發(fā)布時間：2018-11-04 17:19

【摘要】：西藏羌塘中部增生雜巖的不斷解體對于該區(qū)古生代—三疊紀地層格架的厘定及特提斯洋演化研究具有重要的指示意義。對西藏榮瑪鄉(xiāng)亞丹地區(qū)的增生雜巖進行實測剖面時,發(fā)現(xiàn)一段早二疊世大陸斜坡相深水重力流形成的海底扇細碎屑巖沉積,北側(cè)被新生代康托組紅層覆蓋,南側(cè)與玄武巖等基性巖塊呈斷層接觸,沉積序列不完整,主體為一套海底扇中扇-外扇厚層粉砂巖夾水道砂巖透鏡體。碎屑巖層中垮塌沉積的生屑灰?guī)r夾層含Parafusulina,Pseudofusulina,Schwagerina,Chalaroschwagerina parampla共4屬10種■類化石,指示地層時代為早二疊世亞丁斯克期。1∶25萬日干配錯幅區(qū)域地質(zhì)調(diào)查將該地層歸為吞龍共巴組,主要為混積陸棚相沉積。依據(jù)巖石地層及化石組合時代,厘定本套海底扇沉積為下二疊統(tǒng)曲地組。結合前人報道的早—中二疊世含■灰?guī)r建造,以及羌塘中部晚石炭世—早二疊世基性巖的大陸裂谷背景,認為羌塘中部早二疊世沉積代表了中特提斯洋演化的初始階段,并推測在空谷階之后發(fā)育小規(guī)模洋盆。
[Abstract]:The continuous disintegration of the accretive complex in the central Qiangtang, Tibet, is of great significance for the determination of the Paleo-Triassic stratigraphic framework and the study of the evolution of the Tethys ocean. When the accretive complex in Yadan area, Rongma Township, Tibet, was measured, it was found that the subsea fan fine clastic deposits formed by deep-water gravity flow in the early Permian continental slope were covered by the red beds of the Cenozoic Kangto formation on the north side. The southern side is in contact with basalt and other basic rock blocks, the sedimentary sequence is incomplete, and the main body is a set of sandstone lens in the channel between the thick siltstone of the fan and the outer fan of the submarine fan. The intercalation of bioclastic limestone deposited in clastic strata contains 10 species and 4 genera of Parafusulina,Pseudofusulina,Schwagerina,Chalaroschwagerina parampla. The stratigraphic age is the early Permian Adinsk period, and the regional geological survey of the 1: 250 000 dry fault block classifies the formation as Tunlong Gongba formation, which is mainly a mixed continental shelf facies deposit. According to the age of lithostratigraphy and fossil assemblage, this set of submarine fan deposits is determined to be the lower Permian curved formation. Combined with the early and middle Permian limestone formation reported by predecessors and the continental rift background of the basic rocks of the late Carboniferous and early Permian in the central Qiangtang, it is considered that the early Permian sediments in the central Qiangtang represented the initial stage of the evolution of the Middle Tethys Ocean. It is speculated that a small scale ocean basin is developed after the empty valley terrace.
【作者單位】： 中國地質(zhì)大學地球科學與資源學院;
【基金】：中國地質(zhì)調(diào)查局項目《西藏榮瑪鄉(xiāng)南地區(qū)1∶5萬四幅區(qū)域地質(zhì)調(diào)查》(編號:121201103000150004) 中央高�；究蒲袠I(yè)務費項目《西藏羌塘中部藍嶺高壓變質(zhì)帶變質(zhì)、變形作用過程及構造意義》(編號:2652014004)
【分類號】：P534.46

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