Inquiry of Initiation Age of the Qaidam Basin Based on Stratigraphic Study of the Lower Part of the Well Lengke-1
从冷科1井下部地层的归属探讨柴达木盆地成盆时间

Lengke 1,a well for the scientific research drilling project, is the most important exploration well in the northern Qaidam basin. As great thickness of strata was for the first time discovered in the well, there is much controversy over stratigraphic division of the interval from 4 666 to 5 200 m. Based on the sporopollen assemblage, most geologists hold that the interval is of Lower Jurassic, while some others consider it to be Carboniferous according to some detritus of marine fossils found in this interval. Based on analyzing such characteristics of this interval as its lithological associations,palaeontology,seismic sections,well logging data and water medium quality,this paper rules out the possibility of being Lower Jurassic or Carboniferous,and points out that the strata in this interval are Upper Triassic. This research changes the former idea that Qaidam basin originated in Early Jurassic,and reveals that the basin originated from Late Triassic sporadic rifts.