Geomorphology最新文献_第4页

The large distribution of inverted stream channel terrains in the western Qaidam Basin, North Tibetan Plateau, and implications to the fluvial ridges on Mars

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-27 DOI: 10.1016/j.geomorph.2025.109632

Zi-Kang Li, Sheng-Hua Li, Yi-Liang Li

The fluvial ridge, an important landform that has been documented on both Earth and Mars over different geologic times, provides critical evidence of past hydrologic activity. However, the processes of deposition and subsequent erosion of terrestrial fluvial ridges are still largely unclear, and the study of these processes is essential to a better understanding of fluvial ridges on Mars. Here, we report 16 well-preserved regions of inverted stream channels (ISCs), a type of fluvial ridge, with different morphological features and settings, widely distributed in the western Qaidam Basin (QB). Optically stimulated luminescence (OSL) dating of the ISC sediments indicates that these channels were deposited during a cold and dry climatic period (MIS 6). Based on mapping, statistical, and geometric analyses of channel length and sinuosity, we propose a classification scheme that takes into account the architecture of the individual channels and the morphology of channel networks. Our results suggest that the formation of ISCs in the Qaidam Basin occurred during the warming phase following the onset of a cooling cycle, and that the subsequent inversion of ridges is primarily the result of wind and fluvial erosion under a hyperarid climate. The ISCs can also be compared to analogous counterparts on Mars, inverted channels or sinuous ridges, due to their morphological similarities, which could potentially shed light on the hydrological environments of early Mars.

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引用次数: 0

Alongshore runup variability across contrasting beach states: Insights from field observations

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-27 DOI: 10.1016/j.geomorph.2025.109640

Ashley David Gracia-Barrera , Amaia Ruiz de Alegría-Arzaburu , Giovanni Coco , Gonzalo Simarro , Daniel Calvete

Most beaches exhibit alongshore morphological variability, which is often overlooked in predictive empirical parameterizations of the runup. This study examines alongshore runup variations in relation to intertidal and subtidal morphology on an intermediate beach in the NW Pacific of Baja California. UAV imagery, combined with topographic and bathymetric measurements, was used to determine the runup elevation along a 500-m stretch of beach with diverse morphological characteristics: Terraces and Cross-shore Channels (TCC), Transverse Bar and Rip (TBR), Reflective conditions (R), and Reflective beaches with Multiple Channels (RMC). The largest runup variations were observed under intermediate conditions (TBR), where rip channels and transverse bars significantly influenced the runup. Distinct signatures associated with different morphologies were evident in the spectral shape of the swash, with well-developed rip channels promoting more incident swash unless wave breaking occurred at bars at the head of the rip. Swash showed alongshore variability ranging by a factor between 1.4 and 2.7, depending on the beach state. This factor can be much larger when evaluated over the incident and infragravity swash components. Such variability could not be explained by changes in beach slope alone. The setup, as the lower component of the runup, exhibited minimal alongshore change, with a coefficient of variation of <23 %. Wave runup, setup and swash observations were compared against various existing parameterizations. The results showed that the variability of incident swash is well captured by parameterizations based on foreshore slope and deep-water wave parameters. While predictions of infragravity swash improve when accounting for beach morphology, most of the alongshore variability remains unrepresented, particularly for milder slopes. This research highlights the influence of alongshore morphological variations on runup and underscores the necessity of incorporating these variations into parameterizations to enhance accuracy.

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引用次数: 0

Terrain-driven circulation around megadune–lake system in China's Badain Jaran Sand Sea

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-27 DOI: 10.1016/j.geomorph.2025.109633

Ping Lü, Zhibao Dong, Tianjie Shao, Zhengcai Zhang, Fang Ma

China's Badain Jaran Sand Sea has the world's largest megadunes. However, hypothesized explanations of their formation are based on weak evidence. To clarify the formation and maintenance mechanisms for these dunes, it's necessary to describe this landform's circulation. In this study, we measured the wind regime around a magadune–lake system from 2019 to 2021 to comprehensively characterize the terrain - driven circulation primarily induced by the roughness - disturbance impact exerted by the megadunes. The circulation generally disperses outward from the lake's center, and wind speed gradually increased from the megadune's bottom to its top. During the daytime, strong winds rise along the megadune's slope; at night, the megadune produces mountain winds and land winds, with downward airflow from the top of the megadune towards the center of the lake, but with low frequency and low wind speed. This creates a resultant drift direction (RDD) that is consistent between day and night, with both RDD pointing towards the megadune's top. RDD changes little between seasons, and is consistent with the annual RDD (from the megadune's bottom to its top). Two factors drive the circulation: First, the dune's height represents a roughness element that creates a deep convective boundary layer that triggers a strong ascending flow. Second, the flow is driven by differences in the thermal properties between the lake and the sand particles. Our results suggest that the terrain-driven circulation around megadune–lake systems flows from the dune's bottom to its top and explains the characteristics of the world's largest megadunes. Our work provides an empirical basis for a more comprehensive understanding of the formation and maintenance of the megadune–lake system.

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引用次数: 0

Speleogenesis of Valdemino Cave (Borgio Verezzi, Liguria, Northern Italy) shows very slow uplift of this coast since Middle Pleistocene

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-27 DOI: 10.1016/j.geomorph.2025.109636

Jo De Waele , Chuan-Chou Shen , Bartolomeo Vigna , Adriano Fiorucci , Paola Marini , Chun-Yuan Huang , Hsun-Ming Hu

Valdemino show cave (Borgio Verezzi, Northern Italy) is located 600 m from the Ligurian coast. The cave, hosted in Triassic dolostones, is characterised by mixing corrosion morphologies and large collapses, some of which covered with thick speleothems, and lacks typical morphologies and sediments related to turbulent water flow. U/Th dating of speleothems allowed bracketing the timing of collapses, coastal mixing, and speleogenesis. The oldest speleothems indicate the first phases of speleogenesis to have occurred prior to ca. 600 thousand years ago (ka, before 1950 CE), whereas important calcite deposition occurred during both warmer and colder periods. Collapses repeatedly took place during cold stages, since at least 600 ka. Present drip waters are highly mineralised, causing speleothem growth and testifying to a long water-rock contact, despite the poor thickness (<10 m) of the rock above the cave. Speleogenesis is mainly related to coastal mixing corrosion which dissolved portions of the rock mass during various periods of the Middle- to Upper Pleistocene, and occurs still today in deeper parts of the cave. During cold stages, when the sea retreated and the water table lowered, loss of buoyancy caused cave rooms to collapse, creating the voids accessible today. The Valdemino cave system was positioned several times in the fresh-salt water mixing zone during different sea level highstands over the last 600 ka, the highest of which occurred during MIS 5e. This demonstrates that this coastal sector must have been subjected to a slow uplift since 600 ka, with rates of ca. 0.05 m/ka. Six-hundred thousand year old corroded speleothems, that were in the mixing zone during MIS 5e, are now found at +6 m above present mean sea level.

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引用次数: 0

Drainage patterns in the Sudetes Mountains (Central Europe) – A clue to understanding polygenetic relief?

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-27 DOI: 10.1016/j.geomorph.2025.109637

Piotr Migoń, Kacper Jancewicz, Milena Różycka, Mariusz Szymanowski

The Sudetes range is a topographic unit of protracted history that can be traced back to the Variscan orogeny in the Palaeozoic. After marine inundation in the Late Cretaceous and uplift at the turn of the Cenozoic, a phase of long-term denudation ensued and rock-controlled morphology began to evolve. Differential uplift and subsidence resumed in the Neogene, producing the contemporary horst-and-graben relief with altitude differences exceeding 1000 m. Thus, the present-day topographic diversity is the combined outcome of structure-controlled denudation, vertical displacements, and variable erosional response to uplift modulated by rock resistance, over a timescale of ~60 Ma. However, no systematic attempts were made to disentangle this complex topography and to evaluate the role of lithology and structure versus differential uplift. Here we demonstrate that an analysis of regional fluvial network versus topography may provide important clues, allowing to discriminate between drainage patterns which are well-adjusted to lithology and structure, implicitly of long history, and river reaches that reflect fluvial response to younger tectonic forcing. Three lines of inquiry are explored. First, morphometric properties of main rivers in respect to plan and profile, and of their drainage basins, are analysed. Second, relationships of drainage patterns to the surrounding relief, including analysis of water gaps, styles of fluvial incision, and possible water-divide migrations, are investigated. Third, peculiarities in geometric patterns of drainage networks are identified. We propose that despite an important relief-forming role of the Neogene uplift, tectonic perturbations imposed on the drainage pattern were comparatively minor, no major reorganizations occurred, and much of the present-day fluvial network is inherited from the more distant history. The predominant fluvial response to uplift was continuous valley downcutting, perhaps with minor lateral shifts, although ongoing water-divide migrations are hypothesized for the most elevated parts of the Sudetes, which experienced asymmetric uplift.

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引用次数: 0

Event-driven erosion of a glacial till cliff

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-25 DOI: 10.1016/j.geomorph.2025.109626

Jan-Eike Rossius , Tanita Averes , Knut Krämer , Christian Winter

Soft-rock cliff coasts are eroded by various mechanisms. Marine erosion occurs during storm surges and is linked to increased water levels and wave heights while terrestrial erosion by mass movements is affected by precipitation. This study aims at improving the system understanding of soft-rock cliffs by quantifying observed erosion and the boundary conditions necessary for marine erosion and relating terrestrial erosion to certain prerequisites and weather conditions at a glacial till cliff at the German Baltic Sea coast. The changes at the cliff are quantified using digital elevation models obtained from about monthly drone surveys over a period of four years. Marine and terrestrial erosion both occur mostly in winter and set the mutual preconditions. For terrestrial erosion, precipitation is the main enabling factor, a clear quantification is however difficult. For marine erosion, a threshold based on water level and significant wave height is quantified. With a certain increase in water level, a single event is more likely to surpass that threshold than with the same increase in wave height. Moreover, the effects of the exceptionally severe storm Babet in October 2023 are quantified: It eroded more than all other storms during the study period combined and about as much as would be eroded within seven normal years. The findings exemplify a high vulnerability of soft-rock cliffs to sea-level rise and future storm events.

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引用次数: 0

A pre-Pliocene origin of the glacial trimline in the Ellsworth Mountains and the prevalence of old landscapes at high elevations in West Antarctica

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-24 DOI: 10.1016/j.geomorph.2025.109634

David Small , Michael J. Bentley , Stewart P.H.T. Freeman , Angel Rodés , Sheng Xu

A glacial trimline at high elevations in West Antarctica informs on previous warm-based glaciation that occurred during an earlier stage of Antarctic Ice Sheet evolution. A multi-million-year history of theses landscapes has previously been evidenced in a few disparate locations. Here we present new cosmogenic nuclide analyses (¹⁰Be and ²⁶Al) from a total of 60 samples (clasts and bedrock) at high elevations in several hard-to-access locations across the interior of West Antarctica. In the Sentinel Range of the Ellsworth Mountains this trimline occurs at the highest elevations of any sites in West Antarctica (~3000 m asl). These new data reveal that clasts and bedrock, both above and below the trimline, have long exposure histories with minimum exposure-burial histories of 0.9–2.6 Ma. Accounting for low rates of erosion extends these exposure-burial histories to 2.7–4.8 Ma. Under the assumption of cyclical exposure-burial for proportions of glacial-interglacial cycles we show that some of our samples have exposure-burial histories extending back to the Miocene. We also present new data from the nearby Heritage Range where our new data supports previous work potentially extends the inferred persistence of the location of the West Antarctic ice sheet divide to >2.1 Ma. Finally, we present new data from two isolated nunataks (Mount Woollard and Mount Johns) located deep in the interior of the West Antarctic Ice Sheet near the main ice divide. Paired nuclide analyses of samples from these nunataks also shows long exposure histories and unambiguous evidence of past burial within the last ~100 ka. Such a thickening is not currently represented in ice-sheet models.

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引用次数: 0

An archaoseismological investigation of the footprints of human resilience to seismic shaking from the alluvial plains of Gujarat, Western India

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-23 DOI: 10.1016/j.geomorph.2025.109631

Aashna Tandon , S.P. Prizomwala , Tarun Solanki , Abhijit Ambekar , Rakesh Nikam , Pradeep Srivastava , Sumer Chopra

The town of Vadnagar, located on a prominent geomorphic surface ∼ Gujarat Alluvial Plains (GAP) of western India, presents unabetted human occupation for the last 2754 years. An integrated archaeoseismological study (involving tectonogeomorphology, geophysical and geoarchaeological investigation) in the Cambay basin led to the identification of a previously un-noticed the reverse splay fault for the first time with the evidence of the surface rupture in the GAP region. The present study based on electrical resistivity tomography (ERT) and previous investigation of magnetotulleric geophysical surveys in the vicinity, demonstrates it to be the ruptured splay of the East Margin Cambay Basin Fault. The timing of the event is constrained ∼1200–2000 years Before Present (BP) using optical dating, whereas archaeological findings briefs it around 9th – 10th Century CE. Additionally, based on the various empirical relationships between magnitude and maximum displacement of 1.6 m observed in the trench, the magnitude of the event was constrained at M_w 7 ± 0.3. In addition to this, our investigation in the vicinity of the site reveals the tectono-geomorphic expressions of the identified Vadnagar Fault and associated archaeological seismic deformations (i.e. collapsed structures, tilted, and rotated wall fragments) along the hanging wall. The presence of timber-bondings in masonry walls (1st – 4th century CE) suggests earthquake resistant structural know-how in Vadnagar as one of the oldest in Asia. We invite more in-depth scrutiny by seismologists and geologists for assessing the realistic hazard of GAP in light of this new seismic source and the human resilience to earthquakes.

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引用次数: 0

Hillslope surface classification from elevation models by using normal vectors

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-23 DOI: 10.1016/j.geomorph.2025.109614

Guanghui Hu , Sijin Li , Liyang Xiong , Guoan Tang

Hillslope surface classification via digital terrain analysis (DTA) is a current research focus in geomorphology and geographic information science (GIS) studies. However, traditional methods are generally based on raster digital elevation models (DEMs) and window difference methods, which suffer from terrain description and analysis scale mismatch issues. In this study, we propose a hillslope surface classification approach based on the vector structure. Triangulated irregular networks (TINs) are used as an example. Benefiting from free sampling with TINs, we apply terrain surface reconstruction to the original point cloud or DEM and then calculate the terrain derivatives based on the normal vectors of the optimized TINs. Finally, the fuzzy inference method is used to classify hillslope surface elements. We select two cases to evaluate the proposed method: a small watershed with dense point cloud data and a large region with complex landforms and a 30 m resolution Copernicus DEM. The results show that the proposed approach can effectively reduce the influence of DEM errors on classification and mitigate the scale mismatching problem in terrain generalization and analysis. A novel hillslope surface classification method with a new data structure is proposed to extend the application of vector methods and structures in DTA and GIS.

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引用次数: 0

Delineating individual alluvial fans and morphological analysis based on digital elevation models

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2025-01-23 DOI: 10.1016/j.geomorph.2025.109629

Xingyu Zhou, Yang Chen, Wenjie Sun, Xin Yang, Yanxiang Wang, Chenrui Li, Guoan Tang

Alluvial fans are common landforms deposited by streams and/or debris flows. Multiple fans can overlap and connect with each other, developing a bajada. Currently, studies about the evolutionary process of alluvial landscapes and environmental changes in arid areas urgently need clear, detailed and object-based evaluation within bajadas. However, existing methods still struggle to divide these alluvial slopes into individual fans. Accordingly, we proposed a novel method for delineating individual alluvial fans based on free digital elevation models. This method incorporated multi-directional hillshades to accurately extract alluvial slopes, and two flow direction algorithms to support the delineation of individual fans. The method was tested in Death Valley, where a total of 89 individual fans were delineated for morphological analysis. Our result demonstrated high accuracy validated by a Landset-9 L2 satellite image, with an intersection over union (IoU) of 95.51 % for alluvial slopes and a mean IoU of 86.19 % for individual fans, and it also aligned well with the geological map. Additionally, based on the delineated individual fans, we computed morphological features, distinguished the surface differences of both sides and analyzed the feature correlations. Overall, this study accomplished the delineation of individual fans and provided a viable solution for the automated and large-scale mapping of arid alluvial landscapes. The delineated results can act as the foundation for research about the evolutionary process and genetic mechanisms of alluvial fans, and provide opportunities for understanding the tectonic activities, sediment deposition and erosion process and environmental changes in arid regions.

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引用次数: 0