地質(zhì)學

來源出版物：SCIENCE CHINA Earth Sciences，2015，58（6）： 859-875聯(lián)系郵箱：LI Lin-lin，lill@pku.edu.cn

泥河灣盆地晚新生代微體古生物地層及環(huán)境演化的探討

龐其清，翟大有，趙筑簾，等

通過對泥河灣盆地43條剖面和6個鉆孔晚新生代地層和微體古生物（介形類和有孔蟲）的調(diào)查研究，發(fā)現(xiàn)非常豐富的介形類，計26屬70余種，有孔蟲4屬4種，其中介形類自下而上可明顯地劃分為5個組合帶：（1）Potamocypris plana-Candoniella-Ilyocypris組合帶；（2）Leucocythere-Ilyocypris-Candoniella組合帶；（3）Leucocythere-Cytherissa-Limnocythere組合帶；（4）Ilyocypris-Limnocythere flexa-Limnocythere dubiosa組合帶；（5）Limnocythere dubiosa-Limnocythere sancti-Patricii-Ilyocypris組合帶.按以上5個介形類組合帶的分布，第1組合帶及所含地層紅崖村組和石匣組的時代為上新世；第2～4組合帶及所含地層泥河灣組的時代為早更新世；第5組合帶為中-晚更新世，分布于虎頭梁組和許家窯組，虎頭梁組置中更新世為宜，許家窯組為晚更新世.根據(jù)5個介形類組合帶和有孔蟲的分布及介形類的始現(xiàn)、繁盛、興衰的演替特征，對泥河灣古湖和盆地的形成經(jīng)歷了上新世的起始，早更新世早期的擴展，中、晚期穩(wěn)定、發(fā)展、湖面最大，中更新世向西部退縮和晚更新世消亡、桑干河水系形成五個發(fā)展階段的演化進行了探討.

介形類；有孔蟲；生物地層；晚新生代；環(huán)境演化；泥河灣盆地

來源出版物：地質(zhì)學報，2015，89（5）： 817-842聯(lián)系郵箱：龐其清，pangqq802@163.com

封面介紹：Cenozoic sedimentary sequence of southwestern Qaidam Basin shows fluvial，delta and lacustrine facies depositional environments. The evolution of paleogeographic and provenance would be controlled by the tectonism of Altyn Tagh fault zone and Qimen Tagh-East Kunlun fault zone. It is a good way to rebuild the filling history and tectonic condition of the basin by heavy minerals. For more details see the research paper by LI Lin-lin et al. on pages 859-875.

Heavy mineral assemblage characteristics and the Cenozoic paleogeographic evolution in southwestern Qaidam Basin

LI Lin-lin，GUO Zhao-jie，GUAN Shu-wei，et al.

Based on the analysis of heavy mineral assemblages in Cenozoic southwestern Qaidam Basin，we found that different areas have variable heavy mineral assemblage characteristics，which suggested that there were two source areas—the Altyn Mountains and the Qimen Tagh-East Kunlun Mountains. In Ganchaigou-Shizigou-Huatugou（Area A），which was mainly source from the Altyn Mountains，its heavy minerals were mainly composed of zircon，Ti-oxides，and wollastonite in the Paleocene-early Eocene and mainly of unstable minerals，especially amphibole，in the middle Eocene-Oligene. Since the late Oligocene-Miocene，the heavy minerals were still mainly unstable minerals，but the content of epidote increased and the content of amphibole decreased. In Qigequan-Hongliuquan（Area B），which was the mixed source from the Altyn Mountains and the Qimen Tagh-East Kunlun Mountains，its heavy minerals were mainly garnet，epidote，and amphibole. The source of Lücaotan-Dongchaishan-Kunbei（Area C）was mainly from the Qimen Tagh-East Kunlun Mountains，heavy minerals in the sediments in Area C were mainly zircon and Ti-oxides in Paleogene and garnet，epidote，and amphibole in Neogene. In Yuejin-Youshashan（Area D），where the stable minerals and unstable minerals were present simultaneously，the heavy mineral assemblages was controlled by multi-direction source. The variation of heavy mineral assemblages in southwestern Qaidam Basin shows that Altyn Mountains was of low-lying topographic relief in Paleocene-early Eocene，and the rapid uplift of Altyn Mountains started from the middle Eocene. InPaleogene，the Altyn Tagh Fault had a slow strike-slip velocity，but the strike-slip velocity increased greatly since the late Oligocene，leading to a strike-slip displacement above 300 km since Neogene. Meanwhile，the Qimen Tagh-East Kunlun fault zone was under a stable tectonic stage in Paleogene with the Qimen Tagh Mountain being low-lying hills； since the late Oligocene，the fault zone started to activate and the Qimen Tagh Mountain began to uplift rapidly.

southwestern Qaidam Basin； Cenozoic； heavy mineral assemblages； provenance analysis； paleogeography evolution