Mollusk Record of Monsoon Variability during the L2–S2 Cycle in the Luochuan Loess Sequence, China

Molluscan changes that occurred in China over the S2–L2 upper middle Pleistocene series may be caused by monsoon variation. Study of terrestrial mollusks from the loess sequence in Luochuan, gathered in ecological groups according to the moisture and temperature requirements of the identified species, indicates alternating strengthened summer and winter paleomonsoons between 130,000 and 244,000 yr. The four occurrences of species, currently distributed in S.E. China in the sequence, indicate that the climate conditions were warmer and wetter than today between about 242,000 and 233,000 yr, at about 210,000, 164,000, and 140,000 yr. The main occurrence of xerophilous taxa at about 180,000, 154,000, and 138,000 yr is interpreted as indicating a drier environment than today. Such suggestions are in agreement with other proxy data such as grain size distribution. Higher numbers of individuals in the different ecological groups from the S2–L2 sequence indicate more favorable general environmental conditions than in the youngest S1–L1. This may agree with an increase in the regional aridity, since 500,000 yr, deduced from the study of the eolian flux in the northwestern Pacific downwind from China.

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Changes in Paleovegetation and Paleoclimate in China Since the Late Middle Pleistocene: A Case Study of the Dajiuhu Basin

Sustainability ◽

10.3390/su13094848 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4848

Author(s):

Liwei Wu ◽

Xinling Li ◽

Qinghai Xu ◽

Manyue Li ◽

Qiufeng Zheng ◽

...

Keyword(s):

Grain Size ◽

Asian Monsoon ◽

East Asian Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Central China ◽

Middle Pleistocene ◽

Pollen Record ◽

The Difference ◽

Late Middle Pleistocene

The East Asian monsoon system is an important part of global atmospheric circulation; however, records of the East Asian monsoon from different regions exhibit different evolutionary rhythms. Here, we show a high-resolution record of grain size and pollen data from a lacustrine sediment core of Dajiuhu Lake in Shennongjia, Hubei Province, China, in order to reconstruct the paleovegetation and paleoeclimate evolution of the Dajiuhu Basin since the late Middle Pleistocene (~237.9 ka to the present). The results show that grain size and pollen record of the core DJH-2 are consistent with the δ18O record of stalagmites from Sanbao Cave in the same area, which is closely related to the changes of insolation at the precessional (~20-kyr) scale in the Northern Hemisphere. This is different from the records of the Asian summer monsoon recorded in the Loess Plateau of North China, which exhibited dominant 100-kyr change cyclicities. We suggest that the difference between paleoclimatic records from North and South China is closely related to the east–west-oriented mountain ranges of the Qinling Mountains in central China that blocked weakened East Asia summer monsoons across the mountains during glacial periods.

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Pleistocene Deposits in the Southern Egyptian Sahara: Lithostratigraphic Relationships of Sediments and Landscape Dynamics at Bir Tarfawi

Studia Quaternaria ◽

10.1515/squa-2017-0002 ◽

2017 ◽

Vol 34 (1) ◽

pp. 23-38

Author(s):

Christopher L. Hill ◽

Romuald Schild

Keyword(s):

Groundwater Table ◽

Middle Pleistocene ◽

Middle Paleolithic ◽

Stratigraphic Sequence ◽

Climate Conditions ◽

Green Lake ◽

Wet Climate ◽

Topographic Depressions ◽

Hydrologic Conditions ◽

Basin Fill

Abstract The sedimentological and lithostratigraphic record from north-central Bir Tarfawi documents the presence of Pleistocene basin-fill deposits. Three topographic basins were created as a result of deflation during climate episodes associated with lowering of the local groundwater table. In each case, the three deflational basins or topographic depressions were subsequently filled with sediments; these basin aggradations coincided with changes from arid climate conditions to wetter conditions and a rise in the groundwater table. The oldest and highest sedimentary remnant is associated with Acheulian artifacts and may reflect spring-fed pond and marsh conditions during a Middle Pleistocene wet climate episode. Lithofacies for a lower stratigraphic sequence (the “White Lake”) documents deposition in a perennial lake that varied in extent and depth and is associated with Middle Paleolithic artifacts. A third episode of deflation created a topographic low that has been filled with Late Pleistocene sediments that are associated with Middle Paleolithic artifacts and fossil remains. Lateral and vertical variations in the lithofacies of this basin-fill sequence and the sediments of the “grey-green” lake phases provide a record of changing hydrologic conditions. These hydrologic conditions appear to reflect variations in water-table levels related to groundwater recharge and, at times, local rains.

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SEDIMENTOLOGICAL AND PALAEOENVIRONMENTAL CHARACTER OF LAKE KORONIA SEDIMENTS

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11730 ◽

2017 ◽

Vol 50 (1) ◽

pp. 295

Author(s):

S. Doani ◽

K. Albanakis ◽

O. Koukousioura ◽

K.K. Koliadimou

Keyword(s):

Grain Size ◽

Organic Matter ◽

Environmental Conditions ◽

Water Body ◽

Fine Sand ◽

Lake Bottom ◽

Bottom Sampling ◽

Palaeoenvironmental Conditions ◽

Freshwater Ostracods ◽

Ostracod Species

The aim of the present study is to investigate the sedimentological characteristics of Lake Koronia down to a depth of 3.5m below lake bottom. Sampling operations took advandage of a season that the lake bottom was exposed to subaerial conditions. The sedimentological analysis proved that sediments consist of mud to sandy mud, with 2 phases of very fine sand fractions. The proportion of dry organic matter contained into sediment, appears to be generally small while the rates of moisture and volatiles are relatively high. Furthermore, this study examines the distribution of ostracod populations in the sediments of the lake in relation to depth, grain size and other environmental conditions of this water body. Four ostracod species were identified: Candona neglecta, Darwinula stevensoni, Heterocypris spp. and Limnocythere inopinata. The study of freshwater ostracods provides information for the palaeoecological/palaeoenvironmental conditions during the sedimentation.

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Middle Pleistocene human occupation in the interior of the Iberian Peninsula during cold climate conditions: Zooarchaeology and taphonomy of ETB-H02 site in the Manzanares valley (Madrid, Spain)

Quaternary International ◽

10.1016/j.quaint.2018.03.014 ◽

2019 ◽

Vol 520 ◽

pp. 99-109 ◽

Cited By ~ 3

Author(s):

José Yravedra ◽

Joaquín Panera ◽

Susana Rubio-Jara ◽

Alfredo Pérez-González ◽

Nuria Gallego ◽

...

Keyword(s):

Iberian Peninsula ◽

Cold Climate ◽

Middle Pleistocene ◽

Human Occupation ◽

Climate Conditions

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Environmental magnetism study of Lake Cadagno, Switzerland

10.5194/egusphere-egu21-16462 ◽

2021 ◽

Author(s):

Artin Ali ◽

Andrea Biedermann ◽

Jasmine Berg ◽

Mark Lever ◽

Hendrik Vogel

Keyword(s):

Grain Size ◽

Sedimentary Environment ◽

Environmental Magnetism ◽

Late Glacial ◽

Magnetic Minerals ◽

Climate Conditions ◽

Glacial Sediments ◽

Depth Profiles ◽

Magnetic Carriers ◽

Lake Bottom

Climate affects the mineralogy and grain size of sediments deposited in lakes. These properties are reflected in the sediment magnetic properties and can be characterized using magnetic methods. As part of the Cadagno-Project, which recovered several gravity and piston cores spanning the entire lake history from the deglacial to the present from the deepest part of permanently stratified Lake Cadagno, which is due to its peculiar water column chemistry considered an early Earth ocean analogue, our study aims to define changes in climate conditions during sedimentation. Here, we present a rock magnetic dataset (low-field magnetic susceptibility and its temperature dependence, anhysteretic and isothermal remanent magnetization (ARM, IRM), acquired in various fields, AF demagnetization, and hysteresis loops) that helps characterize the concentration, mineralogy, and grain size of magnetic carriers, and their variability with depth. Susceptibility, ARM, and IRM were measured on core sediments down to a depth of 886 cm below the lake bottom, providing a high-resolution record of the sedimentary environment of Lake Cadagno over the last 11,000 years. In addition to these depth profiles, detailed rock magnetic experiments were conducted at specific depths. The cores consist of pelagic sediments, flood turbidites, and late glacial sediments. In order to determine the characteristics of the background sedimentation, only turbidite-free intervals were included in this study. The depth profiles of susceptibility, ARM and IRM have approximately similar variations with depth. They show distinct peaks at the upper parts of the pelagic sediments (156-158 cm below the lake bottom,&#160; &#160;&#820;1280-1320 cal. Yr Bp) and of the late glacial sediments (826-844 cm below the lake bottom), which can be interpreted as increased concentration of ferromagnetic minerals or as a change in the magnetic mineralogy, in addition to decreasing trend in the background. Several intervals within the pelagic sediments are dominated by low-coercivity minerals (<10 mT), while higher coercivity grains (10&#8211;100 mT) contribute significantly at (150-170, 418-448 and 719-735 cm below the lake bottom). Magnetic grain size was analyzed using a Day plot, and shows that single domain magnetite dominates at (844 cm) below the lake bottom, indicating the presence of magnetotactic bacteria, which are believed to dwell mainly in the oxic&#8211;anoxic interface where chemical gradients are high. These results provide important constraints on the environmental conditions and climate change recorded by the magnetic minerals in Lake Cadagno.

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Modelling the Antarctic Ice Sheet across the mid-Pleistocene transition – implications for Oldest Ice

The Cryosphere ◽

10.5194/tc-13-2023-2019 ◽

2019 ◽

Vol 13 (7) ◽

pp. 2023-2041 ◽

Cited By ~ 10

Author(s):

Johannes Sutter ◽

Hubertus Fischer ◽

Klaus Grosfeld ◽

Nanna B. Karlsson ◽

Thomas Kleiner ◽

...

Keyword(s):

Ice Core ◽

Ice Sheet ◽

Middle Pleistocene ◽

Climate Modelling ◽

Geothermal Heat ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

Climate Conditions ◽

West Antarctic ◽

Pleistocene Climate

Abstract. The international endeavour to retrieve a continuous ice core, which spans the middle Pleistocene climate transition ca. 1.2–0.9 Myr ago, encompasses a multitude of field and model-based pre-site surveys. We expand on the current efforts to locate a suitable drilling site for the oldest Antarctic ice core by means of 3-D continental ice-sheet modelling. To this end, we present an ensemble of ice-sheet simulations spanning the last 2 Myr, employing transient boundary conditions derived from climate modelling and climate proxy records. We discuss the imprint of changing climate conditions, sea level and geothermal heat flux on the ice thickness, and basal conditions around previously identified sites with continuous records of old ice. Our modelling results show a range of configurational ice-sheet changes across the middle Pleistocene transition, suggesting a potential shift of the West Antarctic Ice Sheet to a marine-based configuration. Despite the middle Pleistocene climate reorganisation and associated ice-dynamic changes, we identify several regions conducive to conditions maintaining 1.5 Myr (million years) old ice, particularly around Dome Fuji, Dome C and Ridge B, which is in agreement with previous studies. This finding strengthens the notion that continuous records with such old ice do exist in previously identified regions, while we are also providing a dynamic continental ice-sheet context.

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Morphological evolution of the murine rodent Paraethomys in response to climatic variations (Mio-Pleistocene of North Africa)

Paleobiology ◽

10.1017/s0094837300021333 ◽

1999 ◽

Vol 25 (3) ◽

pp. 369-382 ◽

Cited By ~ 30

Author(s):

Sabrina Renaud ◽

Mouloud Benammi ◽

Jean-Jacques Jaeger

Keyword(s):

North Africa ◽

Environmental Conditions ◽

Morphological Evolution ◽

Middle Pleistocene ◽

Metabolic Adaptation ◽

Subsequent Increase ◽

Evolutionary Patterns ◽

The North ◽

Murine Rodent ◽

Evolutionary Response

The North African murine rodent Paraethomys evolved as an anagenetic lineage from the late Miocene until its extinction in the late—middle Pleistocene. A Fourier analysis of the outlines of the first upper and lower molars of this rodent was used to quantify the evolutionary patterns of this lineage and to compare evolutionary patterns to the climatic record. Morphological evolution and long-term environmental variations are strongly correlated. A change in molar shape, which may be related to the development of a more grass-eating diet, corresponds to the global cooling beginning around 3 Ma and the subsequent increase in aridity in North Africa. Concurrently, size increased, which may be related to increased masticatory efficiency or to metabolic adaptation to the cooler environmental conditions according to Bergmann's rule. This adaptive response to changing environmental conditions corresponds to an acceleration of evolutionary rates in the lineage. The modalities of the evolutionary response in size and shape are probably controlled by intrinsic factors such as different genetic determinisms for both characters.

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An Anvilian (Early Pleistocene) Marine Fauna from Western Seward Peninsula, Alaska

Quaternary Research ◽

10.1016/0033-5894(74)90039-8 ◽

1974 ◽

Vol 4 (4) ◽

pp. 441-470 ◽

Cited By ~ 20

Author(s):

D.M. Hopkins ◽

R.W. Rowland ◽

R.E. Echols ◽

P.C. Valentine

Keyword(s):

North Atlantic ◽

Early Pleistocene ◽

Middle Pleistocene ◽

Northwestern Pacific ◽

River Terrace ◽

Bering Strait ◽

Land Bridge ◽

Marine Fauna ◽

Seward Peninsula ◽

Bering Shelf

Cover sediments of the York Terrace exposed near the California River, western Seward Peninsula, Alaska, yield mollusks, ostracodes, and foraminifera that lived during the Anvilian transgression of early Pleistocene age. The fossiliferous sediments lie at the inner edge of the York Terrace, a deformed wave-cut platform that extends eastward from Bering Strait along much of the southern coast of Seward Peninsula. The seaward margin is truncated by the little-deformed Lost River Terrace, carved during the Pelukian (Sangamonian) transgression. The early Pleistocene sediments seem to have been deposited between the first and second of four glaciations for which evidence can be found in the California River area.The California River fauna includes several extinct species and several species now confined to areas as remote as the northwestern Pacific and north Atlantic. The fauna probably lived in water temperatures much like those of the present time but deeper water on the Bering Shelf is suggested.The presence of an early Pleistocene fauna at the inner edge of the York Terrace at California River shows that the terrace was largely carved before and during early Pleistocene time. However, a marine fauna apparently of middle Pleistocene age is found on the York Terrace near Cassiterite Peak, and this seems to indicate that the terrace remained low until middle Pleistocene time. Uplift of the York Terrace probably was accompanied by uplift of Bering Strait. The strait may have been deeper, and there may have been no land bridge between the Seward Peninsula of Alaksa and the Chukotka Peninsula of Siberia during most of early and middle Pleistocene time.

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A Significant middle Pleistocene tephra deposit preserved in the caves of Mulu, Borneo

Quaternary Research ◽

10.1016/j.yqres.2012.01.007 ◽

2012 ◽

Vol 77 (3) ◽

pp. 335-343 ◽

Cited By ~ 2

Author(s):

Joyce Lundberg ◽

Donald A. McFarlane

Keyword(s):

Grain Size ◽

Isotopic Ratio ◽

The Philippines ◽

Plinian Eruption ◽

Middle Pleistocene ◽

Fall Deposit ◽

Potential Source ◽

Tephra Deposit ◽

Potential Sources ◽

Ratio Limit

A distinctive white sediment in the caves of Mulu, Sarawak, Borneo is a well-preserved tephra, representing a fluvially transported surface air-fall deposit, re-deposited inside the caves. We show that the tephra is not the Younger Toba Tephra, formerly considered as most likely. The shards are rod-shaped with elongate tubular vesicles; the largest grains ~ 170 μm in length; of rhyolitic composition; and 87Sr/86Sr ratio of 0.70426 ± 0.00001. U–Th dating of associated calcites suggest that the tephra was deposited before 125 ± 4 ka, and probably before 156 ± 2 ka. Grain size and distance from closest potential source suggests an eruption of VEI 7. Prevailing winds, grain size, thickness of deposit, location of potential sources, and Sr isotopic ratio limit the source to the Philippines. Comparisons with the literature give the best match geochemically with layer 1822 from Ku et al. (2009a), dated by ocean core stratigraphy to 189 ka. This tephra represents a rare terrestrial repository indicating a very substantial Plinian/Ultra-Plinian eruption that covered the Mulu region of Borneo with ash, a region that rarely receives tephra from even the largest known eruptions in the vicinity. It likely will be a valuable chronostratigraphic marker for sedimentary, palaeontological and archaeological studies.

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Quantitative reconstruction of landscape dynamics and tectonics from sediment calibre and architecture: an example from the Kerinitis megadelta, Gulf of Corinth, Greece

10.5194/egusphere-egu2020-10229 ◽

2020 ◽

Author(s):

Daniel Hobley ◽

Alexander Whittaker

Keyword(s):

Grain Size ◽

Middle Pleistocene ◽

Normal Faults ◽

Sudden Increase ◽

Level Control ◽

Data Set ◽

Accommodation Space ◽

Gulf Of Corinth ◽

Climatic Environment ◽

Climatic History

In tectonically active landscapes, fault movement drives both the creation of accommodation space (i.e., basins), and the production of topography on which geomorphic processes act (i.e., mountains). The action of fluvial processes on those mountains will route eroded sediment into the basins; in many extensional mountain belts, this leads to the deposition of coarse alluvial fans or Gilbert deltas in the hanging-walls of normal faults as they slip and create accommodation space. The stratigraphic architecture and sedimentary characteristics of such deposits clearly respond to and thus in principle can record the tectono-climatic environment controlling the system. This implies that key stratigraphic variables, such as grain size and unit thicknesses, can be quantitatively inverted to recover a tectono-climatic history. However, confounding variables also active in erosional-depositional systems (e.g., far-field base level control, stochastic processes, signal degradation during transport) may complicate attempts to decode this archive and may buffer or shred tectono-climatic signals before they are preserved.The well-exposed early to middle Pleistocene deltaic stratigraphy of the Corinth Rift, central Greece, provides a rare opportunity to test these ideas quantitatively. Here, we present a preliminary data set attempting to decode the geomorphic and hence tectono-climatic history of a key section of the rift directly from the grain size and architecture of a very large (~500 m thick), fault controlled, and now uplifted Gilbert delta in the Kerinitis valley, located on the southern margin of the Gulf of Corinth. We used a series of high-resolution drone surveys to obtain 27 vertical transects through the incised delta, from which detailed grain size and sediment thickness data were obtained from photogrammetric analyses (~10,000 images). Our data enabled us to produce a highly detailed correlation of stratal horizons within the deltaic package, from which we were able to describe the evolution of grain size trends both downstream and through the ca. 800 ky lifespan of the delta. We are able to resolve a marked acceleration of the driving fault from the delta stratigraphy itself, which is recorded in a sudden increase in downstream fining rate, driven by more rapid extraction of sediment from the river supplying material to the delta. The timing of this increase correlates with independent constraints from stratigraphic form on the onset of &#8220;rift climax&#8221; in this delta. Post fault acceleration, we demonstrate that the fining rates begin to fall back, consistent with transient response to tectonic perturbation in the upstream catchment and with a wave of incision sweeping up through the terrestrial system. Our results demonstrate that sophisticated insights into fault evolution can be drawn from deltaic stratigraphy, and emphasise the importance of transient landscape response in creating rift zone sedimentary archives.

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