scholarly journals Geomorphological and Geochronological Analysis Applied to the Quaternary Landscape Evolution of the Yeltes River (Salamanca, Spain)

2020 ◽  
Vol 12 (19) ◽  
pp. 7869 ◽  
Author(s):  
Iván Martín-Martín ◽  
Pablo-Gabriel Silva ◽  
Antonio Martínez-Graña ◽  
Javier Elez
Keyword(s):  
Transfer Functions ◽  
Sedimentary Basins ◽  
Central Spain ◽  
Geomorphological Mapping ◽  
Fluvial Terraces ◽  
Digital Elevation ◽  
Late Neogene ◽  
Climate Evolution ◽  
Reported Data ◽  
Geomorphological Evolution

This paper aims to study the Quaternary geomorphological evolution of the Yeltes river-valley (Duero Basin, Central Spain) primarily based on the study of the Late Neogene piedmont dissected by the river and its Quaternary terrace sequence, since fluvial terraces are excellent archives to study the landscape and climate evolution during this period. Detailed geomorphological mapping implemented in GIS-based digital elevation models was used to the further applications of existing fluvial chronofunctions (relative terrace height-age transfer functions) to establish a numerical geochronology to the sequence of fluvial terraces in the zone. The obtained theoretical ages points to an onset of fluvial incision in the zone after 2.0–2.5 Myr ago, with the dissection of the “Raña surface” (a Gelasian alluvial piedmont widely developed in Central Spain). The obtained terrace ages coincide, in most cases, with warm isotopic stages (MIS) or mainly with the transit of cold to warm MIS. Additionally, this study suggests that the full connectivity of the Yeltes drainage (Ciudad Rodrigo Basin) with the Atlantic drainage was not completely effective until MIS 9 (c. 0.29 Myr). The new reported data allows for the exploration of the timing and processes involved in the capture of inland sedimentary basins (Ciudad Rodrigo, Duero basins) by the Atlantic drainage during the early Quaternary.

Recent, rapid and profound changes to glacier morphology and dynamics, Juneau Icefield, Alaska

2021 ◽  
Author(s):  
Bethan Davies ◽  
Jacob Bendle ◽  
Robert McNabb ◽  
Jonathan Carrivick ◽  
Christopher McNeil ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Aerial Photographs ◽  
Equilibrium Line Altitude ◽  
Regional Warming ◽  
Geomorphological Mapping ◽  
Glacier Recession ◽  
Digital Elevation ◽  
High Resolution Satellite Imagery ◽  
Global Sea Level

<p>The Alaskan region (comprising glaciers in Alaska, British Columbia and Yukon) contains the third largest ice volume outside of the Greenland and Antarctic ice sheets, and contributes more to global sea level rise than any other glacierised region defined by the Randolph Glacier Inventory. However, ice loss in this area is not linear, but in part controlled by glacier hypsometry as valley and outlet glaciers are at risk of becoming detached from their accumulation areas during thinning. Plateau icefields, such as Juneau Icefield in Alaska, are very sensitive to changes in Equilibrium Line Altitude (ELA) as this can result in rapidly shrinking accumulation areas. Here, we present detailed geomorphological mapping around Juneau Icefield and use this data to reconstruct the icefield during the “Little Ice Age”. We use topographic maps, archival aerial photographs, high-resolution satellite imagery and digital elevation models to map glacier lake and glacier area and volume change from the Little Ice Age to the present day (1770, 1948, 1979, 1990, 2005, 2015 and 2019 AD). Structural glaciological mapping (1979 and 2019) highlights structural and topographic controls on non-linear glacier recession.  Our data shows pronounced glacier thinning and recession in response to widespread detachment of outlet glaciers from their plateau accumulation areas. Glacier detachments became common after 2005, and occurred with increasing frequency since then. Total summed rates of area change increased eightfold from 1770-1948 (-6.14 km<sup>2</sup> a<sup>-1</sup>) to 2015-2019 (-45.23 km<sup>2</sup> a<sup>-1</sup>). Total rates of recession were consistent from 1770 to 1990 AD, and grew increasingly rapid after 2005, in line with regional warming.</p>

scholarly journals Mapping Glacier Forelands Based on UAV BVLOS Operation in Antarctica

2020 ◽  
Vol 12 (4) ◽  
pp. 630
Author(s):  
Maciej Dąbski ◽  
Anna Zmarz ◽  
Mirosław Rodzewicz ◽  
Małgorzata Korczak-Abshire ◽  
Izabela Karsznia ◽  
...  
Keyword(s):  
Ice Age ◽  
South Shetland Islands ◽  
Ground Moraine ◽  
King George Island ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Geomorphological Mapping ◽  
Digital Elevation ◽  
Glacial Dynamics ◽  
Elevation Model

The aim of this article is to show geomorphological mapping of remote Antarctic locations using images taken by a fixed-wing unmanned aerial vehicle (UAV) during the Beyond Visual Line of Sight (BVLOS) operations. We mapped landform assemblages developed in forelands of Ecology Glacier (EGF), Sphinx Glacier (SGF) and Baranowski Glacier (BGF) in Antarctic Specially Protected Area No. 128 (ASPA 128) on King George Island (South Shetland Islands) and inferred about glacial dynamics. The orthophoto and digital elevation model allowed for geomorphological mapping of glacial forelands, including (i) glacial depositional landforms, (ii) fluvial and fluvioglacial landforms, (iii) littoral and lacustrine landforms, (iv) bodies of water, and (v) other. The largest area is occupied by ground moraine and glacial lagoons on EGF and BGF. The most profound features of EGF are the large latero-frontal moraine ridges from Little Ice Age and the first half of the 20th century. Large areas of ground moraine, frequently fluted and marked with large recessional moraine ridges, dominate on SGF. A significant percentage of bedrock outcrops and end moraine complexes characterize BGF. The landform assemblages are typical for discontinuous fast ice flow of tidewater glaciers over a deformable bed. It is inferred that ice flow velocity decreased as a result of recession from the sea coast, resulting in a significant decrease in the length of ice cliffs and decrease in calving rate. Image acquisition during the fixed-wing UAV BVLOS operation proved to be a very robust technique in harsh polar conditions of King George Island.

scholarly journals Sedimentary dynamics and structural control of Neogene tropical biofacies during the formation of the Central American Isthmus

1992 ◽  
Vol 6 ◽  
pp. 62-62 ◽  
Author(s):  
Anthony Coates ◽  
Jorge Obando ◽  
Herman Gonzalez
Keyword(s):  
Structural Control ◽  
Sedimentary Basins ◽  
Conclusive Evidence ◽  
Central American ◽  
The Pacific ◽  
Pacific Side ◽  
Late Neogene ◽  
The Caribbean ◽  
Final Closure ◽  
Central American Isthmus

The central evolutionary, ecological and paleoceanographic questions of the American tropical Neogene relate to how and during what time the Central American Isthmus formed. Geographically, closure was located between the southern edge of the Chortis Block in southern Nicaragua and the Atrato Valley in Colombia. In this region we describe, on the Caribbean side, five Neogene sedimentary basins. They are the Atrato, Chucunaque, Gatun, Bocas del Toro, and Limon Basins. On the Pacific side the Neogene sediments formed as part of the Central American Trench and are well exposed in a series of uplifted blocks on the Nicoya, Osa and Burica Peninsulas. Our analysis allows 1) a construction of the sequence of contrasting sedimentary environments which characterize the different basins, giving a composite geological history of the isthmus for the Late Neogene and 2) identifies the comparable biofacies from the different basins which allow and constrain the evolutionary and ecological questions to be posed concerning the effect of the isthmus as a biogeographic barrier. Temporally, from it's partial emergence in the Middle Miocene, the isthmus shallows by the Early Pliocene (3.5–3.4 Ma) to less than 50 m (Duque-Caro, 1990) when there is a marked differentiation of shelf marine macrobenthic species between the Caribbean and the Pacific. The evidence from reliably dated, large, diverse exchanges of North and South American vertebrates on land constrains the final closure date to not later than 2.8–2.5 Ma (Marshall, 1988). Given that no conclusive evidence for final closure can come exclusively from a study of sedimentary facies, when depths of less than 50 m are involved, the present window of almost 1 Ma, during which final closure must have occurred, will only be narrowed further by the detailed study of very shallow-water fossil clades and complementary molecular data. Present studies indicate that such clades are abundantly preserved.

scholarly journals Late Neogene Radiolaria from the East Coast Deformed Belt, New Zealand

2021 ◽  
Author(s):  
◽  
Jeffrey Noel Ashby
Keyword(s):  
New Zealand ◽  
Southern Ocean ◽  
Ocean Circulation ◽  
Deep Water ◽  
East Coast ◽  
Sedimentary Basins ◽  
Early Pleistocene ◽  
Time Segment ◽  
Shelf Slope ◽  
Late Neogene

<p>Within the East Coast Deformed Belt there are a number of Late Neogene sedimentary basins with relatively deep-water sediments which, at places, contain abundant radiolarian skeletons. The region was subject to relatively open ocean circulation patterns during the Neogene which, combined with the input of rhyolitic glass shards, has enhanced the siliceous microfossil preservation. A short review of the silica budget is presented and discussed in relation to the preservation of siliceous microfossils in the New Zealand sequences. Techniques were developed to extract and quantitatively study fossil Radiolaria from some of the relatively barren shelf/slope sediments. One hundred and thirty-eight radiolarian taxa are described, most of which can be assigned at the generic level, but thirty-one of which can not be assigned specific names and may eventually prove to be new species. The radiolarian zonation presented is based on detailed analysis of 155 samples from 26 sections and sites ranging in age from basal Tongaporutuan (early Late Miocene) to middle Nukumaruan (early Pleistocene). Sediments of the Kapitean (uppermost Miocene) were generally deposited in shallow water environments or are missing in unconformities in the East Coast Deformed Belt, consequently the radiolarian zonation is based on very poor data in this time segment. Also upper Opoitian and Waipipian (middle Pliocene) sediments, although at places deposited in relatively deep water, generally lack siliceous tuffs, and radiolarian preservation is poor. Five major radiolarian zones can be recognised: Diartus hughesi Zone, Didymocyrtis sp. A Zone, Didymocyrtis sp. A Zone, Didymocyrtis tetrathalmus tetrathalmus Zone, Lamprocyrtis heteroporos Zone, and Lamprocyclas gamphonycha Zone. In samples with good radiolarian preservation six subzones can be identified. The Diartus hughesi Zone can be divided into the Heliodiscus umbonatum Subzone, Didymocyrtis laticonus Subzone, Heliodiscus asteriscus forma large pores Subzone, and Anthocyrtidium ehrenbergi pliocenica Subzone. Additionally the Didymocyrtis tetrathalmus tetrathalmus Zone can be divided into the Lychnocanium sp. aff. grande Subzone and Lamprocyrtis hannai Subzone. The bioevents that define the zonal boundaries are discussed along with other biostratigraphically useful radiolarian datums. These zones and zubzones are correlated to the foraminiferal zonation which in turn has been related, in part, to the paleomagnetic time scale. Correlation are then made with other radiolarian zonations in the north Pacific, tropics, and southern ocean. Points to emerge from these correlations include the apparent provincialism in the transition from Stichocorys delmontense to Stichocorys peregrine in the tropical Pacific. This transition has been reported to occur during approximately 1.5Ma but in New Zealand occurs over a time segment of at least 5.5Ma. The first appearance of Lamprocyclas gamphonycha appears to be an isochronous datum level in temperate radiolarian faunas of the northern and southern Pacific. The last appearance datum of Diartus hughesi at about 7.5Ma is in good agreement with its level in the tropics. The presence of this taxon in lower Gilbert Antarctic cores suggests either a grossly diachronous event between tropical/temperate areas and the southern ocean or, more probably, a misinterpretation of the paleomagnetic signature from key southern ocean piston cores. If the latter situation is the case then the real age estimates on the "Pre middle Gilbert" southern ocean diatom and silicoflagellate stratigraphies are questionable because they are based on the same key cores. Statistical faunal analysis shows that during the Miocene there was not much change in the radiolarian faunas with time and a major change, probably climatically controlled, took place across the Miocene/Pliocene boundary. Variability in preservation has probably affected the faunas to obscure more precise time variation although post-Miocene faunas indicate that some is present. In conclusion, the Radiolaria, although not as common in the fossil record as the foraminifera, definitely contribute to New Zealand Late Neogene integrated stratigraphy and suggest that our knowledge could be greatly enhanced by the study of other siliceous microfossil groups.</p>

scholarly journals Planalto, cuesta, glint: a Geomorfologia da Ibiapaba Setentrional (região noroeste do Ceará, Brasil) (Planalto, cuesta, glint: the Geomorphology of the Northern Ibiapaba (northwestern region of Ceará, Brazil))

2017 ◽  
Vol 10 (6) ◽  
pp. 1846
Author(s):  
Marcelo Martins de Moura-Fé
Keyword(s):  
Theoretical Basis ◽  
Scientific Literature ◽  
The State ◽  
Regional Modeling ◽  
Natural Heritage ◽  
Geomorphological Mapping ◽  
Northwestern Region ◽  
Geomorphological Evolution ◽  
Western Portion

Sob a alcunha generalizante de “serra”, a Ibiapaba representa uma paisagem singular no Ceará ao abranger toda a porção ocidental do estado nos limites com o Piauí e uma rica diversidade geomorfológica ao longo dos seus 380 km. Tal diversidade está relativamente presente na literatura científica, com denominações diferentes, as quais são atreladas a diferentes entendimentos geomorfológicos. Mais do que se sucederem, as conceituações geomorfológicas atribuídas à Ibiapaba estão imbricadas ao longo da sucessão dos estudos feitos sobre a região e, mais do que isso, refletem o crescente interesse sobre a evolução geomorfológica da região, cujos registros estão presentes na paisagem atual. Neste contexto, o objetivo deste trabalho é realizar a análise da geomorfologia da Ibiapaba setentrional, passando pela conceituação e caracterização dos seus segmentos, tecendo abordagens sobre as condições evolutivas pretéritas e as implicações de uso e ocupação. Metodologicamente, o itinerário percorrido foi compartimentado em duas linhas: no embasamento teórico, centrado na abordagem morfoestrutural da ciência geomorfológica (a qual embasou a compartimentação e a análise geomorfológicas feitas) e na utilização de um contingente técnico associado (etapas de gabinete, campo e laboratório). Conforme os resultados apresentados nos mapas, fotos, perfis e na discussão associada, o modelado regional da Ibiapaba apresenta uma caracterização geomorfológica rica em detalhes e possibilidades de abordagem, os quais refletem uma geomorfologia única na região e parte inconteste do patrimônio natural do Ceará. A B S T R A C T  Under the generalizing nickname "serra", the Ibiapaba represents a unique landscape in Ceará encompassing the entire western portion of the state on the border with Piauí and a rich geomorphological diversity along its 380 km. Such diversity is relatively present in the scientific literature, with different denominations, which are linked to different geomorphological understandings. More than succeeding, the geomorphological concepts attributed to the Ibiapaba are intertwined throughout the succession of studies done on the region and, more than that, reflect the growing interest in the geomorphological evolution of the region, whose records are present in the current landscape. In this context, the objective of this work is to perform the analysis of the geomorphology of the northern Ibiapaba, passing through the conceptualization and characterization of its segments, weaving approaches on the previous evolutionary conditions and the implications of use and occupation. Methodologically, the itinerary was compartmentalized in two lines: on the theoretical basis, centered on the morphostructural approach of geomorphological science (which supported geomorphological compartmentalization and analysis) and the use of an associated technical contingent (cabinet, field and laboratory stages ). According to the results presented in the maps, photos, profiles and associated discussion, the Ibiapaba regional modeling presents a geomorphological characterization rich in details and possibilities of approach, which reflect a unique geomorphology in the region and an undisputed part of the natural heritage of Ceará. Keywords: structural geomorphology, landscape, natural heritage, geodiversity. geomorphological mapping.

scholarly journals Karst geomorphology in the Oštarije–Tounj area and its significance in the geomorphological evolution of the broader area

2020 ◽  
Vol 82 (2) ◽  
pp. 5-37
Author(s):  
Neven Bočić ◽  
Keyword(s):  
Spatial Distribution ◽  
Contact Zone ◽  
Surface Runoff ◽  
Dry Valleys ◽  
Dinaric Karst ◽  
Geomorphological Mapping ◽  
Geomorphological Units ◽  
Northern Edge ◽  
Karst Geomorphology ◽  
Geomorphological Evolution

The Oštarije–Tounj area lies in the contact zone of two large geomorphological units: the Ogulin-Plaški basin and the Una-Korana plateau, along the northern edge of Dinaric karst in Croatia. This is a highly karstified landscape, with numerous surface and subterranean karst forms. The objective of this study was to determine the significance of the karst relief and the processes of its formation, with the aim of examining the interaction of these two large units during their geomorphological evolution. General and specific digital geomorphometric analyses were used, with geomorphological mapping. Within the morphogenetic approach, the morphostructural conditions of karstification, spatial distribution and significance of karst, and fluviokarst relief forms were analysed. Several dry valleys were established, indicating that this area was the important corridor for surface runoff from the Ogulin-Plaški basin towards the Una-Korana plateau. Tectonic up-lifting of the narrow zone between these two units created an orographic barrier, which hindered any further surface runoff and created the conditions for the development of karst subterranean watercourses. This paper provides a proposal of the morphogenesis model of the Ogulin-Plaški basin, summarised with the description “flattening and closure”.

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