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Currently, the climatic implications associated with the Cenozoic tectonic history and growth mechanisms of the Tibetan Plateau lack consensus and remain controversial. This is due in part to chronological uncertainties and few paleoelevation records distributed in the central to northern Tibetan Plateau, which we address here with the development of a robust chronology (using magnetostratigraphy, biostratigraphy, detrital zircons, and regional radiochronologic dating) and a paleoelevation reconstruction for the Tuotuohe Basin (central-northern Tibet). We refined the age of the Tuotuohe Formation (37-33 Ma), Yaxicuo Formation (33-23.6 Ma), and Wudaoliang Formation (23.6-19.7 Ma). We estimated early Oligocene (ca. 29 Ma) paleotemperatures of the Tuotuohe Basin from 11 °C to 16.1 °C, which correspond to paleoelevations of 2.9 km (±0.4 km) when the relative humidity is 64% and 2.5 km (±0.5 km) when this value is 75%, using various methods including ostracod assemblages, gastropods, charophytes, branched glycerol dialkyl glycerol tetraether analysis, regional empirical formulas, and climate model simulation. Paleoelevation data and existing geological evidence in the vicinity indicate that late Eocene to late Oligocene uplift was associated with upper-crustal shortening. Since the middle Miocene, uplift has been associated with convective removal of lithospheric mantle and/or lower-crustal flow beneath the Hoh Xil Basin. [ABSTRACT FROM AUTHOR]

Eolian material within pelagic North Pacific Ocean (NPO) sediments contains considerable information about paleoclimate evolution in Asian dust source areas. Eolian signals preserved in NPO sediments have been used as indices for enhanced Asian interior aridity. We here report a detailed eolian dust record, with chemical index of alteration (CIA) and Rb/Sr variations, for NPO sediments from Ocean Drilling Program Hole 885A over the past 4.0 m.y. CIA and Rb/Sr co-vary with the dust signal carried by combined eolian hematite and goethite concentrations. Changes in CIA around the intensification of Northern Hemisphere glaciation (iNHG) event at ca. 2.75 Ma indicate that dust production in source areas was associated mostly with physical and chemical weathering before and after the iNHG event, respectively. We here attribute the eolian flux increase into the NPO across the iNHG event mainly to increased availability of wind-erodible sediment in dust source areas derived from snow and glacial meltwater runoff, which resulted from glacial expansion and enhanced snowfall in the mountains surrounding the Tarim region in response to global cooling. Our results provide a deeper understanding of Asian interior environmental changes in response to global paleoclimate changes, where dust source areas became intermittently moister rather than more arid in response to global cooling. [ABSTRACT FROM AUTHOR]

Numerous geochronological and geochemical studies of the Late Triassic granite plutons in the Qinling orogen have been conducted over the past few decades. These studies have extensively discussed the genesis and correlations of granite plutons with the collisional processes between the North and South China blocks. However, several contradictory conclusions on the tectonic settings of these plutons (subduction, syncollision, postcollision, or intraplate) have been reached. Moreover, in all these studies, compressional or extensional structures have been always considered to control the magma emplacement, but no direct evidence has been presented so far. In order to clarify the emplacement mechanism of these Late Triassic plutons and avoid the ambiguities from purely geochemical studies, we conducted a multidisciplinary structural study on the Mishuling pluton in West Qinling, one of the biggest Late Triassic plutons in the orogen. New single-grain zircon dating confirmed that the Mishuling pluton was emplaced at 212 ± 2 Ma. Gravity investigations show an overall wedge shape to the pluton: A deep root is located in its western part, the thickness gradually decreases to the east, and it finally pinches out at its eastern extremity. We studied internal structures of the Mishuling pluton through field, microscopic, and AMS (anisotropy of magnetic susceptibility) observations, which show that the pluton did not undergo penetrative secondary deformation, and preserved cryptic internal fabrics were mainly acquired during the final stage of emplacement. In the western part of the pluton, internal fabrics display a concentric pattern. In the eastern part, the lineations mainly plunge west, while the foliations form an analogous W-plunging synform, mainly dipping SW in the northern part and dipping NW in the southern part. The three-dimensional shape and internal structures of the Mishulingpluton are concordant with the wrench tectonics of country rocks that developed during the late stage of the Late Triassic collision between the North and South China blocks. We propose an integrated emplacement model involving both the three-dimensional shape and internal fabrics of the Mishuling pluton, and regional structures of the country rocks. In this model, the magma rose in the western part and then spread eastward parallel to the regional strike-slip movements. [ABSTRACT FROM AUTHOR]