scholarly journals Lithospheric Structure of Eastern Tibetan Plateau from Terrestrial and Satellite Gravity Data Modeling: Implication for Asthenospheric Underplating

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-19
Author(s):  
Harshpal Singh ◽  
Rezene Mahatsente
Keyword(s):  
Tibetan Plateau ◽  
Gravity Models ◽  
Spatial Extent ◽  
Driving Mechanism ◽  
The Tibetan Plateau ◽  
Eastern Tibetan Plateau ◽  
The West ◽  
Lithospheric Deformation ◽  
Lithospheric Thickness ◽  
The Past

Abstract The lithosphere of the eastern Tibetan plateau is underlain by a low-velocity zone at shallow depths which is interpreted as asthenospheric material in the upper-most mantle in various seismic tomography studies. The driving mechanism for the presence of asthenospheric material in the upper-most mantle is not well understood, and the spatial extent of the asthenospheric material is not well delineated. We use 2.5D gravity models to assess what drove the asthenospheric flow upwards in the past and determine the lateral extent of the asthenospheric material in the upper-most mantle. The models also allow us to determine the Indian slab configuration below the Tibetan plateau. The gravity models show that lithospheric thickness increases from ~120 km in the central and eastern parts of the plateau to ~150 km in the west, indicating that the lithosphere in the central and eastern parts of the plateau may have been delaminated. The ~30 km shallower Lithosphere-Asthenosphere Boundary in the central and eastern Tibetan plateau may indicate that asthenospheric flow could have been induced in the past by a combination of lithospheric delamination and a slab break-off event of the Greater Indian slab. The spatial extent of the asthenospheric material in the upper-most mantle beneath the Tibetan plateau is ~15,000 km2 (N−S length=500 km and thickness=30 km) between 85°E and 88°E, which could even extend east of 92°E. The Indian slab is dipping more steeply in the east. The slab dip along the Indian plate increases from ~10° in the west to ~18° in the central (~87°E) and ~25° in the eastern part (~91°E) of the plateau, indicating that the style of lithospheric deformation changes from underthrusting to slab roll-back from west to east.

scholarly journals Fire, vegetation and Holocene climate in the south-eastern Tibetan Plateau: a multi-biomarker reconstruction from Paru Co

2018 ◽  
Author(s):  
Alice Callegaro ◽  
Felipe Matsubara Pereira ◽  
Dario Battistel ◽  
Natalie M. Kehrwald ◽  
Broxton W. Bird ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Biomass Burning ◽  
Fire History ◽  
Vegetation Changes ◽  
The Tibetan Plateau ◽  
Eastern Tibetan Plateau ◽  
The South ◽  
South Eastern ◽  
The Past ◽  
High Concentrations

Abstract. The fire history of the Tibetan Plateau over centennial to millennial timescales is still unknown. Recent ice core studies reconstruct fire history over the past few decades but do not extend through the Holocene. Lacustrine sedimentary cores, however, provide continuous records of large-scale and local environmental modifications due to their accumulation of specific organic molecular markers throughout the past millennia. In order to reconstruct Holocene fire events and vegetation changes occurring on the south-eastern Tibetan Plateau and the surrounding areas, we improved and integrated previous analytical methods. The multi-proxy procedure was applied to samples retrieved from Paru Co, a small lake located in the Nyainqentanglha Mountains (29°47'45.6" N; 92°21'07.2" E; 4845 m a.s.l.). The investigated biomarkers include n-alkanes as indicators of vegetation, polycyclic aromatic hydrocarbons (PAHs) as combustion proxies, faecal sterols and stanols (FeSts) as indicators of the presence of humans or grazing animals and finally monosaccharide anhydrides (MAs) as specific markers of vegetation burning processes. Relatively high concentrations of both MAs and PAHs demonstrate intense local biomass burning activity during the early Holocene (10.9–10.7 cal ky BP), which correspond to a drier climate following deglaciation. High concentrations of MAs but not PAHs between 10.7–9 cal ky BP suggest a period of regional biomass burning followed by a decreasing fire trend through the mid-late Holocene. This fire history is consistent with local vegetation changes reconstructed from both n-alkanes and regional pollen records, where vegetation types depend on the centennial-scale intensity of monsoon precipitation. FeSts were below detection limits for most of the samples, suggesting limited direct human influences on fire regime and vegetation changes in the lake's catchment. Climate is the main influence on fire activity recorded in Paru Co over millennial timescales, where biomass burning fluctuates in response to alternating warm/humid and cool/dry periods.

Paleolake salinity evolution in the Qaidam Basin (NE Tibetan Plateau) between ~42 and 29 Ma: Links to global cooling and Paratethys sea incursions

2021 ◽  
Author(s):  
Chengcheng Ye ◽  
Yibo Yang ◽  
Xiaomin Fang ◽  
Weilin Zhang ◽  
Chunhui Song ◽  
...  
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Middle Eocene ◽  
Qaidam Basin ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Driving Mechanism ◽  
The Tibetan Plateau ◽  
Early Oligocene ◽  
Global Cooling

<p>Global cooling, the early uplift of the Tibetan Plateau, and the retreat of the Paratethys are three main factors that regulate long-term climate change in the Asian interior during the Cenozoic. However, the debated elevation history of the Tibetan Plateau and the overlapping climate effects of the Tibetan Plateau uplift and Paratethys retreat makes it difficult to assess the driving mechanism on regional climate change in a particular period. Some recent progress suggests that precisely dated Paratethys transgression/regression cycles appear to have fluctuated over broad regions with low relief in the northern Tibetan Plateau in the middle Eocene–early Oligocene, when the global climate was characterized by generally continuous cooling followed by the rapid Eocene–Oligocene climate transition (EOT). Therefore, a middle Eocene–early Oligocene record from the Asian interior with unambiguous paleoclimatic implications offers an opportunity to distinguish between the climatic effects of the Paratethys retreat and those of global cooling.</p><p>Here, we present a complete paleolake salinity record from middle Eocene to early Miocene (~42-29 Ma) in the Qaidam Basin using detailed clay boron content and clay mineralogical investigations. Two independent paleosalimeters, equivalent boron and Couch’s salinity, collectively present a three-staged salinity evolution, from an oligohaline–mesohaline environment in the middle Eocene (42-~34 Ma) to a mesosaline environment in late Eocene-early Oligocene (~34-~29 Ma). This clay boron-derived salinity evolution is further supported by the published chloride-based and ostracod-based paleosalinity estimates in the Qaidam Basin. Our quantitative paleolake reconstruction between ~42 and 29 Ma in the Qaidam Basin resembles the hydroclimate change in the neighboring Xining Basin, of which both present good agreement with changes of marine benthic oxygen isotope compositions. We thus speculated that the secular trend of clay boron-derived paleolake salinity in ~42-29 Ma is primarily controlled by global cooling, which regulates regional climate change by influencing the evaporation capacity in the moisture source of Qaidam Basin. Superimposed on this trend, the Paratethys transgression/regression cycles served as an important factor regulating wet/dry fluctuations in the Asian interior between ~42 and ~34 Ma.</p>

Extremes in the magnitude of annual temperature cycle on the Tibetan Plateau over the past three centuries

2018 ◽  
Vol 52 (5-6) ◽  
pp. 3599-3608 ◽  
Author(s):  
Jianping Duan ◽  
Zhuguo Ma ◽  
Naiming Yuan ◽  
Lun Li ◽  
Liang Chen
Keyword(s):  
Tibetan Plateau ◽  
Temperature Cycle ◽  
The Tibetan Plateau ◽  
The Past ◽  
Annual Temperature Cycle

Melting Ice Rivers

2012 ◽  
Author(s):  
Cheryl Colopy
Keyword(s):  
Global Warming ◽  
Tibetan Plateau ◽  
The Netherlands ◽  
Sea Level ◽  
The Tibetan Plateau ◽  
Mount Everest ◽  
The Past ◽  
The North ◽  
The World ◽  
The Government

From a remote outpost of global warming, a summons crackles over a two-way radio several times a week: . . . Kathmandu, Tsho Rolpa! Babar Mahal, Tsho Rolpa! Kathmandu, Tsho Rolpa! Babar Mahal, Tsho Rolpa! . . . In a little brick building on the lip of a frigid gray lake fifteen thousand feet above sea level, Ram Bahadur Khadka tries to rouse someone at Nepal’s Department of Hydrology and Meteorology in the Babar Mahal district of Kathmandu far below. When he finally succeeds and a voice crackles back to him, he reads off a series of measurements: lake levels, amounts of precipitation. A father and a farmer, Ram Bahadur is up here at this frigid outpost because the world is getting warmer. He and two colleagues rotate duty; usually two of them live here at any given time, in unkempt bachelor quarters near the roof of the world. Mount Everest is three valleys to the east, only about twenty miles as the crow flies. The Tibetan plateau is just over the mountains to the north. The men stay for four months at a stretch before walking down several days to reach a road and board a bus to go home and visit their families. For the past six years each has received five thousand rupees per month from the government—about $70—for his labors. The cold, murky lake some fifty yards away from the post used to be solid ice. Called Tsho Rolpa, it’s at the bottom of the Trakarding Glacier on the border between Tibet and Nepal. The Trakarding has been receding since at least 1960, leaving the lake at its foot. It’s retreating about 200 feet each year. Tsho Rolpa was once just a pond atop the glacier. Now it’s half a kilometer wide and three and a half kilometers long; upward of a hundred million cubic meters of icy water are trapped behind a heap of rock the glacier deposited as it flowed down and then retreated. The Netherlands helped Nepal carve out a trench through that heap of rock to allow some of the lake’s water to drain into the Rolwaling River.

scholarly journals Time‐dependent warming amplification over the Tibetan Plateau during the past few decades

2020 ◽  
Vol 21 (10) ◽  
Author(s):  
Jianping Duan ◽  
Lun Li ◽  
Liang Chen ◽  
Haoxin Zhang
Keyword(s):  
Tibetan Plateau ◽  
Time Dependent ◽  
The Tibetan Plateau ◽  
The Past
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