Abstract
The northeastern Tibetan Plateau (NE TP) has long been thought to be the last part of the Plateau to be raised, but this assumption has been challenged by recent analyses of fossil leaf energy, which have pointed to the possibility that the present surface altitude of ∼3,000 m above sea level (asl) in the Qaidam Basin (QB) was attained during the Oligocene. Here, for the first time, we present a record of glycerol dialkyl glycerol tetraethers (GDGTs) from a well-dated Cenozoic section in the QB. This record appears to demonstrate that the mean annual average paleotemperature of the QB was 28.4 ± 2.9°C at ∼18.0 Ma. This would suggest that the paleoelevation of the QB was only ∼1,488 m asl at that time and that a ∼1,500 m uplift was attained afterwards, in agreement with the massive shortening of the QB and the rapid drying of inland Asia since the late Miocene.
Highlights
The tectonic collision between India and Asia resulted in the formation of the Himalayan orogen, the largest and best known orogen in the world
We present new glycerol dialkyl glycerol tetraethers (GDGTs) data from fossils and precisely paleomagnetically dated Cenozoic sedimentary rocks identified in the Hongliugou (HLG) section of the Qaidam Basin (QB) (Figure 1B), and quantitatively reconstruct the paleotemperature and the paleoelevation of the early Miocene in the QB
It is possible that the temperature, salinity, and dissolved oxygen conditions found in Cenozoic reddish mudstones in the QB are more beneficial to the formation of GDGTs compounds
Summary
The tectonic collision between India and Asia resulted in the formation of the Himalayan orogen, the largest and best known orogen in the world. In contrast to the southern and central TP, where a variety of modern paleoaltimetries have been applied to reconstruct generally high paleoelevation during the Eocene (Rowley and Currie, 2006; Wang et al, 2008; Ding et al, 2014), the topographic history of the NE TP has been less well studied, with far fewer well-dated archives compiled (Zhuang et al, 2014; Song et al, 2020) This region has long been thought to have been uplifted much later, mostly during the Plio-Quaternary (Tapponnier et al, 2001), or since the late Miocene (Fang et al, 2005, 2007; Li et al, 2014). This challenges the tectonic model and dry climate predictions above and highlights a large discrepancy with a study that reconstructed much lower topographies using the hydrogen isotopes of n-alkanes (Zhuang et al, 2014)
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