Propagating uplift controls on formation of low-relief, high-elevation surfaces in the SE Tibetan Plateau

The SE Tibetan Plateau has extensive broad, low-relief, high-elevation surfaces perched above deep valleys, as well as in the headwaters of the three rivers (the Salween, the Mekong, and the Yangtze). However, understanding the presence of these low-relief surfaces is a long-standing challenge because their formation process remains highly debated. While alternate mechanisms have been proposed to explain the low-relief surface formation in this setting (e.g., drainage-area loss mechanism due to horizontal advection; Yang et al., 2015, Nature), a long-standing hypothesis for the formation of low-relief surfaces is by a step change in uplift and incision into a pre-existing, low-relief surface (Clark et al., 2006, JGR; Whipple et al., 2017, Geology).The morphology of low-relief surfaces in the SE Tibetan Plateau is largely consistent with formation by a step change in uplift, but one problem with this model is that low-relief surfaces formed by a step change in uplift are relatively short-lived, since they are incised and steepened by erosion, which sweeps upstream at the response time of mountain ranges (in the order of several million years). Using a landscape evolution model that combines erosion, sediment transport and deposition processes (Yuan et al., 2019, JGR), we demonstrate that propagating uplift form large parallel rivers, with broad low-relief, high-elevation interfluves that persist for tens to hundreds of million years, consistent with various dated ages. These low-relief surfaces can be long-lived because the drainage areas in these interfluves are insufficient to keep up with rapid incision of the large parallel mainstem rivers. Our simulated features match various observations in the SE Tibetan Plateau: (i) low-relief surfaces are approximately co-planar in headwaters, and decrease in elevation smoothly from northwest to southeast across the plateau margin; (ii) &#967;-elevation plots of the mainstem rivers are convex; (iii) low-relief surfaces have low erosion rates; and (iv) erosion rates are high in the mainstem rivers at the propagating margin.

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Roof of the World: Tibet, Pamirs

Colliding Continents ◽

10.1093/oso/9780199653003.003.0016 ◽

2013 ◽

Author(s):

Mike Searle

Keyword(s):

Tibetan Plateau ◽

High Elevation ◽

Tien Shan ◽

Palm Tree ◽

The Tibetan Plateau ◽

Wet Season ◽

North West ◽

Mountain Ranges ◽

The North ◽

The World

The Tibetan Plateau is by far the largest region of high elevation, averaging just above 5,000 metres above sea level, and the thickest crust, between 70 and 90 kilometres thick, anywhere in the world. This huge plateau region is very flat—lying in the internally drained parts of the Chang Tang in north and central Tibet, but in parts of the externally drained eastern Tibet, three or four mountain ranges larger and higher than the Alps rise above the frozen plateau. Some of the world’s largest and longest mountain ranges border the plateau, the ‘flaming mountains’ of the Tien Shan along the north-west, the Kun Lun along the north, the Longmen Shan in the east, and of course the mighty Himalaya forming the southern border of the plateau. The great trans-Himalayan mountain ranges of the Pamir and Karakoram are geologically part of the Asian plate and western Tibet but, as we have noted before, unlike Tibet, these ranges have incredibly high relief with 7- and 8-kilometre-high mountains and deeply eroded rivers and glacial valleys. The western part of the Tibetan Plateau is the highest, driest, and wildest area of Tibet. Here there is almost no rainfall and rivers that carry run-off from the bordering mountain ranges simply evaporate into saltpans or disappear underground. Rivers draining the Kun Lun flow north into the Takla Makan Desert, forming seasonal marshlands in the wet season and a dusty desert when the rivers run dry. The discovery of fossil tropical leaves, palm tree trunks, and even bones from miniature Miocene horses suggest that the climate may have been wetter in the past, but this is also dependent on the rise of the plateau. Exactly when Tibet rose to its present elevation is a matter of great debate. Nowadays the Indian Ocean monsoon winds sweep moisture-laden air over the Indian sub-continent during the summer months (late June–September). All the moisture is dumped as the summer monsoon, the torrential rains that sweep across India from south-east to north-west.

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Glacial Erosion Rates Determined at Vorab Glacier: Implications for the Evolution of Limestone Plateaus

Geosciences ◽

10.3390/geosciences11090356 ◽

2021 ◽

Vol 11 (9) ◽

pp. 356

Author(s):

Olivia Steinemann ◽

Alicia Martinez ◽

Vincenzo Picotti ◽

Christof Vockenhuber ◽

Susan Ivy-Ochs

Keyword(s):

Eastern Alps ◽

Crystalline Rock ◽

High Elevation ◽

Glacial Erosion ◽

Mountain Ranges ◽

Glacier Forefield ◽

Erosion Rates ◽

Cosmogenic Nuclide ◽

Crystalline Bedrock ◽

The Relationship

Understanding how fast glaciers erode their bedrock substrate is one of the key elements in reconstructing how the action of glaciers gives mountain ranges their shape. By combining cosmogenic nuclide concentrations determined in glacially abraded bedrock with a numerical model, we quantify glacial erosion rates over the last 15 ka. We measured cosmogenic 36Cl in fourteen samples from the limestone forefield of the Vorab glacier (Eastern Alps, Switzerland). Determined glacial erosion rates range from 0.01 mm a−1 to 0.16 mm a−1. These glacial abrasion rates differ quite markedly from rates measured on crystalline bedrock (>1 mm a−1), but are similarly low to the rates determined on the only examined limestone plateau so far, the Tsanfleuron glacier forefield. Our data, congruent with field observations, suggest that the Vorab glacier planed off crystalline rock (Permian Verrucano) overlying the Glarus thrust. Upon reaching the underlying strongly karstified limestone the glacier virtually stopped eroding its bed. We attribute this to immediate drainage of meltwater into the karst passages below the glacier, which inhibits sliding. The determined glacial erosion rates underscore the relationship between geology and the resulting landscape that evolves, whether high elevation plateaus in limestone terrains or steep-walled valleys in granitic/gneissic areas.

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The periglacial engine of mountain erosion – Part 2: Modelling large-scale landscape evolution

Earth Surface Dynamics Discussions ◽

10.5194/esurfd-3-327-2015 ◽

2015 ◽

Vol 3 (2) ◽

pp. 327-369 ◽

Cited By ~ 1

Author(s):

D. L. Egholm ◽

J. L. Andersen ◽

M. F. Knudsen ◽

J. D. Jansen ◽

S. B. Nielsen

Keyword(s):

Large Scale ◽

Landscape Evolution ◽

High Elevation ◽

Climatic Conditions ◽

Mean Annual Temperature ◽

Late Cenozoic ◽

Mountain Ranges ◽

Model Experiments ◽

Erosion Rates ◽

Bedrock Erosion

Abstract. An increasing number of studies point to a strong periglacial control on bedrock erosion in mountain landscapes. Periglacial processes have also been suggested to control the formation of block-fields on high-elevation, low-relief surfaces (summit flats) found in many alpine landscapes. However, to which degree periglacial processes took part in accelerating global erosion rates in response to Late Cenozoic cooling still remains as an unanswered question. In this study, we present a landscape evolution model that incorporates two periglacial processes; frost cracking and frost creep, which both depend on the mean annual temperature (MAT) and sediment thickness. The model experiments allow us to time-integrate the contribution of periglacial processes to mountain topography over million-year time scales. It is a robust result of our experiments that periglacial frost activity leads to the formation of smooth summit flats at elevations dominated by cold climatic conditions through time periods of millions of years. Furthermore, a simplistic scaling of temperatures to δ18O values through the late-Cenozoic indicates that many of the highest summit flats in mid- to high-latitude mountain ranges can have formed prior to the Quaternary. The model experiments also suggest that cooling in the Quaternary accelerated periglacial erosion by expanding the areas affected by periglacial erosion significantly. A computational experiment combining glacial and periglacial erosion furthermore suggests that landscape modifications associated with glacial activity may increase the long-term average efficiency of the frost-related processes.

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

10.5194/egusphere-egu21-15346 ◽

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

The Southeast Tibet is characterized by extensive low-relief high-elevation surfaces that have been interpreted as &#8220;relict surfaces&#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 (<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.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 &#8220;relict surface&#8221;, as proposed by previous studies and its low relief results from in part glacial &#8220;buzzsaw-like&#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.&#160;

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Boulders as a lithologic control on river and landscape response to tectonic forcing at the Mendocino triple junction

Geological Society of America Bulletin ◽

10.1130/b35385.1 ◽

2020 ◽

Author(s):

Charles M. Shobe ◽

Georgina L. Bennett ◽

Gregory E. Tucker ◽

Kevin Roback ◽

Scott R. Miller ◽

...

Keyword(s):

Triple Junction ◽

High Elevation ◽

River Channels ◽

Erosion Rates ◽

Coastal Belt ◽

Sediment Mass ◽

Mendocino Triple Junction ◽

Landscape Response ◽

Channel Steepness ◽

Tectonic Forcing

Constraining Earth’s sediment mass balance over geologic time requires a quantitative understanding of how landscapes respond to transient tectonic perturbations. However, the mechanisms by which bedrock lithology governs landscape response remain poorly understood. Rock type influences the size of sediment delivered to river channels, which controls how efficiently rivers respond to tectonic forcing. The Mendocino triple junction region of northern California, USA, is one landscape in which large boulders, delivered by hillslope failures to channels, may alter the pace of landscape response to a pulse of rock uplift. Boulders frequently delivered by earthflows in one lithology, the Franciscan mélange, have been hypothesized to steepen channels and slow river response to rock uplift, helping to preserve high-elevation, low-relief topography. Channels in other units (the Coastal Belt and the Franciscan schist) may experience little or no erosion inhibition due to boulder delivery. Here we investigate spatial patterns in channel steepness, an indicator of erosion resistance, and how it varies between mélange and non-mélange channels. We then ask whether lithologically controlled boulder delivery to rivers is a possible cause of steepness variations. We find that mélange channels are steeper than Coastal Belt channels but not steeper than schist channels. Though channels in all units steepen with increasing proximity to mapped hillslope failures, absolute steepness values near failures are much higher (∼2×) in the mélange and schist than in Coastal Belt units. This could reflect reduced rock erodibility or increased erosion rates in the mélange and schist, or disproportionate steepening due to enhanced boulder delivery by hillslope failures in those units. To investigate the possible influence of lithology-dependent boulder delivery, we map boulders at failure toes in the three units. We find that boulder size, frequency, and concentration are greatest in mélange channels and that Coastal Belt channels have the lowest concentrations. Using our field data to parameterize a mathematical model for channel slope response to boulder delivery, we find that the modeled influence of boulders in the mélange could be strong enough to account for some observed differences in channel steepness between lithologies. At the landscape scale, we lack the data to fully disentangle boulder-induced steepening from that due to spatially varying erosion rates and in situ rock erodibility. However, our boulder mapping and modeling results suggest that lithology-dependent boulder delivery to channels could retard landscape adjustment to tectonic forcing in the mélange and potentially also in the schist. Boulder delivery may modulate landscape response to tectonics and help preserve high-elevation, low-relief topography at the Mendocino triple junction and elsewhere.

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Impact of Land Use Change on the Local Climate over the Tibetan Plateau

Advances in Meteorology ◽

10.1155/2010/837480 ◽

2010 ◽

Vol 2010 ◽

pp. 1-6 ◽

Cited By ~ 11

Author(s):

Jiming Jin ◽

Shihua Lu ◽

Suosuo Li ◽

Norman L. Miller

Keyword(s):

Land Use ◽

Tibetan Plateau ◽

Land Use Change ◽

Lower Surface ◽

Warming Trend ◽

The Tibetan Plateau ◽

Area Index ◽

Local Climate ◽

Significant Downward Trend ◽

Three Rivers

Observational data show that the remotely sensed leaf area index (LAI) has a significant downward trend over the east Tibetan Plateau (TP), while a warming trend is found in the same area. Further analysis indicates that this warming trend mainly results from the nighttime warming. The Single-Column Atmosphere Model (SCAM) version 3.1 developed by the National Center for Atmospheric Research is used to investigate the role of land use change in the TP local climate system and isolate the contribution of land use change to the warming. Two sets of SCAM simulations were performed at the Xinghai station that is located near the center of the TP Sanjiang (three rivers) Nature Reserve where the downward LAI trend is largest. These simulations were forced with the high and low LAIs. The modeling results indicate that, when the LAI changes from high to low, the daytime temperature has a slight decrease, while the nighttime temperature increases significantly, which is consistent with the observations. The modeling results further show that the lower surface roughness length plays a significant role in affecting the nighttime temperature increase.

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Linking deeply-sourced volatile emissions to plateau growth dynamics in southeastern Tibetan Plateau

Nature Communications ◽

10.1038/s41467-021-24415-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Maoliang Zhang ◽

Zhengfu Guo ◽

Sheng Xu ◽

Peter H. Barry ◽

Yuji Sano ◽

...

Keyword(s):

Tibetan Plateau ◽

Growth Dynamics ◽

High Elevation ◽

Fault System ◽

The Tibetan Plateau ◽

Southeastern Tibetan Plateau ◽

Surface Uplift ◽

Multi Stage ◽

Geodynamic Processes ◽

Underlying Mechanisms

AbstractThe episodic growth of high-elevation orogenic plateaux is controlled by a series of geodynamic processes. However, determining the underlying mechanisms that drive plateau growth dynamics over geological history and constraining the depths at which growth originates, remains challenging. Here we present He-CO2-N2 systematics of hydrothermal fluids that reveal the existence of a lithospheric-scale fault system in the southeastern Tibetan Plateau, whereby multi-stage plateau growth occurred in the geological past and continues to the present. He isotopes provide unambiguous evidence for the involvement of mantle-scale dynamics in lateral expansion and localized surface uplift of the Tibetan Plateau. The excellent correlation between 3He/4He values and strain rates, along the strike of Indian indentation into Asia, suggests non-uniform distribution of stresses between the plateau boundary and interior, which modulate southeastward growth of the Tibetan Plateau within the context of India-Asia convergence. Our results demonstrate that deeply-sourced volatile geochemistry can be used to constrain deep dynamic processes involved in orogenic plateau growth.

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The Making of the Himalaya, Karakoram, and Tibetan Plateau

Colliding Continents ◽

10.1093/oso/9780199653003.003.0019 ◽

2013 ◽

Author(s):

Mike Searle

Keyword(s):

Tibetan Plateau ◽

Plate Boundary ◽

Indian Plate ◽

North West ◽

Geological Interpretation ◽

Mountain Ranges ◽

The Road ◽

The North ◽

On The Road ◽

The Himalaya

My quest to figure out how the great mountain ranges of Asia, the Himalaya, Karakoram, and Tibetan Plateau were formed has thus far lasted over thirty years from my first glimpse of those wonderful snowy mountains of the Kulu Himalaya in India, peering out of that swaying Indian bus on the road to Manali. It has taken me on a journey from the Hindu Kush and Pamir Ranges along the North-West Frontier of Pakistan with Afghanistan through the Karakoram and along the Himalaya across India, Nepal, Sikkim, and Bhutan and, of course, the great high plateau of Tibet. During the latter decade I have extended these studies eastwards throughout South East Asia and followed the Indian plate boundary all the way east to the Andaman Islands, Sumatra, and Java in Indonesia. There were, of course, numerous geologists who had ventured into the great ranges over the previous hundred years or more and whose findings are scattered throughout the archives of the Survey of India. These were largely descriptive and provided invaluable ground-truth for the surge in models that were proposed to explain the Himalaya and Tibet. When I first started working in the Himalaya there were very few field constraints and only a handful of pioneering geologists had actually made any geological maps. The notable few included Rashid Khan Tahirkheli in Kohistan, D. N. Wadia in parts of the Indian Himalaya, Ardito Desio in the Karakoram, Augusto Gansser in India and Bhutan, Pierre Bordet in Makalu, Michel Colchen, Patrick LeFort, and Arnaud Pêcher in central Nepal. Maps are the starting point for any geological interpretation and mapping should always remain the most important building block for geology. I was extremely lucky that about the time I started working in the Himalaya enormous advances in almost all aspects of geology were happening at a rapid pace. It was the perfect time to start a large project trying to work out all the various geological processes that were in play in forming the great mountain ranges of Asia. Satellite technology suddenly opened up a whole new picture of the Earth from the early Landsat images to the new Google Earth images.

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Acricotopus indet. morphotype incurvatus: Description and genetics of a new Orthocladiinae (Diptera: Chironomidae) larval morphotype from the Tibetan Plateau

Zootaxa ◽

10.11646/zootaxa.4656.3.10 ◽

2019 ◽

Vol 4656 (3) ◽

pp. 535-544

Author(s):

ANDREAS LAUG ◽

LADISLAV HAMERLÍK ◽

STEN ANSLAN ◽

STEFAN ENGELS ◽

FALKO TURNER ◽

...

Keyword(s):

Tibetan Plateau ◽

High Mountain ◽

The Tibetan Plateau ◽

Mitochondrial Coi ◽

Mountain Ranges ◽

Central Tibetan Plateau ◽

Peculiar Form ◽

Close Proximity ◽

Coi Sequences ◽

Complex Formations

High mountain ranges such as the Tibetan Plateau with an average altitude above 4500 m are topographically complex formations. Elevational gradients, physiographic diversity and climatic heterogeneity have led to highly biodiverse ecosystems in these regions. Mountain ranges can be seen as cradles of evolution and harbour, due to their unique characteristics, a high number of highly adapted species. At the same time these areas are hard to access and therefore taxonomic information is limited. Here we describe a new Acricotopus (Diptera: Chironomidae: Orthocladiinae) larval morphotype occurring in lakes and ponds of differing salinity and water depths located on the Southern and Central Tibetan Plateau. The description is based on larvae and their genetics (ribosomal 18S, 28S and mitochondrial COI sequences) collected from a shallow pond in close proximity to the large saline lake Selin Co. Larvae of Acricotopus indet. morphotype incurvatus are characterized by a mentum with a cluster of lateral teeth, partially folded inwards, a mandible with a toothed lobe in addition to four inner teeth and a sclerotized plate positioned behind the mentum. Up to now, these morphological features have only been found in early instars of other Acricotopus species. The proposed morphotype name is inspired by the peculiar form of the mentum.

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