Denudation History Research Articles

Uplift and denudation history of the Ellsworth Mountains: insights from low-temperature thermochronology

Abstract. While thermochronological studies have constrained the landscape evolution of several of the crustal blocks of West and East Antarctica, the tectono-thermal evolution of the Ellsworth Mountains remains relatively poorly constrained. These mountains are among the crustal blocks that comprise West Antarctica and exhibit an exceptionally well-preserved Palaeozoic sedimentary sequence. Despite the seminal contribution of Fitzgerald and Stump (1991), who suggested an Early Cretaceous uplift event for the Ellsworth Mountains, further thermochronological studies are required to improve the current understanding of the landscape evolution of this mountain chain. We present new zircon (U–Th) / He (ZHe) ages, which provide insights into the landscape evolution of the Ellsworth Mountains. The ZHe ages collected from near the base and the top of the sequence suggest that these rocks underwent burial reheating after deposition. A cooling event is recorded during the Jurassic–Early Cretaceous, which we interpret as representing exhumation in response to rock uplift of the Ellsworth Mountains. Moreover, our results show that while ZHe ages at the base of the sequence are fully reset, towards the top ZHe ages are partially reset. Uplift and exhumation of the Ellsworth Mountains during the Jurassic–Early Cretaceous was contemporaneous with the rotation and translation of this crustal block with respect to East Antarctica and possibly the Antarctic Peninsula. Furthermore, this period is characterized by widespread extension associated with the disassembly and breakup of Gondwana, with the Ellsworth Mountains playing a key role in the opening of the far southern Atlantic. Based on these results, we suggest that uplift of the Ellsworth Mountains during the disassembly of Gondwana provides additional evidence for major rearrangement of the crustal blocks between the South American, African, Australian and Antarctic plates. Finally, uplift of the Ellsworth Mountains commenced during the Jurassic, which predates the Early Cretaceous uplift of the Transantarctic Mountains. We suggest that the rift-related exhumation of the Ellsworth Mountains occurred throughout two events: (i) a Jurassic uplift associated with the disassembly of southwestern Gondwana and (ii) an Early Cretaceous uplift related with the separation between Antarctica and Australia, which is also recorded in the Transantarctic Mountains.

Low-temperature thermochronology of Ryoke belt granitoids, SW Japan: New insights into the recent cooling history from monazite fission-track dating

Traditional low-temperature thermochronology techniques such as apatite fission track (AFT) and apatite (U-Th-Sm)/He (AHe) have so far produced limited information on the neotectonic (late Miocene and younger) evolution of Japan. However, the development of monazite fission track (MFT) dating, which has an ultra-low temperature sensitivity (<∼25 – 46°C), provides a fresh opportunity to directly analyse recent denudation histories. Low-temperature thermochronology methods have been applied to granitoid samples from the Ryoke belt, located in eastern Yamaguchi and Nara Prefectures, SW Japan. Zircon (U-Th)/He (ZHe), AFT and AHe data and modelled thermal histories reveal Late Cretaceous - Pliocene cooling related to granitoid thermal relaxation combined with paleo-Izanagi and Pacific plate subduction along the eastern Eurasian continental margin. MFT dating reveals Plio – Pleistocene cooling ages, coincident with elastic loading caused by Philippine Sea plate subduction since the Middle - Late Miocene, along with the Quaternary collision of NE and SW Japan at the Itoigawa-Shizuoka Tectonic Line. Silica concentration, non-thermal “radiation assisted” annealing, and changing climatic conditions are proposed as possible caveats on MFT annealing kinetics since the samples are residing in an “open” system. Taking all these factors into consideration, the apparent MFT ages are interpreted as minimum cooling ages, being slightly younger than the thermal events that cooled the samples through the MFT nominal closure temperature. Estimated denudation rates based on MFT dating are higher in Nara relative to eastern Yamaguchi Prefecture, with the difference likely reflecting variations in the tectonic regime, timing of uplift and uplift mechanisms of the two regions.

Denudation history of the Great Escarpment in the southwestern flank of the Angola (Bié) Dome, Africa

Denudation history of the Great Escarpment in the southwestern flank of the Angola (Bié) Dome, Africa

A Compilation of New and Existing Thermochronology Data Concerning the Lhasa Terrane Combined with a Geological Synthesis of the Area

AbstractThe history and geodynamic mechanisms of Cenozoic exhumation and denudation of the Lhasa terrane (LT), southern Tibetan Plateau, remain poorly constrained. Most previous studies investigating the exhumation of the LT have relied on extrapolating interpretations based on a few well‐studied but small areas, which inevitably introduce bias. Here, our compilation of new and published thermochronologic ages are plotted against latitude, longitude, and elevation, to illustrate the distribution of cooling ages across broad regions of the LT. Primary results reveal that (1) the north LT experienced significant exhumation during 80–40 Ma; (2) compared with north LT, exhumation and erosion in the south LT continued after ∼40 Ma; and (3) N–S striking rifting, E–W striking river incision, and thrusts led to continued local denudation of the south LT between 20–5 Ma.

Reorganization of continent‐scale sediment routing based on detrital zircon and rutile multi‐proxy analysis

AbstractThe duration and extent of sediment routing systems are intrinsically linked to crustal‐ to mantle‐scale processes. Therefore, distinct changes in the geodynamic regime may be captured in the detrital record. This study attempts to reconstruct the sediment routing system of the Canning Basin (Western Australia) during the Early Cretaceous to decipher its depositional response to Mesozoic‐Cenozoic supercontinent dispersal. Specifically, we reconstruct source‐to‐sink relationships for the Broome Sandstone (Dampier Peninsula) and proximal modern sediments through multi‐proxy analysis of detrital zircon (U–Pb, Lu–Hf and trace elements) and detrital rutile (U–Pb and trace elements). Multi‐proxy comparison of detrital signatures and potential sources reveals that the majority of the detrital zircon and rutile grains are ultimately sourced from crystalline basement in central Australia (Musgrave Province and Arunta region) and that proximal sediment supply (i.e., Kimberley region) is negligible. However, a significant proportion of detritus might be derived from intermediate sedimentary sources in central Australia (e.g., Amadeus Basin) rather than directly from erosion of crystalline basement. Broome Sandstone data are consistent with a large‐scale drainage system with headwaters in central Australia. Contextualization with other broadly coeval drainage systems suggests that central Australia acted as a major drainage divide during the Early Cretaceous. Importantly, reorganization after supercontinent dispersal is characterized by the continuation of a sediment pathway remnant of an earlier transcontinental routing system originating in Antarctica that provided a template for Early Cretaceous drainage. Review of older Canning Basin strata implies a prolonged denudation history of central Australian lithologies. These observations are consistent with the long‐lived intracontinental tectonic activity of central Australia governing punctuated sediment generation and dispersion more broadly across Australia and emphasize the impact of deep Earth processes on sediment routing systems.

Constraints on Sandstone-Type Uranium Deposits by the Tectonic Uplift and Denudation Process in the Eastern Junggar Basin, Northwest China: Evidence from Apatite Fission Track and Detrital Zircon U-Pb Ages

The uplift and denudation history of the orogenic belt and the basin–mountain coupling process have directly or indirectly affected the generation, scale, and preservation of sandstone-type uranium deposits in the eastern Junggar Basin by controlling the uranium source, lithology, facies, hydrogeology, post-generation modification, and other mineralization conditions. Taking the eastern Junggar Basin as the research area, this study proposes the constraints on sandstone-type uranium deposits by the tectonic uplift and denudation history of the orogenic belt in the basin using the apatite fission track (AFT), detrital zircon geochronology, and other methods. The results of the AFT age test and thermal path simulation indicate that the orogenic belt in the eastern Junggar Basin underwent four rapid uplifts; (from approximately 300 Ma to approximately 250 Ma, from approximately 130 Ma to approximately 90 Ma, from approximately 65 Ma to approximately 30 Ma, and from approximately 20 Ma to 0 Ma). Moreover, the timing of the uplift has a spatial trend of gradually becoming younger from south to north. The detrital zircon U-Pb age test showed that the sediment source area of the basin is mainly distributed in three age intervals, i.e., 460–390, 360–270, and 190–170 Ma. The comprehensive evaluation of the clastic sediment composition, stratigraphic distribution of the erosion source area, and thermal history showed that a large amount of exposed Carboniferous–Permian granites in the Qinglidi and Karameri Mountain erosion source areas contributed dominant sediment material and uranium sources for the Triassic and Middle and Lower Jurassic strata in the basin. The Ordovician–Early Devonian granites only provided sediment sources for the Upper Triassic and Lower Jurassic strata in the basin. Altay Mountain contributed some sediment sources for the Middle and Upper Jurassic strata after the magmatic activity and rapid uplift occurred in the Middle Jurassic. Based on the comprehensive analysis of the influence of the tectonic uplift process of the orogenic belt and the transformation of material source areas on uranium mineralization, the granites in the erosion source areas are proposed to contribute both external and internal uranium sources for uranium mineralization. Uranium mineralization mainly occurred in the tectonic retreat period after the rapid uplifts of the Cretaceous and Paleogene. It was terminated by the intensive uplift-induced stratigraphic deformation in the Miocene.

Upper Oligocene–Lower Miocene Gangdese Conglomerate Along the Yarlung-Zangbo Suture Zone and its Implications for Palaeo-Yarlung-Zangbo Initiation

The upper Oligocene–lower Miocene Gangdese conglomerate is deposited along the Yarlung-Zangbo suture zone, which extends 1,500 km from west to east and is located in the core area of the India–Eurasia plate collision zone. The Gangdese conglomerate records richly uplift and denudation histories of the Lhasa terrane and Tethyan Himalaya on both sides of the suture zone, thus revealing the growth process of the southern Tibetan Plateau during the Late Oligocene–Early Miocene. In this study, we documented the detailed sedimentology and chronology of the Gangdese conglomerate. The Gangdese conglomerate is dominated by conglomerate and sandstone, with minor volumes of siltstone and tuff deposited in an alluvial fan and fluvial system. Based on sedimentology and structural relationships, we suggest that the Gangdese conglomerate was deposited in an extensional tectonic environment in the early period and an extrusion tectonic environment in the late period, which was controlled by Indian slab shearing and breakoff during the Late Oligocene–Miocene. According to the new magnetostratigraphy and detrital zircon U-Pb dating, the main depositional age of the Gangdese conglomerate was likely the Late Oligocene–Early Miocene (26–18 Ma), and it trended younger from west to east. Moreover, paleocurrent data from the Gangdese conglomerate showed westward axial sediment transport; thus, we inferred that a westward axial palaeo-Yarlung-Zangbo River occurred along the whole Yarlung-Zangbo suture zone during the Late Oligocene–Early Miocene, and its flow was opposite to that of the current Yarlung-Zangbo River.

An Evaluation of Erosional‐Geodynamic Thresholds for Rapid Orogenic Denudation

AbstractTectonic and surface processes (e.g., erosion) act in concert to denude and flatten elevated topography during and following collisional uplift. In orogens that collapsed rapidly (&lt;10 Myr), the effectiveness and relative contribution of erosion remains poorly understood. Here, we use 1‐D and 2‐D finite‐difference models to test plausible magnitudes of erosion during denudation of the Scandian orogenic wedge, in northern Scotland, which previous work suggests may have been very rapid. Thermochronologic, stratigraphic, and thermobarometric data constrain initial post‐collision uplift rates as well as the cumulative post‐collisional exhumation magnitude. Using these constraints, we consider an idealized orogen subjected to fluvial incision, hillslope diffusion, and subsequent isostatic compensation for a duration of 10 Myr. Using a range of geomorphic parameters, we evaluate whether erosion alone is sufficient to achieve the observed cumulative exhumation. Additionally, we apply a thermal model during the same period to determine the viability of the previous erosion estimates in the presence of a transient geothermal gradient. For most cases with initial uplift rates of 0.5–2.5 mm yr−1, total erosion is insufficient to account for the observed Scandian denudation history, regardless of whether a fixed or transient geothermal gradient is assumed. Average elevations near the crest of the modeled orogen after 10 Myr are &gt;1.4 km, which is inconsistent with the post‐Scandian landscape relief interpreted from the reconstructed depositional surface of the Emsian (407–403 Ma) Old Red Sandstone, Collectively these findings imply a combination of rapid erosion and tectonic denudation likely accomplished the rapid collapse of the Scandian wedge.

Testing local and extraregional sediment sources for the Late Cretaceous northern Nanaimo basin, British Columbia, using 40Ar/39Ar detrital K-feldspar thermochronology

Abstract Detrital K-feldspar 40Ar/39Ar thermochronology was conducted on clastic sedimentary rock samples collected from northern exposures of the Upper Cretaceous Nanaimo Group on Vancouver Island and adjacent Gulf Islands of British Columbia to constrain the denudation history of the local Coast Mountains batholith source region and determine the origin of extraregional sediment supplied to the basin. Strata of the northern Nanaimo Group deposited between 86 and 83 Ma (Comox and Extension formations) exhibit a 130–85 Ma age distribution of detrital K-feldspar 40Ar/39Ar ages that lack age maxima. These are interpreted to have been sourced from the southwestern Coast Mountains batholith. Younger strata deposited between 83 and 72 Ma (Cedar District and De Courcy formations) yield a broader age range (150–85 Ma) with an age maximum near the depositional age. These results indicate focused denudation of deeper-seated rocks east of the Harrison Lake fault. The youngest units deposited after 72 Ma (Geoffrey, Spray, and Gabriola formations) primarily yield younger than 75 Ma detrital K-feldspar ages with pronounced age maxima near the depositional age. This sediment was sourced extraregionally relative to the Coast Mountains batholith. We sought to constrain the origin of the extraregional sediment by measuring the thermal histories of 74 samples of basement rocks from throughout the Pacific Northwest, and by compiling a database of over 2400 biotite 40Ar/39Ar and K/Ar cooling ages from predominantly Cretaceous batholiths along the western North American margin. This analysis focused upon two previously proposed source regions: the Idaho batholith and the Mojave-Salina margin of southern California. The Nanaimo detrital K-feldspar 40Ar/39Ar age distributions favor the peraluminous Late Cretaceous Idaho batholith and its Proterozoic Belt-Purcell Supergroup sedimentary wall rock as the more likely source of the extraregional sediment and disfavor the Baja–British Columbia hypothesis for 2000–4000-km-scale translation of rocks along the margin during the Late Cretaceous.

Constraints of tectonic uplift and denudation on sandstone-type uranium mineralization in Meso-Cenozoic basins in northern China: A review

The controlling effect of tectonic uplift and denudation on uranium mineralization has been much studied previously, and its important contribution to uranium mineralization has been fully recognized. However, no systematic theory and methodological criteria for uranium prospecting has been summarized. Here we present the results of an in-depth study of the characteristics and formation process of typical sandstone-type uranium deposits in the northern basin of China, and conclude with a uranium metallogenic theory: tectonic uplift and denudation events are the driving force for the formation of sandstone-type uranium deposits (or even mudstone-type uranium deposits). The stage of tectonic uplift and subsequent denudation events since the formation of the target layer determines the mineralization stages: the greater the intensity and duration of uplifting and denudation events, the larger the scale of uranium mineralization. The formation of large and mega-scale sandstone-type uranium deposits requires multiple stages of tectonic uplift and denudation events superimposed in the same direction. Single or polydirectional tectonic uplift and denudation events often do not form industrial uranium deposits. In this paper, a three-step method to predict the occurrence of sandstone-type uranium deposits is established, which includes (1) determining the tectonic framework division of the sedimentary basin being investigated, (2) a burial and denudation history study, and (3) apatite fission-track simulation of the erosion source area. Focusing on the tectonic evolution and the rapid uplift and denudation events of the basin and the erosion source area is critical (the tectonic evolution of the two areas usually is closely coupled). The desired result can be achieved only by combining the aforementioned theory with basic principles of sandstone-type uranium mineralization, and treating uranium mineralization as a result of a special tectonic event. The theory deepens the understanding of sandstone-type uranium mineralization, and the method plays a role in the rapid evaluation of sandstone-type uranium deposits in sedimentary basins, and it can be extended to research and prediction in other basins.

Erosion rates and weathering timescales in the eastern Great Escarpment, South Africa

The eastern escarpment in South Africa has a combination of geology and climate that is unique in the entire Great Escarpment. Yet, no studies have been undertaken before to quantify the landscape changes at this locality. In this study, we assess the denudation history of the eastern escarpment using cosmogenic beryllium-10 (10Be) on quartz from rock outcrops and river sediments, and carry out uranium‑thorium‑helium ((U,Th)-He) and argon‑argon (40Ar/39Ar) dating of Fe-oxides and Mn-oxides, respectively, in the soils. The erosion rates obtained on the eastern escarpment vary from 1.8 m/Ma to 24 m/Ma and are similar in range to values from the entire Great Escarpment. We found that the catchment-averaged erosion rates of the gentle catchments above the eastern escarpment are lower, whereas those from steep catchments draining the escarpment edge are higher. We also determined that the catchment-average erosion rates of the eastern escarpment are similar to those of the western escarpment in Namibia, lower than those of the Drakensberg Escarpment and lower than those of the Lowveld adjacent to it. The 40Ar/39Ar dating of cryptomelane-bearing Mn nodules yield Palaeoproterozoic ages unrelated to the pedogenic processes, and might indicate that these nodules are not pedogenic, but inherited from weathered bedrock. The (U,Th)-He ages of goethite concretions range from 0.85 Ma to 1.05 Ma and they date the last period of intensive chemical weathering on the eastern escarpment, which coincides with the Mid-Pleistocene Transition from humid to more arid conditions on the southern African subcontinent. Given the low erosion rates above the escarpment, an area that experiences intensive chemical weathering, and the high erosion rates down the escarpment we conclude that at the eastern escarpment, pediplanation is a more important driver of denudation than peneplanation.

Cenozoic Dynamic Topography of Madagascar

AbstractIt has been proposed that Oligo‐Miocene regional uplift of Madagascar was generated and is maintained by mantle dynamical processes. Expressions of regional uplift include flat‐lying Upper Cretaceous‐Paleogene marine limestones that crop out at elevations of hundreds of meters along the western seaboard and emergent Quaternary coral‐rich terraces that rim the coastline. Here, we explore the history of subcrustal topographic support through a combined analysis of four sets of observational constraints. First, we exploit published receiver function estimates of crustal thickness and spectral admittance between gravity and topography. An admittance value of ∼+40 ± 10 mGal km−1 at wavelengths &gt;500 km implies that ∼1 km of topography is supported by subcrustal processes. Secondly, new apatite fission‐track and helium measurements from 18 basement samples are inverted, constraining temperature and denudation histories. Results suggest that 0.5–1.6 km of regional uplift occurred after ∼30 Ma. Thirdly, we calculate a history of regional uplift by minimizing the misfit between observed and calculated longitudinal river profiles. Results suggest that topography was generated during Neogene times. Finally, inverse modeling of rare earth element concentrations in Neogene mafic rocks indicates that melting of the asthenospheric source occurred at depths of ≤65 km with potential temperatures of 1300–1370 °C. Melting occurred at higher temperatures beneath Réunion Island and northern Madagascar and at lower temperatures beneath the Comores and southern Madagascar. These inferences are consistent with shear wave velocities obtained from tomographic models. We conclude that Madagascar is underlain by thinned lithospheric mantle and that a thermal anomaly lies within an asthenospheric layer beneath northern Madagascar.

Late Cenozoic Denudation and Topographic Evolution History of the Lhasa River Drainage in Southern Tibetan Plateau: Insights From Inverse Thermal History Modeling

The interaction of surface erosion (e.g., fluvial incision) and tectonic uplift shapes the landform in the Tibetan Plateau. The Lhasa River flows toward the southwest across the central Gangdese Mountains in the southern Tibetan Plateau, characterized by a low-relief and high-elevation landscape. However, the evolution of low-relief topography and the establishment of the Lhasa River remain highly under debate. Here, we collected thermochronological ages reported in the Lhasa River drainage, using a 3D thermokinematic model to invert both late Cenozoic denudation and relief history of the Lhasa River drainage. Our results show that the Lhasa River drainage underwent four-phase denudation history, including two-stage rapid denudation at ∼25–16 Ma (with a rate of ∼0.42 km/Ma) and ∼16–12 Ma (with a rate of ∼0.72 km/Ma). In the latest Oligocene–early Miocene, uplift of the Gangdese Mountains triggered the rapid denudation and the formation of the current main drainage of the Lhasa River. In the middle Miocene, the second stage of the rapid denudation and the high relief were associated with intense incision of the Lhasa River, which is probably due to the enhanced Asian summer monsoon precipitation. This later rapid episode was consistent with the records of regional main drainage systems. After ∼12 Ma, the denudation rate decreases rapidly, and the relief of topography in the central Gangdese region was gradually subdued. This indicates that the fluvial erosion resulting from Asian monsoon precipitation increase significantly impacts on the topographic evolution in the central Gangdese region.

Reconstruction of the exhumation history of the eastern Nepal Himalaya based on provenance changes

The Siwalik Group extending east-west collinear to the Himalayan southern front records Himalayan denudation history. In this study, we present sandstone petrography, heavy mineral assemblages, Nd isotopes and chemical composition of detrital garnet from the Siwalik succession along the Muksar Khola section. This study reveals the Tibetan Tethys Himalaya, Higher Himalayan Crystalline and Lesser Himalaya Sequence as the source of sediments and records a provenance change from the middle Miocene to Pliocene/Pleistocene. This was observed as a shift from shallow to deeper parts of the Higher Himalayan Crystalline as a source area around 10.6 Ma. The Lesser Himalaya Sequence supplied a significant amount of sediments after 7.5 Ma, but the deeper part was only exposed after the late Pliocene to Pleistocene. Around 4.0 Ma an increase in the sediments from the Higher Himalayan Crystalline was observed. This provenance study reveals two stages of the exhumation of the eastern Nepal Himalaya. The first occurred between 11.0 and 5.5 Ma and the second after 4.0 Ma, due to the activation of an out-of-sequence thrust known as the Sun Koshi Thrust, and formation of the Lesser Himalayan duplex respectively.

About this title - The Basins, Orogens and Evolution of the Southern Gulf of Mexico and Northern Caribbean

This volume brings together 17 comprehensive, data-rich analyses to provide an updated perspective on the Mexican sector of the Gulf of Mexico, Florida and the northern Caribbean. The papers span a broad range of scales and disciplines from plate tectonic evolution to sub-basin-scale analysis. Papers are broadly categorized into three themes: (1) geological evolution of the basins of the southern Gulf of Mexico in Mexico, Bahamas and Florida and their hydrocarbon potential; (2) evolution of the region's Late Cretaceous to Neogene orogens and subsequent denudation history; and (3) geological evolution of the basins and crustal elements of the northern Caribbean. This book and its extensive datasets are essential for all academic and exploration geoscientists working in this area. The volume also includes two large maps detailing the Mexican Gulf of Mexico and the Northern Caribbean areas.

Mesozoic uplift exhumation history of East Kunlun

位于中央造山带西段的东昆仑造山带因多期次造山和复杂演化历史而备受关注，约束其中生代隆升剥露历史，对于理解青藏高原大规模隆升在东昆仑地区的扩展及影响颇具意义。东昆仑造山带内中生代侏罗系-白垩系地层缺失严重，体现中生代以来强烈的隆升剥露过程，也是该区热演化的研究难点。本文通过对东昆仑造山带样品的磷灰石、锆石裂变径迹分析和热演化史研究，并结合东昆仑及周缘地区现有低温热年代学研究，识别出东昆仑造山带所经历的五次隆升冷却事件，即201~193Ma（早侏罗世）、172~152Ma（中-晚侏罗世）、120~98Ma（早白垩世末-早白垩世初）、98~20Ma（晚白垩世-中新世）及20~0Ma（中新世至今）。所获5个年龄组响应东昆仑地区所经历的构造热事件，其中201~193Ma年龄组响应南部羌塘地块与昆仑地块的碰撞事件；172~152Ma年龄组为中-晚侏罗世古特提斯洋闭合后，造山后伸展的构造事件的记录；120~98Ma热事件吻合拉萨地块和羌塘地块碰撞事件；98~20Ma年龄组为东昆仑地区长期缓慢剥蚀去顶过程的印证；20~0Ma的快速隆升剥露事件则为东昆仑周缘断裂系活化相伴，多期隆升剥蚀事件均得到地层不整合及沉积记录等研究成果的证实。区内剥蚀起始时间从由南到北逐渐变老，体现东昆仑地区隆升剥蚀的不均一性。;As the western part of the Central Orogenic Belt, the East Kunlun Orogenic Belt draws great attention in the geological community because of its multi-phase orogenesis and complex evolutionary history. Constraining its Mesozoic uplift denudation history has important implications for understanding the expansion and impact of large-scale uplift of the Tibetan Plateau in the East Kunlun region. The absence of the Mesozoic Jurassic-Cretaceous stratigraphy in the East Kunlun Orogenic Belt reflects the intensive uplift and denudation process since the Mesozoic, which is also a difficult research problem in the thermal evolution of the area. In this paper, through the analysis of apatite, zircon fission tracks and thermal evolutionary history of samples within the East Kunlun, we identify five uplift cooling events, i.e. 201~193Ma (Early Jurassic), 172~152Ma (Middle-Late Jurassic), 120~98Ma (Late Early Cretaceous-Early Cretaceous), 98~20Ma (Late Cretaceous-Miocene), and 20~0Ma (Miocene to present). The five age groups obtained respond to the tectonothermal events experienced in the East Kunlun region. The 201~193Ma age group responds to the collision between the Qiangtang Block and the Kunlun Block in the south; the 172~152Ma age group is the record of the tectonic event of post-formation extension after the closure of the Middle-Late Jurassic Paleo-Tethys Ocean; the 120~98Ma thermal event coincides with the collision between the Lhasa Block and the Qiangtang Block; the 98~20Ma age group is the record of the long-term slow denudation process. The rapid uplift and denudation events from 20 to 0Ma are due to the activation of the fault system. The onset of denudation in the area is gradually older from south to north, reflecting the heterogeneity of uplift denudation in the East Kunlun region.

A late Mesozoic – early Cenozoic sedimentary recycling system on the Gondwana rifted margin of southeast Africa

Abstract Detrital zircons in late Cretaceous – Palaeogene, calcareous sandstone and conglomerate deposited in continental basins on the southeastern African margin after the breakup of Gondwana have characteristic combinations of age and epsilon-Hf that indicate an origin by recycling of Palaeoproterozoic (Waterberg, Soutpansberg and Pretoria groups) and Phanerozoic (Karoo Supergroup) cover successions. The latter is dominant in the south and east (Boane, Mahosi, Chilojo Cliffs), and the Palaeoproterozoic sources in the northwest (Pafuri, Wright’s Tower, Masisi). This recycling and mixing regime was restricted to late Mesozoic and Palaeogene time in northeastern South Africa and adjoining parts of Mozambique and Zimbabwe. Detrital zircon distribution patterns in these deposits reflect the denudation history of the southern African continental surface after breakup of the Gondwana supercontinent.

Influence of orographic precipitation on the topographic and erosional evolution of mountain ranges

AbstractThe influence of climate on mountain denudation has been the topic of an intense debate for two decades. This debate partly arises from the covariation of rainfall and topography during the growth of mountain ranges, both of which influence denudation. However, the denudational response of this co‐evolution is poorly understood. Here, we use a landscape evolution model where the rainfall evolves according to a prescribed rainfall–elevation relationship. This relationship is a bell curve defined by a rainfall base level, a rainfall maximum and a width around the rainfall peak elevation. This is a first‐order model that fits a large range of orographic rainfall data at the ca. 1‐km spatial scale. We carried out simulations of an uplifting block with an alluvial apron, starting from an initially horizontal surface, and testing different rainfall–elevation relationships. We find that the denudation history is different from that with constant rainfall models. The results essentially depend on the ratio between the final steady‐state summit elevation Hss and the prescribed rainfall peak elevation Hp. This ratio is hard to predict because it depends on the transient coupling of rainfall and elevation. We identified three types of results according to Hss/Hp. If Hss/Hp &gt; 4 (Type I), the denudation rates peak when the summits reach values close to Hp. If Hss/Hp &gt; 1.5 and &lt; 4 (Type II), the denudation is strongly accelerated when the elevation of the summits approaches Hp, and then the denudation increases slowly towards the uplift rate. If Hss/Hp &lt; 1.5 (Type III), the denudation evolution is similar to situations with constant and homogeneous rainfall. In the Type I and II experiments, the mountain top is subjected to aridification once the summits have passed through Hp. To adapt to this reduced rainfall, the slopes increase. This can lead to a paradoxical situation where the mountain relief increases faster, whereas the denudation increases more slowly. The development of orographic precipitation may thus favour the stability of the mean denudation rate in a rising mountain. Despite the model limitations, including a constant rainfall–elevation relationship, our study suggests that the “classical” exponential increase in the denudation rate predicted by constant rainfall models is not the common case. Instead, the common case involves pulses and acceleration of the denudation even in the absence of uplift or global climate variations.

(U\u2013Th)/He thermochronometric mapping across the northeast Japan Arc: towards understanding mountain building in an island-arc setting

Topographic relief in arc-trench systems is thought to be formed by plate subduction; however, few quantitative investigations have so far been reported, with respect to the related mountain building process. This study applies apatite and zircon (U–Th)/He thermochronometry (AHe, ZHe, respectively) to Cretaceous granite rocks in the north part of the northeast (NE) Japan Arc to reveal its cooling/denudation history. Weighted mean AHe ages ranging from 88.6 to 0.9 Ma and ZHe ages from 83.9 to 7.4 Ma were determined for 10 rock samples. Using the AHe data, denudation rates were obtained for each sample. On the fore-arc side, denudation rates of < 0.05 mm/year were calculated, indicating a slow denudation process since the Paleogene. However, in the Ou Backbone Range and on the back-arc side, denudation rates at > 0.1–1.0 mm/year were computed, probably reflecting a recent uplift event since ~ 3–2 Ma. These data indicate a clear contrast in thermal and denudation histories between the tectonic units in this study area, similar to that previously reported from the southern part of NE Japan Arc. A comparison of the thermal/denudation histories between the N- and S- traverses, revealed the arc-parallel trend, the uplift model of the volcanic arc, and some minor variations of thermal/denudation histories in each tectonic unit. This study offers some further insights into the understanding of tectonic processes in an island-arc setting.

Mesozoic denudation history of the lower Orange River and eastward migration of erosion across the southern African Plateau

Abstract Topographic uplift of the southern African Plateau is commonly attributed to mantle causes, but the links between mantle processes, uplift, and erosion patterns are not necessarily straightforward. We acquired apatite (U-Th)/He (AHe) dates from eight kimberlite and basement samples from the lower reaches of the large westward-draining Orange River system with the goal of evaluating the roles of lithospheric modification and river incision on the erosion history here. Average AHe dates range from 79 to 118 Ma and thermal history models suggest that most samples are consistent with a main erosion phase at ca. 120–100 Ma, with some variability across the region indicating a complex erosion history. Major erosion overlaps with the timing of strong lithospheric thermochemical modification as recorded in xenoliths from the studied kimberlites, but the denudation pattern does not mimic the northward progression of lithospheric alteration across the study region. We attribute this area’s denudation history to a combination of mantle effects, rifting, establishment of the Orange River outlet at its current location, and later faulting. When considering these results with other kimberlite-derived surface histories from an ∼1000-km-long E-W transect across the plateau, an eastward-younging trend in denudation is evident. The interplay of mantle processes and the shape of the large, west-draining Orange River basin likely control this first order-pattern.