Tibetan plateau aridification linked to global cooling at the Eocene–Oligocene transition

Abstract

Continental aridification and the intensification of the monsoons in Asia are generally attributed to uplift of the Tibetan plateau and to the land-sea redistributions associated with the continental collision of India and Asia, whereas some studies suggest that past changes in Asian environments are mainly governed by global climate. The most dramatic climate event since the onset of the collision of India and Asia is the Eocene-Oligocene transition, an abrupt cooling step associated with the onset of glaciation in Antarctica 34 million years ago. However, the influence of this global event on Asian environments is poorly understood. Here we use magnetostratigraphy and cyclostratigraphy to show that aridification, which is indicated by the disappearance of playa lake deposits in the northeastern Tibetan plateau, occurred precisely at the time of the Eocene-Oligocene transition. Our findings suggest that this global transition is linked to significant aridification and cooling in continental Asia recorded by palaeontological and palaeoenvironmental changes, and thus support the idea that global cooling is associated with the Eocene-Oligocene transition. We show that, with sufficient age control on the sedimentary records, global climate can be distinguished from tectonism and recognized as a major contributor to continental Asian environments.

A late Eocene palynological record of climate change and Tibetan Plateau uplift (Xining Basin, China)

“…In light of their results and the new magnetostratigraphic framework (Dai et al, 2006;Dupont-Nivet et al, 2007;Abels et al, 2011), an exploratory palynological study permits a better understanding of environmental and climatic developments in the late Eocene of China ). The palynological approach in this study is explained below.…”

“…In the upper part of the Paleogene succession, the gypsum layers disappear and red beds remain. This shift is indicative of a change from salinelake environments to predominant dry mudflat environments and has been interpreted as regional aridification (Dupont-Nivet et al, 2007). In time, the disappearance of the gypsiferous saline lake deposits has been precisely correlated to the first step of the EoceneOligocene greenhouse to icehouse transition (G.Q.…”

“…The gypsum layers in the lower part of the succession are laterally continuous and formed by decimeter-to meter-thick tabular, nodular or laminar beds of albastrine massive gypsum. These beds grade into green mudstone with lacustrine laminations (Dupont-Nivet et al, 2007). In the Mahalagou Formation green-white muddy gypsum alternate with red gypsiferous mudstone at meter scale.…”

“…Recently it has been demonstrated, from the stratigraphy in the Xining Basin, that Asian palaeoenvironment is also governed by global climate changes. Using high-resolution chronostratigraphy, aridification recorded in the studied stratigraphy is closely correlated to the Eocene-Oligocene transition; an abrupt cooling event at 34 Ma associated with the glaciation of Antarctica (Dupont-Nivet et al, 2007;G.Q. Xiao et al, 2010).…”

“…The accurate age control from magnetostratigraphy makes the long, continuous sedimentary succession in the Xining Basin ( Fig. 1) perfect for studying the tectonic and climatic processes during the Eocene and Oligocene (Dupont-Nivet et al, 2007;Abels et al, 2011). The Cenozoic successions in the Xining Basin lay discomformably on the Mesozoic alluvial sediments of the Hekou and Minhe Groups (possibly lower and upper Cretaceous respectively) or uncomformably on older basement rocks.…”