scholarly journals Paleocryogenic processes in the Volyn` Upland

2018 ◽  
Vol 26 (1) ◽  
pp. 3-16
Author(s):  
О. S. Bonchkovskyi
Keyword(s):  
Late Pleistocene ◽  
Loess Soil ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Climate Conditions ◽  
Cold Stage ◽  
Short Period ◽  
Different Types ◽  
Cryogenic Processes

On the basis of the study of 13 Quaternary loess-soil sections in the Volyn’ Upland, cryogenic horizons of different ranges have been recorded and positioned within the Quaternaty stratigrpahical framework of Ukraine. A short-period cyclicity in development of cryogenic processes has been revealed. Time units of formation of cryostuctures − ‘cryostages’ – have been ranged into four categories in correspondence with landscape-climate conditions of their formation and their relations with the units of paleogeogrpahic framework of Ukraine. The differences in cryostructures and cryodeformations for each category of cryostages are shown. A variety of cryostructures and their sizes became larger from the beginning to the end of the Pleistocene that reflects an increase in the climate harshness. Six cryogenic stages were revealed for Early Pleistocene: mr2, sl, lb1b1-b2, lb2, lb3b1-b2, tl. At these times, small ice wedges, ground wedges, solifluction and different types of postcryogenic textures were formed. The cryogenic processes during the Middle Pleistocene developed more intensely. Six Middle Pleistocene cryostages were established: zv2, zv3b1-b2, or, pt2, pt3b-c, dn. The complex of cryostructures of the majority of these stages include large ice wedges, different types of ground wedges, diverse solifluction forms, and tundra spots-medallions. The largest cryogenic structures and deformations are revealed for the cold time spans during the Late Pleistocene: ice wedges (reach up to 5 m in depth), tundra spots-medallions, sand wedges, solifluction and congelifluction forms, different types of ground wedges and postcryogenic textures. Sixteen Last Pleistocene cryostages are revealed: kd1a-b, kd1b1-b2, kd2, kd3b1-b2, ts, pl1a-b, pl1b1-b2, pl1b-c, pl2, pl3b1-b2, ud, vt1b1-b2, vt2, bg, pc1, pc3. The specific features and sizes of cryostructures and cryodeformation of each cold stage, substage and phase have been used as a base for reconstruction of their geocryological conditions.

scholarly journals Palaeoclimate characteristics in interior Siberia of MIS 6–2: first insights from the Batagay permafrost mega-thaw slump in the Yana Highlands

2017 ◽  
Vol 13 (7) ◽  
pp. 795-818 ◽  
Author(s):  
Kseniia Ashastina ◽  
Lutz Schirrmeister ◽  
Margret Fuchs ◽  
Frank Kienast
Keyword(s):  
Late Pleistocene ◽  
Detailed Comparison ◽  
Plant Macrofossils ◽  
Middle Pleistocene ◽  
Climate Conditions ◽  
Cold Stage ◽  
Dry Conditions ◽  
Winter Time ◽  
Geochronological Dating ◽  
Ice Complex

Abstract. Syngenetic permafrost deposits formed extensively on and around the arising Beringian subcontinent during the Late Pleistocene sea level lowstands. Syngenetic deposition implies that all material, both mineral and organic, freezes parallel to sedimentation and remains frozen until degradation of the permafrost. Permafrost is therefore a unique archive of Late Pleistocene palaeoclimate. Most studied permafrost outcrops are situated in the coastal lowlands of northeastern Siberia; inland sections are, however, scarcely available. Here, we describe the stratigraphical, cryolithological, and geochronological characteristics of a permafrost sequence near Batagay in the Siberian Yana Highlands, the interior of the Sakha Republic (Yakutia), Russia, with focus on the Late Pleistocene Yedoma ice complex (YIC). The recently formed Batagay mega-thaw slump exposes permafrost deposits to a depth of up to 80 m and gives insight into a climate record close to Verkhoyansk, which has the most severe continental climate in the Northern Hemisphere. Geochronological dating (optically stimulated luminescence, OSL, and 14C ages) and stratigraphic implications delivered a temporal frame from the Middle Pleistocene to the Holocene for our sedimentological interpretations and also revealed interruptions in the deposition. The sequence of lithological units indicates a succession of several distinct climate phases: a Middle Pleistocene ice complex indicates cold stage climate. Then, ice wedge growth stopped due to highly increased sedimentation rates and eventually a rise in temperature. Full interglacial climate conditions existed during accumulation of an organic-rich layer – plant macrofossils reflected open forest vegetation existing under dry conditions during Marine Isotope Stage (MIS) 5e. The Late Pleistocene YIC (MIS 4–MIS 2) suggests severe cold-stage climate conditions. No alas deposits, potentially indicating thermokarst processes, were detected at the site. A detailed comparison of the permafrost deposits exposed in the Batagay thaw slump with well-studied permafrost sequences, both coastal and inland, is made to highlight common features and differences in their formation processes and palaeoclimatic histories. Fluvial and lacustrine influence is temporarily common in the majority of permafrost exposures, but has to be excluded for the Batagay sequence. We interpret the characteristics of permafrost deposits at this location as a result of various climatically induced processes that are partly seasonally controlled. Nival deposition might have been dominant during winter time, whereas proluvial and aeolian deposition could have prevailed during the snowmelt period and the dry summer season.

scholarly journals Pleistocene climate characteristics in the most continental part of the northern hemisphere: insights from cryolithological features of the Batagay mega thaw slump in the Siberian Yana Highlands

2016 ◽  
Author(s):  
Kseniia Ashastina ◽  
Lutz Schirrmeister ◽  
Margret Fuchs ◽  
Frank Kienast
Keyword(s):  
Northern Hemisphere ◽  
Late Pleistocene ◽  
Fine Sand ◽  
Detailed Comparison ◽  
Ground Temperature ◽  
Middle Pleistocene ◽  
Climate Conditions ◽  
The Holocene ◽  
Cold Stage ◽  
Ice Complex

Abstract. Syngenetic permafrost deposits formed extensively on and around the arising Beringian subcontinent during the Late Pleistocene sea level low stands. Syngenetic deposition implies that all material, both mineral and organic, gets frozen parallel to sedimentation and remains frozen until degradation of the permafrost. Permafrost is therefore a unique archive of late Pleistocene paleoclimates. Most studied permafrost outcrops are situated in the coastal lowlands of NE Siberia and are thus under certain influence of today’s rather maritime climate. Permafrost sections more inland are in contrast scarcely available. Here we describe the cryolithological and geochronological characteristics of a permafrost sequence near Batagay in the Siberian Yana Highlands, the interior of the Republic Sakha (Yakutia), Russia. The recently formed Batagay mega thaw slump exposes permafrost deposits to a depth of up to 80 m and gives insight into a sought climate record close-by the Pole of Cold – the place with the most severe continental climate of the Northern Hemisphere. We provide a detailed stratigraphic description of this profile and present results of cryolithological and geochemical analyses to deduce the genesis of the permafrost sequence, which comprised, according to our observations and sedimentological results, five lithological units. Geochronological dating (OSL and 14C ages) and stratigraphic implications delivered a temporal frame from the Middle Pleistocene to the Holocene for our sedimentological interpretations and also revealed interruptions in the deposition of the sequence. The sequence of lithological units indicates a succession of several distinct climate phases: a middle Pleistocene Ice Complex indicates cold stage climate conditions resulting in a mean annual ground temperature at least 8 °C lower than today; then, ice wedge growth stopped due to highly increased sedimentation rates and eventually a rise of temperature; full interglacial climate conditions existed during accumulation of an organic-rich layer - plant macrofossils reflected open forest vegetation existing under dry conditions during MIS 5e, the late Pleistocene YIC (MIS 4-2) proves again severe cold-stage climate conditions with a mean annual ground temperature 8 to 10 °C lower than today. In the Holocene cover, no alas deposits indicating thermokarst processes, were detected. The main focus of our studies was material from the late Pleistocene Yedoma Ice Complex. The permafrost section was sampled over a depth of 60 m and analyzed for a range of sedimentological properties. The sequence is composed mainly of fine-sand with percentages from 40 % to 70 % varying between as well as within the units. Total organic carbon changes from 0.1 wt % to 4.8 wt %, magnetic susceptibility values are within the range of 13.7–30 SL. A detailed comparison of the permafrost deposits exposed in the Batagay thaw slump with well-studied permafrost sequences, both coastal and inland, is made to highlight common features and differences in their formation processes and palaeoclimatic histories. Despite stratigraphical similarities to coastal outcrops, the Batagay sequence differs in some characteristics from them. Fluvial and lacustrine influence is common for certain depositional periods in the majority of permafrost exposures but have to be excluded for the Batagay sequence. We interpret the characteristics of Yedoma deposits at this location as a result of various involved climatically induced processes that are partly seasonally controlled: nival deposition might have been dominant during winter time, whereas proluvial and aeolian deposition could have prevailed during the snowmelt period and the dry summer season.

Bayesian analysis of sea-level sensitivity to CO2 forcing across the mid-Pleistocene transition: possible implications for early-Pleistocene ice-sheet extent

2021 ◽  
Author(s):  
Parker Liautaud ◽  
Peter Huybers
Keyword(s):  
Energy Balance ◽  
Bayesian Analysis ◽  
Sea Level ◽  
Late Pleistocene ◽  
Radiative Forcing ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Model Parameters

<p><span>Foregoing studies have found that sea-level transitioned to becoming approximately twice as sensitive to CO</span><span><sub>2</sub></span><span> radiative forcing between the early and late Pleistocene (Chalk et al., 2017; Dyez et al., 2018). In this study we analyze the relationships among sea-level, orbital variations, and CO</span><span><sub>2</sub></span><span> observations in a time-dependent, zonally-averaged energy balance model having a simple ice sheet. Probability distributions for model parameters are inferred using a hierarchical Bayesian method representing model and data uncertainties, including those arising from uncertain geological age models. We find that well-established nonlinearities in the climate system can explain sea-level becoming 2.5x (2.1x - 4.5x) more sensitive to radiative forcing between 2 and 0 Ma. Denial-of-mechanism experiments show that the increase in sensitivity is diminished by 36% (31% - 39%) if omitting geometric effects associated with thickening of a larger ice sheet, by 81% (73% - 92%) if omitting the ice-albedo feedback, and by more than 96% (93% - 98%) if omitting both. We also show that prescribing a fixed sea-level age model leads to different inferences of ice-sheet dimension, planetary albedo, and lags in the response to radiative forcing than if using a more complete approach in which sea-level ages are jointly inferred with model physics. Consistency of the model ice-sheet with geologic constraints on the southern terminus of the Laurentide ice sheet can be obtained by prescribing lower basal shear stress during the early Pleistocene, but such more-expansive ice sheets imply lower CO</span><span><sub>2</sub></span><span> levels than would an ice-sheet having the same aspect ratio as in the late Pleistocene, exacerbating disagreements with </span><span>𝛿</span><span><sup>11</sup></span><span>B-derived CO</span><span><sub>2</sub></span><span> estimates. These results raise a number of possibilities, including that (1) geologic evidence for expansive early-Pleistocene ice sheets represents only intermittent and spatially-limited ice-margin advances, (2) </span><span>𝛿</span><span><sup>11</sup></span><span>B-derived CO</span><span><sub>2</sub></span><span> reconstructions are biased high, or (3) that another component of the global energy balance system, such as the average ice albedo or a process not included in our model, also changed through the middle Pleistocene. Future work will seek to better constrain early-Pleistocene CO</span><span><sub>2</sub></span><span> levels by way of a more complete incorporation of proxy uncertainties and biases into the Bayesian analysis.</span></p>

scholarly journals Historical biogeography of the leopard (Panthera pardus) and its extinct Eurasian populations

2018 ◽  
Author(s):  
Johanna L.A. Paijmans ◽  
Axel Barlow ◽  
Daniel W. Förster ◽  
Kirstin Henneberger ◽  
Matthias Meyer ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Dna Sequences ◽  
Sister Group ◽  
Historical Biogeography ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Recent Common Ancestor ◽  
Panthera Pardus ◽  
Phylogenetic Placement ◽  
Out Of Africa

AbstractBackgroundResolving the historical biogeography of the leopard(Panthera pardus)is a complex issue, because patterns inferred from fossils and from molecular data lack congruence. Fossil evidence supports an African origin, and suggests that leopards were already present in Eurasia during the Early Pleistocene. Analysis of DNA sequences however, suggests a more recent, Middle Pleistocene shared ancestry of Asian and African leopards. These contrasting patterns led researchers to propose a two-stage hypothesis of leopard dispersal out of Africa: an initial Early Pleistocene colonisation of Asia and a subsequent replacement by a second colonisation wave during the Middle Pleistocene. The status of Late Pleistocene European leopards within this scenario is unclear: were these populations remnants of the first dispersal, or do the last surviving European leopards share more recent ancestry with their African counterparts?ResultsIn this study, we generate and analyse mitogenome sequences from historical samples that span the entire modern leopard distribution, as well as from Late Pleistocene remains. We find a deep bifurcation between African and Eurasian mitochondrial lineages (∼710 Ka), with the European ancient samples as sister to all Asian lineages (∼483 Ka). The modern and historical mainland Asian lineages share a relatively recent common ancestor (∼122 Ka), and we find one Javan sample nested within these.ConclusionsThe phylogenetic placement of the ancient European leopard as sister group to Asian leopards suggests that these populations originate from the same out-of-Africa dispersal which founded the Asian lineages. The coalescence time found for the mitochondrial lineages aligns well with the earliest undisputed fossils in Eurasia, and thus encourages a re-evaluation of the identification of the much older putative leopard fossils from the region. The relatively recent ancestry of all mainland Asian leopard lineages suggests that these populations underwent a severe population bottleneck during the Pleistocene. Finally, although only based on a single sample, the unexpected phylogenetic placement of the Javan leopard could be interpreted as evidence for exchange of mitochondrial lineages between Java and mainland Asia, calling for further investigation into the evolutionary history of this subspecies.

Biostratigraphic Correlation of Pleistocene Marine Deposits and Sea Levels, Atlantic Coastal Plain of the Southeastern United States

1980 ◽  
Vol 13 (2) ◽  
pp. 213-229 ◽  
Author(s):  
Thomas M. Cronin
Keyword(s):  
North Carolina ◽  
South Carolina ◽  
Sea Level ◽  
Late Pleistocene ◽  
Coastal Plain ◽  
Atlantic Coastal Plain ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Sea Levels ◽  
Atlantic Coastal

AbstractMarine ostracodes from 50 localities were studied to determine the age and elevation of Pleistocene sea levels in the Atlantic coastal plain from Maryland to northern Florida. Using ostracode taxon and concurrent ranges, published planktic biostratigraphic, paleomagnetic, and radiometric data, ostracode assemblage zones representing early (1.8-1.0 my), middle (0.7-0.4 my), and late (0.3-0.01 my) Pleistocene deposition were recognized and used as a basis for correlation. Ostracode biofacies signifying lagoonal, oyster bank, estuarine, open sound, and inner sublittoral environments provided estimated ranges of paleodepths for each locality. From these data the following minimum and maximum Pleistocene sea-level estimates were determined for the southeastern coastal plain: late Pleistocene, 2–10 m from Maryland to northern Florida; middle Pleistocene, 6–15 m in northern South Carolina; early Pleistocene, 4–22 m in central North Carolina, 13–35 m in southern North Carolina, and 6–27 m in South Carolina. Climatically induced glacio-eustatic sea-level fluctuations adequately account for the late Pleistocene sea-level data, but other factors, possibly differential crustal uplift, may have complicated the early Pleistocene record.

scholarly journals Long-term landscape evolution of the Molise sector of the central-southern Apennines, Italy

2017 ◽  
Vol 68 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Vincenzo Amato ◽  
Pietro P.C. Aucelli ◽  
Vito Bracone ◽  
Massimo Cesarano ◽  
Carmen Maria Rosskopf
Keyword(s):  
Late Pleistocene ◽  
Landscape Evolution ◽  
Temporal Distribution ◽  
Structural Data ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Southern Apennines ◽  
Geomorphological Evolution ◽  
Present Setting

AbstractThis paper concerns the reconstruction of the main stages of the long-term landscape evolution of the Molise portion of the central-southern Apennines along a transect divided into three sectors (SW, Central and NE). Analysis mainly focused on geomorphological, stratigraphical and structural data supported by chronological constraints, coming from an overall review of past literature and several studies carried out by the authors of the paper during the last 20 years. The results obtained allowed the elaboration of a conceptual model of the long-term evolution of the Molise sector of the central-southern Apennines. Starting from the Pliocene, the emersion of the Molise area occurred gradually from SW to NE, allowing a polycyclic landscape to evolve under the major controls first of compression then transtensional to extensional tectonics as well as climatic variations. Principal markers of the Quaternary geomorphological evolution of the Molise area are represented by the infill successions of the intermontane tectonic depressions located in its internal, SW sector and by four orders of palaeosurfaces that developed between the Early Pleistocene and the beginning of the Late Pleistocene across the region. These markers testify to the alternation of phases of substantial tectonic stability and uplift whose spatial-temporal distribution could be assessed along the investigated transect. Results highlight that the most important stages of landscape evolution occurred during the Early and Middle Pleistocene. At the beginning of the Late Pleistocene, the Molise sector of the Apennine chain had already reached its present setting and further landscape evolution occurred under the major control of climate and land-use.

scholarly journals ABOUT THE REASONS OF CLIMATE WARMING BASED ON STUDYING THE HISTORY OF QUATERNARY GLACIOSES OF THE CAUCASUS (ON THE EXAMPLE OF THE INTERDURCHIE TEREK AND THE ANDIAN KOISU)

2020 ◽  
Vol 12 (3) ◽  
pp. 461-471
Author(s):  
Valeriy DOTSENKO ◽  
◽  
Ibragim KERIMOV ◽  
Keyword(s):  
Climate Change ◽  
Late Pleistocene ◽  
Volcanic Activity ◽  
Late Holocene ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
The Caucasus ◽  
Late Pliocene ◽  
Climate Fluctuations ◽  
Greater Caucasus

The Greater Caucasus experienced repeated glaciation during the Quaternary (early, middle, upper Pleistocene, late Glacial, and late Holocene), which occurred under changing climatic conditions and differentiated tectonic movements. These glaciations, of course, are associated with changes in terrain, the formation of new deposits, transgressions and regressions of the Caspian Sea, changes in vegetation and soil types, so the problem of glaciation affects all earth Sciences to varying degrees. The study of Quaternary glaciation, especially Holocene glaciation, is currently relevant for understanding climate change. Against the background of significant climate fluctuations within the epochs of glaciation, there are smaller cooling phases that cause the temporary onset of glaciers. Short-term climate fluctuations are manifested in oscillations – minor fluctuations in the languages of glaciers. All this indicates that the climate undergoes significant changes in a short time, which are reflected in the morphosculpture of the terrain, the latest deposits and modern precipitation. Glaciation of the Greater Caucasus in the Prikazbeksky region reached its maximum in the middle Pleistocene,when glaciers went far into the Ossetian basin. All these traces have been preserved due to the lower capacity of the Chanty-Argun glacier and its fluvioglacial flow, which developed during the late Pleistocene epoch. Volcanic activity, especially active in the late Pliocene and continuing up to the present time, is associated with the late horn stage of development of the Caucasus. The formation of the Rukhs-Dzuar molass formation more than 2 km thick in the late Pleistocene in the Ossetian basin of the Tersky-Caspian flexure is associated with the activity of volcanoes in the Kazbek volcanic region. In the early Pleistocene, volcanic activity on the BC decreased significantly. The most intense outbreak of volcanism in the Kazbek and Elbrus volcanic regions occurred at the beginning of the late Pleistocene, which roughly coincided with the maximum phase of the late Pleistocene (Bezengian) glaciation. Then, in the second half of the late Pleistocene, volcanic activity was manifested on the mount Kazbek. The last outbreak of volcanic activity occurred in the Holocene no more than 2-3 thousand years ago. Fresh lavas are available on Elbrus, Kazbek, in the Terek valley near villages. Sioni and on the Kel volcanic plateau. Fumarolic activity still continues on Elbrus. Thus, in the Kazbek region, eruptions occurred from the late Pliocene to the late Holocene inclusive. Keywords: Pleistocene, Holocene, glaciation stages, nival-glacial processes, causes of glaciations, climate change, anthropogenic factors, natural factors, Earth degassing, magmatogenic degassing branch, seismotectonic degassing branch, greenhouse gases, newest geodynamics, volcanism, mud regimes, volcanism, methane hydrates, land degradation, water reclamation.

Increased sea-level sensitivity to CO2 forcing across the Middle Pleistocene Transition from ice-albedo and ice-volume nonlinearities

2021 ◽  
pp. 1
Author(s):  
Parker Liautaud ◽  
Peter Huybers
Keyword(s):  
Sea Level ◽  
Late Pleistocene ◽  
Radiative Forcing ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Early Pleistocene ◽  
Balance Model ◽  
Middle Pleistocene ◽  
Model Parameters ◽  
The Past

AbstractProxy reconstructions indicate that sea level responded more sensitively to CO2 radiative forcing in the late Pleistocene than in the early Pleistocene, a transition that was proposed to arise from changes in ice-sheet dynamics. In this study we analyse the links between sea level, orbital variations, and CO2 using an energy-balance model having a simple ice sheet. Model parameters, including for age models, are inferred over the late Pleistocene using a hierarchical Bayesian method, and the inferred relationships are used to evaluate CO2 levels over the past 2 My in relation to sea level. Early-Pleistocene model CO2 averages 246 ppm (244 ppm - 249 ppm 95% c.i.) across 2-1 Ma and indicates that sea level was less sensitive to radiative forcing than in the late Pleistocene, consistent with foregoing δ11B-derived estimates. Weaker early-Pleistocene sea-level sensitivity originates from a weaker ice-albedo feedback and the fact that smaller ice sheets are thinner, absent changes over time in model equations or parameters. An alternative scenario involving thin and expansive early-Pleistocene ice sheets, in accord with some lines of geologic evidence, implies 15 ppm lower average CO2 or ~10-15 m higher average sea level during the early Pleistocene relative to the original scenario. Our results do not rule out dynamical transitions during the middle Pleistocene, but indicate that variations in the sea-level response to CO2 forcing over the past 2 My can be explained on the basis of nonlinearities associated with ice-albedo feedbacks and ice-sheet geometry that are consistently present across this interval.

Early Pleistocene−to−present paleoclimate archive for the American Southwest from Stoneman Lake, Arizona, USA

2021 ◽  
Author(s):  
Spencer E. Staley ◽  
Peter J. Fawcett ◽  
R. Scott Anderson ◽  
Gonzalo Jiménez-Moreno
Keyword(s):  
Late Pleistocene ◽  
Climate Model ◽  
Volcanic Eruptions ◽  
American Southwest ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Future Climate Change ◽  
Radiocarbon Dates ◽  
Middle And Late Pleistocene ◽  
Natural Climate

Long, continuous records of terrestrial paleoclimate offer insights into natural climate variability and provide context for geomorphological studies, climate model reconstructions, and predictions of future climate change. STL14 is an 80 m lacustrine sediment core that archives paleoenvironmental changes at Stoneman Lake, Coconino County, Arizona, from the early Pleistocene (ca. 1.3 Ma) to present. Full-core sedimentology was analyzed using smear slides and core face observations. Lithofacies strongly correlate with wet bulk density and bulk magnetic susceptibility (MS), and these data resemble a sawtooth pattern characteristic of glacial-interglacial climate cycles. A linkage between deep to shallow lake depth transitions and glacial terminations is supported by an age model that incorporates accelerator mass spectrometry radiocarbon dates and tephrochronology of ashes from the Lava Creek B and multiple Long Valley, California, volcanic eruptions. We correlated middle and late Pleistocene glacial maxima to deep lake deposits defined by well-preserved bedding, increased biosilica, boreal pollen taxa (i.e., Picea), and lower density and MS. Interglacial periods are associated with shallow-water deposits characterized by banded-to-massive siliciclastic material, some authigenic calcite, the alga Phacotus, and higher density and MS. Prior to the marine isotope stage (MIS) 24−22 interval, smaller-amplitude changes in the lake environment suggest milder glacial conditions compared to those of the middle and late Pleistocene. Thus, abrupt intensification of glacial conditions may have occurred ca. 900 ka in the American Southwest, mirroring a global characteristic of the mid-Pleistocene transition. The STL14 record suggests that lake environments throughout the history of this small (3.5 km2), internally drained, basaltic catchment are sensitive to the regional hydrologic balance, which, at orbital time scales, is largely influenced by the northern cryosphere and associated changes in atmospheric circulation. The predominance of quartz in sediment throughout the record indicates significant eolian inputs. Few paleoclimate records from this region extend beyond the last glacial cycle, let alone the middle Pleistocene, making STL14 a valuable resource for studying environmental responses to a range of natural climate states and transitions throughout much of the Quaternary.

The Kovban` site – a complex loess-soil sequence in the Volyn Upland

2018 ◽  
Vol 90 (2) ◽  
pp. 24-33
Author(s):  
Оleksandr Bonchkovskyi
Keyword(s):  
Podzolic Soil ◽  
Loess Soil ◽  
Grain Size Analysis ◽  
Middle Pleistocene ◽  
Size Analysis ◽  
Brown Forest Soil ◽  
Upper Pleistocene ◽  
River Incision ◽  
Five Phases ◽  
Cryogenic Processes

The loess-soil section of Kovban` includes all the stratigraphical units of the Upper Pleistocene, as well as pedosediments and alluvial facies of the Middle Pleistocene pre- and early Dnieper times. On the basis of the field pedolithomorphological description and grain-size analysis, it is proved that the majority of the main stratigraphic units show smaller subdivisions. The Prychernomorsk unit includes two loesses (pc1, pc3) and a Luvisol (pc2). The Dofinivka unit consists of three subunits: two incipient soils are divided by a thin loess subunit (df2). The Bug unit is represented in this section by hillwash and solifluction deposits. The Vytachiv unit is a pedocomplex made up of three well-developed soils, separated by loesses. The soils are a Molic Cambisol (vt3), a Cambisol (vt1b2) and a humic gleysol (vt1b1). The Uday unit consists of two subunits: the lower comprises solifluction deposits, whereas the upper is a loess-like bed. The soil succession of the Pryluky unit is well developed. It consists of three soils – a Molic Cambisol (pl3), a Mollisol (pl1b2) and a sod-podzolic soil (pl1b1). On slopes, the lower soil (pl1b1) is formed on the sands of Tyasmyn unit. The Kaydaky unit is represented by polygenetic sod-podzolic soil. Brown forest soil pedosediments of the last warm period of the Middle Pleistocene overlie Middle Pleistocene alluvial facies. These pedosediments were deformed by syngenetic cryogenic processes and dissected by ground wedges during the Dnieper cryogenic stage. The data obtained indicate that at the end of the Mid Pleistocene, the study area was subjected to uplift that controlled intense river incision and denudation processes. Five phases of cryogenesis have been revealed in the section: dn, ts, pl1b1-b2, ud, bg.

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