Late Pleistocene fans and terraces in the Majes valley, southern Peru, and their relation to climatic variations

This study investigates the connection between sediment aggradation, erosion and climate in a desert environment of the Majes valley, southern Peru. Luminescence dating of terraces and fans shows that sediment aggradation correlates with wet time intervals on the Altiplano, suggesting a climatic influence on the aggradation-degradation cycles. Major periods of aggradation occurred between ~110-100, ~60-50 and 12-8ka. More precipitation in the Majes catchment resulted in increased erosion and transportation of sediment from the hillslopes into the trunk river. As a result, the sediment loads exceeded the transport capacity of the Majes River and aggradation started in the lower reaches where the river gradient is less. Depletion of the hillslope sediment reservoirs caused a relative increase in the capacity of the trunk river to entrain and transport sediment, resulting in erosion of the previously deposited sediment. Consequently, although climate change may initiate a phase of sediment accumulation, degradation can be triggered by an autocyclic negative feedback and does not have to be driven by climatic chang

Causes and Consequences of Channel Changes – A Spatio-Temporal Analysis Using Remote Sensing and Gis— Jaldhaka-Diana River System (Lower Course),

Channel changes with respect to time and space play a significant role in stream flow dynamics. The rambling and trailing of  channels in the studied region has been studied  through systematic analysis and interpretation of diverse channel configuration and multi-channel orientation using multi-temporal Topographical maps and Satellite images for a period spanning nearly 80 years (1930–2011). For this specific purpose lower course of Diana River in the Jaldhaka-Diana river system has been selected in the Duars region of the Jalpaiguri district, West Bengal which is virtually a zone of transition between the Himalayan Mountains and the North Bengal plain.  The prime objective of the study is to reveal the spatio-temporal sequences of channel changes, consequent movement of confluence point and the factors and causes of such movement. For this particular extraction, Base map has been generated with the help of SOI Topographical maps and satellite images of the respective area. For this purpose updated version of ERDAS Imaging is employed as image processing tool for enhancing, merging and to update the spatial information of channel configuration and Arc GIS for final product generation. Following the specific objective of the study it has been deduced that during this span the confluence point has moved and re-oriented both upstream and downstream on a historical time scale and new confluence points have been created by repeated shifting and migration of channels. No definite trend is observed in the movement of the confluence points. However, but it is noticed that some distinct flow dynamics and channel maintaining processes are actively performing in this spatio-temporal analysis of channel changes. Keywords: Morphogenetic complex, Multi-channel system, Confluence Dynamics, Channel avulsion, Channel shifting, Erosion-accretion proces

Satellite imagery evaluation of soil moisture variability in north-east part of Ganges Basin, India

Soil moisture variability across four river systems in Ganges Basin, from the Tista and Kosi Rivers in the east to the Gandak and Ghaghra-Rapti Rivers in the west, was assessed using Landsat TM Band 6 imagery dating from 1999-2003. The Band 6 thermal channel of Landsat is sensitive to soil temperature variability resulting from differences in moisture content and as such is a proxy for soil moisture variability in this environment. In order to take advantage of this relationship we analyzed the imagery focusing on the range of thermal values across the fans. This range calculation separates seasonally dry and perennially wet soils on the basis of variability in their moisture content throughout the year. Soils that have a high range (high variability) show significant drying after the monsoon, while those that exhibit a low range indicate either constant wet or dry conditions and/or vegetation that does not vary seasonally. Ground based assessments of soil characteristics on the Tista and Kosi fans support this image analysis. Our work, supported by literature, indicates that the Tista DFS (Distributive Fluvial System) and the Ghaghra-Rapti interfluve, where river is currently incised and detached from its floodplain, show an increase in soil moisture content downstream. However, the Kosi and Gandak DFSs, which have higher rate of subsidence and are not incised under current climatic conditions, show no trend in soil moisture distribution. This study indicates that degree of incision and water table depth are important controls for soil moisture distribution across the DFSs in this area

Landscape formation, environmental changes and prehistoric occupation (Jacaré-Guaçu River Lowlands, Araraquara area, Southeast Brazil, Late Pleistocene-Holocene interval): correlation between geomorphological, pedological, geochronological and archaeological data

This paper presents a geomorphological, pedological and geochronological characterization and contextualization of geomorphogenetic, chronomorphological and environmental sequences from the Araraquara area (central São Paulo State, Southeast Brazil), and their relationship to lithic material from hunter-gatherer archaeological lithic sites. A special emphasis is given to a detailed study of the lowlands of the Jacaré-Guaçu River (between the cities of Araraquara and Boa Esperança do Sul, São Paulo state, Brazil), near the Boa Esperança II hunter-gatherer archaeological site, BES II, in an area of clear asymmetry of the alluvial plain and adjacent slopes. Data derived from the survey of estimated morphogenetic and environmental dynamics are used to contextualize the archaeological material of the BES II site, which is discussed as being associated with the Pleistocene-Holocene transition (an unusual occupation age for the Brazil southeast). We pointed to alternation between successions linked to a quaternary manifestation of a longer pattern of changes of lateral flatting processes and stability of base level with others linked to vertical incision and adequacy to a new base level. We propose a geomorphological model for the Lowlands of Jacaré-Guaçu River, highlighting the possibility that the asymmetry of the plain would be linked to a wider heterogeneity of its geomorphological context of semidetails, partially correlated with the overlapping of neotectonic influence and environmental fluctuations. It is suggested that data from the physical environment of the above mentioned lowlands are compatible with absolute ages obtained by OSL (lower terrace Ia, 14,500±3000 years BP, basal gravel level of the surface coverings, to 10,900±1500 and 4090±340 years BP at the sandy soils and sediments above the gravel) and 14C (8630 years BP, at the level of gleyed sandy-clay soil of 120 cm deep of the low terraces IIa) on archaeological levels of the low terraces of the Jacaré-Guaçu river, in a context of climatic transition from semi-arid conditions to higher humidity, hydrological changes (ephemeral and torrential channels changing to oscillating regimes of perennial channels, with sets of meanders of variable widths of paleochannels, suggesting climatic changes related to the modifications of the fluvial patterns), successive fluctuations (< 10 m) of base levels and large (500 m) lateral migration of the main river to the north guiding the local chronomorphological successions between Late Pleistocene and Late Holocene. The landscape and fluvial dynamics changes over time has influenced the availability of attributes needed for the hunter-gatherer lifestyle (such as fluctuations in the deposition/exposure of river pebbles used as raw material for tool making). Those oscillations are presented as a contribution to explain alternation between more and less dense archaeological levels along the vertical cuts of the low terraces and the location of exception of the BES II site (installed on a fluvial plain and low terraces in a segment characterized by the rarity of rocky outcrops, while most sites in the Araraquara area are linked to slopes, proximal to rocky outcrops - primary sources of lithics artifacts making) on the geomorphological Araraquara area context

The potential of portable luminescence readers in geomorphological investigations : a review

The development of functional portable optically stimulated luminescence (OSL) readers over the last decade has provided practitioners with the capability to acquire luminescence signals from geological materials relatively rapidly, which allows for expedient preliminary chronostratigraphic insight when working with complex depositional systems of late Quaternary age. Typically, when using the portable OSL reader, infrared (IR) or blue post-IR OSL signals are acquired from bulk unprocessed materials, in contrast to regular luminescence dating which is usually based on measurements on pure quartz or feldspar mineral separates, or on select silt-sized polymineralic portions. To demonstrate the utility of portable OSL measurements, this paper outlines the basic features of portable OSL readers and their constraints. Afterwards, case studies in which the instrument has been used to elucidate cryptostratigraphic variations in sedimentary sequences for geomorphological applications are reviewed. The studies can generally be grouped into three main categories. The first includes studies where the variation of portable OSL reader luminescence signal intensities with depth are plotted to generate profiles that contextualise sediment stratigraphy. In the second group, portable OSL reader luminescence signal intensities are used to interpret sediment processes that shed light on depositional histories. In the last category, luminescence signals from the portable OSL reader are calibrated to approximate numerical burial ages of depositional units. The paper concludes with a discussion of possible future directions.PostprintPeer reviewe

The American Geophysical Union Chapman Conference on Tectonics and Topography

The Chapman Conference on Tectonics and Topography was held 31 Aug. - 4 Sep. 1992. The conference was designed to bring together disparate groups of earth scientists who increasingly found themselves working on similar problems but in relative isolation. Thus, process geomorphologists found themselves face-to-face with numerical modelers and field geomorphologists, hydrologists encountered geologists, and tectonophysicists found people with related data. The keynote speakers represented a wide variety of disciplines, all of which were relevant to the interdisciplinary theme of the conference. One of the most surprising issues that surfaced was the relative dearth of data that exists about erosion--process and rates. This was exacerbated by a reminder that erosion is critical to the evaluation of surface uplift

The geomorphology of the Anthropocene:emergence, status and implications

This is the peer reviewed version of the following article: BROWN, A.G. ... et al, 2017. The geomorphology of the Anthropocene: emergence, status and implications. Earth Surface Processes and Landforms, 42(1), pp.71-90., which has been published in final form at http://dx.doi.org/10.1002/esp.3943. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The Anthropocene is proposed as a new interval of geological time in which human influence on Earth and its geological record dominates over natural processes. A major challenge in demarcating the Anthropocene is that the balance between human-influenced and natural processes varies over spatial and temporal scales owing to the inherent variability of both human activities (as associated with culture and modes of development) and natural drivers (e.g. tectonic activity and sea level variation). Against this backdrop, we consider how geomorphology might contribute towards the Anthropocene debate focussing on human impact on aeolian, fluvial, cryospheric and coastal process domains, and how evidence of this impact is preserved in landforms and sedimentary records. We also consider the evidence for an explicitly anthropogenic geomorphology that includes artificial slopes and other human-created landforms. This provides the basis for discussing the theoretical and practical contributions that geomorphology can make to defining an Anthropocene stratigraphy. It is clear that the relevance of the Anthropocene concept varies considerably amongst different branches of geomorphology, depending on the history of human actions in different process domains. For example, evidence of human dominance is more widespread in fluvial and coastal records than in aeolian and cryospheric records, so geomorphologically the Anthropocene would inevitably comprise a highly diachronous lower boundary. Even to identify this lower boundary, research would need to focus on the disambiguation of human effects on geomorphological and sedimentological signatures. This would require robust data, derived from a combination of modelling and new empirical work rather than an arbitrary ‘war of possible boundaries’ associated with convenient, but disputed, `golden spikes’. Rather than being drawn into stratigraphical debates, the primary concern of geomorphology should be with the investigation of processes and landform development, so providing the underpinning science for the study of this time of critical geological transition

Morfološke značilnosti in porazdelitev vrtač v Sloveniji, študija vrtač na osnovi lidarskih podatkov

Dolines are small to intermediate enclosed depressions and are the most numerous karst feature in Slovenia. They are circular in plan form and vary in diameter from a few metres to over a kilometre. They are developed in limestone, dolomite, carbonate breccia and conglomerate and occupy different geomorphic settings. They were formed by various processes like dissolution, collapse, suffosion and transformation of caves to surface features by denudation. Publicly accessible lidar data, provided by a nationwide laser scanning project of Slovenia, was used for this study. To catalogue the dolines, we manually label a fraction of the digital elevation model (DEM) with a binary mask indicating if the area is a doline or not. We then train a slightly modified u-net, a type of machine learning algorithm, on the labelled territory. Using the trained algorithm, we infer the binary mask on the entire DEM. We convert the resulting mask into an ESRI Shapefile and manually verify the results. We note that the training and inference are error prone on types of relief that were less common in the training set (e.g., the relatively uncommon collapse dolines). We believe manual verification mitigates most of these errors, so the resulting map is a good basis for the doline study. We have made our georeferenced catalogue of dolines available at https://dolines.org/ (Mihevc &amp; Mihevc 2021). Dolines are found in most of the karst areas, except mountains where they were eroded by glacial action or covered by glacial deposits. We detected 471,192 dolines and divided them into three genetic types. Most abundant are solution dolines (470,325). The average doline is 9 m deep, has a diameter of 42 m and a volume of 14,098 m3. The density of dolines on levelled surfaces can be as high as 500/ per km2. They are absent from the floors of poljes and steeper slopes, and are less abundant on sloping surfaces. We have identified 314 dolines to be of collapse origin. The mean depth of collapse dolines is 49 m, and 20 of them are deeper than 100 m. The mean volume is 1.2 million m3, with the largest having a volume of 11.6 million m3. Most of the collapse dolines can be found close to ponors or springs or corridors where large underground rivers flow. We have detected 553 suffosion dolines formed by suffosion of sediments in blind valleys or on poljes. This basic data set for dolines enables further study and comparison of dolines with the geology and topography of the karst.Vrtače so majhne do srednje velike zaprte depresije in so najštevilčnejša kraška oblika v Sloveniji. So krožne oblike in imajo premer od nekaj metrov do več kot kilometer. Nastanejo na apnencu, dolomitu, karbonatni breči in konglomeratu. Nastanejo v različnih geomorfnih okoljih, in to z različnimi procesi, kot so raztapljanje, grezanje, sufozija in pretvorba jam v površinske oblike z denudacijo. Za to študijo so bili uporabljeni javno dostopni lidarski podatki, ki so bili zajeti s skeniranjem celotnega ozemlja Slovenije. Za katalogiziranje vrtač del digitalnega modela višin ročno označimo z binarno masko, ki označuje, ali je območje vrtača ali ne. Nato na označenem ozemlju učimo algoritem globokega strojnega učenja u-net. Z algoritmom napovemo binarno masko na celotnem ozemlju Slovenije. Nastalo masko pretvorimo v format SRI Shapefile in ročno preverimo rezultate. Pri delu smo ugotovili, da so napake strojnega učenja in napovedovanja binarne maske večja pri tistih vrstah vrtač, ki so bile manj pogoste v učnih podatkih (npr. pri razmeroma redkih udornih vrtačah). Menimo, da smo z ročnim preverjanjem odpravili večino napak, zato je dobljeni katalog vrtač dobro izhodišče za nadaljnjo študijo. Georeferencirani katalog vrtač je dostopen na spletnem naslovu https://dolines.org/. Vrtače zasedajo večino kraških območij, razen planot, kjer so bile zaradi ledeniškega delovanja erodirane ali prekrite z ledeniškimi nanosi. Odkrili smo 471.192 vrtač in jih razvrstili v tri tipe glede na njihov izvor. Najpogostejše so korozijske vrtače (470.325 primerkov). Povprečna vrtača je globoka 9 m, ima premer 42 m in prostornino 14.098 m3. Gostota vrtač na uravnanih površinah je lahko tudi do 500/ vrtač na km2. Vrtač ni na dnu polj in na strmih pobočjih, manj jih je na nagnjenih površinah. Določili smo 314 udornih vrtač. Povprečna globina udornih vrtač je 49 m, 20 pa jih je globljih od 100 m. Povprečna prostornina je 1,2 milijona m3, največja pa ima prostornino 11,6 milijona m3. Večina udornih vrtač je blizu ponorov, izvirov ali tokov velikih podzemnih rek. Odkrili smo še 553 sufozijskih vrtač, ki so nastale s spiranjem sedimentov v slepih dolinah ali na poljih. Narejeni katalog vrtač omogoča nadaljnje proučevanje in primerjavo vrtač z geologijo in topografijo krasa