Northeastward growth and uplift of the Tibetan Plateau: Magnetostratigraphic insights from the Guide Basin

Abstract

[1] Most of the evidence for the uplift of the Tibetan Plateau comes from its southern and central parts. Although the northern rim has been less studied, it may greatly contribute to the understanding of the mechanism and timing of the uplift. Recent studies on the northeastern part of the plateau suggest that the uplift can largely be explained by Cenozoic thrusting and folding linked to the movement of the Altyn Tagh and Kunlun faults and that diffuse shortening might be a realistic way to explain the thickening of the continental interior. Nevertheless, the age of sediments that record the tectonic processes is poorly known. The terrigenous formations in the Guide-Gonghe Basin, NE Tibet, show several phases of deformation and include thick deposits of conglomerates, interbedded with sandstones and siltstones that are thought to be the result of an increased sediment flux. Dating of these gravel deposits with magnetostratigraphic and faunal studies has permitted the precise timing of the basin infilling and its tectonic evolution to be established. Our results indicate that the onset of conglomerate accumulation occurs in the Pliocene, an observation that is in agreement with those of the Linxia Basin, just east of the Plateau. If the high sedimentation rates ($22 cm/kyr) in the Guide Basin are mostly due to tectonism, then significant uplift occurred as late as Pliocene.

Climatic and tectonic controls on sedimentation and erosion during the Pliocene-Quaternary in the Qaidam Basin (China)

“…Unit 3 represents lacustrine shale and evaporite deposition in a shallow, internally drained lake basin, similar to the sedimentation occurring today within the lake depocenters (Phillips et al, 1993). Gypsum concentration increases in both bed density and within individual beds.…”

“…Both tectonic uplift and climate change can infl uence sedimentation patterns, and thus any causal interpretation of stratigraphy must account for both tectonic and climatic infl uences. Strata preserved within the Qaidam and other nearby basins in the northeastern Tibetan Plateau record tectonic and climatic changes since at least Paleocene time (Pares et al, 2003;Fang et al, 2003Fang et al, , 2007Horton et al, 2004;Zhou et al, 2006;Yin et al, 2008;Craddock et al, 2011;Zhuang et al, 2011b;H.-P. Zhang et al, 2012). Differentiating the tectonic versus climatic controls on sedimentation at any of these localities, however, is complicated by the competing infl uences of both tectonics and climate on sedimentation.…”

“…The change to a cooler (i.e., glacial or stadial) climate likely caused increased erosion, which resulted in the observed increase in sedimentation rates and grain size within many depocenters in central Asia (Métivier et al, 1999;Zhang et al, 2001). Alternatively, sedimentation rate and grain-size increases could also be caused by rapid uplift along the northern margin of the Tibet-Qinghai Plateau in the absence of precipitation changes (Sun and Liu, 2000;Zheng et al, 2000;Pares et al, 2003;Fang et al, 2007;Liu et al, 2010;Suarez et al, 2011). Orographic blocking by the Tibetan Plateau is widely regarded as the major forcing mechanism for the observed global climate change between 3.6 and 2.6 Ma (Ruddiman and Kutzbach, 1989;Raymo and Ruddiman, 1992;Hsu and Liu, 2003;Li et al, 2011;Kapp et al, 2011), although direct links between tectonic uplift and climate change remain debated (Molnar, 2005).…”

Constraints on the early uplift history of the Tibetan Plateau

“…How such high topography, which should have an effect on climate, monsoon intensity, and ocean chemistry (1)(2)(3)(4)(5), has developed through geologic time remains disputed. Various lines of investigation, including evidence from the initiation of rift basins (6), potassium-rich (K-rich) volcanism (7), tectonogeomorphic studies of fluvial systems and drainage basins (8), thermochronologic studies (9), upper-crustal deformation histories (10,11), stratigraphic and magnetostratigraphic studies of sediment accumulation rates (12), paleobotany (13), and oxygen isotope-based paleoaltimetry (14)(15)(16)(17)(18)(19)(20)(21)(22), have suggested different uplift histories. Authors of recent geologic studies (11) have proposed that significant crustal thickening (and by inference, surface uplift) in the Qiangtang terrane occurred in the Early Cretaceous [Ϸ145 mega-annum (Ma) age], followed by major crustal thickening within the Lhasa terrane between Ϸ100 and 50 Ma ago.…”

A late Mesozoic high plateau in eastern China: Evidence from basalt vesicular paleoaltimetry

“…Over the past decades, several techniques have been developed for measuring rock uplift and exhumation, such as tectonogeomorphic studies of fluvial systems and drainage basins [16], thermochronologic studies like those using apatite fission track dating [17], or (U-Th)/He thermochronology [18,19], stratigraphic and chronologic studies of erosional sediments and their accumulation rates [20], enthalpy or paleo-pCO 2 estimates based on paleoflora [21][22][23][24], and oxygen and hydrogen isotope studies of meteoric water and its proxies [25][26][27][28][29].…”