scholarly journals Late Quaternary Morphotectonics of the Hetauda Dun, Nepal Sub Himalaya

1995 ◽  
Vol 11 ◽  
Author(s):  
Kazuo Kimura
Keyword(s):  
Stress Field ◽  
Late Pleistocene ◽  
Late Quaternary ◽  
Hanging Wall ◽  
Crustal Movement ◽  
Fault Propagation ◽  
Gangetic Plain ◽  
Anticlinal Structure

The Hetauda Dun, a tectonic valley in the Sub-Himalaya, is separated from the Gangetic plain by the Outer Churia Range. This range was upheaved in the late Pleistocene giving rise to the Dun valley. The tectonics of the area are characterised by fault propagation tectonics caused by the migration of the active front from the Central ChuriaThrust (CCT) to the Himalayan Front Thrust (HFT). After the closure of the Dun, another active anticlinal structure related to thrust imbrication has developed in the central part of the valley on the hanging wall of the CCT. The crustal movement continues under the same stress field of the prior tectonic phase, characterised by the shortening of the Sub-Himalaya along the NNW-SSE direction.

Tectonic and climatic controls on the late Pleistocene to Holocene evolution of Paleolake Ullum-Zonda in the Precordillera of the central Andes, Argentina

2017 ◽  
Vol 88 (2) ◽  
pp. 248-264 ◽  
Author(s):  
Pablo A. Blanc ◽  
Laura P. Perucca
Keyword(s):  
Late Pleistocene ◽  
Late Quaternary ◽  
Hanging Wall ◽  
Central Andes ◽  
Alluvial Deposits ◽  
Growth Strata ◽  
Middle Holocene ◽  
San Juan River ◽  
Late Pleistocene To Holocene ◽  
Holocene Activity

AbstractThe Ullum-Zonda tectonic depression located in the central Andes Precordillera records several lacustrine episodes from frequent natural damming of the San Juan River during the late Quaternary. We analyzed stratigraphic, geomorphic, and geologic data and obtained new radiocarbon ages for Paleolake Ullum-Zonda. Results show the existence of a late Pleistocene age (16.7–15.2 ka BP) unit and an early to middle Holocene (9475–7685 yr BP) unit. Subsurface data show lacustrine episodes were common during the late Pleistocene, with probably nine episodes occurring during that period. Two transgressive events are evident in the Holocene unit, dated to ~8420±30 and shortly after 7460±30 14C yr BP. The maximum extent of the paleolake occurred at 6930±30 14C yr BP, shortly before the lake desiccated. Fault propagation folds and growth strata in Quaternary alluvial deposits relate to the Villicum-Zonda Fault and may indicate early to middle Holocene activity for this fault. The deformation observed in an ancient shoreline of the paleolake could be related to middle to late Holocene activity of the Cerro Zonda Norte Fault at a mean vertical uplift rate of ~0.8 mm/yr in the hanging wall block.

scholarly journals Ultrastructure, dissolution and "pyritization" of Late Quaternary and Recent echinoderms

1987 ◽  
Vol 36 ◽  
pp. 275-287
Author(s):  
Margit Jensen ◽  
Elsebeth Thomsen
Keyword(s):  
Late Pleistocene ◽  
Sea Water ◽  
Late Quaternary ◽  
Pore Space ◽  
Water Interface ◽  
Sea Stars ◽  
Northern Norway ◽  
History Of ◽  
Organic Tissue ◽  
Diagenetic History

The diagenetic history of the skeletal elements of Late Pleistocene-Holocene Ophiura sarsi from the shelf off northern Norway (Andfjorden, Malangsdjupet) is elucidated by comparison with natural and induced degradation of the skeletal elements of Recent ophiuroids (brittle stars) and asteroids (sea stars) from Danish waters. Dissolution features ("core-and-rind") in the trabeculae of fossil and Recent echinoderm stereom are initiated during death and early decay of organic tissue in the animals. The trabeculae have a polycrystal­line lamellar ultrastructure and lose their older central part during later stages of dissolution, which are dependant on undersaturation of the sea-water with regard to CaC03• The presence of undersaturated sea-water is supported by palaeoecological studies (Thomsen & Vorren 1984, 1986) implying oxygen deficient periods in the Late Pleistocene and an increased biogenic production in the Holocene. Pyrite framboids are situated in the secondary voids within the trabeculae and in the pore space of the stereom of the Late Pleistocene elements. No pyrite is observed within the polycrystalline lamellar ultrastructure of the trabeculae. The Late Pleistocene "pyritization" took place during oxygen deficient periods at the sediment-water interface or within the reduced zone of the topmost sediment.

scholarly journals Homogenization of carnivorous mammal ensembles caused by global range reductions of large-bodied hypercarnivores during the late Quaternary

2020 ◽  
Vol 287 (1929) ◽  
pp. 20200804
Author(s):  
Owen S. Middleton ◽  
Jörn P. W. Scharlemann ◽  
Christopher J. Sandom
Keyword(s):  
Functional Diversity ◽  
Late Pleistocene ◽  
Late Quaternary ◽  
Geographical Range ◽  
Functional Roles ◽  
Main Driver ◽  
Herbivorous Species ◽  
Out Of Africa ◽  
Dietary Strategies ◽  
Structural Shifts

Carnivorous mammals play crucial roles in ecosystems by influencing prey densities and behaviour, and recycling carrion. Yet, the influence of carnivores on global ecosystems has been affected by extinctions and range contractions throughout the Late Pleistocene and Holocene (approx. 130 000 years ago to the current). Large-bodied mammals were particularly affected, but how dietary strategies influenced species' susceptibility to geographical range reductions remains unknown. We investigated (i) the importance of dietary strategies in explaining range reductions of carnivorous mammals (greater than or equal to 5% vertebrate meat consumption) and (ii) differences in functional diversity of continental carnivore ensembles by comparing current, known ranges to current, expected ranges under a present-natural counterfactual scenario. The present-natural counterfactual estimates current mammal ranges had modern humans not expanded out of Africa during the Late Pleistocene and were not a main driver of extinctions and range contractions, alongside changing climates. Ranges of large-bodied hypercarnivorous mammals are currently smaller than expected, compared to smaller-bodied carnivorous mammals that consume less vertebrate meat. This resulted in consistent differences in continental functional diversity, whereby current ensembles of carnivorous mammals have undergone homogenization through structural shifts towards smaller-bodied insectivorous and herbivorous species. The magnitude of ensemble structural shifts varied among continents, with Australia experiencing the greatest difference. Weighting functional diversity by species’ geographical range sizes caused a threefold greater shift in ensemble centroids than when using presence–absence alone. Conservation efforts should acknowledge current reductions in the potential geographical ranges of large-bodied hypercarnivores and aim to restore functional roles in carnivore ensembles, where possible, across continents.

scholarly journals Bird populations and species lost to Late Quaternary environmental change and human impact in the Bahamas

2020 ◽  
Vol 117 (43) ◽  
pp. 26833-26841 ◽  
Author(s):  
David W. Steadman ◽  
Janet Franklin
Keyword(s):  
Late Pleistocene ◽  
Migratory Birds ◽  
Late Quaternary ◽  
Bird Communities ◽  
Greater Antilles ◽  
The Bahamas ◽  
Bird Populations ◽  
Modern Distribution ◽  
Distributional Information ◽  
Fossil Records

Comparing distributional information derived from fossils with the modern distribution of species, we summarize the changing bird communities of the Bahamian Archipelago across deep ecological time. While our entire dataset consists of 7,600+ identified fossils from 32 sites on 15 islands (recording 137 species of resident and migratory birds), we focus on the landbirds from four islands with the best fossil records, three from the Late Pleistocene (∼25 to 10 ka [1,000 y ago]) and one from the Holocene (∼10 to 0 ka). The Late Pleistocene sites feature 51 resident species that have lost one or more Bahamian populations; 29 of these species do not occur in any of the younger Holocene sites (or in the Bahamas today). Of these 29 species, 17 have their closest affinities to species now or formerly living in Cuba and/or North America. A set of 27 species of landbirds, most of them extant somewhere today, was more widespread in the Bahamas in the prehistoric Holocene (∼10 to 0.5 ka) than they are today; 16 of these 27 species were recorded as Pleistocene fossils as well. No single site adequately captures the entire landbird fauna of the combined focal islands. Information from all sites is required to assess changes in Bahamian biodiversity (including endemism) since the Late Pleistocene. The Bahamian islands are smaller, flatter, lower, and more biotically depauperate than the Greater Antilles, resulting in more vulnerable bird communities.

scholarly journals The role of a proto-Schelde River in the genesis of the southwestern Netherlands, inferred from the Quaternary successions and fossils in Moriaanshoofd Borehole (Zeeland, the Netherlands)

2013 ◽  
Vol 92 (1) ◽  
pp. 69-86 ◽  
Author(s):  
A.A. Slupik ◽  
F.P. Wesselingh ◽  
D.F. Mayhew ◽  
A.C. Janse ◽  
F.E. Dieleman ◽  
...  
Keyword(s):  
The Netherlands ◽  
Late Pleistocene ◽  
Late Quaternary ◽  
Source Region ◽  
Fossil Material ◽  
Mammal Faunas

AbstractWe investigated the Quaternary lithological succession and faunas in a borehole near Moriaanshoofd (Province of Zeeland, SW Netherlands), in order to improve our understanding of the depositional context of classical Gelasian mammal faunas from the region. The fossils mostly derive from the base of a fossil-rich interval between 31 m and 36.5 m below the surface, that was initially interpreted as a Middle or Late Pleistocene interglacial marine unit, but turned out to be a Late Quaternary fluvial unit with large amounts of reworked fossils and sediments. Eocene mollusc taxa pinpoint Flanders (Belgium) as the source region for this river. Within the base of this paleo-Schelde River fossil material of various stratigraphic provenance became incorporated.

Late-Pleistocene geomorphological and geochronological history of the former Patagonian Ice Sheet in north-eastern Patagonia (43°S)

2020 ◽  
Author(s):  
Tancrede P.M Leger ◽  
Andrew S. Hein ◽  
Angel Rodes ◽  
Robert G. Bingham ◽  
Derek Fabel
Keyword(s):  
Late Pleistocene ◽  
Late Quaternary ◽  
Ice Sheet ◽  
Glacial History ◽  
Climatic Fluctuations ◽  
Eastern Sector ◽  
North Eastern ◽  
Westerly Winds ◽  
Proglacial Lake ◽  
Exposure Ages

<p>The former Patagonian Ice Sheet was the most extensive Quaternary ice sheet of the southern hemisphere outside of Antarctica. Against a background of Northern Hemisphere-dominated ice volumes, it is essential to document how the Patagonian Ice Sheet and its outlet glaciers fluctuated throughout the Quaternary. This information can help us investigate the climate forcing mechanisms responsible for ice sheet fluctuations and provide insight on the causes of Quaternary glacial cycles at the southern mid-latitudes. Moreover, Patagonia is part of the only continental landmass that fully intersects the precipitation-bearing southern westerly winds and is thus uniquely positioned to study past climatic fluctuations in the southern mid-latitudes. While Patagonian palaeoglaciological investigations have increased, there remains few published studies investigating glacial deposits from the north-eastern sector of the former ice sheet, between latitudes 41°S and 46°S. Palaeoglaciological reconstructions from this region are required to understand the timing of late-Pleistocene glacial expansion and retreat, and to understand the causes behind potential latitudinal asynchronies in the glacial records throughout Patagonia. Here, we reconstruct the glacial history and chronology of a previously unstudied region of north-eastern Patagonia that formerly hosted the Rio Huemul and Rio Corcovado (43°S, 71°W) palaeo ice-lobes. We present the first detailed glacial geomorphological map of the valley enabling interpretations of the region’s late Quaternary glacial history. Moreover, we present new cosmogenic 10Be exposure ages from moraine boulders, palaeolake shoreline surface cobbles and ice-moulded bedrock. This new dataset establishes a high-resolution reconstruction of the local LGM through robust dating of five distinct moraines limits of the Rio Corcovado palaeo-glacier. Our results demonstrate that, in its north-eastern sector, the Patagonian Ice Sheet reached its last maximum extent during MIS 2, thus contrasting with the MIS 3 maxima found for the southern parts of the ice sheet. We also present geomorphological evidence along with chronological data for the formation of two ice-dammed proglacial lake phases in the valley caused by LGM ice-extent fluctuations and final glacial recession. Furthermore, this dataset allows us to determine the timing and onset of glacial termination 1 in the region. Finally, our findings include the reconstruction of a proglacial lake drainage and Atlantic/Pacific drainage reversal event caused by ice sheet break-up in western Patagonia. Such findings have significant implications for climate fluctuations at the southern mid-latitudes, former Southern Westerly Winds behaviour and interhemispheric climate linkages during and following the local LGM. They provide further evidence supporting the proposed latitudinal asynchrony in the timing of expansion of the Patagonian Ice Sheet during the last glacial cycle and enable glacio-geomorphological interpretations for the studied region.</p>

Expansion of Magellanic Moorland during the Late Pleistocene: Palynological Evidence from Northern Isla de Chiloé, Chile

1988 ◽  
Vol 30 (3) ◽  
pp. 304-314 ◽  
Author(s):  
Carolina Villagrán
Keyword(s):  
Late Pleistocene ◽  
Late Quaternary ◽  
Marked Change ◽  
Climatic Conditions ◽  
Annual Precipitation ◽  
Palynological Analysis ◽  
Wetland Development ◽  
Average Temperature ◽  
Rio Negro

The late Quaternary vegetation of northern Isla de Chiloé is inferred from palynological analysis of a section in the Río Negro drainage (42°03′S, 73°50′W). At ca. 30,500 yr B.P., maxima of Astelia and Donatia occurred, suggesting wetland development. From that time until ca. 27,000 yr B.P., steppe indicators such as Compositae/Gramineae dominated, suggesting drier conditions. After 27,000 yr B.P., the moorland shrub Dacrydium gradually increased, reaching a maximum by 18,000 yr B.P. At this time Astelia increased again, suggesting development of cushion bog during cold and wet conditions. The glacial-postglacial transition is characterized by a marked change from peaty sediments to clays, a decrease in the cushion bog flora, and the prevalence of Gramineae/ Compositae and swamp taxa. This vegetation prevailed until ca.7000 yr B.P. when forest taxa became dominant. The floristic pattern inferred from the pollen spectra of the Rio Negro section suggests that the late Pleistocene vegetation of Chiloé resembled modern Magellanic Moorland vegetation (52°–56°lat S). Based on climatic conditions presently associated with Magellanic Moorland, its occurrence in Chiloé at low elevations during the late Pleistocene implies a decrease in average temperature of at least 4°C and an increase in annual precipitation of at least 1500 mm.

scholarly journals Climate warming and humans played different roles in triggering Late Quaternary extinctions in east and west Eurasia

2017 ◽  
Vol 284 (1851) ◽  
pp. 20162438 ◽  
Author(s):  
Xinru Wan ◽  
Zhibin Zhang
Keyword(s):  
Climate Change ◽  
Late Pleistocene ◽  
Climate Warming ◽  
Human Impacts ◽  
Late Quaternary ◽  
Extinction Risk ◽  
Early Holocene ◽  
Large Mammals ◽  
Predominant Factor ◽  
Late Pleistocene To Holocene

Climate change and humans are proposed as the two key drivers of total extinction of many large mammals in the Late Pleistocene and Early Holocene, but disentangling their relative roles remains challenging owing to a lack of quantitative evaluation of human impact and climate-driven distribution changes on the extinctions of these large mammals in a continuous temporal–spatial dimension. Here, our analyses showed that temperature change had significant effects on mammoth (genus Mammuthus ), rhinoceros (Rhinocerotidae), horse (Equidae) and deer (Cervidae). Rapid global warming was the predominant factor driving the total extinction of mammoths and rhinos in frigid zones from the Late Pleistocene and Early Holocene. Humans showed significant, negative effects on extirpations of the four mammalian taxa, and were the predominant factor causing the extinction or major extirpations of rhinos and horses. Deer survived both rapid climate warming and extensive human impacts. Our study indicates that both the current rates of warming and range shifts of species are much faster than those from the Late Pleistocene to Holocene. Our results provide new insight into the extinction of Late Quaternary megafauna by demonstrating taxon-, period- and region-specific differences in extinction drivers of climate change and human disturbances, and some implications about the extinction risk of animals by recent and ongoing climate warming.

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