scholarly journals Contrasting exhumation histories and relief development within the Three Rivers Region (south-east Tibet)

Solid Earth ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 563-580
Author(s):  
Xiong Ou ◽  
Anne Replumaz ◽  
Peter van der Beek
Keyword(s):  
High Elevation ◽  
Mekong River ◽  
The West ◽  
Surface Modelling ◽  
The Core ◽  
River Incision ◽  
Three Rivers Region ◽  
Eastern Tibet ◽  
Three Rivers ◽  
Moderate Elevation

Abstract. The Three Rivers Region in south-east Tibet represents a transition between the strongly deformed zone around the Eastern Himalayan Syntaxis (EHS) and the less deformed south-east Tibetan Plateau margin in Yunnan and Sichuan. In this study, we compile and model published thermochronometric ages for two massifs facing each other across the Mekong River in the core of the Three Rivers Region (TRR), using the thermo-kinematic code Pecube to constrain their exhumation and relief history. Modelling results for the low-relief (< 600 m), moderate-elevation (∼ 4500 m) Baima Xueshan massif, east of the Mekong River, suggest regional rock uplift at a rate of 0.25 km/Myr since ∼ 10 Ma, following slow exhumation at a rate of 0.01 km/Myr since at least 22 Ma. Estimated Mekong River incision accounts for 30 % of the total exhumation since 10 Ma. We interpret exhumation of the massif as a response to regional uplift around the EHS and conclude that the low relief of the massif was acquired at high elevation (> 4500 m), probably in part due to glacial “buzzsaw-like” processes active at such high elevation and particularly efficient during Quaternary glaciations. Exhumation of the Baima Xueshan is significantly higher (2.5 km since ∼ 10 Ma) than that estimated for the most emblematic low-relief “relict” surfaces of eastern Tibet, where apatite (U–Th) / He (AHe) ages > 50 Ma imply only a few hundreds of metres of exhumation since the onset of the India–Asia collision. The low-relief Baima Xueshan massif, with its younger AHe ages (< 50 Ma) that record significant rock uplift and exhumation, thus cannot be classified as a relict surface. Modelling results for the high-relief, high-elevation Kawagebo massif, to the west of the Mekong, imply a similar contribution of Mekong River incision (25 %) to exhumation but much stronger local rock uplift at a rate of 0.45 km/Myr since at least 10 Ma, accelerating to 1.86 km/Myr since 1.6 Ma. We show that the thermochronometric ages are best reproduced by a model of rock uplift on a kinked westward-dipping thrust striking roughly parallel to the Mekong River, with a steep shallow segment flattening out at depth. Thus, the strong differences in elevation and relief of two massifs are linked to variable exhumation histories due to strongly differing tectonic imprint.

scholarly journals Contrasting exhumation histories and relief development within the Three Rivers Region (Southeast Tibet)

2020 ◽  
Author(s):  
Xiong Ou ◽  
Anne Replumaz ◽  
Peter van der Beek
Keyword(s):  
Mekong River ◽  
Development History ◽  
The Core ◽  
River Incision ◽  
Three Rivers Region ◽  
Eastern Tibet ◽  
Southeast Tibet ◽  
Three Rivers ◽  
Eastern Himalayan Syntaxis ◽  
Southeast Tibetan Plateau

Abstract. The Three Rivers Region in Southeast Tibet represents a transition between the strongly deformed zone around Eastern Himalayan Syntaxis and the less deformed southeast Tibetan plateau margin in Yunnan and Sichuan. In this study, we compile and model published thermochronologic ages for two massifs facing each other across the Mekong River in the core of the Three Rivers Region, by using the thermo-kinematic code Pecube to constrain their exhumation and relief development history. Modelling results for the low-relief, mean-elevation BaimaXueshan massif, east of the Mekong River, suggest regional rock uplift at a rate of 0.25 km/Myr since ~ 10 Ma, following slow exhumation at a rate of 0.01 km/Myr since at least 22 Ma. River incision accounts for only 15 % of the total exhumation in the BaimaXueshan. Exhumation since ~ 10 Ma is significantly higher (2.5 km) than that estimated (~ 0.23 km) for the most emblematic low-relief or relict surfaces of Eastern Tibet, which are characterized by apatite (U-Th)/He ages older than the collision age (> 50 Ma). We conclude that the BaimaXueshan massif, which shows younger ages (

scholarly journals Contrasting exhumation histories and relief development within the Three Rivers Region (Southeast Tibet)

2021 ◽  
Author(s):  
Xiong Ou ◽  
Anne Replumaz ◽  
Peter van der Beek
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
High Elevation ◽  
Mekong River ◽  
The Tibetan Plateau ◽  
River Incision ◽  
Three Rivers Region ◽  
Southeast Tibet ◽  
Three Rivers ◽  
Eastern Himalayan Syntaxis

&lt;p&gt;The Southeast Tibet is characterized by extensive low-relief high-elevation surfaces that have been interpreted as &amp;#8220;relict surfaces&amp;#8221;, where thermochronological data generally show old ages and very little exhumation during the India-Asia collision. Those relict surfaces are proposed either to be formed at low elevation and then uplifted and dissected by large rivers since middle Miocene, or to inherit a pre-existing low-relief landscape by or prior to the collision, as revealed by stable-isotope paleoaltimetry. Among these relict surfaces, the BaimaXueshan low-relief (&lt;600 m), moderate-elevation (~4500 m) massif is the closest to the Eastern Himalayan Syntaxis (EHS) in the Three Rivers Region, where Salween, Mekong and Yangtze rivers flow southward parallelly and closely, showing large-scale shortening during the collision.This region represents a transition between the strongly deformed zone around EHS and the less deformed southeast Tibetan plateau margin in Yunnan and Sichuan, and is an appropriate zone to examine the relief development and the interaction between pre-existing structures, Cenozoic tectonics and river incision during the Tibetan plateau growth.&lt;/p&gt;&lt;p&gt;We compile and model published thermochronometric ages for BaimaXueshan massif, east of the Mekong River, to constrain its exhumation and relief history using the thermo-kinematic code Pecube. Modelling results show regional rock uplift at a rate of 0.25 km/Myr since ~10 Ma, following slow exhumation at a rate of 0.01 km/Myr since at least 22 Ma. Estimated Mekong River incision accounts for a maximum of 30% of the total exhumation since 10 Ma. We interpret moderate exhumation of the BaimaXueshan massif since 10 Ma as a response to a regional uplift due to the continuous northward indentation of NE India in a zone around the Eastern Himalayan Syntaxis (EHS) and delimited by Longmucuo-Shuanghu suture in the north. Thus BaimaXueshan massif with significant exhumation could not be classified as &amp;#8220;relict surface&amp;#8221;, as proposed by previous studies and its low relief results from in part glacial &amp;#8220;buzzsaw-like&amp;#8221; processes at high elevation, enhancing since ~2 Ma. In contrast, modelling results for the high-relief, high-elevation Kawagebo massif to the west of the Mekong River, facing the BaimaXueshan massif, imply a similar contribution of Mekong River incision (25%) to exhumation, but much stronger local rock uplift at a rate of 0.45 km/Myr since at least 10 Ma, accelerating to 1.86 km/Myr since 1.6 Ma. We show that the thermochronometric ages are best reproduced by local rock uplift related to late Miocene reactivation of a kinked westward-dipping thrust, striking roughly parallel to the Mekong River, with a steep shallow segment flattening out at depth. Thus, the strong differences in elevation and relief that characterize both massifs are linked to variable exhumation histories due to a strongly differing tectonic imprint.&amp;#160;&lt;/p&gt;

scholarly journals Southwestward growth of plateau surfaces in eastern Tibet

2020 ◽  
Author(s):  
Kai Cao ◽  
Anne Replumaz ◽  
Yuntao Tian ◽  
Laurent Husson ◽  
Guo-can Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
High Elevation ◽  
Tectonic Activity ◽  
Kinematics And Dynamics ◽  
The Tibetan Plateau ◽  
Slow Cooling ◽  
River Incision ◽  
Eastern Tibet ◽  
Lower Crustal ◽  
Transcurrent Faults

Abstract Both the kinematics and dynamics for topographic growth of the Tibetan Plateau remain debated despite their significance for understanding the evolution of continental lithospheric geodynamics, climate, and biodiversity in Asia. Morphometric analysis reveals the continuity of high-elevated peneplains through the Songpan-Garze-Yidun, Qiangtang and Lhasa terranes in eastern Tibet. Inverse thermal-history modeling of thermochronological data indicates slow cooling of these terranes since 80-60 Ma, 40-35 Ma and 20-5 Ma, respectively, which is interpreted as marking tectonic and topographic stabilization of the plateau surfaces. The diachronous stabilization of flat plateau surfaces and early encroachment suggests decoupling of plateau surface formation from Neogene river incision and tectonics. This southwestward piecemeal expansion of small plateaus suggests that the high-elevation, low-relief landscape of eastern Tibet has been constructed during distinct orogenic episodes prior and during the early stages of India-Asia collision. A late stage of tectonic activity during Neogene only moderately remodeled the outer rims of the plateaus and the valleys that delineate the transcurrent faults, while lower crustal channel flow only leveled the distinct plateaus to a unique elevation, thereby triggering river incision in eastern Tibet.

Chemical weathering in the Three Rivers region of Eastern Tibet

2009 ◽  
Vol 73 (7) ◽  
pp. 1857-1877 ◽  
Author(s):  
Hyonjeong Noh ◽  
Youngsook Huh ◽  
Jianhua Qin ◽  
Andre Ellis
Keyword(s):  
Chemical Weathering ◽  
Three Rivers Region ◽  
Eastern Tibet ◽  
Three Rivers

scholarly journals Palaeomagnetic study of eastern Tibet-deformation of the Three Rivers region

1990 ◽  
Vol 103 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Y. Otofuji ◽  
Y. Inoue ◽  
S. Funahara ◽  
F. Murata ◽  
X. Zheng
Keyword(s):  
Three Rivers Region ◽  
Eastern Tibet ◽  
Three Rivers

Managing rivers for conservation and ecotourism in the Kruger National Park

1995 ◽  
Vol 32 (5-6) ◽  
pp. 227-233 ◽  
Author(s):  
F. J. Venter ◽  
A. R. Deacon
Keyword(s):  
National Park ◽  
Good Condition ◽  
Kruger National Park ◽  
Rapid Expansion ◽  
Natural Environments ◽  
The West ◽  
The Past ◽  
Management Actions ◽  
Flow Through ◽  
Three Rivers

Six major rivers flow through the Kruger National Park (KNP). All these rivers originate outside and to the west of the KNP and are highly utilized. They are crucially important for the conservation of the unique natural environments of the KNP. The human population growth in the Lowveld during the past two decades brought with it the rapid expansion of irrigation farming, exotic afforestation and land grazed by domestic stock, as well as the establishment of large towns, mines, dams and industries. Along with these developments came overgrazing, erosion, over-utilization and pollution of rivers, as well as clearing of indigenous forests from large areas outside the borders of the KNP. Over-utilization of the rivers which ultimately flow through the KNP poses one of the most serious challenges to the KNP's management. This paper gives the background to the development in the catchments and highlights the problems which these have caused for the KNP. Management actions which have been taken as well as their results are discussed and solutions to certain problems proposed. Three rivers, namely the Letaba, Olifants and Sabie are respectively described as examples of an over-utilized river, a polluted river and a river which is still in a fairly good condition.

scholarly journals Environmental justice, settler colonialism, and more-than-humans in the occupied West Bank: An introduction

2021 ◽  
Vol 4 (1) ◽  
pp. 3-27
Author(s):  
Irus Braverman
Keyword(s):  
United States ◽  
Environmental Justice ◽  
West Bank ◽  
Settler Colonialism ◽  
The United States ◽  
Special Issue ◽  
The West ◽  
The Core ◽  
Waste Concrete

Our special issue provides a first-of-its kind attempt to examine environmental injustices in the occupied West Bank through interdisciplinary perspectives, pointing to the broader settler colonial and neoliberal contexts within which they occur and to their more-than-human implications. Specifically, we seek to understand what environmental justice—a movement originating from, and rooted in, the United States—means in the context of Palestine/Israel. Moving beyond the settler-native dialectic, we draw attention to the more-than-human flows that occur in the region—which include water, air, waste, cement, trees, donkeys, watermelons, and insects—to consider the dynamic, and often gradational, meanings of frontier, enclosure, and Indigeneity in the West Bank, challenging the all-too-binary assumptions at the core of settler colonialism. Against the backdrop of the settler colonial project of territorial dispossession and elimination, we illuminate the infrastructural connections and disruptions among lives and matter in the West Bank, interpreting these through the lens of environmental justice. We finally ask what forms of ecological decolonization might emerge from this landscape of accumulating waste, concrete, and ruin. Such alternative visions that move beyond the single axis of settler-native enable the emergence of more nuanced, and even hopeful, ecological imaginaries that focus on sumud, dignity, and recognition.

scholarly journals 265 Evaluation of the genetic relationship amongst high elevation pulmonary arterial pressure, feedlot and carcass performance traits

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 197-197
Author(s):  
Emma A Briggs ◽  
Scott Speidel ◽  
Mark Enns ◽  
Milt Thomas ◽  
Tim Holt
Keyword(s):  
Arterial Pressure ◽  
Genetic Relationship ◽  
Feed Intake ◽  
Pulmonary Arterial Pressure ◽  
Carcass Traits ◽  
Genetic Correlations ◽  
High Elevation ◽  
Pulmonary Arterial ◽  
Carcass Performance ◽  
Moderate Elevation

Abstract The objective of the study was to evaluate if a genetic relationship exists between pulmonary arterial pressure (PAP) measured at high elevation with traits associated with moderate elevation feedlot and carcass traits. For this analysis, PAP, feed intake, and carcass data were taken from 6,898, 558, and 1,627 animals, respectively. At an elevation of 2,115 m, PAP measurements were collected, then a selective group of steers was relocated to a moderate elevation feedlot (1,500 m) where feed intake data were collected. Genetic relationships were evaluated with 5-trait animal models using REML statistical analysis. For all traits in the analysis, fixed effects and contemporary groups were assigned as well as a direct genetic random effect. For weaning weight, a maternal permanent environmental effect was applied in the analysis. For PAP, the heritability estimate was 0.29 ± 0.03. Genetic correlations between PAP with feedlot traits was positive, with estimates of 0.34 ± 0.20 (average dry matter intake) and 0.05 ± 17 (average daily gain). The strongest genetic correlation between PAP and carcass performance traits were those of rib eye area (-0.30 ± 0.12) and calculated yield grade (0.29 ± 0.13). Genetic correlations between PAP and marbling score, back fat, or hot carcass weight were 0.00 ± 0.13, -0.07 ± 0.13, and 0.14 ± 0.10, respectively. These results suggest a favorable genetic relationship exists between PAP with feedlot and carcass traits.

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