Carbonate stable and clumped isotopic evidence for late Eocene moderate to high elevation of the east-central Tibetan Plateau and its geodynamic implications

2018 ◽  
Vol 131 (5-6) ◽  
pp. 831-844 ◽  
Author(s):  
Lin Li ◽  
Majie Fan ◽  
Nathaniel Davila ◽  
Greg Jesmok ◽  
Bryce Mitsunaga ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
High Elevation ◽  
Late Eocene ◽  
East Central ◽  
Isotopic Evidence ◽  
Central Tibetan Plateau

scholarly journals Seasonal variation of secondary organic aerosol tracers in Central Tibetan Plateau

2015 ◽  
Vol 15 (15) ◽  
pp. 8781-8793 ◽  
Author(s):  
R.-Q. Shen ◽  
X. Ding ◽  
Q.-F. He ◽  
Z.-Y. Cong ◽  
Q.-Q. Yu ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Tibetan Plateau ◽  
Temperature Effect ◽  
Secondary Organic Aerosol ◽  
Global Climate ◽  
Organic Aerosol ◽  
High Elevation ◽  
Isoprene Emission ◽  
Central Tibetan Plateau ◽  
Dominant Process

Abstract. Secondary organic aerosol (SOA) affects the earth's radiation balance and global climate. High-elevation areas are sensitive to global climate change. However, at present, SOA origins and seasonal variations are understudied in remote high-elevation areas. In this study, particulate samples were collected from July 2012 to July 2013 at the remote Nam Co (NC) site, Central Tibetan Plateau and analyzed for SOA tracers from biogenic (isoprene, monoterpenes and β-caryophyllene) and anthropogenic (aromatics) precursors. Among these compounds, isoprene SOA (SOAI) tracers represented the majority (26.6 ± 44.2 ng m−3), followed by monoterpene SOA (SOAM) tracers (0.97 ± 0.57 ng m−3), aromatic SOA (SOAA) tracer (2,3-dihydroxy-4-oxopentanoic acid, DHOPA, 0.25 ± 0.18 ng m−3) and β-caryophyllene SOA tracer (β-caryophyllenic acid, 0.09 ± 0.10 ng m−3). SOAI tracers exhibited high concentrations in the summer and low levels in the winter. The similar temperature dependence of SOAI tracers and isoprene emission suggested that the seasonal variation of SOAI tracers at the NC site was mainly influenced by the isoprene emission. The ratio of high-NOx to low-NOx products of SOAI (2-methylglyceric acid to 2-methyltetrols) was highest in the winter and lowest in the summer, due to the influence of temperature and relative humidity. The seasonal variation of SOAM tracers was impacted by monoterpenes emission and gas-particle partitioning. During the summer to the fall, temperature effect on partitioning was the dominant process influencing SOAM tracers' variation; while the temperature effect on emission was the dominant process influencing SOAM tracers' variation during the winter to the spring. SOAM tracer levels did not elevate with increased temperature in the summer, probably resulting from the counteraction of temperature effects on emission and partitioning. The concentrations of DHOPA were 1–2 orders of magnitude lower than those reported in the urban regions of the world. Due to the transport of air pollutants from the adjacent Bangladesh and northeastern India, DHOPA presented relatively higher levels in the summer. In the winter when air masses mainly came from northwestern India, mass fractions of DHOPA in total tracers increased, although its concentrations declined. The SOA-tracer method was applied to estimate secondary organic carbon (SOC) from these four precursors. The annual average of SOC was 0.22 ± 0.29 μgC m−3, with the biogenic SOC (sum of isoprene, monoterpenes and β-caryophyllene) accounting for 75 %. In the summer, isoprene was the major precursor with its SOC contributions of 81 %. In the winter when the emission of biogenic precursors largely dropped, the contributions of aromatic SOC increased. Our study implies that anthropogenic pollutants emitted in the Indian subcontinent could be transported to the TP and have an impact on SOC over the remote NC.

scholarly journals Dating Human Settlement in the East-Central Tibetan Plateau during the Late Holocene

Radiocarbon ◽  
2017 ◽  
Vol 60 (1) ◽  
pp. 137-150 ◽  
Author(s):  
LeLe Ren ◽  
GuangHui Dong ◽  
HaiMing Li ◽  
Dave Rhode ◽  
Rowan K. Flad ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Late Holocene ◽  
Archaeological Sites ◽  
Multidisciplinary Research ◽  
East Central ◽  
Prehistoric Agriculture ◽  
Northern Tibetan Plateau ◽  
Central Tibetan Plateau ◽  
Animal Bones ◽  
Dating Method

AbstractRecent multidisciplinary research indicates that prehistoric agriculture innovation promoted permanent human settlements of areas up to 3400 m above sea level (asl) in the northern Tibetan Plateau, but when and how ancient humans extensively occupied areas above that altitude remains uncertain. In this paper, we investigated 12 archaeological sites situated above 3600 m asl in the Yushu autonomous prefecture, east-central Tibetan Plateau, to explore this issue. We determined the ages of five sites using the radiocarbon (14C) dating method and identified animal bones sampled from three sites. The dating results show that humans occasionally occupied the Yushu area around 900 BC, and permanently inhabited the area between AD 540 and 1620. Preliminary faunal identifications indicate human-raised livestock including yak, sheep, and horse during the latter period. Stone-constructed tombs and rock painting were found at some investigated sites, suggesting humans perhaps engaged in a pastoral lifestyle during the very late Holocene in the high altitude Yushu area, where nomadic livestock production remains the current primary subsistence strategy focus.

scholarly journals Aridification signatures from fossil pollen indicate a drying climate in east-central Tibet during the late Eocene

2020 ◽  
Vol 16 (6) ◽  
pp. 2255-2273
Author(s):  
Qin Yuan ◽  
Natasha Barbolini ◽  
Catarina Rydin ◽  
Dong-Lin Gao ◽  
Hai-Cheng Wei ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Central Asia ◽  
Late Eocene ◽  
Western China ◽  
Desert Ecosystem ◽  
Temporary Increase ◽  
The Tibetan Plateau ◽  
East Central ◽  
History Of ◽  
Central Tibet

Abstract. Central Asia experienced a number of significant elevational and climatic changes during the Cenozoic, but much remains to be understood regarding the timing and driving mechanisms of these changes as well as their influence on ancient ecosystems. Here, we describe the palaeoecology and palaeoclimate of a new section from the Nangqian Basin in Tibet, north-western China, dated as Bartonian (41.2–37.8 Ma; late Eocene) based on our palynological analyses. Located on the east-central part of what is today the Tibetan Plateau, this section is excellently placed for better understanding the palaeoecological history of Tibet following the Indo-Asian collision. Our new palynological record reveals that a strongly seasonal steppe–desert ecosystem characterized by drought-tolerant shrubs, diverse ferns, and an underlying component of broad-leaved forests existed in east-central Tibet during the Eocene, influenced by a southern monsoon. A transient warming event, possibly the middle Eocene climatic optimum (MECO; 40 Ma), is reflected in our record by a temporary increase in regional tropical taxa and a concurrent decrease in steppe–desert vegetation. In the late Eocene, a drying signature in the palynological record is linked to proto-Paratethys Sea retreat, which caused widespread long-term aridification across the region. To better distinguish between local climatic variation and farther-reaching drivers of Central Asian palaeoclimate and elevation, we correlated key palynological sections across the Tibetan Plateau by means of established radioisotopic ages and biostratigraphy. This new palynozonation illustrates both intra- and inter-basinal floral response to Qinghai–Tibetan uplift and global climate change during the Paleogene, and it provides a framework for the age assignment of future palynological studies in Central Asia. Our work highlights the ongoing challenge of integrating various deep time records for the purpose of reconstructing palaeoelevation, indicating that a multi-proxy approach is vital for unravelling the complex uplift history of Tibet and its resulting influence on Asian climate.

scholarly journals Aridification signatures from middle–late Eocene pollen indicate widespread drying across the Tibetan Plateau after 40 Ma

2020 ◽  
Author(s):  
Qin Yuan ◽  
Natasha Barbolini ◽  
Catarina Rydin ◽  
Dong-Lin Gao ◽  
Hai-Cheng Wei ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Central Asia ◽  
Middle Eocene ◽  
Global Climate ◽  
Late Eocene ◽  
Desert Ecosystem ◽  
The Tibetan Plateau ◽  
Pollen Record ◽  
East Central ◽  
History Of

Abstract. Central Asia experienced a number of significant elevational and climatic changes during the Cenozoic, but much remains to be understood regarding the timing and driving mechanisms of these changes, as well as their influence on ancient ecosystems. Here we describe the palaeoecology and palaeoclimate of a new section from the Nangqian Basin in Tibet, northwestern China, here dated as late Lutetian–Bartonian (late middle–late Eocene) based on our palynological analyses. Located on the east-central part of the Tibetan Plateau, this section is excellently placed for better understanding the palaeoecological history of Tibet following the India-Asia collision. Our new pollen record reveals that a strongly seasonal steppe-desert ecosystem characterised by drought-tolerant shrubs, diverse ferns and an underlying component of broad-leaved forests existed in east-central Tibet during the Eocene, influenced by a southern monsoon. Warming during the Middle Eocene Climatic Optimum only prompted a temporary vegetation response, while a drying signature in our pollen record after 40 Ma demonstrates that proto-Paratethys sea retreat caused widespread long-term aridification across the plateau. To better distinguish between local climatic variation and farther-reaching drivers of Central Asian palaeoclimate and elevation, we correlated key palynological sections across the Tibetan Plateau by means of established radioisotopic ages and biostratigraphy. This new palynozonation illustrates both intra- and inter-basinal floral response to plateau uplift and global climate change during the Paleogene, and provides a framework for the age assignment of future palynological studies in Central Asia. Our work highlights the ongoing challenge of integrating various deep time records for the purpose of reconstructing palaeoelevation, indicating that a multiproxy approach is vital for unravelling the complex uplift history of the Tibetan Plateau and its resulting influence on Asian climate.

scholarly journals Seasonal variation of secondary organic aerosol in Nam Co, Central Tibetan Plateau

2015 ◽  
Vol 15 (5) ◽  
pp. 7141-7169 ◽  
Author(s):  
R.-Q. Shen ◽  
X. Ding ◽  
Q.-F. He ◽  
Z.-Y. Cong ◽  
Q.-Q. Yu ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Tibetan Plateau ◽  
Temperature Dependence ◽  
Global Climate ◽  
Organic Aerosol ◽  
High Elevation ◽  
Nam Co ◽  
Central Tibetan Plateau ◽  
Similar Temperature Dependence ◽  
Similar Temperature

Abstract. Secondary organic aerosol (SOA) affects the earth's radiation balance and global climate. High-elevation areas are sensitive to global climate change. However, at present, SOA origins and seasonal variations are understudied in remote high-elevation areas. In this study, particulate samples were collected from July 2012 to July 2013 at the remote Nam Co (NC) site, Central Tibetan Plateau and analyzed for SOA tracers from biogenic (isoprene, monoterpenes and β-caryophyllene) and anthropogenic (aromatics) precursors. Among these compounds, isoprene SOA (SOAI) tracers represented the majority (26.6 ± 44.2 ng m−3), followed by monoterpene SOA (SOAM) tracers (0.97 ± 0.57 ng m−3), aromatic SOA (SOAA) tracer (2,3-dihydroxy-4-oxopentanoic acid, DHOPA, 0.25 ± 0.18 ng m−3) and β-caryophyllene SOA tracer (β-caryophyllenic acid, 0.09 ± 0.10 ng m−3). SOAI tracers exhibited high concentrations in the summer and low levels in the winter. The similar temperature dependence of SOAI tracers and isoprene emission suggested that the seasonal variation of SOAI at the NC site was mainly influenced by isoprene emission. The ratio of high-NOx to low-NOx products of isoprene (2-methylglyceric acid to 2-methyltetrols) was the highest in the winter and the lowest in the summer, due to the influence of temperature and relative humidity. The seasonal variation of SOAM tracers was impacted by monoterpenes emission and tracers partitioning. The similar temperature dependence of SOAM tracers and monoterpenes emission was only observed during winter to spring. SOAM tracer levels did not elevate with increased temperature in the summer, probably resulting from the counteraction of temperature effects on gas/particle partitioning and monoterpenes emission. The concentrations of DHOPA were 1–2 orders of magnitude lower than those reported in the urban regions of the world. Due to the transport of air pollutants from the adjacent Bangladesh and the eastern India, DHOPA presented relatively higher levels in the summer. In the winter when air masses mainly came from the northwestern India, mass fractions of DHOPA in total tracers increased, although its concentrations declined. The SOA-tracer method was applied to estimated secondary organic carbon (SOC) from these four precursors. The annual average of SOC was 0.22 ± 0.29 μg C m−3, with the biogenic SOC (sum of isoprene, monoterpenes and β-caryophyllene) accounting for 75%. In the summer, isoprene was the major precursor with its SOC contributions of 81%. In the winter when the emission of biogenic precursors largely dropped, the contributions of aromatic SOC increased. Our study implies that anthropogenic pollutants emitted in the Indian subcontinent could transport to the TP and have impact on SOC over the remote NC.

Late Eocene two-pyroxene trachydacites from the southern Qiangtang Terrane, central Tibetan Plateau: High-temperature melting of overthickened and dehydrated lower crust

2021 ◽  
Author(s):  
Yun-Chuan Zeng ◽  
Ji-Feng Xu ◽  
Ming-Jian Li ◽  
Jian-Lin Chen ◽  
Bao-Di Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Tibetan Plateau ◽  
Thermal State ◽  
Middle Eocene ◽  
Volcanic Rocks ◽  
Late Eocene ◽  
Integrated Analysis ◽  
Central Tibetan Plateau ◽  
Anhydrous Mineral ◽  
Qiangtang Terrane

Abstract Orthopyroxene-bearing granitic rock (e.g., charnockite) is relatively rare but provides an excellent opportunity to probe the thermal and tectonic evolution of deep orogenic crust because of its distinct mineral assemblage. Here we present petrological, mineralogical, elemental, and Sr–Nd–Hf–O isotopic data for late Eocene (ca. 36 Ma; zircon U–Pb ages) volcanic rocks exposed in the Ejiu region in the southern Qiangtang Terrane to investigate how the central Tibetan crust evolved to its modern thickness and thermal state. The Ejiu volcanic rocks (EVRs) are trachydacites with anhydrous mineral assemblages (i.e., two pyroxenes, sanidine, plagioclase, and ilmenite, without amphibole and biotite) and geochemical characteristics (e.g., high P2O5 and TiO2) that resemble those of charnockite-type magmatic rocks. Mineral and whole-rock thermometry and hygrometry suggests that the parent magma crystallized under hot (~1000 °C) and dry (H2O < 2 wt.%) condition. Besides, the EVRs display adakitic affinities according to their high SiO2 and Al2O3 contents, high Sr/Y, La/Yb, and Gd/Yb ratios, and low Y and Yb contents, without marked negative Eu anomalies. The calculated melts in equilibrium with pyroxenes also display adakitic compositions (e.g., high Sr/Y and La/Yb ratios), indicating that the adakitic compositions of the EVRs did not result from late-stage magmatic evolution. In addition, the melts of the EVRs were saturated in TiO2, as inferred from the high TiO2 contents of these rocks and the presence of ilmenite. An integrated analysis of the geochemical, petrological, and mineralogical data suggests that the EVRs were neither evolutional products nor partial melts of hydrous mafic materials at normal crustal pressures, but were formed by fusion of an eclogitized mafic protolith with residue containing garnet and rutile but lacking amphibole and plagioclase. The whole-rock Sr–Nd and zircon Hf isotope compositions of the EVRs [(87Sr/86Sr)i = 0.7053 to 0.7066; εNd(t) = −1.40 to −0.99; zircon εHf(t) = +1.08 to +5.31] indicate that the parental protolith was relatively juvenile in nature, but also contained some supracrustal materials given the high zircon δ18O values [zircon δ18O = +8.21‰ to +11.00‰]. The above arguments lead us to propose that of partial melting of a previously dehydrated—but chemically undepleted—mafic lower continental crust at high pressure (>1.5 GPa) and high temperature (>1000 °C) generated the EVRs. Based on a synthesis of independent geological and geophysical data, we further suggest that the southern Qiangtang Terrane crust of the central Tibetan Plateau was thick, dry, and elevated during the Late Cretaceous to early Eocene time, and that it became abnormally hot owing to the ascending asthenosphere after lithospheric foundering during the middle Eocene.

Role of late glacial to mid-Holocene climate in catchment weathering in the central Tibetan Plateau

2005 ◽  
Vol 63 (2) ◽  
pp. 161-170 ◽  
Author(s):  
Zhang-Dong Jin ◽  
Yanhong Wu ◽  
Xiaohui Zhang ◽  
Sumin Wang
Keyword(s):  
Tibetan Plateau ◽  
Chemical Weathering ◽  
Late Glacial ◽  
High Elevation ◽  
Climatic Conditions ◽  
Central Plateau ◽  
The Holocene ◽  
Physical Weathering ◽  
Central Tibetan Plateau ◽  
Weathering Intensity

The lightness (L*) and concentrations of Rb, Sr and organic carbon (Corg) have been measured in the age-constrained lake sediment cores recovered from Co Ngoin in the central Tibetan Plateau. Dissolved Sr flux is a dominant control on the variation of Rb/Sr ratios in the sediments. Variations in color and geochemical proxies of Co Ngoin sediments display a continuous history of late glacial to mid-Holocene chemical versus physical weathering intensity in response to past climatic changes between approximately 13,500 and 4500 cal yr B.P. A lower chemical weathering under a late glacial climate was followed by a higher weathering during the Holocene Optimum. Weathering intensity in the central Tibetan Plateau catchment also responds to well-known climatic events, such as the Younger Dryas (YD), and possibly the Holocene Event 5 (HE-5). Although there are differences in time or duration of the climatic events, many of the well-known late glacial to mid-Holocene events occurred in high-elevation Co Ngoin where atmospheric circulation might play a hemispherical role in climatic forcing. The sediment hiatus since c. 4200 14C yr B.P. in the Co Ngoin indicates a period of desiccation that was probably associated with a sharp decrease in summer monsoon strength. Our lascustrine results not only imply catchment weathering variations in response to late glacial to mid-Holocene climatic conditions in the central plateau, but also provide further evidence for global connections between regional climates.

Models and measurements of seven years of evapotranspiration on a high elevation site on the Central Tibetan Plateau

2020 ◽  
Vol 17 (12) ◽  
pp. 3039-3053
Author(s):  
Li-hui Wang ◽  
Xiao-bo He ◽  
Jakob F. Steiner ◽  
Dong-wei Zhang ◽  
Jin-kui Wu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
High Elevation ◽  
High Elevation Site ◽  
Central Tibetan Plateau
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