成都理工大学夏国清及其团队在研究青藏高原中部始新世-渐新世的冰川作用上取得新成果。2023年4月12日出版的《地质学》杂志发表了这项成果。

该研究团队报告了从上始新世到下渐新世牛堡组(Fm)出现的霜痕、冰携碎屑(IRD)和钙芒硝假象方解石，沉积于青藏高原中部(CTP)伦坡拉盆地冰湖砾岩和杂砂岩相之上的冰前湖泊中。磁性地层学测定这些低温层沉积物的年代约为ca. 36.2 31.8 Ma，与格陵兰岛东南部近海以及巴伦支海、楚科奇海和拉普捷夫海的冰携碎屑地层间隔同步，表明了强烈的大陆-海洋耦合。

研究结果为始新世晚期和始新世-渐新世过渡时期，北半球中纬度地区的间歇性冰冻过程提供了有力的大陆证据。如牛堡组记录的那样，全球寒流始新世-渐新世过渡时期-1影响了已经冰川化的高海拔山脉，降低了冰川的平衡线高度(ELAs)，并引起冰原、冰盖和具有冰前湖泊系统的山谷冰川的局部发展。在始新世-渐新世过渡时期-1开始前，冰携碎屑、钙芒硝假象方解石和霜痕的记录表明在ca.36.2 Ma时，高原上有一个活跃的冰冻圈。

附：英文原文

Title: EoceneOligocene glaciation on a high central Tibetan Plateau

Author: Guoqing Xia, Chihua Wu, Ahmed Mansour, Xin Jin, Haisheng Yi, Gaojie Li, Qiushuang Fan, Zhiqiang Shi, Julian B. Murton, Junling Pei, Juan Pedro Rodríguez-López

Issue&Volume: 2023-04-12

Abstract: The nature of glaciation (bipolar vs. unipolar) during the EoceneOligocene transition (EOT) remains unresolved. Here, we report the occurrence of frost marks, ice-rafted debris (IRD), and glendonites from the Upper Eocene to Lower Oligocene Niubao Formation (Fm.) deposited in a proglacial lake above glaciolacustrine conglomerates and diamictite facies in the Lunpola Basin, central Tibetan Plateau (CTP). Magnetostratigraphy dates these cryospheric deposits to ca. 36.231.8 Ma, synchronous with a stratigraphic interval containing IRD offshore of SE Greenland and in the Barents, Chukchi, and Laptev Seas, suggesting a strong continental-oceanic coupling. Our results provide robust continental evidence for intermittent cryospheric processes in the midlatitude Northern Hemisphere during the late Eocene and EOT. The global cold snap EOT-1 influenced already glacierized high-altitude mountains, lowering equilibrium line altitudes (ELAs) of glaciers and leading to local development of ice fields, ice caps, and valley glaciers with proglacial lake systems, such as the one recorded in the Niubao Fm. The record of IRD, glendonites, and frost marks before the onset of EOT-1 points to an active cryosphere on a plateau already elevated by ca. 36.2 Ma.

DOI: 10.1130/G51104.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51104.1/622181/Eocene-Oligocene-glaciation-on-a-high-central