Pleistocene Loess Research Articles

Occurrence and palaeoenvironmental implications of the Late Pleistocene loess along the eastern coasts of the Bohai Sea, China

Abstract Loess is found to blanket various landforms of different altitudes in the eastern coastal areas of the Bohai Sea, from Liaodong Peninsula to the Miaodao Islands and Jiaodong Peninsula in eastern China. Two major lithological units have been recognized: the Penglai Loess and the Dalian Loess. Recent studies reveal a weathered unit within the Dalian Loess and confirm the occurrence of Holocene loess. Random distribution of marine microfossils and concomitant occurrence of contrasting species in the loess rule out the possibility of the coastal loess being a marine sediment. The coastal loess is coarser and contains a higher content of unstable minerals compared to the inland equivalents. Regional variations in texture and heavy mineral assemblage within the coastal loess zone are also observed, suggesting that the primary source of the coastal loess is not northwestern China but is more likely to be from the coastal areas and the adjacent Bohai Sea basin. When the coastline was displaced a few hundred kilometres eastwards during the last glacial period, vast areas of the continental shelf of the Bohai Sea were exposed. Coastal dunefields may have been expanded and perhaps developed locally into a desert shelf environment. With intensified aeolian process, fine particles in the ancient fluvial and marine sediments were transported by small-scale low-level northwesterly and northerly winds and deposited along the eastern coasts of the Bohai Sea. The basal age of the Late Pleistocene Dalian Loess was previously estimated to be 11–25 ka, but preliminary thermoluminescence dating results suggest that it started to accumulate at least 30 ka earlier.

Loess in the longxi basin of gansu province

The Nuanquangou loess section in the Longxi Basin has been examined in terms of stratigraphic investigation, including14C dating, paleomagnetic polarity, spore-pollen diagram, and mineral and chemical analyses. The results indicate that the section is one of the ancient loess sections with a continuous sedimentation and composed of homogeneous materials with abundant carbonate. The Brunhes / Matuyama boundary and the Jaramillo event were recorded in the section. Stratigraphically, this section can be divided into the Holocene and the Pleistocene loess. The latter includes Malan, Lishi and Wucheng loess in descending order. They were developed at about 1.2 Ma ago, whereas the Nuanquangou loess section possesses some local characteristics different from those observed in other areas.

Late Pleistocene chronology of loess deposition near Luochuan, China

Loess near Luochuan was sampled for thermoluminescence (TL) dating simultaneously with magnetic susceptibility measurements to provide the first independent age estimates on a susceptibility record from the Loess Plateau of China. TL age estimates on late Pleistocene loess (L1) are stratigraphically consistent with no statistical difference in TL ages by the total or partial bleach techniques or by measuring ultraviolet or green wavelengths in the TL analysis. Loess below the last interglacial soil (S1) yielded disparate results and is in many localities in central and eastern China unsuitable for TL dating because of complications of TL saturation and uncertainties in estimating the environmental radiation. TL age estimates on the L1 loess are consistent with previously reported TL ages for sites near Beijing and Xian as well as in general agreement with age models for loess deposition based on paleomagnetics and magnetic susceptibility. The convergence of a variety of geochronologic indices indicate that the last major period of loess deposition in central China began 70,000 ± 10,000 yr B.P. and terminated <20,000 yr B.P. This event is probably recorded in sediments from the adjacent Pacific Ocean and possibly in dust records from the Antarctic Ice Sheet.

Soil-Age Relationships on Late Quaternary Moraines, Arrowsmith Range, Southern Alps, New Zealand

Loess on Holocene moraines has accumulated steadily since moraine deposition resulting in soils that generally lack buried horizons and have a degree of development which closely reflects the age of the underlying till. The progressive development of two field indices and five laboratory properties of these soils are best described by logarithmic functions. Indices of pedogenic iron and rubification yield the highest correlation with age of deposit. Rates of soil development are faster than those reported for other parts of the eastern Southern Alps and curves of most soil properties flatten within ca. 10 ka. In contrast, the use of soils to date pre-Holocene moraines is greatly hindered by loess redistribution which commonly results in eroded and/or buried soils. Radiocarbon dates from charcoal within loess on pre-Holocene moraines suggest that loess reworking has been episodic, resulting in soils that are far younger than underlying tills. Holocene reworking of loess on upland sites in response to fires, frost action, and high winds may serve as an analog for large-scale late Pleistocene loess reworking on the Canterbury Plains.

Sedimentary and pedological processes in the Upper Pleistocene loess of northern Italy. The Bagaggera sequence

The Bagaggera sequence consists of two Late Pleistocene loesses superimposed on the top of Middle Pleistocene fluviatile sediments. The lower loess includes at its base a Mousterian archaeological level represented by artifacts (dated by TL as 60,500 ± 7500 BP) and charcoal from hearths which mainly consists of boreal forest species. At the top of the lower loess, Aurignacian artifacts occur which suggest a tentative date of 35,000 BP. The sedimentary and pedological processes which lead to the formation of the sequence, were reconstructed by means of mineral and textural analyses and thin section analysis and can be summarized as follows: - Erosion and colluviation of the Eemian soil at the base of the sequence during the Early Würm (Isotopic Substages 5 a-c). - Sedimentation of the lower loess deposits during the first Pleniglacial period (Isotopic Stage 4). A large number of coarse pedofeatures in this soil suggests that primary aeolian dust has been redistributed in place or for short distances by syngenetic slight pedogenesis and by water reworking, as a result of alternating phases of wet and dry climate. - An alfisol characterized by strong clay illuviation developed in the lower loess during the Hengelo-Arcy interstadial phase. Its top was affected by reworking and slight frost activity at the beginning of the second Pleniglacial period (Isotopic Stage 2). - The upper loess was deposited in a drier environment during the second Pleniglacial period (Isotopic Stage 2). Water reworking was less effective. - Holocene weathering is expressed by clay illuviation and slight hydromorphism.

Mineralogical and clay mineralogical aspects of loess research

Mineralogical and clay mineralogical investigations under certain circumstances allow conclusions regarding the rate and kind of pedogenetic weathering, especially clay mineral formation. Together with soil physical and chemical and mainly micromorphological investigations, paleoclimatic conclusions can be drawn. In Central European Holocene and Pleistocene loess soils as well as in relict loess soils in the central and northern part of the Great Plains of the U.S.A., smectite is the dominant pedogenetically formed mineral in the fine clay fraction (< 0.2 μm); illites are dominant in the coarse clay. In contrast in Holocene and Pleistocene loess soils of Central Asia (Kashmir Valley, loess plateau of Central China) mainly illites are formed pedogenetically and predominate in the coarse and fine clay fractions. Even in intensively weathered and rubefied Earthy Braunlehms (Rhodudalfs) of mid and old Pleistocene age, no, or only very small amounts of kaolinite were formed pedogenetically.

Traces of frost activity and ice segregation in Pleistocene loess deposits and till of northern Italy: Deep seasonal freezing or permafrost?

This paper describes traces of ice lensing preserved in loessic deposits, in till, and in shelters and cave infillings. Most of the observed traces correspond to seasonal frost activity, rather well-preserved in poorly drained sites or in the shadow of shelters. No distinct evidence of permafrost dating to the Last Glaciation has been found: the preservation of ice lensing traces in soil is poor, due to intense biological activity and dry climate conditions. This shows that during the glacial time, the Po plain belonged to the southeastern European domain, though presently included in the western, sub-Mediterranean climate zone.

New magnetostratigraphic dates of Lantian Homo erectus

Skeletal remains of Homo erectus found in Pleistocene loess at two sites near Lantian in central China are of greatly different geologic age. The cranium found in the fossil-bearing strata at Gongwangling is about 1.15 myr old whereas the remains found at the Chenjiawo locality in middle Pleistocene loess are about 0.65 myr old. The dating is based on new paleomagnetic polarity determinations and on the lithostratigraphic position of the fossils in the loess-paleosol sequence. Our results confirm that both localities are older than the first occupation of Zhoukoudian. New dates, palaeoenvironmental settings, and morphological features of the hominids from Lantian localities have significant bearing on the understanding of adaptive radiations of the middle and late hominids in Asia.

Upper pleistocene loess stratigraphy and paleolithic site chronology on the Russian plain

AbstractLoess stratigraphy provides the best existing means of establishing an accurate geochronology for the Paleolithic of the Russian Plain, especially for time periods beyond the range of radiocarbon dating. Loess/paleosol sequences in adjoining regions, particularly Central Europe where correlation with oxygen‐isotope stratigraphy has been achieved, represent a useful standard for the correlation and dating of loess deposits on the Russian Plain. However, better control is needed over local paleoenvironmental conditions and colluvial redeposition. Correlation is facilitated by two key marker horizons: buried soils of the Last Interglacial (127,000‐116,000 B.P.) and the terminal Middle Pleniglacial (30,000‐25,000 B.P.); assignment of paleosols and loess beds between these markers to time‐stratigraphic units in the Upper Pleistocene sequence is sometimes problematic. Paleolithic remains on the Russian Plain are typically contained in colluvial loam, but can often be related to primary loess stratigraphy. Analysis of the latter suggests sharp contrasts with Western and Central Europe in the timing and distribution of Paleolithic settlement, apparently reflecting the harsher environments of the Russian Plain.

Pleistocene Climatic Changes and Landscape Evolution in the Kashmir Basin, India: Paleopedologic and Chronostratigraphic Studies

AbstractThe Kashmir Basin is filled with Pliocene-Pleistocene fluvio-lacustrine sediments. On the flank of the Pir Panjal these sediments, called “Lower Karewas”, are covered with loess deposits up to 25 m thick that contain numerous middle and late Pleistocene paleosols, mostly polygenetic pedocomplexes, which were classified by micromorphological studies. Thermoluminescence dates provide a chronostratigraphy of the late Pleistocene loess-paleosol sequences. On the Himalayan flank, the “Upper Karewas” are covered only with late Pleistocene loess-paleosol sequences. Their base is the last interglacial soil, developed ca. 110,000 ± 10,000 yr B.P. This soil is genetically comparable to the modern soil and, therefore, is thought to have developed under a deciduous forest in a “xeric” soil moisture regime. The loesses of last glacial age on both flanks of the basin contain three humus-rich Ah, mostly Aht, horizons, indicating three warm and mostly humid climatic episodes between ca. 80,000 and 50,000 yr B.P. The middle Pleistocene loesses contain at least four Bwt, or thick Bt, horizons developed during four interglacial periods, having climates similar to the present. Large parts of the Karewa Lake must have lasted until the end of the penultimate glacial age.

INAA determination of major and trace elements in loess, paleosol and precipitation layers in a pleistocene Loess Section, China

Instrumental neutron activation analysis was used for the determination of 31 major and trace elements in 32 samples from the Xinji Loess Section, Shaanxi Province, China. Interferences, including those from uranium fission products, were evaluated and corrections applied where necessary. The 39.7-meter deep section comprises of Lishi Loess of the middle Pleistocene (Q2) and Malan Loess of the late Pleistocene (Q3). The section is characterized by the presence of 5 layers of paleosol, and each paleosol is underlain by a precipitation layer. When the elemental abundances are converted to a carbonate-free basis, there is little compositional difference among the carbonate-free fractions of loess, paleosol and precipitation layers. This indicates that dissolution of carbonate minerals by downward-moving surface water was an important process in paleosol formation while other minerals were not severely weathered and elemental fractionation was minimal. The parent materials of the paleosol and precipitation layers closely resemble the loess layers in their elemental abundances, which suggests that all layers in the section have a compositionally similar source.

Palacomagnetic and rock magnetic investigation of Late Pleistocene loess deposits in Belgium

The results of a palaeomagnetic and rock magnetic investigation of two loess profiles of Late-Pleistocene age in Tongrinne (TG) and Rocourt (RC) in Belgium are given. We examined the possibility of using this type of sediment, which is, strictly speaking, eolian in origin, to gain information about the dynamic behaviour of the ancient geomagnetic field. The influence of geological processes, especially those known to occur in periglacial environments, were examined. A field test was applied to the upturned strata near a fossil frost wedge of Weichselian age in Tongrinne to demonstrate that at least some large directional changes found in periglacial sediments, and which could be mistaken for ‘excursions’, cannot be attributed to the Earth's magnetic field, but are due to mechanical disturbances. The DRM/ARM method and the requirements for uniformity by Levi et al. to obtain relative geomagnetic palaeointensities were tested on those loess deposits which contain a large silt fraction.

Grain Surface Textures and Carbonate Content of Late Pleistocene Loess from West Germany and Poland

ABSTRACT Energy-dispersive analysis and X-ray mapping of West German and Polish loess grains observed under the scanning electron microscope (SEM) have shown that carbonate occurs primarily as detrital calcite and dolomite grains and not, as some earlier workers have suggested, as surface encrustations or gnarls on quartz and feldspar grains. This provides strong evidence against a process of loessification and indicates that the loess has experienced only slight postdepositional weathering and diagenesis. Secondary carbonate encrustations are sometimes found on grains in the B horizons of soils present within the loess, but such layers form only a relatively small proportion of the total loess thickness. All of the larger loess grains examined exhibit rough surface textures because of a hering fine silt- and clay-size particles of quartz, feldspar, mica, and calcium carbonate. No differences were observed between the surface textures of grains from fresh carbonate-bearing loess and those from decalcified samples treated with 50 percent HCl. Much of the fine debris can be removed from the grain surfaces by sonic vibration or, in more resistant cases, by HF treatment. The surface textures of quartz grains treated in this way typically show fresh, angular breakage features which are consistent with a glacio-fluvio-eolian origin.

Der jungpleistozäne Löß am Mittel- und Niederrhein anhand neuer Untersuchungsmethoden

Der jungpleistozäne Löß am Mittel- und Niederrhein anhand neuer Untersuchungsmethoden

Distant source of 1976 dustfall in Illinois and Pleistocene weather models

Very turbid skies were accompanied by dust deposition in western Illinois on October 15, 1976. Atmospheric circulation in central North America at the time was such that the dust was apparently transported to Illinois from sources in North Dakota or perhaps even southern Saskatchewan. This event indicates how some of the finer grained component of Pleistocene loesses of Illinois may have been derived from a distant source. Current models of Woodfordian atmospheric circulation patterns portray mid-tropospheric and lower tropospheric circulation, cyclonic activity, and climatic tendencies during summer months that are similar to the conditions that prevailed during this particular dust event.

A study of Late Pleistocene loess deposits, South Canterbury, New Zealand: Part II. Paleosols and their stratigraphic implications

Examination of loess columns in coastal South Canterbury, New Zealand, and the recognition of paleosols with comparable morphology to surface soils allowed the division of the loess column into six members. The upper loess members 1–4 are grouped into a proposed Dashing Rocks Formation. This commonly overlies an erosion surface on Timaru Basalt, but in some situations is underlain by loess member 5 and mixed loess and weathered basalt member 6. The paleosol developed on loess member 5, on both morphological and chemical evidence, is indicative of a period of soil formation of longer duration or greater intensity than is indicated by the overlying paleosols or surface soils. Therefore members 5 and 6 are grouped into a separate formation. A radiocarbon chronology for loess members 1 and 2 of the Dashing Rocks Formation, suggests loess accumulation phases from 9900 to 11,800 and prior to 31,000 radiocarbon yr BP, followed by periods of soil formation and contemporary peat development in surface depressions. A hypothesis is presented suggesting that at least loess members 1 and 2 of the Dashing Rocks Formation accumulated during periods of glacial recession which in turn precipitated fluvial and eolian erosion, transport and redeposition of fluvioglacial deposits. The periods of soil development indicated by the paleosols were initiated during warm interstadial conditions and continued throughout the cooling of the following stadial. Such an interpretation has its parallels in the northern hemisphere but is in slight disagreement with previous glacial and fluvioglacial chronologies accepted in New Zealand.

A study of late Pleistocene loess deposits, South Canterbury, New Zealand: Part I. Forms and amounts of phosphorus compared with other techniques for identifying paleosols

Four paleosols, and soil horizons within paleosols, were clearly identified in the thick calcium carbonate-free loess sections at Timaru, South Island, New Zealand, by changes in the distribution of total phosphorus and calcium phosphate in the upper 2 m to each paleosol. Extractable manganese was also sensitive in identifying paleosols, particularly the upper horizons. The distribution of bulk density values was useful in identifying paleosols; however, the maximum bulk density (>1.7 g/cc) occurred in horizons identified as B2 rather than fragipan horizons in three of four cases. The distribution of clay particles was useful in understanding the genesis of the modern soil and paleosols, but not in identifying paleosols.

Sequence of Bedform and Stratification in Silts, Based on Flume Experiments: ABSTRACT

Flume experiments with 2 silt sediments indicate development of a sequence of bed forms and stratification which is systematically related to flow intensity. At a fixed flow depth, each silt is transported as ripples over a wide range of mean velocities above the threshold for movement. With still higher velocities, ripples disappear abruptly and a flat-bed mode of transport occurs. Dunes are not present at velocities intermediate between rippled and flat beds, as they are for sand. At lower velocities, ripples develop forms very similar to sand ripples: planar lee slopes accrete by slumping End_Page 654------------------------------ and meet the crest and trough at sharp angles; stoss slopes are wholly erosional. At higher velocities, ripples become progressively lower and more rounded, and the resulting laminae are complex and sigmoidal; stoss-slope laminae become more common, resulting in temporary development of ripple-drift configurations, even in the absence of net bed aggradation. Low ripples are succeeded by a flat bed with relatively crude lamination and textural lineation parallel with flow. At the lowest velocities capable of maintaining ripple migration, sediment is transported entirely as bed load. Suspended-sediment concentration is high at velocities near and above the transition from ripples to flat bed, but the sediment-water mix behaves as a turbulent fluid rather than as a slurry. The 2 silts, derived from Illinois Pleistocene loess, have median diameters of 30 and 40 µ, are well sorted, and consist mainly of angular quartz chips. The flume used is a recirculating open channel 36 ft long and 3 ft wide. End_of_Article - Last_Page 655------------

Morphological Classification of Grass Phytoliths

AbstractOpal phytoliths derived from epidermal cells of grass leaves have been identified in atmospheric dust, soils, paleosols, Pleistocene loess, and deep‐sea sediments. By comparing oriented shapes of phytoliths in spodograms of 17 common grass species, four classes and 26 types are proposed which distinguish three groups of subfamilies of Gramineae. The Festucoid class contains eight types that are circular, rectangular, elliptical, or oblong forms. The Chloridoid class contains two types of saddle‐shaped bodies. The Panicoid class contains 11 types that are variations of crosses and dumbbells. The Elongate class contains five types that have no subfamily implications and occur in all 17 species. Because phytoliths of native tall grasses (Panicoid), short grasses (Chloridoid), and common domestic grasses of the humid regions (Festucoid) can be distinguished, it is possible to determine whether phytoliths in dust, soils, and sediments were derived from local or remote sources.

Progress Report on Two Unusual Alaskan Sediments--Recent Beach Carbonate From Three Entrance Bay, and Polished Grains From Easter Egg Hill: ABSTRACT

Modern southeastern Alaska cold-water skeletal carbonates are composed chiefly of whole and fragmented mollusks, barnacles, echinoderms, and foraminifers mixed with basalt pebbles and sand from the island bedrock. Average CaCO3 content is about 80 percent by weight and increases from 0 percent at -4^phgr (16.0 mm) to 88 percent at 4^phgr (0.0625 mm). Texturally this beach sediment is polymodal, with two dominant modes: a gravel mode about -4^phgr and a sand mode about 2^phgr (0.25 mm). Traces of carbonate mud are present. Fractionating this sediment into carbonate and silicate mineral phases shows that these gravel and sand modes are present in each mineral phase. This suggests that selective size sorting in the beach environment, rather than fragmentation into certain size classes, may be the chief process involved in the formation of modal size classes for this sediment. Highly polished particles occur in (?)Pleistocene pebbly sandy loess on a topographic ridge in interior Alaska. Most polished particles have near-perfect roundness and occur in all sizes between -5.1^phgr (34 mm) and 4^phgr (0.0625 mm). Polished grain surfaces essentially are smooth, with some pits and very few facets. Rounded and polished grains are mixed with totally angular and dull grains. Polished grains seem to have bimodal size distribution, being abundant about -3.6^phgr (12 mm) and 0.5^phgr (0.25 mm). Modes from size analysis of loess do not correspond to modes for abundance of polished grains. Attempts to duplicate polished grains by tumbling unpolished grains from the same locality with wet and dry loess failed. Most polished grains are quartz; some are chert. Origin of the e polished grains is uncertain. The following origins have been rejected: polish by wind-blown silt or ice crystals, solifluction, in situ chemical polish, and inheritance. It is believed that these polished grains are gizzard stones produced by Pleistocene bird(s). Gizzard stones collected from grouse and ptarmigan in late winter are highly polished. Unfortunately, modal classes of gizzard stones from birds now living in interior Alaska do not coincide with modes of polished grains from the loess; average size of grouse gizzard stones is -1.0^phgr (2.00 mm) and of ptarmigan stones is -1.3^phgr (2.5 mm). End_of_Article - Last_Page 532------------