扬子台地西缘早、中三叠世古地理重建  

PALAEOGEOGRAPHIC RECONSTRUCTION OF THE WESTERN MARGIN OF THE YANGTZE PLATFORM DURING THE EARLY AND MIDDLE TRIASSIC

作　　者：吴应林[1] 颜仰基[1] 秦建华[1] 

机构地区：[1]成都地质矿产研究所

出　　处：《沉积与特提斯地质》1995年第3期17-33,共17页Sedimentary Geology and Tethyan Geology

摘　　要：扬子台地西缘由于构造的逆冲推覆与平移走滑而受到严重破坏，因此，对其古地理重建就不能简单地依据现今露头岩相分布原封不动地来拟定古地理格架。为此，本文尝试采用“构造岩块分析法”，对这些位移了的岩块（断块）进行构造复位后，再编制早、中三叠世古地理复原图，重建其古地理演化格架。扬子台地西部边缘在早三叠世发育了进积的碳酸盐鲕粒浅滩，滩后为海湾或局限台地，滩前为碳酸盐缓坡；中三叠世时，边缘的南、北段有差异，北段滩前由缓坡（早世）演化成末端变陡的碳酸盐缓坡，而南段则发展成镶边陆架。The western margin of the Yangtze platform was once a passive continental margin during the Early and Middle Triassic,and dismembered into a number of displaced structural blocks(fault blocks)owing to subsequent thrust napping and translation gliding.This study is intended to conduct tectonic restoration and palaeogeographic reconstruction with the aid of tectonic block techniques in terms of the deep-seated geophysical data.The Triassic sediments display conformable contact with the Permian sediments in the platform and basin regions,while in the slope areas in the northern part of the western margin,the Early Triassic basin sediments are onlapped over the Early Permian slope sediments. The Middle and Late Triassic strata are also conformable in the slope-basin areas,whereas in the platform areas,the pseudoconformities predominate with the exception of the Yangtze region on the western side of the Kang-Dian ancient land.This is due to the formation of the forebuldges in the Yangtze craton(platform)created by the collision ofthe Yangtze block and North China plate between the Middle and Late Triassic.The sea-level rises during the early Early Triassic are responsible for the constructionof the Early Triassic carbonate ramps on the Permian rimmed carbonate shelves. Duringthis period,the rates of platform production were greater than those of the relative sea-level rises.As a result,the progradational carbonate oolitic shoals began to be generated onthe western margin of the platform. The sedimentary environments consist,basinwards,ofrestricted platform(gulf),shoal,ramp and basin.There were larger discrepancies in sediment evolution between northern and southernparts during the Middle Triassic. The former went through the evolution from ramps(Early Triassic)to distally-steepened carbonate ramps,whereas the latter passed from carbonate ramps(Early Triassic)into rimmed carbonate shelves.

关 键 词：古地理重建 构造岩块法 早、中三叠世 扬子台地西缘 

分 类 号：P531[天文地球—古生物学与地层学]