Search

Fault segmentation plays a critical role in assessing seismic hazards, particularly in tectonically complex regions. The Laji-Jishi Shan Fault Zone (LJSFZ), located on the northeastern margin of the Tibetan Plateau, is a key structure that accommodates regional tectonic stress. This study integrates geomorphic indices, cross-fault deformation rate profiles, and 3D crustal electrical structure data to analyze the varying levels of tectonic activity across different segments of the LJSFZ. We extracted 160 drainage basins along the strike of the LJSFZ from a 30 m resolution digital elevation model and calculated geomorphic indices, including the hypsometric integral (HI), stream length-gradient index (SL), and channel steepness index (ksn), to assess the variations in tectonic activity intensity along the strike of the LJSFZ. The basins were categorized based on river flow directions to capture potential differences across the fault zone. Our results show that the eastern basins of the LJSFZ exhibit the strongest tectonic activity, demonstrated by significantly higher SL and ksn values compared to other regions. A detailed segmentation analysis along the northern Laji Shan Fault and eastern Jishi Shan Fault identified distinct fault segments characterized by variations in SL and ksn indices. Segments with high SL values (>500) correspond to higher crustal uplift rates (~3 mm/year), while segments with lower SL values exhibit lower uplift rates (~2 mm/year), as confirmed by cross-fault deformation profiles derived from GNSS and InSAR data. This correlation demonstrates that geomorphic indices effectively reflect fault activity intensity. Additionally, 3D crustal electrical structure data further indicate that highly conductive mid- to lower-crustal materials originating from the interior of the Tibetan Plateau are obstructed at segment L3 of the LJSFZ. This obstruction leads to localized intense uplift and enhanced fault activity. These findings suggest that while the regional stress–strain pattern of the northeastern Tibetan Plateau is the primary driver of the segmented activity along the Laji-Jishi Shan belt, the direction of localized crustal flow is a critical factor influencing fault activity segmentation. [ABSTRACT FROM AUTHOR]

El Niño‐Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability and profoundly affects river flooding globally, especially in East Asia. However, ENSO also has ∼2,000 and ∼1,000‐year cycles, but due to the lack of flood records with sufficient length, little is known about the ENSO's impact on floods at these millennial timescales. Here we test this in the middle‐lower Yangtze River by reconstructing the first Holocene flood record with optically stimulated luminescence and 14C ages of flood deposits. We find the periods with high flooding probability generally correspond with intervals of weakened solar activity. Importantly, the flood record displays 2,000 and 1,000‐year cycles similar to the ENSO record, and band‐pass filter results show the two records are synchronous at these bands. Our results reveal a persistent control of ENSO on millennial‐scale hydroclimatic variability in the Yangtze basin and likely other basins. Plain Language Summary: El Niño‐Southern Oscillation (ENSO) is the prominent pattern of interannual climate variability, profoundly affecting the river flow and flooding at the global scale. However, the ENSO's interannual cycle was strongly damped or even non‐existent in most of the Holocene, compared with a more robust millennial periodicity. It remains unclear whether a link exists between the flood and ENSO at millennial timescales due to the lack of sufficiently long flood series. Here we test this in the Yangtze River (YR) because ENSO has the most significant impact on this drainage area. We compiled the most detailed flood ages over the middle and lower YR to reconstruct the Holocene flood record. We found that the flood variations have prominent 2,000 and 1,000‐year cycles, and they exhibit in‐phase relationship with ENSO at these cycles, suggesting a persistent modulation of ENSO on the flooding at millennial timescales in the middle and lower Yangtze basin. This study contributes to a more comprehensive understanding of the driving forces of floods in the Yangtze catchment at millennial timescales, thereby aiding to accurately assess flood hazards and flooding prediction in hydroclimatic modeling for the densely populated Yangtze basin. Key Points: We reconstructed the Holocene flood record for the middle and lower Yangtze River by compiling optically stimulated luminescence and 14C ages of flood depositsThe flood record displays clear 2,000 and 1,000‐year cyclesThe flood record is synchronous with El Niño‐Southern Oscillation at 2,000 and 1,000‐year cycles [ABSTRACT FROM AUTHOR]

The Yellow River Basin (YRB) is characterized by active geological and tectonic processes, rapid geomorphological evolution, and distinct climatic diversity. Correspondingly, major disasters in the YRB are characterized by varied types, extensive distributions, and sudden occurrences. In addition, major disasters in the YRB usually evolve into disaster chains that cause severe consequences. Therefore, major disasters in the YRB destroy ecologies and environments and influence geological and ecological safety in the basin. This paper systematically reviews research on geological and surface processes, major disaster effects, and risk mitigation in the YRB, discusses the trends and challenges of relevant research, analyzes the key scientific problems that need to be solved, and suggests prospects for future research based on the earth system science concept. Themes of research that should be focused on include geological, surface and climatic processes in the YRB and their interlinking disaster gestation mechanisms; formation mechanisms and disaster chain evolutions of giant landslides in the upper reach of the YRB; mechanisms and disaster chain effects of loess water-soil disasters in the middle reach of the YRB; occurrence patterns and amplifying effects of giant flood chains in the lower reach of the YRB; and risk mitigations of major disasters in the YRB. Key scientific problems that need to be solved are as follows: how to reveal the geological, surface and climatic processes that are coupled and interlinked with gestation mechanisms of major disasters; how to clarify the mutual feedback effects between major disasters and ecology; and how to develop a human-environmental harmony-based integrated risk mitigation system for major disasters. Prospects for future studies that follow the earth system science concept include the following: highlighting interdisciplinary research to reveal the interlinked disaster gestation mechanisms of the geology, surface and climate in the YRB in the past, present, and future; forming theories to clarify the regional patterns, dynamic mechanisms, and mutual-feedback effects between disaster chains and ecology in the YRB on land and in rivers in the region; solving technological bottlenecks to develop assessment models and mitigation theories for integrated risks in the YRB by following the human-environment harmony concept; and finally, establishing a demonstratable application pattern characterized by "whole-basin coverage" and "zonal controls", thereby guaranteeing ecological and geological safety in the basin and providing scientific support for ecological conservation and high-quality development of the YRB. [ABSTRACT FROM AUTHOR]

Understanding the evolution of river systems in southern Africa is fundamental to constrain the evolution of landscape and sediment dispersal patterns. It is widely considered that the upper Zambezi River was connected with the Limpopo River during the Cretaceous, forming what was then the largest river in Africa. Crustal flexure during the Paleogene severed the upper Zambezi drainage from the Limpopo, setting the framework of the modern Zambezi and Limpopo River systems. We present first evidence—based on heavy‐mineral assemblages from cores drilled offshore of the Limpopo River mouth and samples collected in different reaches of the modern Limpopo River, integrated with magnetic susceptibility, detrital‐zircon geochronology, and geomorphological analysis—suggesting that the current Limpopo River formed recently in the Plio‐Quaternary. Plio‐Quaternary climate change is envisaged to have controlled the recent dynamics of river drainage and consequent distribution of sediment loads, as observed in many other transcontinental rivers worldwide. Plain Language Summary: Landscape evolution, sediment dispersal patterns, and the accumulation of hydrocarbon and mineral resources in southern Africa, were largely determined by the evolution of the vast Zambezi‐Limpopo River system. It is widely believed that this river system attained its current configuration during the late Paleogene as a consequence of mantle‐driven dynamic uplift. Based on heavy‐mineral assemblages from river sediments and an International Ocean Discovery Program ocean core, we argue here instead for a Plio‐Pleistocene age for the formation of the modern characteristics of the Limpopo River (i.e., tens of millions of years younger than previously thought). This challenges the current paradigm on both formation modality and driving mechanisms of this vast river system. Plio‐Pleistocene climate change is envisaged to have controlled the dynamics of river drainage and consequent distribution of sediment loads, as observed in several other transcontinental rivers worldwide, underscoring the importance of these climate changes in driving river evolution world‐wide. Key Points: The modern Limpopo River of South Africa formed in the Plio‐PleistocenePlio‐Pleistocene drainage reorganization was driven by climate changeFormation age and driving mechanisms of South African rivers are revisited [ABSTRACT FROM AUTHOR]

The upper Yellow River drains the central and northeastern Tibetan Plateau. Understanding the origin of this river is essential for unraveling the interplay between fluvial incision, basement uplift, and climate change. However, the formation age of the upper Yellow River is highly debated, with estimates ranging from Eocene to late Pleistocene. In order to clarify the history of the upper Yellow River, we present a heavy‐mineral dataset from drill core in the Yinchuan Basin, a depositional sink at the end of the upper Yellow River course. Our results reveal that the drainage area of the upper Yellow River (i.e., northeastern Tibetan Plateau) has been serving as a major sediment source region for the Yinchuan Basin since at least 3.3 Ma. A late Pleistocene formation of the upper Yellow River, and erosion of neighboring deserts or bounding mountains as an explanation for thick sediment accumulations in this area, is thus ruled out. Plain Language Summary: The Yellow River, the sixth longest in the world, is often called "the cradle of Chinese civilization." However, due to high sediment loads, it often flows above the level of surrounding farm fields in the Yinchuan‐Hetao Basin, the depositional zone of the upper Yellow River. Catastrophic flooding has occurred several times here in the recent past. Thus, the river is also called "China's Sorrow." Understanding where the vast amount of sediments in the Yinchuan‐Hetao Basin came from would help to guide river management. Here we present a first investigation of sediment sources in the Yinchuan Basin using heavy‐mineral data of long drill cores spanning the last 3.3 million years. Our results suggest that the majority of the sediments in this region were transported from the northeastern Tibetan Plateau by the upper Yellow River and not from erosion of the neighboring deserts/drylands or mountains. Only during the last 10,000 years might human activities have increased erosion of neighboring deserts/drylands, causing a provenance shift. Key Points: We present provenance evidence for establishment of the upper Yellow River since at least the late PlioceneThe evidence from the Yinchuan Basin drill core supports a prolonged history of the upper Yellow RiverThe sediments in the Yinchuan Basin were transported from the northeastern Tibetan Plateau mainly by the Yellow River [ABSTRACT FROM AUTHOR]

Fluvial response to allogenic and autogenic controls concerns the understanding of landform evolution related to the interaction between tectonic movements, climate, surface process and human activity. Paleo-channels, as part of geomorphic archives, have been widely employed to study this issue during recent decades. Previous work has however concentrated on the mechanisms driving river migration. A new approach, in which multiple elements are considered, is employed here in the examination of paleo-channel formation in the Jiudong Basin, located at the northeastern margin of the Tibetan Plateau and characterized by active tectonic deformation, a dry climate and ancient human activity. Based on geomorphic and sedimentary analysis, eight paleo-channels formed by the Taolai and Hongshuiba rivers (two tributaries of the Beida River catchment) have been identified. AMS14C dating of the overlying lacustrine sediments defined their respective abandonment at ca. 22.2, 20.9, 15.3, 18.8, 13.9, 11.9, 3.5 and 1.1 cal. Ka BP. The migration histories of the two rivers have been reconstructed, and then well correlated with reference to archives of tectonic, climatic and human influence. Our results suggest that these controlling factors seem to be coupled and have a competitive relationship in driving river migration. In the northeastern margin of the Tibetan Plateau, channel migration can therefore be regarded as a result of fluvial response to the interaction between rapid tectonic activity, climatic fluctuation and human influence. • 8 paleo-channels have been identified in the northeastern margin of the Tibetan Plateau. • These paleo-channels have been constrained by AMS14C dating in the last glacial period. • These paleo-channels are coupled record of climate, tectonics and human influence. [ABSTRACT FROM AUTHOR]

Despite decades of study, the factors that controlled the formation and evolution of the upper reaches of the Yellow River, including uplift of the northeastern Tibetan Plateau, Pliocene-Pleistocene climate change, and autogenetic processes are still poorly constrained. The stratigraphic record of such paleogeographic evolution is recorded in the sequence of nine terraces formed during progressive incision of the Yellow River in the last 1.7 Ma. This article investigates in detail for sediment provenance in terraces of the Lanzhou area, based on heavy-mineral and geochemical (REE) signatures. Two main provenance changes are identified, pointing each to a major paleogeographic reorganization coupled with expansion of the upper Yellow River catchment and enhanced sediment fluxes. The first change took place between the deposition of terrace T9 (formed around 1.7 Ma) and terrace T8 (formed around 1.5 Ma), when rapid fluvial incision point to tectonic control and active uplift of northeastern Tibetan Plateau. The second change took place between deposition of terrace T4 (formed around 0.86 Ma) and terrace T3 (formed around 0.14 Ma), during a period of low incision rates and notably enhanced sediment fluxes as a response to enhanced East Asian Summer Monsoon and consequently increased precipitations, pointing instead chiefly to climatic control. [ABSTRACT FROM AUTHOR]

Knowledge of the composition of modern fluvial sediments is important for understanding the combined effect of lithology and climatic factors on the erosion and sedimentation within drainage basins, However, this information is incomplete in arid and semiarid environments. In this study, 37 modern fluvial sediment samples were collected from the Heihe River and its major tributaries, in the NE Tibetan Plateau, and for analyses of heavy minerals, trace and rare earth elements (REEs) and grain size. The main aim was to explore the influence of erosion, transport and deposition processes on sediment composition, and to define appropriate provenance indicators specific to these rivers. Along the Heihe River, the amount of unstable minerals is abundant and not changing, these result suggests that chemical weathering plays only a minor role. The composition of six sediment samples obtained from the upper-middle reaches of Heihe River are influenced by hydrodynamic sorting processes, which resulted in enrichment of heavy minerals. In addition, the mineralogical and geochemical compositions lead to different conclusions regarding the contributions from tributaries to the sediments in the middle-lower reaches of the Heihe River. This may reflect the occurrence of contrasting hydrodynamic conditions in Heihe River and its tributaries which result in the transport of different size fractions. Moreover, the <63 μm fraction of the sediments from the Heihe River basin has been affected by inputs of eolian dust, which means that this fraction is less influenced by the rock types within the sediment source areas than is the case for the other size fractions. Therefore, we conclude that the sand fraction is more suitable for source to sink analysis of fluvial sediments within this and comparable environments. In the upper areas of the Fengle River basin, the combination of low temperature, sparse vegetation coverage and high precipitation have resulted in intense erosion. This case reminds us to note the effect of the climatic zonation on the provenance analysis in arid regions. [ABSTRACT FROM AUTHOR]

• A cross-disciplinary method quantifies river biogeomorphic succession phases at the reach scale. • A trial application shows that Biogeomorphic landform ratios effectively differentiate phases of river evolution. • The approach is generic and can be used in different situations. The Fluvial Biogeomorphic Succession phase model (FBS model) differentiates Geomorphic (G), Pioneer (P), Biogeomorphic (B) and Ecological (E) phases of hydro-geophysical-biological interactions in river systems. To date, quantitative applications of this model have been restricted to field surveys of vegetation composition analysis at the patch-scale. Here we develop a biogeomorphic landform mapping approach to determine the dominant biogeomorphic succession phase at the reach scale. We categorize river morphology into four biogeomorphic landform types (G-, P-, B- and E-landforms) that have particular geomorphic, substrate and vegetation cover characteristics. Ratios of these landforms are used to calculate the dominant succession phase in a given reach. A test of this method conducted for two contrasting anabranching reaches of the Upper Yellow River indicates that landform ratios provide an efficient and reliable approach to assess river biogeomorphic succession phase. The approach can be adapted to support systematic cross-scalar analyses across the range of river environments. [ABSTRACT FROM AUTHOR]

Continental-scale drainage reorganization is generally understood to result from landform evolution forced by the coupling between tectonic activity and climate change, attracting worldwide attention. Planation surfaces and river terraces constitute the most direct geomorphological archives for integrating the history of river systems and for reconstructing processes of drainage reorganization based on provenance analysis of the fluvial sediments. The Middle Yellow River has incised into the Ordos Block, which was previously levelled by a planation surface, creating the Jinshaan Gorge and linking the Hetao Basin to the north and the Fenwei Basin to the south. Multiple lines of evidence, from terraces correlation, sedimentary characteristics, and fluvial provenance, suggest that the Middle Yellow River catchment was occupied by fluvio-lacustrine systems before drainage integration, accumulating a sedimentary sequence derived from surrounding Red Clay and bedrocks during the period between 8.3 and 3.7 Ma. The planation surface was uplifted subsequently, forcing reorganization of the fluvio-lacustrine systems. Their integration resulted in the formation of the Jinshaan Gorge prior to 1.2 Ma. Numerous terraces were created during incision by the Middle Yellow River from north to south along the gorge. Our data, obtained from zircon U Pb dating and lithological composition of fluvial gravels, further points to a remarkable discrepancy in provenance between the fluvio-lacustrine systems overlying the planation surface and the terraces sequence formed by the integrated Middle Yellow River, confirming the drainage reorganization process constrained by the geomorphic records. • Fluvio-lacustrine systems occupied the Middle Yellow River before integration. • Yellow River terraces are different from fluvio-lacustrine systems in provenance. • The Middle Yellow River has been excavated and integrated during Plio–Pleistocene. [ABSTRACT FROM AUTHOR]

The fluvial archives in the upper-reach Yellow River basins provide important information about drainage history of the northeastern Tibetan Plateau (TP) associated with geomorphologic evolution and climate change. However, the Pliocene fluvial strata within this region have not been studied in detail, hence limiting the understanding of the late Cenozoic development of regional fluvial systems. In this paper, we present the results of a study of the geochronology, sedimentology, and provenance of the fluvial sequence of the Wuquan Formation in the Lanzhou Basin in the northeastern TP. Magnetostratigraphic and cosmogenic nuclide burial ages indicate that the Wuquan Formation was deposited during 3.6–2.2 Ma. Furthermore, sedimentary facies, gravel composition, paleocurrent data, and detrital zircon U Pb age spectra reveal that the fluvial sequence resembles the terraces of the Yellow River in terms of source area, flow direction, and depositional environment. Our results indicate that a paleo-drainage system flowing out of the northeastern TP was established by ca. 3.6 Ma and that the upstream parts of the Yellow River must have developed subsequently from this paleo-drainage system. The late Pliocene drainage system fits well with the dramatic uplift of the northeastern TP, an intensified Asian summer monsoon, and global increase in erosion rates, which may reflect interactions between geomorphic evolution, tectonic deformation, and climate change. [ABSTRACT FROM AUTHOR]

• We report detrital zircon U-Pb geochronology data from the Tengger Desert. • Tengger sediments were sourced from the Qilian Shan, local basements and Gobi Altay sources. • Precipitation is important for middle to late Quaternary desertification in China. Dust plays a critical role in global biogeochemical and carbon cycles. The deserts of northern China have been important East Asian dust sources throughout the Quaternary. The Tengger Desert, one such major arid dust-producing region in northern China, is thought to have started resembling its current form during the middle to late Pleistocene. As such, understanding the nature of the Tengger Desert's formation and the associated import, storage, and export of sediments are consequential for the regional, and potentially global, climate. The U-Pb detrital zircon geochronology data reported here from both present-day and middle to late Pleistocene Tengger Desert sediments support derivation from the Shiyang River system sourced from the Qilian Mountains mixed with sediments eroded from local basement uplifts and Gobi Altay sources. This interpretation is different from the view that sediments of this age were primarily transported to the Tengger Desert from the arid East Asian continental interior upwind. We note that this analysis suggests a common provenance for Quaternary sediments in the Tengger, Badain Jaran, and Mu Us Deserts wherein these deserts received riverine-sourced sediments from the Qilian Mountains and northeastern Tibetan Plateau. This observation highlights the importance of precipitation at elevation along the present-day margin of the East Asian summer monsoon in driving sediment supply during the middle to late Quaternary desertification within the East Asian continental interior. [ABSTRACT FROM AUTHOR]

Surface sediment samples concurrently collected in the catchment of the Ningxia-Inner Mongolian reach of Yellow River (NIMYR) were analyzed to determine the phosphorus and correlated physiochemical properties of sediments. Samples were obtained from three main areas: the riverbed surface sediment (RSS), the floodplain surface sediment (FSS) and the desert surface sediment (DSS). The sequence of phosphorus-contamination level in this catchment, determined by a cumulative distribution function and multivariate statistical analysis, were FSS > RSS > DSS. Moreover, because of the impacts of anthropogenic activities, the sampling site with the highest and lowest phosphorus concentration (mg kg − 1 ) of this catchment appeared in RSS (749.40) and DSS (200.10) respectively. In addition, this is the first study to present a qualification of the effect of the sediment's physicochemical properties on phosphorus by the multivariate regression tree analysis. Co-precipitation of phosphate with calcite [i], phosphate absorbed onto ferric hydroxides [ii] and grain-size effect [iii] were the three main mechanisms for phosphorus distribution in the sediment of NIMYR. The contributions of these three mechanisms to RSS and FSS were, respectively, [i] > [iii] > [ii] and [i] > [ii] > [iii]. The heaviest phosphorus-contaminated group of RSS was primarily controlled by [i], whereas the heaviest phosphorus-contaminated group of FSS was controlled by [i] and [ii], indicating that the FSS had a higher potential risk of releasing phosphorus from the sediment to overlying water. [ABSTRACT FROM AUTHOR]