Search

The timespan recorded in deposits from fluvial activity is a key gap in our understanding of ancient environments on Earth and Mars. Because riverine sediment transport occurs under time‐variable water discharge, common models that represent sediment transport with a single bankfull discharge require an intermittency factor. For this reason, the ability to predict intermittency factor values based on environmental factors would improve estimates of time from fluvial deposits. To address this knowledge gap, we calculated intermittency factors from 201 modern rivers and six fans and deltas with depositional timespans of months to millions of years. Intermittency factors range from 0.0064–0.73; they are uncorrelated with averaging timescale, bed‐material grainsize, or climate aridity, but are larger in river catchments with greater rates of denudation relative to precipitation. Application to ancient fluvial systems on Mars indicates long‐lived depositional river systems for up to 104–106 years. Plain Language Summary: To estimate the lifespan of ancient river courses, geologists estimate the time it took to transport and deposit all of the sediment within a landform, such as an alluvial fan or delta. This method relies on sediment‐transport calculations, which often assume a single reoccurring flood event that fills the river channel, even though river discharge varies in time from low flows to large floods. While the discharge of the channel‐filling flood event can be constrained from channel geometry or deposit characteristics, flow variability is unknown, and an intermittency factor is needed to adjust the sediment transport calculation. In this work, we calculated intermittency factors for 201 rivers and six river deposits on Earth. We also examined correlations between intermittency factor and environmental variables, and found no correlation with averaging timescale, bed‐material grainsize, or climate aridity. However, intermittency factors are larger in catchments that receive a large supply of sediment. Applying the new intermittency factor values to river deposits on Mars suggests that some of those rivers persisted for millions of years. Key Points: Rivers transport sediment intermittently; intermittency factor relates river duration to deposit volume and bankfull river characteristicsIntermittency factors we calculated have a 5–95 percentile range of 0.0064–0.73, independent of timescale, grainsize, and climateApplication to Mars implies fluvial activity over thousands to millions of years [ABSTRACT FROM AUTHOR]

The flora of the Cianowice 2 borehole (c. 20 km NW of Cracow, Poland), dominated by cycadophytes (mainly bennettitaleans) and conifers, shows high taxonomic diversity relative to the low number of specimens. Twenty species were identified in the 96 determinable plant fragments found in 27 core samples: Cladophlebis sp. (ferns), Pachypteris rhomboidalis (Ettingshausen) Nathorst and Ptilozamites cycadea (Berger) Möller (seed ferns), Anomozamites nilssonii (Phillips) Seward, Nilssoniopteris solitaria (Phillips) Cleal & Rees, Otozamites mimetes Harris, Otozamites parallelus Phillips, Pterophyllum thomasii Harris, Pterophyllum cf. aequale (Brongniart) Nathorst, Ptilophyllum cf. okribense forma ratchiana Doludenko & Svanidze, Ptilophyllum pecten Phillips, Ptilophyllum sirkennethii Watson & Sincock, Cycadolepis sp. (bennettitaleans), Pseudotorellia grojecensis Reymanówna, Pseudotorellia samylinae Nosova & Kiritchkova, Pseudotorellia sp. (Gymnospermae incertae sedis), Bilsdalea dura Harris, Mirovia szaferi Reymanówna, and Brachyphyllum stemonium Kendall (conifers). The floristic composition is supplemented by palynological data. The taxa were connected to five depositional successions distinguished along the core: one, alluvial fans; two, four and five, meandering/ anastomosing river depositional systems with fluvial plain deposits; and three, lacustrine/backswamp environment developed on fluvial plain. The composition of the fossil plant assemblage changes with the depositional setting within the same range of taxa, seen mainly in changed combinations of taxa, which are most diverse in the fluvial plain deposits. Some taxa occur in a single depositional succession; some are present in two or three. The sporomorph assemblages of particular depositional environments differ significantly from the composition of the co-occurring macroflora: ferns occur sporadically in the macroflora of each depositional environment but they strongly dominate the sporomorph assemblage. Our proposed reconstruction of the palaeoenvironment is a slight rise descending into a valley with a depositionary basin, with gymnosperms on the slope and ferns at the base. Some species are shared between Cianowice and nearby Middle Jurassic localities in Grojec and Zabierzów, and the majority of taxa are known from the Middle Jurassic, suggesting that the Cianowice deposits are of that age. [ABSTRACT FROM AUTHOR]

During Pangea breakup, several Jurassic extensional to transtensional basins were developed all around the world. The boundaries of these basins are major structures that accommodated continental extension during Jurassic time. Therefore, reconstructing the geometry of Jurassic basins is a key factor in identifying the major faults that produced continental attenuation during Pangea breakup. We reconstruct the tectono-sedimentary evolution of the Jurassic Tlaxiaco Basin in southern Mexico using sedimentologic, petrographic, and U-Pb geochronologic data. We show that the northern boundary of the Tlaxiaco Basin was an area of high relief composed of the Paleozoic Acatlán Complex, which was drained to the south by a set of alluvial fans. The WNW-trending Salado River-Axutla fault is exposed directly to the north of the northernmost fan exposures, and it is interpreted as the Jurassic structure that controlled the tectono-sedimentary evolution of the Tlaxiaco Basin at its northern boundary. The eastern boundary is represented by a topographic high composed of the Proterozoic Oaxacan Complex, which was exhumed along the NNW-trending Caltepec fault and was drained to the west by a major meandering river called the Tlaxiaco River. Data presented in this work suggest that continental extension during Pangea breakup was accommodated in Mexico not only by NNW-trending faults associated with the development of the Tamaulipas-Chiapas transform and the opening of the Gulf of Mexico, but also by WNW-trending structures. Our work offers a new perspective for future studies that aim to reconstruct the breakup evolution of western equatorial Pangea. [ABSTRACT FROM AUTHOR]

The processes and deposits of tide‐dominated river deltas and estuaries are well‐understood, but the sedimentary dynamics of tide‐dominated straits and seaways are relatively little studied. Although recent depositional models have started to fill this gap, many aspects of tidal strait sedimentation such as interaction with strait‐margin alluvial fans and marginal marine systems remain poorly understood. This paper presents a study of the late Miocene basal carbonate member of the Bouse Formation exposed along the lower Colorado River, where prior studies have suggested a tidal influence on deposition. This study explores the applicability of tidal strait models in a continental oblique‐rift setting, and tests hypotheses for depositional processes and environments through detailed analysis of sedimentary facies, cross‐bedding architecture and palaeocurrent data. Mixed carbonate–siliciclastic facies on the west margin of the southern Blythe Basin record sedimentation in alluvial fans and fan‐fringing tidal flats at the retreating margin of a transgressive tidal strait. Pre‐Bouse normal faults established a narrow, tectonically confined basin architecture that led to amplification of tidal currents. Basin‐margin deposits pass laterally and up‐section into high‐energy cross‐bedded grainstone facies that record southward migration of compound dunes in the dune‐bedded strait zone of a shallow (ca 25 m) tidal strait. These findings provide the basis for recognition of strait‐margin facies in other settings where complex facies associations result from along‐strike variations in palaeobathymetry and current velocity. The results support a tidal origin for the southern Bouse Formation and provide new evidence for post‐Miocene uplift of the lower Colorado River Valley and adjacent areas. [ABSTRACT FROM AUTHOR]

Climate factors and human activities are the leading causes of changes in the hydrological cycle. In addition to being an important part of the hydrological cycle, runoff is also an important indicator for assessing the amount of available water. Therefore, it is necessary to explore the reasons that have caused changes in runoff. In this study, the causes of runoff changes in the alluvial fan of the Choshui River from 1980-2018 are explored. Two simple methods, including a decomposition method based on the Budyko structure and a method based on climate elasticity, for which the necessary data are easy to obtain, are used to quantify the impact of climate factors and human activities on runoff changes. The results show that the runoff in the long term shows a significant transition point in 2003, where climate factors have contributed more than 90% of the change, while the influence of human activities on the changes in runoff appears to be relatively small. Moreover, the Budyko method and the Normalized Difference Vegetation Index (NDVI) show that the vegetation cover has decreased. In addition to providing a simple method to assess the causes of changes in runoff, this study also analyzes the causes of changes in the runoff of the alluvial fan of the Choshui River to provide a reference for water resource policy and land use management. [ABSTRACT FROM AUTHOR]

This study aims to determine the effect of a flood-spreading system on the morphometric characteristics of alluvial fans (AFs) in Gribayegan Fasa, Iran, and its relationship with erosion, age, texture, and type of formations. After determining the AFs using the semiautomatic method and determining their recharged watersheds, 25 morphometric characteristics were investigated. The most important morphometric characteristics were identified using principal component analysis (PCA). The group method of data handling (GMDH) neural network is used to predict erosion, soil texture, age, and formation material based on the morphometric characteristics of the fan. The results demonstrate that the semiautomatic method can effectively extract AF from the landscape. The results of AF morphometry before and after flood spreading show that the fan area, drainage basin circularity (Cirb), fan perimeter, relief ratio of the fan, fan length, minimum fan height, and maximum fan height were higher before flood spreading, and basin shape, St (soil texture), upper fan slope, fan volume, and sweep angle had higher values after the flood. In addition, the results of PCA show that fan area, fan perimeter, fan length, fan radius, fan volume, basin area, basin perimeter, main channel length, basin length, and drainage density are important factors. The results of the GMDH algorithm reveal that this method can accurately predict the formation, age, soil texture, and erosion rate using morphometric characteristics. Therefore, the R2 is 0.92 for the formation age and R2 is 0.86 for the erosion rates, formation types, and soil texture, respectively. Therefore, the most important morphometric parameters can be determined using PCA, and the conditions and processes in the basin, such as formation material, age, soil texture, and erosion rate, can be predicted with high accuracy using the GMDH algorithm. [ABSTRACT FROM AUTHOR]

The research aims to study the pHysical and chemical properties of agricultural soils and their role in establishing an economically feasible agricultural investment in the eastern regions of Maysan Governorate, which lies within the international border belt with the Republic of Iran. The results of laboratory analyzes conducted for (36) models of the first two depths (0-30 cm) revealed ) and the second (31-60 cm). It included the pHysical properties (soil texture, porosity, moisture content), chemical properties (pH, electrical conductivity, Ec, total organic carbon, Toc), as well as some nutrients dissolved in the soil solution (nitrogen N, pHospHorous Po4, potassium K), which Together, they contribute to influencing the reality of agricultural investment in the region. And it became clear that there is a diversity in the soils of the region, as it represents the soils of the eastern hills, alluvial fans, the soils of the rivers and their basins, as well as the soils of the marshes and sand dunes. agricultural investment in it. [ABSTRACT FROM AUTHOR]

Rio graben is a region of significant stratigraphic and palaeontological interest where several environmental changes have been recorded during the Quaternary. These changes are a result of active tectonism, related to the well-known rifting process that has been occurring in the geotectonic region of the Corinth-Patras Rift, as well as of the influence of continuous eustatic and climatic changes. Fossil assemblages from Middle to Upper Pleistocene transitional to marine and terrestrial sedimentary sequences located at Sichaena (Rio Graben) on the west side of Charadros river in NW Peloponnesus, Greece, are analyzed herein in order to distinguish tectonic and eustatic controls. The name of the studied section is Vigla 1 (50 m thickness), belonging to the NE-trending Rio graben, a structure bridging the Corinth graben to the east and the Patras graben to the west. The presence of two normal antithetic second order faults and an unconformity were identified separating the studied stratigraphic section into four distinct sedimentological sequences. The purpose of this work is to determine the palaeoenvironmental conditions of the studied section and to unravel the Middle-Late Pleistocene palaeoenvironmental changes. The micro-fauna evidences oligohaline lagoon sediments at the lower sequence (Sequence 1). Conversely, at the middle (Sequence 2) and at the upper sequence (Sequence 3), the recorded species indicate lagoonal to shallow marine depositional environments. At the top of the section, an unconformity brings into contact Sequence 3 with a sequence consisting a red conglomerate (Sequence 4) that indicates an alluvial fan environment. In order to constrain chronologically the sediments Optically Stimulated Luminescence (OSL) dating was applied. According to the OSL dating results, an Upper Middle Pleistocene age has been attributed for the studied sequences. Moreover, projecting the dating results to the marine isotope curve, a high degree of consistency can be seen between the OSL ages and MIS 7e, 7c and 6d, where the transition from lagoonal facies to shallow marine alternations in sequence 2 correlates well with the MIS 7c highstand, and sequence 3 with MIS 7e and the MIS 6d low stand. Thus, our results indicate the spatial palaeoenvironmental evolution of the studied area which during the Upper Middle Pleistocene is characterised by intense local tectonic movements in conjunction with eustatic sea level changes. [ABSTRACT FROM AUTHOR]

Although alluvial fans are widely distributed along the western margin of the Junggar basin, NW China, uncertainties in their formation age and associated environment need to be resolved. In a well-developed alluvial fan in the upper reaches of the Baiyang River, a 137 m-deep hydrogeological drilling core (ZK1) has been extracted. Paleomagnetic analysis shows that this section has been deposited since 8 Ma, during three distinct phases: (1) a lower segment of muddy facies formed during 8–5.6 Ma; (2) a middle segment of alternating muddy and sandy and gravel layers formed during 5.6–3.6 Ma, and (3) the upper layer of gray conglomerate formed from 3.6 Ma to present. The fan began to develop at ~5.6 Ma, perhaps driven by the Mediterranean Messinian salinity crisis originally. At 3.6 Ma, the deposition rate increased significantly and the climate further dried and cooled, likely due to the uplift of the Qinghai-Tibet Plateau and its far-field structural and environmental impacts. However, the direct causes of the two events recorded in this section are related to the rapid uplift of Wuerkashier Mt., and to regional and global climate cooling. [ABSTRACT FROM AUTHOR]

Erzincan Plain is located on the most active tectonic zone of Anatolia and has the pull-apart basin character in terms of its formation. The plain is a large geomorphological unit that creates a sedimentation area between mountainous regions (Esence and Munzur Mountains) higher than 3000 m bounded by fault lines and contains different geographical formations. One of these geographical formations is the common alluvial cone and fans, which are one of the characteristic landforms of fluvial topography on earth and manifest themselves as deposit formations as a result of the interaction of fluvial erosion and deposition processes. The streams, which take their source from the high mountainous areas around the Erzincan Plain and leave their load due to the sudden change of slope and decrease in speed, formed the alluvial cone and fan systems as a belt on the northern and southern foothills. The most important factors in the formation of cone and fan shapes in the field of study are the tectonic situation, slope and vegetation, topographic elevation difference, lithological and climatic features, and hydrographic conditions in the region. In the study, the effect of morphodynamic factors and processes on the formation and development of alluvial forms in the plain was revealed by considering the tectonic, geomorphological, ecological, climatic, and geological conditions in the Erzincan Plain. Alluvial cones and fans were classified, and the main characters of the formations were determined in the classification made according to the slope values. As a result of the classification, 26 alluvial formations were determined and 22 of them were found to be alluvial fans and 4 of them to be alluvial cones. The study also focused on humaninduced degradation in the alluvial cones and fans, which present various examples in terms of land use, and interventions on the formations such as anthropogenic degradation activities, construction processes, uncontrolled sand quarries, and agricultural activities were discussed and explained. [ABSTRACT FROM AUTHOR]

The research aims to study the pHysical and chemical properties of agricultural soils and their role in establishing an economically feasible agricultural investment in the eastern regions of Maysan Governorate, which lies within the international border belt with the Republic of Iran. The results of laboratory analyzes conducted for (36) models of the first two depths (0-30 cm) revealed ) and the second (31-60 cm). It included the pHysical properties (soil texture, porosity, moisture content), chemical properties (pH, electrical conductivity, Ec, total organic carbon, Toc), as well as some nutrients dissolved in the soil solution (nitrogen N, pHospHorous Po4, potassium K), which Together, they contribute to influencing the reality of agricultural investment in the region. And it became clear that there is a diversity in the soils of the region, as it represents the soils of the eastern hills, alluvial fans, the soils of the rivers and their basins, as well as the soils of the marshes and sand dunes. agricultural investment in it. [ABSTRACT FROM AUTHOR]

Karst aquifers have distinct characteristics that make them complex compared to non-karstic aquifers. The complexity increases in coastal areas, due to the complicated mixing dynamics between groundwater and seawater. The combined use of hydrochemical and isotopic data is proved to be a useful tool to better understand the circulation of groundwater at coastal karst aquifer in southwest Turkey. The "Azmak Streamflow Karst System" is composed of about 150 spring outlets whose electrical conductivity values range between 1300 and 15,000 μS/cm on the coast of the Aegean Sea. The total average flow is about 11 m3/s and the average total dissolved solids at the complete mixing point is about 3000 mg/l. This slightly brackish water is regarded to be strategic owing to its possible availability for future use. Major ions and stable isotope analyses as well as in situ measurements of physical parameters were carried out during a period of 2 years and evaluated to better understand the hydrogeological setting. Spatial and temporal variations of hydrochemical and isotopic constituents of sampled waters also provided a significant tool to elucidate the salinization mechanism in the study area. The results revealed that the Azmak streamflow—opposed to the common assumption—is the outflow of a multi-component hydrogeological system whose components are karst aquifer, alluvial aquifer, alluvial fan, seawater, and surface runoff. In addition, the results showed that sources other than seawater mixing contribute to the salinization of groundwater in the system. [ABSTRACT FROM AUTHOR]

Soil classification is a useful tool for understanding and managing soils. The objective of the present research was to compare the capability of Soil Taxonomy (ST, 2014) and World Reference Base for soil resources (WRB, 2015) systems related to soil description and classification in Lut Desert. Marginal and central parts of Lut with typical aridic/thermic and extreme aridic/hyperthermic soil moisture/temperature regimes were selected. Twelve representative pedons on alluvial fan, plain, rock pediment, Gandom Beryan lava plateau, and playa were described and sampled. The obtained results showed further capability of the WRB system to reflect soil forming processes. However, it could be recommended to add anhydritic qualifier to Solonchaks, Solonetz, and Gypsisols, aquatic qualifier to Solonchaks and Solonetz, and abruptic, leptic, and paralithic qualifiers to Solonchaks. The ST system has not been successful in expressing soil forming processes due to considering only two great groups for saline soils and giving priority to Salids in comparison with the other suborders of Aridisols. That is why Petrosalids, Gypsisalids, Natrisalids, and Argisalids great groups and Anhydritic Natrisalids, Anhydritic Argisalids, Anhydritic gypsisalids, Anhydritic Petrosalids, Calcic Natrisalids, Calcic Argisalids, Calcic Gypsisalids, Natric Petrosalids, Natric Haplosalids, Natric Gypsisalids, Petrogypsic Petrosalids, and Epipetrosalic Aquisalids subgroups are suggested to be added to Soil Taxonomy system. Meanwhile, defining anhydritic horizon and considering textural differences in strongly contrasting particle size class of family level and aquic conditions in playa are among the merits of Soil Taxonomy. Nonetheless, it could be suggested to remove (or adopt) color (Hue) requirement of anhydritic horizon. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the College Of Basic Education is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Söke alluvial fan is located in the north of the Büyük Menderes Delta, one of the important delta areas in Western Anatolia. The alluvial fan, which is named with the Söke district center on which the settlement is located, is adjacent to the Büyük Menderes Delta from the south. The Büyük Menderes Delta, which limits the alluvial fan from the south, is one of the areas where natural environmental changes occur in Holocene. Therefore, the development of the alluvial fan was affected that sea level changes, coastal line changes and the development of the Büyük Menderes Delta. One of the most appropriate methods to determine these relationships is drilling work. In order to evaluate these effects, 5 drillings were made on and around the alluvial fan. Samples were taken for sedimentological and paleontological analyzes from different levels of drillings. The grain size analysis and fossil investigations were carried out different levels of sediments. Grain size; determined using hydrometer and sieve analysis. Fossil investigation was carried out by examining the samples taken under a microscope in detail. As a result of these investigations, macro and micro fossils belonging to Foraminifer, Ostracod and Mollusks (Bivalvia and Gastropod) reflecting fresh water, brackish water and marine environment were found. The development of the alluvial fan in Holocene was evaluated based on the results on field observations, the sedimentological and paleontological analyses of the sediments that were obtained from drillings. [ABSTRACT FROM AUTHOR]

Kağızman district center is located in Northeast Anatolia, within the Kars region of the Erzurum Kars Section. The district center is located on an alluvial fan formed by the Kağızman Stream in Aras Valley, which has a base altitude of approximately 1100 meters relative to the Kars province, most of which is located on the Kars Plateau with an average altitude of 2000 meters. For this reason, terrestrial climate characteristics with more moderate conditions are observed in the district center and in the Aras Valley compared to the city in general. The district center is more populated than the surrounding rural settlements due to the agricultural opportunities provided by the fertile alluvial soils on which it is located, and therefore it has become an administrative and commercial center. The number of registered population in the district center, which was 3,626 in the first years of the foundation of the Republic, has shown a fluctuating course in the period until today and reached 18,795 according to ADNKS 2020 data and constitutes 45 % of the total population of the district, which is 45,441. The population in the district center shows a heterogeneous distribution. [ABSTRACT FROM AUTHOR]

Determining sediment discharge out of watersheds is a global, long‐term challenge. In the vast, usually data‐poor, hyperarid regions of the world, this is a greater challenge. Here, we present a unique, decades‐long dataset of individual floods and their respective sediment discharge out of Nahal Yael, an experimental, well‐instrumented, hyperarid (~25–30 mm year−1) watershed in southern Israel. The high correlation between directly measured sediment yield by discrete individual floods and their respective total energy, represented by flood‐integrated stream power (FISP), serves here as a rating curve. Using this rating curve, the 51‐year‐long series of FISP in Nahal Yael, calculated from the detailed individual flood hydrographs, was converted into a series of sediment yield by these floods. This, in turn, allows determining the long‐term frequency‐magnitude of sediment exported out of this hyperarid basin. This can assist in landscape evolution modeling, in testing impacts of flood frequency changes enforced by altered regional climatology, and hint at changes needed in forming the observed alluvial fans. We conclude that, at the decadal scale, moderate floods are the most effective in terms of total sediment transport. However, the recurrence intervals of these moderate hyperarid floods are longer than in temperate regions and reach 5–10 years. [ABSTRACT FROM AUTHOR]

The presence of ecotones in transition zones between geological strata (e.g. layers of gravel and sand interbedded with layers of silt in distal alluvial fan deposits) in aquifers plays a significant role in regulating the flux of matter and energy between compartments. Ecotones are characterised by steep physicochemical and biological gradients and considerable biological diversity. However, the link between organic pollutants and degradation potential in ecotones has scarcely been studied. The aim of this study is to relate the presence of ecotones with the dehalogenation of chloroethenes. A field site was selected where chloroethene contamination occurs in a granular aquifer with geological heterogeneities. The site is monitored by multilevel and conventional wells. Groundwater samples were analysed by chemical, isotopic, and molecular techniques. The main results were as follows: (1) two ecotones were characterised in the source area, one in the upper part of the aquifer and the second in the transition zone to the bottom aquitard, where the aged pool is located; (2) the ecotone located in the transition zone to the bottom aquitard has greater microbial diversity, due to higher geological heterogeneities; (3) both ecotones show the reductive dehalogenation of perchloroethylene and trichloroethylene; and (4) these ecotones are the main zones of the reductive dehalogenation of the pollutants, given the more reductive conditions at the centre of the plume. These findings suggest that ecotones are responsible for natural attenuation, where oxic conditions prevailed at the aquifer and bioremediation strategies could be applied more effectively in these zones to promote complete reductive dehalogenation. [ABSTRACT FROM AUTHOR]

Although biodegradation of organic matter is well-known to trigger enrichment of arsenic (As) in groundwater, the effects of DOM sources and biodegradability on As enrichment remain elusive. In this study, groundwater samples were collected from the Hetao basin to identify DOM source and evaluate biodegradability by using spectral and molecular techniques. Results showed that in the alluvial fan, DOM was mainly sourced from terrestrially derived OM, while DOM in the flat plain was more originated from microbially derived OM. Compared to terrestrially derived DOMs, microbially derived DOMs in groundwater, which had relatively higher H/C wa ratios, NOSC values and more biodegradable molecules, exhibited higher biodegradability. In the flat plain, microbially derived DOMs with higher biodegradability encountered stronger biodegradation, facilitating the reductive dissolution of Fe(III)/Mn oxides and As enrichment in groundwater. Moreover, the enrichment of As depended on the biodegradable molecules that was preferentially utilized for primary biodegradation. Our study highlights that the enrichment of dissolved As in the aquifers was closely associated with microbially derived DOM with high biodegradability and high ability for primary biodegradation. [Display omitted] • Groundwater DOM was mainly sourced from terrestrially derived OM in the alluvial fan. • Groundwater DOM was more originated from microbially derived OM in the flat plain. • Microbially-derived DOMs had high H/C, NOSC values, and more biodegradable molecules. • Microbially-derived DOM encountered strong biodegradation, promoting As enrichment. • As enrichment depended on DOM molecules being prone to primary biodegradation. [ABSTRACT FROM AUTHOR]

• Hydrologic connectivity shifts from high to low throughout the summer. • Shallow flow paths are important for late summer streamflow generation. • Spatial origin of groundwater discharge varies with hydrologic connectivity. • Dynamic storage explains variability in groundwater flux and stream water origin. Geologic features (e.g., fractures and alluvial fans) can play an important role in the locations and volumes of groundwater discharge and degree of groundwater-surface water (GW-SW) interactions. However, the role of these features in controlling GW-SW dynamics and streamflow generation processes are not well constrained. GW-SW interactions and streamflow generation processes are further complicated by variability in precipitation inputs from summer and fall monsoon rains, as well as declines in snowpack and changing melt dynamics driven by warming temperatures. Using high spatial and temporal resolution radon and water stable isotope sampling and a 1D groundwater flux model, we evaluated how groundwater contributions and GW-SW interactions varied along a stream reach impacted by fractures (fractured-zone) and downstream of the fractured hillslope (non-fractured zone) in Coal Creek, a Colorado River headwater stream affected by summer monsoons. During early summer, groundwater contributions from the fractured zone were high, but declined throughout the summer. Groundwater contributions from the non-fractured zone were constant throughout the summer and became proportionally more important later in the summer. We hypothesize that groundwater in the non-fractured zone is dominantly sourced from a high-storage alluvial fan at the base of a tributary that is connected to Coal Creek throughout the summer and provides consistent groundwater influx. Water isotope data revealed that Coal Creek responds quickly to incoming precipitation early in the summer, and summer precipitation becomes more important for streamflow generation later in the summer. We quantified the change in catchment dynamic storage and found it negatively related to stream water isotope values, and positively related to modeled groundwater discharge and the ratio of fractured zone to non-fractured zone groundwater. We interpret these relationships as declining hydrologic connectivity throughout the summer leading to late summer streamflow supported predominantly by shallow flow paths, with variable response to drying from geologic features based on their storage. As groundwater becomes more important for sustaining summer flows, quantifying local geologic controls on groundwater inputs and their response to variable moisture conditions may become critical for accurate predictions of streamflow. [ABSTRACT FROM AUTHOR]

The Atacama Desert in northern Chile provides a unique setting for investigating the short-term impact of extreme rain events on desert landscape evolution. A decadal-extreme rain event during January and February 2019 was scrutinized through radar and optical remote sensing. We evaluated its impact, contrasting it with a century-extreme 2015 rain event and established geological-timescale rates of change in the region. Five target features were selected for detailed analysis, encompassing all major landforms of the Atacama Desert, excluding mountain hillslopes. Our analysis distinguished active landforms (e.g., alluvial fans toes with mudflows) from static landforms (relict alluvial fans with calcium sulfate soil or eolian soil) and also landforms evolving from surface water and groundwater contributions, such as salt flats at drainage terminations. SAR coherence analysis and Sentinel 1-A Ground Range Detected (GRD) backscattering time series, complemented by Landsat 8 OLI scenes, detect surface changes between December 2018 and November 2019. The sedimentological record of alluvial deposits indicates that thicker and wider mudflows occurred during the last millennia compared to the 2019 event. Relict alluvial fans displayed minimal changes during the 2019 rain event, and any changes were transient. The evolution of the salt flats, over both short and long time spans, is highly variable, depending on the location in the arid high Andes or in the hyperarid lowland. Yet, a small part of the latter salt flat experienced a strong, transient SAR coherence decline spanning five to eight months after the rain ended that is suggestive of time-lagged groundwater flow. Aggregation of numerous events like the 2019 rain shaped the Atacama landscape fan toes and salt pans, yet higher magnitude rain events or extended periods of rains must have been responsible for geologically recorded substantial landscape modification and evolution. Larger events, like that of 2015, are needed to cause a significant impact on soil development on relict alluvial surfaces. • Styles of landform changes depend on the amount of water and material properties. • Five month-delayed change occurred due to shallow groundwater movements in salt flat. • Landforms short and long-term evolution rates, in general correlates to each other. • Stronger and/or more frequent rains than 2019 event are needed to shape the Atacama. [ABSTRACT FROM AUTHOR]

Land-surface quantitative analysis based on digital elevation model (DEM) has been applied for improving the geomorphological mapping of piedmont alluvial fans. Indeed, these fans are frequently along a mountain front, where a series of coalescing fans may eventually occur. The margins of adjacent fans are rather difficult to map, thus preventing accurate and meaningful quantification of fan morphometric properties such as fan area, length, and slope. These morphometric properties are essential for informing on the influence of climatic conditions and tectonic factors on the fan-building processes. Therefore, in this paper, we propose a quantitative digital mapping approach along a stretch of about 50 km in the southern front of the Anti-Lebanon Mountains. Here, the Geomorphological Map of Syria at 1:1,000,000 scale (1963) reported at least nine piedmont alluvial fans, but these were poorly characterized in terms of geomorphometric characteristics and construction processes. Adopting the 1-arcsec SRTMv3 DEM, we propose a four-step workflow to analyse the feeding catchments morphology and fan morphometry. In this manner, the identification and geomorphological mapping of coalescent piedmont fans as well as the recognition of the main construction process have been improved. The proposed approach can support geomorphological investigations of wide and inaccessible areas—especially where arid and semi-arid climate conditions prevail—as well as where socio-political issues may prevent effective field work. • Land-surface quantitative analysis is suitable for geomorphological mapping and characterization of piedmont alluvial fans. • Recognition of the construction processes of the alluvial fan is challenging for a remotely-desk study. • Fluvial fans (FFs) are wider, with longer axis, gentle slope, and extended feeding catchment. • Alluvial fans (AFs) are smaller, with shorter axis, steeper slope, and small feeding catchment. [ABSTRACT FROM AUTHOR]

In the piedmont of uplifting mountains, alluvial fan rivers undergo significant aggradation-degradation processes, which are usually attributed to climate change. An ongoing debate is whether this process requests the participation of glaciation. To address this debate, we need the knowledge of the quantitative relationship between the ratio of water to sediment flux (q w / q s) with the aggradation/degradation process. This study examined the aggradation and degradation processes in three alluvial rivers at the piedmont of the Qilian Shan (Shan referes to Mountain) and simulated the river processes by a one-dimensional numerical model based on the transport-limited principle. Along the studied piedmont rivers, field measurements show a magnitude of 120–200 m degradation and aggradation in the Late Pleistocene. Through simulation analysis, we explored how factors like the ratio of water to sediment flux (q w / q s), channel width, and sediment grain size influence river processes and longitudinal profiles, and found distinct morphologies in different processes, where aggradation is characterized by concave-up profiles, while degradation is characterized by convex-down profiles. Additionally, the water flux is inversely proportional to the time required for the river to reach a new equilibrium profile. The simulated degradation amplitude aligns closely with the measured data in the Qilian Shan, indicating that precipitation during the Last Glacial Maximum in the region amounted to approximately ∼32% of the Holocene precipitation. This supports the notion that changes in water flux or precipitation alone can induce significant piedmont deepening without the necessity of glaciation. • Built a model to quantify the link between water-sediment fluxes and river processes. • Simulated Qilian Shan piedmont river incision: ∼32% LGM precipitation vs. Holocene. • Precipitation alone can create deep canyons without requiring glaciation. [ABSTRACT FROM AUTHOR]

The northeastern part of the Ebro Basin (NE Spain) features loess that cover an area of about 40 km2 on the northern slopes of the Serra d'Almenara anticline. The deposits and soils developed from them were mapped, described, and dated by luminescence. Additionally, grain size, percentage of heavy minerals (>2.8 g/cm3), and the mineralogical composition of the heaviest fraction (>3.2 g/cm3) were analysed. The coarse textures of the deposits indicate a very proximal origin. Therefore, potential source areas of the sands and silts were analysed with special attention given to the extensive river floodplains and alluvial fans close by, as well as gypsum-rich rocky outcrops. The mineral signature of the loess shows that it mainly originates from the alluvial plain of the Segre River, located about 10–30 km to the west. In some places, the loess also received particles from the alluvial fans of the Ondara and Corb rivers located south of the Almenara reliefs. In addition, the gypsum present in the loess is apparently derived from Eocene deposits. The loess in the study area was deposited during cold phases of the last two glacial cycles when the topographic obstacle of the Serra d'Almenara blocked the dominant winds from the southwest. Analysis of the almost 4-meter-thick profile of Pilar d'Almenara shows initial but limited accumulation phases in Marine Isotope Stages (MIS) 6, followed by the formation of a red soil during MIS 5e. Accumulation resumed during MIS3, with more energetic and powerful wind transport during the final phase of MIS 3 (ca. 34–30 ka) and early MIS 2, but prior to the Last Glacial Maximum. Our data highlights the prominent role of large rivers and alluvial fans as the sources of particles that are later reworked by the wind. • The most important heavy mineral species as tracers are zircon, staurolite, rutile and inosilicates. • Diiodomethane facilitates the recognition of very heavy minerals in sands. • Luminescence dating, together with the particle size and mineralogical results, allow for the identification of periods of maximum activity and the origin of materials in each era. [ABSTRACT FROM AUTHOR]

• A three-stage alluvial fan pattern was built since MIS3. • Cold-dry conditions promote the aggradation of debris flow deposits. • Warm-humid climate leads to perennial streamflow on the fan surface. • Climate is the main factor controlling the evolution of Xiangpi fan. Alluvial fans in the piedmont zones of mountains respond most rapidly to tectonic activity, base-level conditions, and climate changes. These allogenic signals are effectively recorded by the external morphology and internal sedimentary characteristics of the fan. Based on field survey interpretation and integrated optically stimulated luminescence (OSL) chronology, we selected a case study of the modern Xiangpi Fan on the south bank of Lake Qinghai, NE Tibetan Plateau, and built a three-stage alluvial fan pattern since Marine isotope stages 3 (MIS3), namely, the debris flow lobe building stage (DFLBS), aeolian building stage (ABS), and streamflow reworking stage (SRS). The climatic indicators, such as the total organic carbon (TOC) flux, precipitation, and sediment particle size flux, are highly correlated with the above stages, indicating that the sedimentary process and changes in fan morphology effectively record orbital climate changes in the Lake Qinghai basin. During the DFLBS, the cold-dry climate accelerated the sediment yield sufficiently, leading to many coarse-grained sediments and low TOC flux being imported into the basin through debris flow processes. During the ABS, the extreme dry-cold climate caused the stagnation of fan development, and aeolian processes dominated the transport of fine sediment. In the SRS, warm-humid conditions led to limited sediment yield and perennial stream power, which promoted the transport of fine-grained material and TOC to the basin by braided–meandering channels. This study provides an excellent case showing how an alluvial fan responds to climate oscillations through changes in sedimentology and geomorphology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Late Cretaceous eolianites were formed in intermontane erg in South China. • Association of eolian and arid alluvial fan facies suggests a secular arid climate. • We argue paleowind directions in South China reflected planetary wind system. Late Cretaceous eolian sandstones found in several basins in South China were previously interpreted as indicators of desert environments. To better understand the environment and climate conditions of that period more accurately, a comprehensively in-depth study of the eolianites was undertaken across multiple basins. Two primary lithofacies were identified within the eolianite-bearing sequences. The eolian facies is classified into four subfacies, namely dune, interdune, sand-sheet, and Gobi, while the alluvial fan facies are categorized into three subfacies, i.e. ephemeral channel, sheet flood, and debris flow. These two facies signify recurring interactions of eolian and water-laid systems, highlighting instances of eolian dune migration and deflation in conjunction with the intrusion of alluvial flows. The coexistence of the two facies in conjunction with the spatial distribution and morphometric characteristics associated with paleowind directions, suggests the following: 1) Eolian sandstones were formed within local intermontane ergs confined to narrow basins, negating their formation in broadly expansive desert or sand sea environments; 2) The alluvial fan facies evolved under localized ephemeral arid conditions; 3) South China experienced a relatively prolonged arid climate during the middle Late Cretaceous period, as opposed to the alternating humid and arid conditions. It is argued that the paleowind directions, recovered from the azimuths of cross-beddings in eolianites are reflective of the planetary wind system that was present in South China at that time, given their consistence with the strikes of basins and tectonic axial orientations. [ABSTRACT FROM AUTHOR]

• Spatial correlation overcomes the data density demand of the deconvolution approach. • Spatial interpretation gives a proxy for time spent in the groundwater system. • Proportions of groundwater inputs vary over time on a 100 year timescale. • Spatial interpretation informs site conceptualization, including recharge points. • Alluvial fan channels interpreted to be pathways for episodic recharge events. Informing groundwater recharge in arid environments is both challenging and necessary for understanding complex and changing water systems, and for making well-informed aquifer management decisions. The difficulty with interpreting aquifer recharge in arid environments lies in the sporadic and often unpredictable recharge opportunities. There is a gap between theoretical groundwater age distributions based on the physics of groundwater flow and the interpretation of real groundwater age tracer data. This gap is amplified in transient environments. This study uses a deconvolution approach constrained by probable recharge events to interpret variable groundwater recharge in the Weeli Wolli Creek alluvial fan, in the semi-arid Pilbara region. This approach is paired with spatial correlation to establish relationships between wells, making space a proxy for time in the recharge interpretation. Spatial correlation also helps address the data density requirement of deconvolution. The resulting model was able to identify specific events in the last 100 years as contributors to recharge, as well as highlighting effects of mine dewatering in the catchment. In addition, spatial interpretations showed water recharging along specific channels in the fan, and showed active channels varying over time. This level of detail in groundwater recharge studies is a move toward more meaningful environmental interpretation and aquifer planning. [ABSTRACT FROM AUTHOR]

The depositional history of alluvial fans on Mars provides insight into the climatic conditions during the time of fan formation in the late Hesperian to early Amazonian. However, traditional stratigraphic analysis of the alluvial fan deposits is not possible across most of Mars. This study assesses the use of thermal inertia data as a tool for sedimentologic interpretation of 437 Mars alluvial fans. Based on previous work demonstrating the relationship between depositional style, grain size, and thermophysical properties, this study uses analysis of the thermal inertia of alluvial fan surfaces across the global population of fans on Mars to make an assessment of depositional styles that built the alluvial fans. The thermal inertia values across the global population of fans are indicative of sand- to pebble-sized sediment. The variability of grain sizes across the global population is more homogenous than expected based on comparisons to terrestrial alluvial fans. Nearly all Mars alluvial fans have an average thermal inertia that corresponds to pebble and smaller grain size, and < 1% of Mars alluvial fans have an average thermal inertia that corresponds to cobble-sized grains. Spatial patterns of thermal inertia variability on alluvial fan surfaces show a small number of fans with evidence for either downslope fining or channelization, but the majority of fans show no recognizable geologic patterns in surface thermal inertia. The interpretation of the thermal inertia-derived grain size suggests that either there is widespread mantling of unconsolidated sand across the surface, or that Mars alluvial fans were built by primarily sand-sized sediment, which may be indicative of lower energy sediment transport events. • Thermal inertia of alluvial fan surfaces indicates primarily sand-sized sediment. • Thermal inertia of Mars alluvial fan surfaces is surprisingly homogeneous globally. • Alluvial fans built by sand-sized sediment suggest low energy fluvial processes. • Fluvial depositional processes may correlate to lack of clay in catchments. [ABSTRACT FROM AUTHOR]

Records of tide-reworked fan delta facies models are rare in literature, attributed to their lower abundances due to complex sediment distribution pattern by two exclusive end-member flows, viz., a seaward directed subaerial to subaqueous debris flow, and dominant tidal current system interfering with and reworking the debris flow. Lack of appropriate analogues of tide-reworked fan deltas makes the ancient examples more significant. The analysis of such rare tide-reworked fan deltas from deep-time, e.g., Mesoproterozoic, turns out to be unique due to the gap in clear understanding of the alluvial-fluvial vs marine processes in non-vegetated land parts. The lower part of the Mesoproterozoic Rajgarh Formation, Lalsot Basin, North Delhi Fold Belt, Aravalli Craton in NW India, provides a rare record of a tide-reworked fan delta depositional system. Sedimentary facies analysis reveals eleven lithofacies grouped under three major facies associations, viz., (i) gravel-rich conglomerate facies association, characterized by stacked debris flow deposits forming a subaerial alluvial fan, representing the delta topset component, followed downslope by (ii) pebbly, cross-stratifed sandstone facies association, characterized by reworking of the subaqueously emplaced debris flows by ebb-tidal currents, to produce the mouth bar and the delta front depositional systems, and finally, (iii) sandstone-mudstone heterolithic facies association, characterized by abundant tidal signatures in pebble-free thin-bedded sandstone-mudstone heteroliths with tidal bundles, herringbone cross-strata and wave ripples, characterizing a stable platformal subtidal-intertidal flat depositional system. The lower-middle part of the succession records an aggradational stratal stacking pattern of the subaerial alluvial fan changing to progradational stratal stacking of the laterally accreted debris-rich tide-led clinoforms producing the delta topset – mouth bar – delta front transiton of a tide-reworked fan-delta under successive regressive conditions, representing syn-rift deposition near the basin margin. A retrogradational stratal stacking pattern overlies the fan-delta succession, and signifies a transgression by landward encroaching tidal flat system over the fan-delta system during post-rift phase in a stable platformal setup, where debris supply is ceased. A regressive-transgressive model characterizing the transition from a fan-delta to tidal flat depositional systems portrays fluctuations in the accommodation conditons in response to complex interplay of basin tectonics and relative sea level changes in the Mesoproterozoic riftogenic Lalsot Basin. • Sedimentary facies model of tide-reworked fan-delta from Mesoproterozoic rift basin. • Syn-rift, aggrading debris flows led to a subaerial alluvial fan (the delta plain). • Progradation of fan delta by subaqueous tide-reworked debris flows (mouth bar). • Post-rift stable platformal transgression by a retrograding tidal flat on fan delta. • Transgressive-regressive cycle by interaction of autogenic vs. allogenic processes. [ABSTRACT FROM AUTHOR]

• Thick alluvial soil-stratigraphic sequences serve as paleoenvironmental archives. • The tallgrass prairie experienced significant bioclimatic change over the past 27 ka. • From ca. 25–4.5 ka, C 4 biomass increases, suggesting general warming for that period. • Warming and C 4 grass expansion occurred in a non-linear fashion. • A major warming event occurred in the region between ca. 3–1.3 ka. The tallgrass prairie of the Central Plains is one of the largest North American biomes, yet little is known about the history of late-Quaternary bioclimatic change in the region because settings that are favorable for the preservation of traditional paleoenvironmental proxies, such as pollen and plant macrofossils, are rare. However, the valleys of large streams contain thick soil-stratigraphic sequences that span the Holocene and terminal Pleistocene and are archives of other paleoenvironmental proxies. To better understand late-Quaternary bioclimatic change in the tallgrass prairie, we analyzed the stable carbon isotope (δ13C) composition of soil organic matter (SOM) preserved in buried soils in floodplain, terrace, and alluvial fan deposits in the Big Blue River valley of northeast Kansas. A combination of eight cores and three outcrops at six localities were investigated, and 27 radiocarbon ages provide a robust numerical chronology. Based on our analysis, the tallgrass prairie has experienced significant bioclimatic changes over the past 27,000 years. From the LGM to the beginning of the late Holocene (ca. 25,000–4500 cal yr BP), there is an overall increase in C 4 plant contributions to SOM, suggesting general warming for that period. However, warming and C 4 grass expansion occurred in a non-linear fashion, with minor variations in the abundance of C 4 vs C 3 plants reflecting either small fluctuations in temperatures during general warming trends or other environmental factors, such as landscape disturbance, periods of drought, or the seasonal distribution of precipitation. The δ13C record also suggests that a major warming event occurred in the region between ca. 3000–1300 cal yr BP, when the contribution of C 4 biomass to SOM exceeded 95 %. This climatic event does not appear to be an anomaly, as multiple paleoenvironmental proxies indicate a brief but exceedingly warm and dry interval occurred from 3300 to 2800 cal yr BP. [ABSTRACT FROM AUTHOR]

A unique synthesis of grain size-distance data is presented, comparing, for the first time, grain size and fining trends in a wide range of modern and ancient axial sediment dispersal systems, and tracking grain-size from source to sink across several sedimentary basins. In general, grain-size decreases exponentially with distance down system, and modern and ancient examples fine at broadly comparable rates in similar depositional settings. Linear fining rates vary by eight orders of magnitude, being higher in coarser-grained settings. Very few data sets have a median grain size between 1 and 5 mm in diameter, supporting the idea that material of this calibre is rare. Alluvial fans fine at the highest rates, by up to 450 cm/km (216%/km) in modern and 115 cm/km (427%/km) in ancient examples, but more typically by around 1 to 12 mm/km (87 to 1%/km), whereas fluvial gravels fine by 0.8 to 4 mm/km (0.4 to 5%/km). Sand-prone systems fine more slowly, by a few tens of microns per kilometre or less: 1 to 23 μm/km (0.25 to 2.5%/km) in distributive fluvial systems, ∼1 to 8 μm/km (∼1 to 6%/km) in fluvio-deltaic channels, 0.2 to 44 μm/km (0.08 to 14%/km) in ergs, and from 0.45 to 29 μm/km (0.18 to 7%/km) in basin-plain turbidites. At the basin scale, fining rates increase where gravels pinch out down-system at the fluvial gravel-sand transition, and where sands pinch out at the toe of the shoreface. Modern fluvial gravel-sand transitions are relatively well characterised, with fining rates ranging from 71 to 0.2 mm/km (483 to 2%/km), and lower rates and wider transitions in wider, longer rivers, insights that appear applicable to the rock record. Downstream fining predominantly reflects selective deposition of coarser material and preferential transport of finer grains, with subsidence increasing fining rates as coarser grains are preferentially extracted up-dip to form stratigraphy. Across short segments, grain-size can increase down system as a result of winnowing, bypass, or lateral sediment input. Comminution is largely considered a secondary factor in rivers, but important in ergs, where lateral sediment input can overwhelm downstream fining effects, and grain-size sorting across dunes may obscure longer downwind trends. In deep water, when the slope is bypassed, basin-floor fans can fine at rates comparable to contemporaneous up-dip fluvial channels, by 30 μm/km (5%/km), but if sediment is deposited on the slope, fining rates increase (225 μm/km 75%/km) as distances are shorter. Axial flow lines across basin-plain turbidites with diverse grain-size, and dimension, can be closely comparable on mass-balance plots, suggesting that the properties of one bed could inform predictions of those of another. As yet there are no studies of fining rates in conglomeratic deep-water systems, where the transition from conglomerate to sand-dominated systems is of particular interest, given its importance for fining rates in fluvial systems. The dataset has potential to constrain computer simulation models of sediment calibre, and subsurface models that address, for example, aquifer flow, and petroleum migration. [ABSTRACT FROM AUTHOR]

The paleo-uplift is an important tectonic element which is key to control the sedimentary system in petroleum basins. The evolution of Mesozoic paleo-uplifts and differential control on sedimentation on the southern margin of Kuqa Depression, northern Tarim Basin, is still unclear, restricting successful petroleum exploration and development. Based on borehole and 3D seismic reflection data on the southern margin of the Kuqa Depression, the parameters of paleo-uplifts, such as residual thickness, eroded thickness, slope height, slope angle, slope height difference were extracted. Combined with the composition of the detrital minerals in the Cretaceous Shushanhe Formation which was one of the target layers and the Paleo-lithofacies map before the deposition of Cretaceous, the paleo-uplifts could be further divided into four sub-uplifts. The paleo-uplifts grew and extended in the Triassic to Jurassic, decreased in the Jurassic to Cretaceous, and transformed into subaqueous low uplift in the upper part of Cretaceous Shushanhe Formation. The evolution of paleo-uplifts controlled strata and facies, resulting in no Triassic strata were deposited in the north of Yaha-Kudong and Luntai sub-uplifts, while the Jurassic strata in the Xinhe and Qiaogu sub-uplifts experienced extensive erosion. The faults in the Xinhe sub-uplift and steep slopes in the Luntai sub-uplift controlled the deposition of alluvial fans and fan deltas, while the gentle slopes of Qiaogu and Yaha-Kudong sub-uplifts controlled the distribution of braided river deltas. The evolution of the paleo-uplifts was synchronized with regional tectonism, including the south Tianshan collision orogeny and the post-orogenic stress relaxation. This study will help elucidate the development and evolution of the paleo-uplifts on the southern margin of Kuqa Depression, northern Tarim Basin, clarify the relationship between provenance and sedimentary system, and guide the oil and gas exploration in Tarim Basin and other basins with the similar background globally. • The paleo-uplift on the southern margin of the Kuqa depression can be subdivided into four sub-uplifts. • The evolution of four sub-uplifts controlled the distribution of the Mesozoic strata and facies. • The evolution process of the paleo-uplift was closely related to the regional tectonic activities and coupled synchronously. [ABSTRACT FROM AUTHOR]

The Altyn Tagh Fault (ATF) is the boundary between the Tarim Basin and the Tibetan Plateau, which is crucial for the tectonic evolution and uplift of the Tibetan Plateau. However, the Mesozoic tectonic evolution of the ATF remains controversial. This study reconstructed the Early-Middle Jurassic palaeogeographic pattern of the southeast depression of the Tarim Basin (SDTB) and revealed potential source-sink relationships between the SDTB and its adjacent mountains to constrain the Mesozoic tectonic evolution of the ATF based on sedimentology and provenance analyses. The results indicated that the SDTB was infilled with alluvial fan facies during the Early Jurassic and the late Early Jurassic, giving rise to the braided-river delta to lacustrine facies. During the Middle Jurassic, the lacustrine basin expanded with the wide development of lacustrine facies, and the lacustrine basin contracted and was primarily infilled with braided delta facies in the late Middle Jurassic. The Jurassic sedimentary center, the SDTB situated in front of the Altyn Tagh Mountain and East Kunlun Mountain, played a crucial role in the development of three types of hydrocarbon source rocks: charcoal mudstone, coal beds, and dark mudstone. Combined with seismic reflection data interpretations, the Early Jurassic the STDB is a rift basin that underwent a rift-depression transition in the late Early Jurassic, solidifying the characteristics of the depression basin in the Middle Jurassic. The extensional environment in the SDTB resulted from the tectonic effects of slab break-off following the closure of the Tethys Ocean and the spreading of the distal stress field of the Bangonghu–Nujiang Ocean. The analyses of gravel component and heavy mineral indicated that the Jurassic source of the basin was traced back to the ancestral Altyn Mountains, the East Kunlun Mountains, and the internal palaeo-uplift of the basin, which demonstrated that the SDTB and Western Qaidam Basin (WQB) shared a common lacustrine basin during the Jurassic, suggesting that the ATF did not initiate strike-slip movements during this period. This study significantly enhanced our understanding of the Mesozoic tectonic evolution in Northwest China, providing valuable insights into exploring Mesozoic oil-bearing basins in the northern Tibetan Plateau. Furthermore, it served as a useful reference for constraining the timing of the initial slip of similar plate boundary strike-slip faults. • The Southeastern Depression of the Tarim Basin is a rift-depression basin with a rapid facies shift. • The Altyn Tagh Fault did not initiate strike-slip movements during the Early-Middle Jurassic. • This study offers a reference for exploring oil basins in the Tibetan Plateau. • This study aids in constraining timing of initial slip in similar faults. [ABSTRACT FROM AUTHOR]

We analysed spatial development of traditional and modern settlements on active alluvial fans in the Upper Sava Valley (NW Slovenia), by using old cadastral data from the beginning of the 19th century, time series of aerial photographs from the middle of the 20th century and recent building cadastre. The valley is surrounded by the mountainous Julian Alps in the south and the Karavanke Mountains in the north where there is a lack of space for settlements due to steep slopes that are increasing the danger of slope processes, torrential processes and floods. By using a very high-resolution 1m LiDAR digital elevation model, we defined the morphometry of alluvial fans and the characteristics of the drainage system of contributing tributaries. We classified the areas according to the threat posed by the modelled torrents and debris flows. We analysed the resilience of settlement in different periods from this perspective and evaluated the integration of natural processes effects in modern spatial planning projects. We found that geomorphic processes threaten a relatively large proportion of some new and old settlements on alluvial fans and that safe planning of areas of settlement has been successful neither in the past nor in recent decades.

Aims & Backgrounds: Based on field and literature studies, one of the most important features of Sabalan Quaternary landscape, are climate changes and tectonic activities. So tectonic activities and climate changes, along with other internal and external factors simultaneously had an undeniable role in the formation and evolution of Quaternary fans of Meshkin Shahr depression. The purpose of this study was to investigate the role of tectonic and climatic factors of quaternary period in geomorphological evolution of Meshkin Shahr fans. Methodology: To achieve this goal, first of all, using contour line, stream network and elevation points, the digital elevation model of region, was prepared as a base map. Then the data needed to calculate geomorphic indices and various profiles were extracted. Geological logs are used to investigate sedimentary evidence. In addition, Arc hydro and Google earth have been used to outline catchments and fans area. In addition, to draw geological logs, Rock works 16 software was used. Most importantly, we have used extensively field observations. Findings: The two major phenomena of volcanic-tectonic and climate changes in the Quaternary period have played a decisive role in the formation and development of the Quaternary fans of Meshkin Shahr depression. Simultaneously, the Sabalan volcanic activity with glacial dominate or tundra storm during the late Pleistocene led to the formation of a mudflow periodically and sedimentation in fans and basins. In contrast, climate change from glacial period to interglacial during the Holocene and tectonic relaxation has caused the incision of basins and fans. Conclusion: Sabalanchr('39')s landscape as the main controller of Meshkin Shahr Depression Fans is at a transitional stage, which means that it has undergone a tectonic stage to a non-tectonic stage, and also, it has undergone a glacial to an interglacial period such as the present conditions.

Understanding the sources areas and transport mechanisms of pollen grains is important for reconstructing vegetation and climate from fossil pollen data. We studied the modern pollen assemblages of 28 surface samples from different geomorphic units (mountains, the central basin, and the riverine zone) in the Yinchuan Basin in China. Our aim was to compare the characteristics of the pollen assemblages from the different sedimentary environments and to determine the differences in pollen source areas and transport mechanisms. The results show that: (1) The pollen assemblages from the mountain and piedmont alluvial fan environments were dominated by trees, with the tree pollen content decreasing with decreasing altitude. The pollen in the piedmont alluvial fan environment was mainly transported by surface runoff, and assemblage combines the characteristics of both the mountain and the local vegetation. (2) The pollen assemblages from the central basin were dominated by pollen produced by the zonal desert-steppe vegetation. (3) The pollen assemblages from the riverine zone were dominated by a long-distance component from within the upper part of the drainage area. The results suggest that in sedimentary pollen records from the Yinchuan Basin, the arboreal pollen component primarily reflects vegetation changes within the surrounding mountains; the herbaceous pollen component is an indicator of changes in desert-steppe vegetation; and the long-distance fluvially-transported pollen component reflects vegetation changes in the upstream drainage area. [ABSTRACT FROM AUTHOR]

Facies architecture and benthic foraminiferal biostratigraphy were interpreted to reconstruct the depositional environments of the Upper Campanian–Maastrichtian Qahlah and Simsima formations in the Faiyah Anticline Range, north‐central United Arab Emirates. Obduction of the Oman ophiolite controlled the palaeo‐configuration of the Upper Cretaceous deposits and resulted in an irregular palaeogeography which caused rapid lateral and vertical facies changes and the building up of 19 types of facies. The Qahlah Formation was deposited dominantly as an inner clastic wedge facies association containing alluvial fan, alluvial plain, and proximal shallow marine mass‐ flow deposits. The Simsima Formation is represented by deposits characteristic of variable settings, including intertidal, restricted lagoon, inner edge shallow platform, and forereef shelf that formed in the outer carbonate wedge. Towards the southwest of the Faiyah Anticline Range, the Simsima Formation exhibits distal turbidites and contains remobilized carbonate conglomerates and marl that were deposited in a foredeep environment. This lateral variation has been caused by tectonics associated with increased global sea level. A tectonically‐driven long‐time hiatus caused the absence of Danian age strata. From the sequence stratigraphic perspective, three forced sequence boundaries are reported within the Upper Campanian–Maastrichtian successions. This sequence boundaries match well with those documented from the entire Arabian Plate. [ABSTRACT FROM AUTHOR]

Reconstruction of Cretaceous geological evolution of Tibetan Plateau growth is critical for assessing the effect of India-Asia collision on the formation of its high elevation. However, Cretaceous topographic evolution and geodynamic mechanism in northern Lhasa remain ambiguous. Here we present results from sedimentology, zircon U-Pb ages, and detrital Crspinel composition of the Tangza Formation in the western part of northern Lhasa. Sedimentary lithofacies document that orbitolinid foraminifera--limestone beds were deposited in a shallow-marine setting, while clastic rocks accumulated in an alluvial fan during the middle Cretaceous. Zircon U-Pb ages of interbedded volcanic rocks place a robust constraint on the initiation of clastic rock deposition at ca. 106 Ma. Sandstones are enriched lithic fragments with abundant volcanic grains. U-Pb ages of detrital zircon display a prominent age population at 101-130 Ma with a 120 Ma peak. These data indicate that the clastic rocks were mainly derived from northern Lhasa, including an Early Cretaceous magmatic arc. Sedimentary and provenance characteristics are most consistent with deposition in a local foreland basin. The activation of south-vergent local thrusting may be responsible for loading of the Tangza foreland basin. This thrust faulting may be associated with crustal shortening induced by the continuous convergence of Lhasa and Qiangtang since collision initiated during the Early Cretaceous. The initial uplift of western and central parts of northern Lhasa and eastern Gangdese arc occurred at ca. 106 Ma, while the widespread uplift of northern and central Lhasa probably initiated at ca. 92 Ma. The mid--Late Cretaceous uplift in Lhasa was significantly earlier than the early Cenozoic India-Asia collision. [ABSTRACT FROM AUTHOR]

Avulsion is a key process in building alluvial fans, but it is also a formidable natural hazard. Based on laboratory experiments monitored with novel high‐frequency photogrammetry, we present a new model for avulsion on widely graded gravel fans. Previous experimental studies of alluvial fans have suggested that avulsion occurs in a periodic autogenic cycle, that is thought to be mediated by the gradient of the fan and fan‐channel. However, those studies measured gradients at low spatial or temporal resolutions, which capture temporally or spatially averaged topographic evolution. Here, we present high‐resolution (1 mm), high‐frequency (1‐minute) topographic data and orthophotos from an alluvial fan experiment. Avulsions in the experiment were rapid and, in contrast to some previous experimental studies, avulsion occurrence was aperiodic. Moreover, we found little evidence of the back‐filling observed at coarser temporal and spatial resolutions. Our observations suggest that avulsion is disproportionately affected by sediment accumulation in the channel, particularly around larger, less mobile grains. Such in‐channel deposition can cause channel shifting that interrupts the autogenic avulsion cycle, so that avulsions are aperiodic and their timing is more difficult to predict. [ABSTRACT FROM AUTHOR]

We study the morphodynamics of reversing dunes on the gravel deposits of the alluvial fan of the Molcha river at the border between the Tibetan Plateau and the Taklamakan Desert. Independent sets of wind data show that this area of low sand availability is exposed to two prevailing winds from opposite directions and of different strengths. The predicted resultant transport direction of sand particles is westward. Nevertheless, satellite observations combined with field measurements and ground‐penetrating radar surveys reveal that isolated dunes a few meters high migrate eastward. This apparent dune migration paradox is resolved using numerical and analytical models that take into account the speed‐up effect and the continuous change in dune shape after each wind reversal. When a newly established wind hits what was before the steeper lee slope of the dune, the sand flux at the crest abruptly increases before relaxing back to a constant value as the crest migrates downwind and as the dune reaches a new steady shape. Integrated over the entire wind cycle, we find that this non‐linear behavior causes reversing dunes to migrate against the resultant transport direction. This migration reflects the difference in dune slope seen by irregular storm events blowing to the east and the westward wind of the daily cycle. Thus, we explore the impact of extreme events on dune morphodynamics and examine new aspects of the permanent feedback between dune topography and wind speed. We conclude that transient behaviors associated with crest reversals contribute to the observed diversity of dune patterns, even within the same area for dunes of different sizes. Plain Language Summary: The wind accelerates when it is deflected over a dune so that the sand flux at the crest is several times greater than on a flat sand bed far from any topography. This speed‐up effect varies as the steepness of the dune slopes exposed to the wind. Here we show that, in zones of frequent wind reversals, the speed‐up effect can cause the dunes to migrate against the transport direction of windblown sand particles. This apparent dune migration paradox requires specific conditions which are met in the study area, a large (8,000 km2) alluvial fan at the margin between the Tibetan Plateau and the Taklamakan Desert. First, it is an area of low sand availability and the dunes that develop on the gravel deposits of the alluvial fan do not exceed a few meters in height. Second, this area is submitted to two opposite winds with different strengths. Westward winds are weak but occur daily, while eastward winds are associated with storm events. Since the infrequent storm winds always blow over a dune that is regularly smoothed by daily winds from the opposite direction, they produce much greater sand flux at the crest of the so‐called reversing dunes, which can then migrate against the sand flow path. This singular behavior governed by the permanent feedback between airflow and dune topography illustrates the critical role of extreme events in sediment transport dynamics. Key Points: Reversing dunes can migrate against the resultant drift directionSpeed‐up effect and frequent wind reversals explain the dune migration paradoxDaily and storm cycles illustrate the control of wind sequence on dune dynamics [ABSTRACT FROM AUTHOR]

Pipelines in mountainous terrain often cross alluvial fans formed by steep creek processes of debris flows and debris floods and are thus exposed to their associated hazards. The design of new pipeline infrastructure and maintenance of existing pipelines necessitates steep creek risk assessments and appropriate mitigation design. We present methodology for assessing steep creek risk along pipeline routes that evaluates the probability of such processes causing a pipeline loss of containment or disruption in service. The methodology consists of estimating event frequency, scour potential, and the vulnerability of the pipeline to break if impacted by boulders. The approach can be adapted to other landslide geohazards so that different geohazard locations can be evaluated with a common metric. Steep creek process frequency is estimated based on field observations and review of documented events, historical air photo records, and terrain mapping based on LiDAR-generated topography. Scour potential is estimated based on channel morphology, presence of bedrock, and grain size distribution of channel bed material. Vulnerability is estimated based on flow width and velocity and can be modified for different pipe diameters and wall thicknesses. Mitigation options for buried pipelines include those intended to decrease the likelihood of the pipeline being exposed and to increase the resiliency of the pipeline to boulder or organic debris impacts, if exposed. The methodology presented is embedded in risk-informed decision making where pipeline owners and regulators can define probability thresholds to pipeline exposure or rupture, and pipeline designers can demonstrate that proposed mitigation measures achieve these threshold criteria. [ABSTRACT FROM AUTHOR]

Regional-scale assessments for debris-flow and debris-flood propagation and avulsion on fans can be challenging. Geomorphological mapping based on aerial or satellite imagery requires substantial field verification effort. Surface evidence of past events may be obfuscated by development or obscured by repeat erosion or debris inundation, and trenching may be required to record the sedimentary architecture and date past events. This paper evaluates a methodology for debrisflow and debris-flood susceptibility mapping at regional scale based on a combination of digital elevation model (DEM) metrics to identify potential debris source zones and flow propagation modeling using the Flow-R code that is calibrated through comparison to mapped alluvial fans. The DEM metrics enable semi-automated identification and preliminary, process-based classification of streams prone to debris flow and debris flood. Flow-R is a susceptibility mapping tool that models potential flow inundation based on a combination of spreading and runout algorithms considering DEM topography and empirical propagation parameters. The methodology is first evaluated at locations where debris-flow and debrisflood hazards have been previously assessed based on field mapping and detailed numerical modeling. It is then applied over a 125,000 km² area in southern British Columbia, Canada. The motivation for the application of this methodology is that it represents an objective and repeatable approach to susceptibility mapping, which can be integrated in a debris-flow and debris-flood risk prioritization framework at regional scale to support risk management decisions. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The specific aim of the study was to investigate how four adjacent geomorphological systems – a lake, a dune field, a small alluvial fan and a slope system – responded to the same impacts. Lake Tresssee is a shallow lake in the North of Germany (Schleswig-Holstein). During the Holocene, the lake's water surface declined drastically, predominately as a consequence of human impact. The adjacent inland dune field shows several traces of former sand drift events. Using 30 new radiocarbon ages and the results of 16 OSL samples, this study aims to create a new timeline tracing the interaction between lake and dunes, as well, as how both the lake and the dunes reacted to environmental changes. The water level of the lake is presumed to have peaked during the period before the Younger Dryas (YD; start at 10.73 ka BC). After the Boreal period (OSL age 8050 ± 690 BC) the level must have undergone fluctuations triggered by climatic events and the first human influences. The last demonstrable high water level was during the Late Bronze Age (1003–844 cal. BC). The first to the 9th century AD saw slightly shrinking water levels, and more significant ones thereafter. In the 19th century, the lake area was artificially reduced to a minimum by the human population. In the dunes, a total of seven different phases of sand drift were demonstrated for the last 13,000 years. It is one of the most precisely dated inland-dune chronologies of Central Europe. The small alluvial fan took shape mainly between the 13th and 17th centuries AD. After 1700 cal. BC (Middle Bronze Age), and again during the sixth and seventh centuries AD, we find enhanced slope activity with the formation of Holocene colluvia. [ABSTRACT FROM AUTHOR]