Trunk Channel Research Articles

Late Pleistocene to Holocene alluvial deposits of the Inaouène Valley and their paleoenvironmental significance (north Morocco)

This study investigates the paleoenvironmental changes and fluvial dynamics in the Inaouène River Valley of central northern Morocco over the last 22,000 years. Through comprehensive field study and radiocarbon dating of Upper Pleistocene and Holocene alluvial deposits, the research identifies six main alluvial units reflecting distinct phases of fluvial activity and environmental conditions. These phases include coarse gravel aggradation between ∼22 and 15 cal kaBP, indicating a braided channel system, followed by multiple fine-dominated alluviation phases occurring at ∼13, ∼10, ∼6–5, ∼3, ∼0.7–0.3, and ∼0.1-0 cal kaBP. The trunk channel evolved from a low-sinuosity wandering style in the Early-Middle Holocene to a high-sinuosity pattern in the Late Holocene. Periods of landscape stability, evidenced by soil formation, were dated around 0.3 and 0.8 cal kaBP, with additional episodes estimated just after ∼12 cal kaBP and around 3.8 cal kaBP. Notably, the study also uncovered evidence of significant human intervention during the Middle Holocene.A comparison with other archives enabled us to reconstruct late Pleistocene and Holocene palaeoenvironmental conditions on both regional and supraregional scales, linking specific stages of floodplain development to prevalent influencing factors. Emphasizing the fluvial system response, we present a cause-effect model that focuses on long-lasting climatic phases (e.g., Last Glacial Maximum, MIS2-MIS1 transition, African Humid Period) as well as sub-millennial to centennial Rapid Climate Changes, North Atlantic cooling events, and solar activity minima. Human intervention played a key role in the Inaouène's evolution during the Middle Holocene, as evidenced by clear anthropogenic markers found in the associated deposits. These findings not only contribute to our understanding of the area's geomorphological history but also highlight its significant archaeological potential, opening new avenues for interdisciplinary research in this understudied region.The study offers new insights into central northern Morocco's late Quaternary alluvial geochronology and paleoenvironmental evolution, aligning with regional findings and contributing to a broader understanding of climate-driven landscape changes and human-environment interactions across North Africa and the Mediterranean.

The Channel Branches & Network Channels on the Tianhui Lacquered Meridian Figurine — Taking the Heart-Regulated Channel as an Example

Abstract: Along with the surge of unearthed medical literature and cultural relics in recent years, the network of channels in the system of medical channels (meridians) during the early Western Han dynasty have become much clearer gradually. Among them, the increasing number of channel branches, network channels and needle insertion holes (acupoints) is an important feature of the development of classical channel medicine during the Western Han dynasty. This is not only a reflection of the expanding requirements of the theoretical system of the main trunk channels, but also an inevitable result of the continuous enrichment and accumulation of clinical experience. This article integrates the information about channel branches, network channels, inscriptions, dots and further relics on the Tianhui (天回) Lacquered Meridian Figurine to compare the unearthed literature of the channel genre with the transmitted classical literature about acupuncture. The "Heart-Regulated Channel" in Medical Manuscripts on Bamboo Slips from Tianhui (《天回医简》) serves as an example to explain the occurrence, development and changes of the channel branches and network channels in the early system of medical channels.

Excess topography and outburst flood: Geomorphic imprint of October 2023 extreme flood event in the Teesta catchment of Eastern Himalayas

The 2023 South-Lohnak Lake outburst flood event across the upstream Teesta catchment triggered short-lived, high-magnitude flooding and substantial socioeconomic disruption downstream. We performed landscape analysis across the Teesta catchment using topographic metrics to understand the geomorphic response to this extreme flood event. We estimated the various topographic metrics such as ksn anomaly (normalized channel steepness index) (∼500–2500 m0.9), SL-index (stream-length gradient index) (∼5000–7000 m), and KsnQ (channel steepness-weighted discharge) along the trunk channel draining through the South-Lohnak Lake, which shows high magnitude in flooded regions and numerous spikes in their longitudinal profiles across mass-wasting regions downstream. We used the KsnQ metric as an event characteristic to investigate the changes in the channel morphology due to high-magnitude flooding. There was a sudden increase in the magnitude of the KsnQ metric when the river traversed through the Chungthang dam over the high ranges of excess topography (∼0–1700 m). This shows that the downstream channel morphology changes rapidly during this flood event, and KsnQ is a significant indicator of geomorphic change. To understand the spatial relationship between the physical drivers that trigger this outburst flood, we quantified the causal relationship between glacial-hydrological drivers over the upstream Zemu-sub catchment. Our observations suggest that precipitation intensity and surface temperature had a significant direct causal influence on snowmelt and snow depth (in terms of water equivalent) over the event duration with a 5-day and 1-day lag composite. Through the inclusion of lagged composites and causal linkages, the drivers across the glaciated landscape serve as event anomalies, which trigger the glacier hillslope failure and subsequent high-magnitude outburst flooding. Therefore, we suggest that the interaction of topographic discontinuity with hydrological extremes and their causal interdependencies influences this outburst event in the upper reaches, followed by high-magnitude flooding in the downstream reaches of the Teesta River. However, the long-term geomorphic consequences of such events on the evolution of the regional landscape remain unclear.

Sedimentary Characteristics and Evolution of the Late Miocene to Quaternary Tributary Channels in the Head of Bounty Channel, New Zealand

The Bounty Channel is a large-scale submarine channel system located in the eastern continental margin of New Zealand. Extending along the axis of the Bounty Trough, the channel system comprises three main tributaries (C1–C3) at its head, which merge downstream into a trunk channel leading to a terminal submarine fan. In this study, we use high-quality two-dimensional multichannel seismic data to investigate the formation and evolution of tributary channels C1 and C2. Four types of seismic facies are identified in the tributary channels: fill-type, mounded divergent, wavy, and subparallel facies. These seismic facies are correspondingly interpreted as topographic depression or channel fills, levees, sediment waves, and hemipelagic deposits. The Late Miocene tributary channels were developed above a pre-existing NE–SW-oriented depression. The Pliocene to Quaternary tributary channels are characterized by preferential development of higher levees on their left hand, and the presence of sediment waves on the lower levees of their right-hand, signaling an effect of the Coriolis force. The formation and evolution of the tributaries are primarily linked to regional tectonics, including increased convergence rate between the Pacific and Australian plates along the Alpine Fault in the Late Miocene and enhanced uplift and erosion at the Southern Alps during the Pliocene.

New data on tributary terraces and a reappraisal of the incision history of the Jinshan Gorge, middle Yellow River

River channel profiles and river terraces are two typical landscape features to investigate river incision history. However, incision history inferred from the two markers can be inconsistent. For example, along the Jinshan Gorge in the middle Yellow River, pseudo-terraces (a virtual metric derived from channel profile modelling) suggest a recent acceleration in incision rates only in the southern gorge, and the northern keeps steady, while river terraces in the trunk channel indicate recently increased incision rates all along the gorge. To mitigate these discrepancies, we investigate six tributaries along the Jinshan Gorge by mapping and dating several strath terraces at various distances from the confluence to the trunk channel. By comparing tributary terraces of similar age, we find generally increasing incision rates towards the confluence with the trunk river in the southern Jinshan Gorge. North to south increasing incision rates along the gorge are also observed from coeval tributary terraces. In addition, two different landscapes between the southern and northern tributaries near the confluence are recognized, one with a deeply incised gorge and another one with floodplains, suggesting incision rate in the northern gorge is steady through time. Integrating the new infrared stimulated luminescence (IRSL) and Accelerator Mass Spectrometry (AMS) 14C data from tributaries with the abundant literature data of terrace samples mostly in the Jinshan Gorge dated with various methods, we suggest published ages from optically stimulated luminescence (OSL) might be too young. The methodological limitation associated to the dating method can explain the observed mismatch of incision history in the northern gorge inferred from pseudo-terraces and from river terraces in the trunk channel, and reconcile some contradicting patterns in published trunk terrace data.

Investigating the Influence of River Geomorphology on Human Presence Using Night Light Data: A Case Study in the Indus Basin

Human settlements have historically thrived near rivers due to enhanced navigation and trade, and the availability of water supply and resources. The use of night light data, representing economic activities, provides a novel approach to studying the interactions between human activity and rivers over time. Here, we use the Defense Meteorological Satellite Program (DMSP) stable night light data from 2000 to 2013 as a proxy for human presence and activities to quantify the statistical relationships between night light presence and intensity in the Indus Basin, Asia. We test how these data are affected by proximity to trunk channels and by channel type (single/multi-thread) in the study area. We find that night light presence is enhanced by 26% within a 0 to 5 km proximity range of the Indus River and its tributaries, relative to the basin as a whole. We interpret this to represent increased human presence and activity within this zone. However, the mean intensity is lower near the river and higher away from the river, signifying denser settlements, such as towns and cities, which are preferentially located away from the Indus and its tributaries. Moreover, the enhancement of lit pixels signifying human presence and activities is increased by 18% near single-thread sections of the Indus River, compared to segments of the Indus displaying multi-thread morphologies. We suggest that this is due to the enhanced stability of single-threaded channels, relative to mobile multi-threaded channel reaches. This study demonstrates how night lights are an important tool in studying the relationship between human presence and river dynamics in large catchments such as the Indus, and we suggest that these data will have an important role in assessing differential flood spatial and social vulnerability at a regional scale.

Identifying geomorphic domains using hierarchically clustered drainage area‐slope scaling

AbstractArea‐slope scaling is an important tool for analysing geomorphic processes. In this study, we used hierarchical clustering to sort the area‐slope scaling data for both the numerical landscape created using the LandLab model and real landscapes. Random forest analysis was used to explore the effect of hierarchical clustering. We aimed to illustrate the heterogeneous features of area‐slope clustering and their influencing factors and to test whether they can be used to distinguish geomorphic domains. Our results showed that hierarchical clustering can easily detect the heterogeneous features of area‐slope scaling constrained by tectonic uplift and fluvial erodibility but not those constrained by the diffusion coefficient. The slope gradients over the inflection/transition zone of the colluvial and fluvial domains play a key role in identifying area‐slope scaling from different geomorphic domains. Case studies show that area‐slope scaling of clusters would be affected by different lithology and distance away from the trunk channel. In the high erosion circumstance, the fluvial process caused by tectonics leads to increasing slope gradients over whole geomorphic domains, as well as to retreating inflection between the colluvial and fluvial process domains. In low erosion circumstances or steady state, the fluvial process caused by nearby rivers cannot effectively change the slope gradients but can retreat the inflection. The real landscapes suggest that basins should be carefully selected for area‐slope scaling analysis to ensure that they are representative of the entire study area. Before geomorphological research, more basins of a specific research region need to be selected to conduct hierarchical clustering to select representative basins. Our study could be helpful in the identification of area‐slope domains, the extraction of geomorphic metrics and geomorphic process research.

A liquid metal based, integrated parallel electroosmotic micropump cluster drive system.

The application of liquid metal in a microfluidic system enables the fabrication of highly integrated on-chip electroosmotic micropumps (EOPs). In this work, a low-voltage driveable integrated parallel EOP cluster drive system is proposed. This system consists of two layers, a branch-channel layer and a trunk-channel layer. The lower branch-channel layer contains separate parallel pumping channels and a pair of comb liquid metal electrodes. The separated branch channels are connected together through the trunk channels in the upper layer. With this structural arrangement, the parallel micropumps form an integrated micropump cluster for larger pumping capacity. The distance between the pumping channel and the electrode next to it is controlled to 20 μm. To guide the pump design, parametric studies are performed and fully discussed. According to the experimental results, the micropump cluster can be driven at a low voltage of 0.5 V, and the flow rate reaches 274 nL min-1 at 5 V. In addition, the paper finally proposes an electrode protection strategy and an integrated pump-valve drive system which is expected to solve the shortcoming of electroosmotic pumps in terms of long-time storage and driving.

Genesis, Distribution, and Characterization of a Paleokarst Subsurface River System in the Tahe Area, Tarim Basin, Western China

Summary Subsurface river systems constitute one of three major paleokarst types that make up Ordovician reservoirs in the Tahe area of the Tarim Basin. The total length of the river system is approximately 400 km, and the reserves associated with this karst type are more than 200 million tons. However, it is manifested that 47% of drilled wells have not encountered river paleokarst, while 50% of wells that have encountered river paleokarst are fully filled due to the poor understanding of the paleokarst of this region, resulting in a significant variation of production capacities. In this study, we propose a detailed data integration approach with outcrops, drilling, logging, seismic profiles, and dynamic data to delineate the complex paleokarst river system in the Tahe area. The karst geological theory with reservoir characterization is combined in particular. The workflow of clarifying the main controlling factors, architecture types, and development distribution modes of the subsurface river system is established. Fill material type, sequence of fill structure, and fill controlling factors are also revealed. A quantitative characterization method of the subsurface rivers is established adopting predictions based on seismic data and high-resolution geostatistical and geological modeling. The Ordovician reservoirs in the Tahe area comprise three paleokarst river systems with different characteristics. Karst paleogeomorphology is the main control over the overall flow direction and plane distribution of the subsurface rivers. Changes in the surface of the phreatic zone are crucial in controlling the vertical layers and scale of the rivers. The combined action of faults plays a decisive role in controlling the anastomosing pattern of the rivers. Single-branch channels, reticulated channels, and structural corridors in single-layer or multilayer styles are the main subsurface river types. Trunk channels, branch channels, hall caves, and inlets/outlets are dominant structures in the architecture of the river system. Sand-mud, breccia, and chemically precipitated materials are the most common fill types. Three typical sequences of fill structure and four spatial combination modes exist in the subsurface river system. The morphology and fill characteristics of rivers are predictable using seismic attributes, such as frequency division energy, frequency division inversion, and coherent energy gradient. 3D models are constructed by multivariate control multipoint geostatistical method, which can characterize the strong heterogeneity characteristics of subsurface river systems. This complex paleokarst system enables remarkable results for the adjustment of the reservoir development plan through quantitative characterization.

Spatial Pattern Characteristics and Factors for the Present Status of Rural Settlements in the Lijiang River Basin Based on ArcGIS.

In China, rural settlements have undergone significant changes in response to dramatic socioeconomic shifts. However, there has not been any report on rural settlements in the Lijiang River Basin. In this study, ArcGIS 10.2 (including hot spot analysis and kernel density estimation) and Fragstats 4.2 (such as the landscape pattern index) software were used to analyze the spatial pattern and causes of rural settlements in the Lijiang River Basin. The Lijiang River Basin is mainly dominated by micro- and small-sized rural settlements with small areas. Moreover, the results of a hot spot analysis showed that micro- and small-sized rural settlements were mainly located in the upper reaches, and medium- and large-sized rural settlements were mainly located in the middle and lower reaches. The kernel density estimation results showed that the distribution characteristics of the rural settlements in the upper, middle, and lower reaches were significantly different. The spatial forms of rural settlements were affected by physiographic factors such as elevation and slope, karst landforms, and river trunk channels as well as the national policy system, tourism economic development, town distribution, historical heritage, and minority culture. This study is the first to systematically elaborate on the rural settlement pattern and its internal logic from the perspective of the Lijiang River Basin, providing a basis for the optimization and construction of the rural settlement pattern.

Investigating how river flow regimes impact on river delta salinization through idealized modeling

IntroductionExcessive salinity can harm ecosystems and compromise the various anthropogenic activities that take place in river deltas. The issue of salinization is expected to exacerbate due to natural and/or anthropogenic climate change. Water regulations are required to secure a sufficient water supply in conditions of limited water volume availability. Research is ongoing in seek of the optimum flow distribution establishing longer lasting and fresher conditions in deltas.MethodsIn this study a three–dimensional (3D) numerical model built for an idealized delta configuration was utilized to investigate how different river discharge annual distributions affect saltwater in deltas. Five simulations were carried out by implementing annual distributions of equal water volume but different shape.ResultsThe results showed that peak flow magnitude, time of occurrence and the length of a hydrograph’s tails can be important parameters affecting stratification, freshwater residence, and renewal times. Hydrographs of small flow range and light tails were the most successful in keeping the delta and its trunk channel fresher for longer periods. Salinity distributions showed a slower response to decreasing rather than increasing river discharges. An increase in the flow rate can result in salinity standards demanded for certain activities (e.g., farming, irrigation etc.) in much shorter times. On the other hand, hydrographs with heavy tails can push the salt intrusion limit further away and be more efficient in mixing the water column. However, they present low freshwater residence and high-water renewal times.DiscussionThese results provide strong indications that it is possible to improve the freshwater conditions in deltas without seeking for additional water resources but by modifying the water distribution. The main outcomes of this work may be able to support and assist coastal scientists and stakeholders dealing with the management of freshwater resources in river deltas across the world.

Crevasse splay morphodynamics near a non-vegetated, ephemeral river terminus: Insights from process-based modelling

Crevasse splays generate subtle local relief and contribute to fluvial basin sedimentary filling but controls on splay development along dryland rivers remain poorly understood owing to limited field, laboratory, and numerical modelling studies. Based on previously-acquired field data and new remote sensing observations of splay morphology and sedimentology (e.g. slope, width, length, grain size) and flooding characteristics (e.g. discharge, water depth and extent) near the terminus of the non-vegetated, ephemeral Río Colorado on the southeastern margin of Salar de Uyuni, Bolivia, we undertake process-based modelling using Delft3D to isolate the role of hydrological controls on crevasse splay morphodynamics. Holding the potential sediment supply constant, we focus on the role of discharge (outflow from trunk channel to crevasse channel during rising stage), floodplain water levels, and backflow (reflux to the trunk channel during falling stage). Using nine different model runs, each with 10 simulated flood cycles, we show that the processes associated with these hydrological controls result in various outcomes, from short crevasse splay channels that may bifurcate and develop depositional bars to longer splays with one primary channel that mainly transfers sediment across the floodplain. Results reveal that increases in flood discharge lead to more rapid splay sedimentation and stabilization of a single crevasse channel. Increases in floodplain water level lead to shorter but wider splays and facilitate the formation of multiple stable crevasse channels. High floodplain water levels probably restrict splay length owing to deceleration of outflow as floodplain water is encountered, but separate crevasse channels may form downstream as backflow breaches the trunk channel levee during falling stage. These findings support and extend previous observations from the Río Colorado and other dryland rivers worldwide. Future modelling studies that consider a wider range of hydrological, sedimentological, and floodplain topographic conditions will help develop more comprehensive numerical models of splay development. A combination of insights from field, laboratory experimentation, remote sensing and modelling will improve knowledge of the cascades of channel-floodplain dynamics that characterise many dryland endorheic basins.

The Method of Predicting the Confidence Interval by the Culvert Capacity of Channels at the Design Stage

The purpose of the research is to develop a methodology for predicting confidence intervals of functional parameters of main channels at the design stage, taking into account the probability of absolute changes occurring in their hydraulic parameters during construction and operation. In this regard, taking into account that during the construction and operation of main channels, the frequency of absolute changes in the values of the living cross-section area, wetted perimeter, hydraulic radius and bottom slope obeys the normal distribution law, and the channel roughness coefficient is an increasing and arbitrarily variable random variable, the possibility of predicting the probable confidence interval for the channel’s culvert over the period of operation is investigated. For this purpose, the Monte Carlo method and the Excel program were used, and a method for predicting the confidence interval of the design value of the channel flow rate was proposed. The corresponding analyses were carried out according to the design values of hydraulic parameters on the studied sections of the main channels operated in the Republic of Azerbaijan. Assuming that the design value of each hydraulic parameter is an average value, and the mean square deviation is within the probability, the generation of normally distributed random variables is compiled (provided that the channel roughness coefficient is an increasing and arbitrarily variable value in the appropriate limit), and according to the flow formula for a steady uniform movement, the maximum flow rate of the channel is calculated. The confidence interval of the average value of the predicted maximum flow rate is determined and compared with the design value of the maximum flow rate on the studied section of the trunk channel. Based on the proposed method, the effect of influencing the average value of the maximum flow rate was analyzed in the case of the roughness coefficient of the channel remains unchanged, and probabilistic scattering of other hydraulic parameters occurs around the design values, as well as, in general, the corresponding hydraulic parameters are scattered around the design values.

Quantitative analysis of crevasse-splay systems from modern fluvial settings

ABSTRACTAlthough crevasse splays are a common constituent of many fluvial and fluvio-deltaic systems, they remain less well understood than the channel deposits in those settings, especially with respect to controls on their occurrence, distribution, and geometry. The current study aims to redress this balance and investigate controls on 1) splay formation and occurrence and 2) splay size and geometry. The study has used Google Earth-based satellite imagery to examine crevasse-splay deposits from eight modern fluvial systems. A total of 1556 crevasse splays were identified using imagery from 1984 to 2020. Most of the splays (c. 70%) occur on the outer sinuous river bank with offtake angles ranging from 10° to 140° (mean 75°) to the channel flow direction. Three different types of splays have been identified: i) single crevasse splays, ii) laterally amalgamated crevasse splays, and iii) crevasse-splay complexes. The areal extent of splay bodies varies widely and ranges from less than 1 km2 up to 221 km2. The single crevasse splays are the primary and smallest form of splay, with an average area of 0.61 km2. Compensational stacking or progradation significantly increase the splay area and form laterally amalgamated splays and splay complexes, respectively. The average areal extent of laterally amalgamated splays is 1.33 km2, and of splay complexes, 39 km2.The climate, discharge, floodplain morphology, vegetation, trunk channel slope, sinuosity, and sediment load primarily control the occurrence, geometry, and dimensions of crevasse splays. Results demonstrate that sparse or no floodplain vegetation favors the formation of elongated tongue-shaped crevasse splays while densely vegetated floodplains produce more lobate splays. The highest splay frequency occurs in systems where the river experiences sudden high magnitude variation in discharge, has a low cross-sectional area, and noncohesive bank materials. Larger splay size is correlated with lower river slope angles and higher sinuosity, discharge, and floodplain relief. Channel size has little influence on the extent of splays. This work suggests that autogenic factors such as trunk-channel slope and sinuosity are more influential in arid–semiarid settings while allogenic factors such as discharge are important in temperate–equatorial settings.

Sandstone body character and river planform styles of the lower Eocene Willwood Formation, Bighorn Basin, Wyoming, USA

AbstractThe lower Eocene Willwood Formation of the Bighorn Basin, Wyoming, USA, is an alluvial succession with a sand content varying around 25%. It has been studied intensively for palaeontology, palaeoenvironments and palaeoclimates, as well as sedimentological and stratigraphic analysis. Channel dynamics were studied at a relatively low resolution throughout the basin over the geological time from late Palaeocene to early Eocene. Here, a high‐resolution study is reported to complement previous research at the basin scale. Efforts are made to document the characteristics and river planform styles of most sandstone bodies encountered through ca 300 m of alluvial stratigraphy in a 10 km2 area of the Deer Creek part of the McCullough Peaks area situated in the basin axis of northern Bighorn Basin. Four channel facies associations are recognized and ascribed to four river planform styles: crevasse channel, trunk channel, braided‐like channel and sinuous‐like channel, with the latter two types dominant. Braided‐like and sinuous‐like channel sandstone bodies differ significantly in thicknesses, being on average 6.1 m versus 9.0 m, but they have similar palaeoflow–perpendicular widths of on average 231 m and palaeoflow directions of on average N 003°. Braided‐like and sinuous‐like river planform styles show no spatial dependency in the 10 km2 study area. Results of this study are in line with existing basin‐scale depositional models that are composed of a single axial system fed by several transverse systems dominantly from the west. The feeding of these systems could be influenced by palaeoclimate changes possibly controlling their contribution over time, thereby impacting river planform styles. At the same time, changing water discharge hydrograph, sediment load and overbank cohesiveness may have equally driven the observed river planform style changes within the basin without a major role of catchments.

Long-term hillslope erosion and landslide–channel coupling in the area of the catastrophic Wenchuan earthquake

Approximately 200,000 landslides were triggered by the 2008 Wenchuan earthquake and subsequent strong rainfall events, and the amount of landslide sediment delivered to the channels within catchments depended on the amount of landslide debris generated by the earthquake and the amount of post-earthquake rainfall. To better understand long-term hillslope erosion and the long-term changes in landslide–channel coupling, this study quantifies the coupling degree of landslide–channel by defining a landslide-channel coupling index (LCCI) and estimates the long-term hillslope erosion driven by landslides within 12 debris flow basins. We track landslide activity using multiyear imagery from 2008 to 2019, and the landslide ratio, landslide new regeneration ratio, and landslide reactivated ratio indicate that the overall landslide activity decayed following the Wenchuan earthquake. The calculation results of the coupling index illustrate that the coupling degree of landslide–channel in the study area follows a power law trend of decay over time. However, due to the influence of landslide activity, the coupling index decreased significantly in the first 5 years after the Wenchuan earthquake and then decreased slowly. The hillslope erosion driven by landslides is estimated using a conservative statistical model. The result shows that the landslide-driven hillslope erosion has decayed following a power law, and elevated levels of erosion may last for an unexpectedly long period. In addition, the landslide–channel coupling degree affects the movement of landslide sediment to channels. While the coupling degree of landslide–channel and the amount of landslide sediment supplied to the channels have decreased significantly in recent years, abundant landslide sediment could still be delivered to the channels when strong rainfall occurs in this region. Furthermore, a considerable amount of sediment appears to remain within the tributary channels and trunk channels, which means the activity of debris flow may last longer period than hillslope erosion.

Comparison of basin-scale in situ and meteoric <sup>10</sup>Be erosion and denudation rates in felsic lithologies across an elevation gradient at the George River, northeast Tasmania, Australia

Abstract. Long-term erosion rates in Tasmania, at the southern end of Australia's Great Dividing Range, are poorly known; yet, this knowledge is critical for making informed land-use decisions and improving the ecological health of coastal ecosystems. Here, we present quantitative, geologically relevant estimates of erosion rates for the George River basin, in northeast Tasmania, based on in situ-produced 10Be (10Bei) measured from stream sand at two trunk channel sites and seven tributaries (mean: 24.1±1.4 Mgkm-2yr-1; 1σ). These new 10Bei-based erosion rates are strongly related to elevation, which appears to control mean annual precipitation and temperature, suggesting that elevation-dependent surface processes influence rates of erosion in northeast Tasmania. Erosion rates are not correlated with slope in contrast to erosion rates along the mainland portions of Australia's Great Dividing Range. We also extracted and measured meteoric 10Be (10Bem) from grain coatings of sand-sized stream sediment at each site, which we normalize to measured concentrations of reactive 9Be and use to estimate 10Bem-based denudation rates for the George River. 10Bem/9Bereac denudation rates replicate 10Bei erosion rates within a factor of 3 but are highly sensitive to the value of 9Be that is found in bedrock (9Beparent), which was unmeasured in this study. 10Bem/9Bereac denudation rates seem sensitive to recent mining, forestry, and agricultural land use, all of which resulted in widespread topsoil disturbance. Our findings suggest that 10Bem/9Bereac denudation metrics will be most useful in drainage basins that are geologically homogeneous, where recent disturbances to topsoil profiles are minimal, and where 9Beparent is well constrained.

Recognizing key sedimentary facies and their distribution in mixed turbidite–contourite depositional systems: The case of the Pacific margin of the Antarctic Peninsula

AbstractInterplay of deep‐water sedimentary processes is responsible for building a myriad of features and deposits across mixed turbidite–contourite systems, from <5 cm beds to >200 km long sedimentary drifts. Investigations of the spatial and temporal variability of their sedimentary facies and facies associations is crucial to reveal the dynamics between along‐slope bottom currents and down‐slope turbidity currents, as well as their impact on drift construction and channel erosion. This study focuses on extensive modern mixed (turbidite–contourite) systems, developed across the continental rise of the Pacific margin of the Antarctic Peninsula. Nine sediment cores were sampled and analysed, through grain size and geochemical methods, to study the sedimentary facies at high‐resolution (ca 1 to 20 cm). Three main facies associations have been identified across distinct morphological features (i.e. mounded drifts and trunk channels), comprising intercalations of hemipelagites, bottom current reworked sands (which include fine to coarse‐grained contourites) and gravitational facies (turbidites and mass‐transport deposits). These facies associations reflect fluctuations of the background sedimentation, oscillations of the bottom‐current velocity and of the frequency of gravity‐driven currents. The sedimentary record features cyclic alternations during the Late Quaternary (>99 kyr), suggesting that variations between along‐slope bottom currents and down‐slope turbidity currents are strongly linked to glacial–interglacial cycles during Marine Isotope Stages 1 to 6. Sedimentary records affected by bottom currents on polar margins, such as those of the Antarctic Peninsula, are essential to decipher the facies and facies sequences of bottom‐current deposits, as the low degree of bioturbation throughout most of the sediments allows us to observe the original sedimentary structures, which are poorly preserved in similar deposits from other continental margins.

Sedimentary model for mixed depositional systems along the Pacific margin of the Antarctic Peninsula: Decoding the interplay of deep-water processes

Mixed (turbidite-contourite) depositional systems are formed by a complex interplay of deep-water processes. An evaluation of their morphological elements and their lateral and spatial distribution is crucial to better understand the interplay of transport and depositional processes, involving along-slope bottom currents and down-slope turbidity currents. This work investigates extensive and still active mixed depositional systems developed along the Pacific margin of the Antarctic Peninsula, which comprise large asymmetric mounded drifts, dendritic channel-complex systems and wide trunk channels. These systems offer a unique setting to investigate diverse morphological elements at a high-resolution spatial scale (10–100 m), using multibeam bathymetry and acoustic sub-bottom profiles. Four main seismic units define distinct evolutionary stages for the Pleistocene to present day record: a) 1.3–1 Ma, characterized by aggradational mounded drifts built by a dominant along-slope bottom current; b) 1–0.6 Ma, built by synchronous interactions between a SW-flowing bottom current and NW-directed turbidity currents; c) 0.6–0.2 Ma, characterized by deposition of thick gravitational deposits across the margin under a weak SW-flowing bottom current comprising modified Lower Circumpolar Deep Water (LCDW); and d) 0.2 Ma – present, when synchronous interactions between the bottom current, characterized by flow speed fluctuations, and ephemeral turbidity currents led to intercalations of turbidites, contourites, reworked turbidite deposits and hemipelagites. Alternations in the stratigraphic stacking pattern suggest cyclic spatial and temporal variations of gravity-driven down-slope processes and along-slope bottom currents, which were responsible for the construction of these modern mixed depositional systems and which themselves were controlled by glacial-interglacial changes. The new results are compared with similar mixed depositional systems to decode the main processes involved in their formation, explore their interactions at short- and long-term time scales, and propose a conceptual sedimentary model.

Episodic habitation and abandonment of Neolithic civilization sites in the Vaigai River Basin, Southern India

Recent studies have unearthed and recovered multiple sites with evidences of past human habitations in terms of ceramic, metal, precious stone, jewel, and stone tool industries and places of varied methods of burial and worship are being unearthed at different stratigraphic levels from floodplains of the Vaigai River Basin, Southern India. In this contribution, we present high-resolution 14C chronology of the archaeological artefacts, cultural evidence and the textural characteristics of sediments collected from the excavated pits. These data along with the information on regional geology, geomorphology, sedimentary facies, texture, petrography, and mineralogy constrain the older phase of the Vaigai River Basin Civilization to be microlithic in age, followed by affirmative evidence of ca. 5511-5147 BCE (7455-7091 cal yr BP). This was followed by few more colonization/cultural/habitation sites/surfaces at ca. 2976-2961 BCE (4938-4908 cal yr BP), 1860-1489 BCE (3543-3503 cal yr BP),530-390 BCE (2435-2314 cal yr BP), 596-629 CE (1353-1321 cal yr BP) and post 1225-1312 CE (729-619 cal yr BP). These are designated as habitation sites/surfaces namely HS-1, HS-2, HS-3, HS-4, HS-5 and HS-6, respectively. Evidences of urbanism, industrial and leisure activities besides cohabitation of at least three groups that practiced mutually exclusive burial customs are documented. Microlithic tools and buried habitation stages, together with the prevalence of modern habitations, make this basin unique with human occupation at least since the mid-Holocene. Major shifts of the trunk channel of the Vaigai River, perhaps associated with flood events, marooned/buried/destroyed the ancient habitation sites that forced the inhabitants to abandon old sites and led to the reestablishment of newer ones. Inevitable dependence of the ancient societies on the riverbanks and the flood plains for settlements and livelihood compounded with the lack of knowledge on extreme climatic events possibly caused the decimation of several settlements of this important civilization from south India.