扬子台区二叠-三叠系界线层综合地层学研究

华南二叠－三叠系界线研究一直在地学界备受瞩目．目前被广泛接受的界线标准化石为牙形石Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ,该化石的首现位置被定义为二叠－三叠系界线层型剖面点．然而在全球研究精度最高的４个候选层型剖面中,生物地层单位的对比问题尚存在分歧,从而影响了区域高精度地层对比框架的建立．在扬子台区丰富的资料及大量二叠－三叠系界线剖面进一步研究的基础上,发现许多剖面上二叠－三叠系界线处具有相似的岩石地层特征．其基本结构为粘土岩层、灰岩或泥灰岩层及粘土岩层沉积组合．从综合地层学角度的研究表明：该套沉积组合（界线层）在岩性特征、生物群总体面貌以及其他事件标志（如同位素年龄、磁性地层、地球化学特征等）上具有一定的对比意义．认为界线层应该是等时的地层单位,是扬子台区二叠－三叠系界线处重要的标志层组,并对这套地层进行了区域性对比．这套地层的发现大大提高了扬子台区二叠－三叠系界线处地层的对比精度．

INTEGRATED STUDY ON PERMIAN_TRIASSIC BOUNDARY BED IN YANGTZE PLATFORM

The study on Permian_Triassic boundary (PTB) in South China has been one of the most important topics among geologists all over the world. Momentarily the conodont Hindeodus parvus , the first appearance of which is determined as the PTB stratotype point, is widely accepted as the index fossil for defining the PTB. But up to now, the correlation on biostratigraphic unit among the four candidate stratotype sections, which are the most detailed studied sections on PTB throughout the world, remains unresolved. So the regional high_resolution stratigraphic framework can't be achieved. Based on field observation and compilation of data, similar strata near the PTB, which are the assemblage of claystone, limestone or marl and claystone, were discovered at many sections in Yangtze region. The isochroneity of these strata is discussed in integrated stratigraphic study, such as the lithological character, the whole feature of biota, the isotopic dating, the magnetostratigraphy and the chemostratigraphy etc.. It is concluded that the boundary bed is one isochronous unit and an important bed group marker near the PTB in Yangtze region.