie origins. Studies on impact-related minerals, geochemical anomalies, impact microspherules and microtektites enable us to define frequencies, magnitudes and types of impact bodies of extraterrestrial impact events. Impact layers and ejectas may not only provide distinct event markers in high-resolution stratigraphical correlation, but also potential interpretations for the catastrophic changes and their causes of life and global environment.