Late Quaternary eolian sand depositional record for southwestern Kansas: Landscape sensitivity to droughts

Eolian deposits and landforms are ubiquitous in western Kansas, particularly south of the Arkansas River with the presence of a stabilized dune field. Stratigraphic studies and associated optical dating reveal a complex depositional history for this dune field spanning the late Quaternary. The oldest eolian deposits from ca. 16 to 12 ka completely or partially bury high terraces with ages of ca. 16 and 33 ka. It is unknown whether these eolian deposits reflect regional aridity and/or a change in sediment availability with the transition of the Arkansas River from a single channel to a braided system. There is pervasive evidence for episodic eolian erosion and deposition ca. 9.8 to 6.3 ka, generally coincident with loess deposition on upland surfaces [Olson, C.G., Nettleton, W.D., Porter, D.A., Brasher, B.R., 1997. Middle Holocene aeolian activity on the High Plains of west-central Kansas. Holocene, 7(3): 255–261], and thus it is inferred to reflect regional aridity. Sites within the dune field show a sequence of eolian sands and weak buried soils, reflecting either dune migration or sand sheet accretion at ca. 1490, 430, 380–320, 180, and 70 yr ago, which correspond well with continental-scale droughts in the tree-ring record. Eolian sand in the Arkansas River dune field may be derived principally with variability in fluvial activity and in climate during the late Pleistocene to the middle Holocene, with substantial reactivation of eolian systems during decadal-scale drought variability in the past 2000 yr.     

Miocene to recent eolian dust record from the Southwest Pacific Ocean at 40° S latitude

A 14-meter long pelagic clay core recovered at Marlin Rise (40°00.531′S, 154°2.601′W; 4775 m water depth) in the Southwest Pacific Basin contains a record of eolian dust deposited since the early Miocene. Downcore analysis of detrital minerals reveals a dominantly eolian signature with relatively constant proportions of quartz, feldspar and illite and trace amounts of chlorite, kaolinite and smectite, consistent with a continental (loess-like) source region. Fish tooth Sr isotope stratigraphy reveals the base of the core to be 17.5 Ma, with low sedimentation rates (< 0.5 mm/kyr LSR) indicated for the interval 17.5 to 10 Ma; several hiatuses in deposition appear to be present upcore, but are beyond the age resolution of the fish teeth stratigraphy. These intervals are revealed as apparent discontinuities in the Sr isotope record, accompanied by pulses of anomalously rapid sedimentation at ~ 10 Ma, 6.7 Ma and 4.1 Ma. Bulk mass accumulation rates (MAR) are calculated at ~ 10 mg/cm²/kyr over the last 4 Myr, consistent with previously estimated Quaternary eolian flux rates to this part of the Pacific. Nd, Pb and Sr radiogenic isotopic compositions of the detrital mineral extract (< 38 µm) show no trends with age, while ⁴⁰Ar/³⁹Ar ages show an upcore younging trend (~180 Ma to ~150 Ma), in concert with a slight coarsening of eolian grain-size distributions. These ages likely reflect mixing of Mesozoic illite-dominated clay from at least two continental source areas: southeastern Australia (Murray–Darling Basin/Lake Eyre Basin) and New Zealand (South Island). The data indicate remarkable constancy of continental eolian sources exposed to weathering and dispersal at this latitude during the Neogene.     

Late Pleistocene and Holocene environments of the Southeastern United States from the stratigraphy and pollen content of a peat deposit on the Georgia Coastal Plain

A 5.4 m peat core from the Sandy Run Creek (SRC) valley in the upper Coastal Plain of Georgia shows that before 30 ka the valley had an aggradational sandy floor with shallow swales and low ridges of 1–2 m amplitude suggesting a braided stream pattern and a low water table. The climate from 30–25 ka was cool and dry and the vegetation open grassland with stands of pine and spruce that produced few fires. At ca. 16 ka a warmer, wetter climate caused SRC to meander and incise the valley fill removing some previously deposited sediment at the site of our peat core so that sediments of 13 ka rest directly on sediments deposited at 25 ka. After ca. 13 ka higher groundwater levels initiated vertical accretion of floodplains allowing peat accumulation in shallow depressions across the valley. Pollen from the Younger Dryas period (ca. 13–11 ka) indicates a cool, moist environment of open oak woodland, mesic trees, riparian populations of alder, and reduced levels of pine. By the early to mid Holocene, tupelo and oak dominated over pine indicating wetter conditions, while sand stringers in peat record periodic heavy rains, an elevated water table, and intervals of substantial runoff. Cooling after ca. 4.5 ka brought drier and more variable conditions. Fires increased and southern pine replaced tupelo and oak. The absence of sand stringers in peat younger than 4.5 ka indicates fewer intense rainfall events.     

许家窑-侯家窑遗址地层穷究

许家窑-侯家窑遗址是中国旧石器时代中期一处重要的考古遗址, 出土的化石"许家窑人"属于早期智人。按照现行地层古生物学常规判断, 其地层应该属于上更新统。目前, 许家窑组是泥河湾盆地乃至东亚地区发现的上更新统包含古人类及其旧石器文化遗物和古哺乳动物化石相当丰富的一个地层剖面, 但断代存在理念误区。     

The fossil palynoflora,geological age,and climatostratigraphy of the earliest deposits of the Karama site (Early Paleolithic,Altai Mountains)

The results of palynological analysis of the Early Paleolithic Karama site (northeastern Altai Mountains) are presented. The Karama site is among the most unique and ancient archeological sites of Eurasia. Detailed palynological study has refined the geological age of the sediments that enclose pebble industry artifacts. The landscape and climatic conditions of Early Paleolithic man are reconstructed. A detailed characterization of the changes in the flora and vegetation that occurred during the most ancient Neo-Pleistocene interglacials and glacials is provided.     

中国的石叶技术

在旧石器时代晚期,中国北方的地域性石器工业之中也有石叶技术。最典型的实例是山西峙峪的,其特征是:1)制作技术简单;2)生产小型—中型石叶;3)石料的材料较好;4)在技术体系当中的作用较低。根据这些特征的有无,可以将中国北部的石叶技术划分为许家窑以前的阶段、许家窑阶段(10—3.5万年前)、峙峪—小南海阶段(3.5—1.7万年前)这样3个阶段。本文主张这3个阶段分别相当于欧亚大陆西部的旧石器时代早、中、晚期。     

Relationship of environmental changes in central Sri Lanka to possible prehistoric land-use and climate changes

A radiocarbon-dated pollen-analysed peat sequence from the Horton Plains (> 2000 m a.s.l.), in central Sri Lanka, together with physical and chemical parameters (organic carbon, mineral magnetics, carbon isotopes and phytoliths), indicates major environmental changes during the last 24,000 years. The results suggest that a mobile life form, i.e. a hunter–forage culture, predominated in an open landscape, associated with xerophytic vegetation, e.g. Chenopodium spp. at  17.5 ka BP. Incipient management of cereal plants and slash-and-burn techniques seem to have prevailed between 17.5 and 13 ka BP, which was indigenous and associated with grazing. Evidence of systematic cereal cultivation in the form of oat and barley pollen grains is found from the late Pleistocene ( 13 ka BP). This is the earliest evidence of farming activities noted in Sri Lanka as well as in south Asia. After 13 ka BP, cereal cultivation was associated with an increase in humidity. With a later abrupt increase in aridity, agricultural land-use decreased from  8 to  3.6 ka BP, when the area appears to have been almost deserted. After a severe middle Holocene arid phase (i.e. 5.4–3.6 ka BP), the agricultural activity with a limited extension was again initiated by  2.9 ka BP. During the next  900 years, cultivation ceased allowing the upper montane rain forest to dominate. Between 0.2 and 0.15 ka BP, new phases of agricultural activities were undertaken and potato cultivation took place lately, between 1950 and 1969 AD.     

Environmental inferences and chironomid-based temperature reconstructions from fragmentary records of the Weichselian Early Glacial and Pleniglacial periods in the Niederlausitz area (eastern Germany)

We inferred past climate conditions from lacustrine sediments intercalated in Weichselian Early Glacial and Early Pleniglacial fluvial and aeolian sediments, exposed in two opencast lignite mines from the Niederlausitz area (eastern Germany). A chronology was established using radiocarbon and luminescence dating methods. Both lithology and chironomid fauna indicate that the former shallow lakes were situated on a floodplain. Palaeotemperature estimates calculated from the fossil chironomid-assemblages of the Early Glacial lacustrine deposit indicate mean July air temperatures of ca. 15 °C, which is in line with results derived in earlier studies from the Niederlausitz area and from northwestern Europe. The Early Pleniglacial lacustrine deposits consist of an organic-rich gyttja, intercalated with sand and silt lenses. The chironomid-assemblages show that a shallow meso- to eutrophic lake was present at the study site, and chironomid-inferred palaeotemperature estimates indicate an abrupt decline in July air temperatures from 15–16 °C to ca. 13 °C. In combination with other proxies from the same record, this suggests a Dansgaard/Oeschger like climate event.     

At the end of the 14C time scale--the Middle to Upper Paleolithic record of western Eurasia

The dynamics of change underlying the demographic processes that led to the replacement of Neandertals by Anatomically Modern Humans (AMH) and the emergence of what are recognized as Upper Paleolithic technologies and behavior can only be understood with reference to the underlying chronological framework. This paper examines the European chronometric (mainly radiocarbon-based) record for the period between ca. 40 and 30 ka ¹⁴C BP and proposes a relatively rapid transition within some 2,500 years. This can be summarized in the following falsifiable hypotheses: (1) final Middle Paleolithic (FMP) “transitional” industries (Uluzzian, Chatelperronian, leaf-point industries) were made by Neandertals and date predominantly to between ca. 41 and 38 ka ¹⁴C BP, but not younger than 35/34 ka ¹⁴C BP; (2) initial (IUP) and early (EUP) Upper Paleolithic “transitional” industries (Bachokirian, Bohunician, Protoaurignacian, Kostenki 14) will date to between ca. 39/38 and 35 ka ¹⁴C BP and document the appearance of AMH in Europe; (3) the earliest Aurignacian (I) appears throughout Europe quasi simultaneously at ca. 35 ka ¹⁴C BP. The earliest appearance of figurative art is documented only for a later phase ca. 33.0/32.5-29.2 ka ¹⁴C BP. Taken together, the Middle to Upper Paleolithic transition appears to be a cumulative process involving the acquisition of different elements of “behavioral modernity” through several “stages of innovation.”     

High-resolution sea surface temperature records derived from foraminiferal Mg/Ca ratios during the last 260 ka in the northern South China Sea

High-resolution sea surface temperatures (SST) derived from Mg/Ca ratios of Globeriginoides sacculifer at ODP Site 1144 were reported to reveal the SST changes during the last 260 ka in the northern South China Sea (SCS). The results indicate an average Holocene SST of about 26.7 °C, about 3.6 °C increase from LGM to the Holocene, and higher temperature during MIS 5.5 than the Holocene. These agree well with other foraminifer Mg/Ca and U^k₃₇ SST records in this region. The Mg/Ca records suggest warmer SSTs during MIS 3 in the northern SCS, compared with those in the eastern Pacific. Strong East Asian summer monsoon during MIS 3 indicated by paleoclimate records from nearby continents may account for it. Step-wise increases during terminations are shown in our SST record, and the beginning of deglacial warming occurs at about 19 ka, which precedes the change of oxygen isotopes, suggesting a tropical driven forcing for the SST change in the northern SCS. This is further supported by a robust semi-precessional cycle centering at  9.1 ka in the spectra of the SST record, which is absent in that of the oxygen isotopes. However, tropical driven forcing seems not to be indicated in another Mg/Ca SST record in the northern SCS [Oppo, D.W. and Sun, Y.B., 2005. Amplitude and timing of sea-surface temperature change in the northern South China Sea: Dynamic link to the East Asian monsoon. Geology, 33 (10): 785–788.]. The discrepancy may be caused by different post-deposition dissolutions of foraminifer tests at these two sites. Details about the modification of foraminifer Mg/Ca ratios after burial, however, are not well known in this region, and further studies are needed.     

Lake Baikal climatic record between 310 and 50 ky BP: Interplay between diatoms, watershed weathering and orbital forcing

The environmental record from Lake Baikal, Russia, from 310 to 50 ky BP (MIS 9a to MIS 3) was interpreted using rock magnetic, UV–Vis spectral, mineralogical, and diatom analyses. The age model was based on a correlation of the diatom and chemical weathering records and the summer insolation curve at 55°N and checked against an age model based on the proxy of relative palaeointensity of the Earth's magnetic field. Peaks in chemical weathering within the watershed, inferred from maximum concentration of magnetic and coloured minerals and mica, the lowest mean Fe oxidation state in silicates and highs in expandable clay minerals correlated with the Northern Hemisphere summer insolation minima at 55°N. Reconstructed changes in weathering intensity are better correlated to insolation patterns than to global ice volume records. We propose a scheme of yet missing palaeoenvironmental interpretation of the diatom assemblage, including also some extinct species. Aulacoseira baicalensis and Aulacoseira skvortzowii were abundant in the early stages of lake flora recovery immediately after deglaciation and during MIS 7e and MIS 5e; periods of more pronounced continental climate and peak chemical weathering. Stephanodiscus formosus var. minor, Cyclotella minuta and Cyclotella ornata dominated in intervals of decreased seasonality and decreased humidity at the end of most interglacial/interstadial diatom zones. Stephanodiscus grandis, Stephanodiscus carconeiformis and Stephanodiscus formosus were ubiquitous between MIS 8 and MIS 5, an interval marked by high seasonality, i.e., large differences between winter and summer insolation, and low humidity revealed by a low hydrolysis of expandable clay minerals in the watershed. Diatom concentrations peaked in the climatic optima of MIS 7e and MIS 5e and in the short periods marked by shifts to warmer conditions in the upper sections of MIS 5: MIS 5c (103–99 ky BP), MIS 5b (90–88 ky BP), and MIS 5a (84–79 ky BP) in which increased humidity resulted in enhanced hydrolysis of clay minerals. No such short similar climatic optimums were found from MIS 9a to MIS 6. Sharp climate deteriorations recorded in the diatom and clay mineral records at 107, 94, and 87 ky BP, however, occurred within 1–2 ky of cold extremes in North Atlantic sea surface temperature emphasizing the strong teleconnections between the two localities.     

Time series analysis of magnetic susceptibility variations in deep marine sedimentary rocks: A test using the upper Danian–Lower Selandian proposed GSSP, Spain

It has been clearly demonstrated that past climate fluctuations are recorded in marine sedimentary rocks. However, for many reasons, extracting the climate signature is difficult. Initial low-field mass-specific magnetic susceptibility (MS) data can potentially provide a measure of climate variability and thus become a proxy characterizing climate cyclicity in a wide range of marine sediments. This is due to the fact that climate change (warm, wet versus cold, dry) drives cyclic weathering and erosional variations that are recorded as the detrital components of marine sediment that dominates the MS. To test the utility of MS to yield climate proxies in marine sediments showing major changes in lithology, we have sampled the well-studied Danian/Selandian boundary interval (Lower Paleocene) at Zumaia (Zumaya), Spain. This interval represents a dramatic, rapid lithologic change from Danian carbonate-dominated limestone–marl couplets to a detrital-dominated marl-shale sequence in the Selandian, indicating onset of a major regression-erosional event beginning in the lowest Selandian. Sampling included a continuous sequence from the uppermost Danian Stage (3.71 m) into the lowermost Selandian Stage (5.2 m), a suite of 175 samples collected at 5 cm intervals. Our results indicate that MS measurements reflect changes in detrital sediment at the site, first by closely tracking high-frequency limestone–marl couplets, second with a large, rapid shift toward higher MS values beginning at the Danian/Selandian boundary resulting from a major regression, and third by tracking low-frequency climate-controlled variations known to have occurred during deposition of these sediments. MS zones developed from the cyclicity observed throughout the sequence, supported by time series analysis using Fourier Transform (FT) methods applied to the MS results, exhibit Milankovitch cyclicities in the precessional (19–24 kyr), obliquity (41–54 kyr) and eccentricity bands (100 kyr). This is in excellent agreement with previous FT work on the section using measured variations in cyclic bed thicknesses. With the new MS data set and FT results, we then developed a Floating Point Time Scale (FPTS) for the sequence sampled (covering  550 kyr through the Danian/Selandian boundary interval), yielding a time-scale resolution for the uppermost Danian to  10,000 years. However, only the  100,000 year eccentricity band for the Selandian is sufficiently well developed for an FPTS estimate, and yields a time-scale resolution of  50,000 years. Our test of the utility of MS data sets in this varying depositional setting demonstrated that these data can provide a climate proxy that is not disrupted by large lithologic changes.     

Late Quaternary stratigraphy and sedimentology of Orphan Basin: Implications for meltwater dispersal in the southern Labrador Sea

Orphan Basin is a deep-water basin on the continental margin off Newfoundland, which throughout the late Quaternary received proglacial sediment from local ice that crossed the continental shelf. Sediment from more distant sources was transported southward in the Labrador Current as proglacial plumes and in icebergs. Five sedimentary facies related to glacial processes are distinguished in cores recovered from Orphan Basin: hemipelagic sediment, nepheloid-layer deposits (layered mud), beds rich in ice-rafted detritus (IRD), sand and mud turbidites, and glaciogenic debris-flow deposits. IRD-rich beds correspond to periods of intensified iceberg calving, and layered mud, turbidites, and glaciogenic debris-flow deposits with glacial meltwater discharge.

In the Late Wisconsinan, eight periods of meltwater discharge and iceberg calving from the Newfoundland ice sheet are interpreted from the sediment facies in Orphan Basin. These discharges coincide with the terminations of the colder periods of the D–O cycles recorded in Greenland ice cores. The oldest minor meltwater event (27.5–28.5 cal ka) corresponds to the first Late Wisconsinan ice advance across the Grand Banks and NE Newfoundland Shelf. The following three meltwater discharges (23–23.5, 23.8–24.5, and 25–27 cal ka) deposited sand turbidites and glaciogenic debris-flow deposits seaward of Trinity Trough, which was occupied by an ice stream at this time, and mud turbidites in the southern part of the basin derived from a mid-shelf ice margin on the Grand Banks. Four periods of meltwater discharge occurred during the deglaciation and are centered at 15, 18.5, 19.75, and 20.75 cal ka. The youngest is correlated to Heinrich event 1. In the literature, the 18.5 and 20.75 cal ka events have been recorded in multiple glacial settings in the North Atlantic, and therefore, are interpreted as large-scale events of meltwater discharge and iceberg calving, but in Orphan Basin the 19.75 cal ka event is also of similar scale.     

Dating the Lower to Middle Paleolithic transition in the Levant: A view from Misliya Cave,Mount Carmel,Israel

The transition from the Lower to the Middle Paleolithic in the Levant is a crucial event in human evolution, since it may involve the arrival of a new human population. In the current study, we present thermoluminescence (TL) dates obtained from 32 burnt flints retrieved from the late Lower Paleolithic (Acheulo-Yabrudian) and Early Middle Paleolithic (Mousterian) layers of Misliya Cave, Mount Carmel, Israel. Early Middle Paleolithic industries rich in Levallois and laminar products were assigned mean ages ranging from ∼250 to ∼160 ka (thousands of years ago), suggesting a production of this industry during MIS 7 and the early part of MIS 6. The mean ages obtained for the samples associated with the Acheulo-Yabrudian (strengthened by an isochron analysis) indicate a production of this cultural complex ∼250 ka ago, at the end of MIS 8. According to the Misliya TL dates, the transition from the Lower to the Middle Paleolithic in the site took place at the limit MIS 8/7 or during the early part of MIS 7. The dates, together with the pronounced differences in lithic technology strongly suggest the arrival of a new population during this period.     

Hominin-carnivore interactions during the Chinese Early Paleolithic: taphonomic perspectives from Xujiayao

The ability of archaic Homo sapiens to survive in more northerly latitudes was contingent on securing a regular source of animal fat and protein. We present a taphonomic study that examines how successful these hominins were at acquiring these food sources during the latter part of the Early Paleolithic in Northeast Asia. This study focuses on the long bone midshaft surface modifications observed on the faunal remains from Xujiayao, a middle-late Pleistocene open-air site located at 40 degrees latitude in the western Nihewan Basin, northern China. The faunal assemblage is dominated by equid remains. Analysis of the percussion, tooth, and cut mark frequencies on the long bone midshafts demonstrates that the Xujiayao hominins had primary access to high utility (meat-bearing and marrow-rich) long bones. Investigation of the dual-patterned (tooth-marked and butchery-marked) bone fragments suggests that hominins were under little pressure from competing carnivores to abandon their kills. The lack of significant differences between the size of fragments with only percussion-marks and those with only tooth-marks supports these findings. Fragmentation ratios indicate that forelimbs were more intensively processed than hind limbs. Based on the water rounding and abrasion data, the Xujiayao assemblage is likely of autochthonous origin. Since the age of Xujiayao is still in question, we can only conclude that archaic Homo sapiens were successful predators of large game in Northeast Asia some time during the latter part of the Early Paleolithic.     

Geomorphology and chronology of Late Quaternary dune fields of western Argentina

Stabilized dune fields are common in western Argentina and potentially reflect drought variability in the Late Quaternary. This study focussed on deciphering geomorphic and stratigraphic record of three vegetated dune fields from east to west, San Luis, Médanos Negros and Médanos Grandes, with a mean annual precipitation from ∼ 700 to 91 mm. Optically stimulated luminescence single-aliquot regeneration protocols yield ages on eolian quartz grains, constraining depositional events. The San Luis dune field, the wettest area, exhibits evidence for repeated activation during the last glaciation, ca. 33-20 ka, generally coincident with regional loess deposition These dunes were locally reformed in the past 100 years which is apparently coincident with intensified agrarian use and drying in the late 19th and early 20th century. The two driest and western-most dune fields, Médanos Negros and Médanos Grandes, show reactivation at ca. 2.5 ka 0.9 and 0.5 ka; and ca. 4.3-4, 2.1 and 0.6-0.4 ka, respectively. Eolian depositional events at ca. 2.5-2.1 ka and 0.6-0.4 ka may be coeval for Médanos Grandes and Negros dune fields. Sustained drought conditions conducive for eolian activity is associated with warmer sea surface temperatures in the South Atlantic, a weakened South American Convergent Zone and a dispersed and southeasterly flow of tropical moisture from the Low Level Chaco Jet. This nascent analysis indicates drought variability beyond historic observations with potentially at least four dune reactivation events in the past ca. 4.5 ka.     

Late Quaternary millennial-scale variability in pelagic aragonite preservation off Somalia

In order to better understand Late Quaternary pelagic aragonite preservation in the western Arabian Sea we have investigated a high-resolution sediment core 905 off Somalia. Pteropod preservation is enhanced in times of reduced monsoon-driven productivity, indicated by low amounts of C_org and low barium to aluminium (Ba/Al) ratios. All periods corresponding to Heinrich events in the North Atlantic are represented by maxima in shell preservation of the common pteropod Limacina inflata (LDX values < 2, except for H5-equivalent with a poorer shell preservation, LDX > 2.66). Good shell preservation is also found during stadials at 52.1–53.2, 36, 33.2, and 31.9 ka. Relative abundance of pteropods and their fragments in the coarse fraction reaches maxima during Marine Isotope Stage (MIS) 5.2, during time-equivalents of Heinrich events 4–6 and in stadials at  53,  42.5, and 41.4 ka.On longer time scales, the pteropod abundance corresponds to the ‘Indo-Pacific carbonate preservation type’ with poor preservation during interglacials and better preservation during glacials. Late MIS 5 to early MIS 4 sections (84.1–64.8 ka) and the Late Holocene interval (6.5–0 ka) of core 905 contain only traces of pteropods. The early Holocene (9.2–6.5 ka) part is characterized by low pteropod amounts. Between 64.8 and 43.4 ka strong fluctuations occur and an intermediate average relative pteropod abundance is revealed. Between 43.4 and 9.2 ka the highest amounts in relative pteropod abundance in core 905 are observed. Besides the regional monsoonal influence on deepwater chemistry, changes in deepwater circulation occurring on glacial/interglacial and stadial/interstadial time scales might have affected pteropod preservation. However, it remains elusive whether 1) deep water formation in the Arabian Sea, 2) inflow of Glacial North Atlantic Intermediate Water or 3) change in water mass properties of the Circumpolar Deep Water (which is the water mass currently bathing this site) contributed to the observed pteropod preservation pattern.     

The Quaternary eolian sequence of Madeira: stratigraphy, chronology, and paleoenvironmental interpretation

A thick (ca. 40 m) sequence of coastal eolian sediments occurs on a narrow peninsula on the eastern end of the island of Madeira, located in the Eastern Atlantic at 33°N latitude. The sediments consist of black volcanic sands (with or without bioclasts) as well as clay units up to 2 m thick. A series of inceptisols (Eutrochrepts) and one alfisol (a Hapludalf) are developed in these sediments. Land snail shells and secondary carbonates, in the form of well-developed rhizoliths, calcretes, fissure-fills, and soil nodules, are present in abundance. The chronology of the sequence was determined by ¹⁴C and U---Th analyses of land snail shells and secondary carbonates and amino acid epimerization analysis of land snail shells. All sediments, including the clay units, are originally of eolian origin, derived from the beach to the south of the deposit, but some have been redeposited by colluviation. Temporal variation in the lithology of the sediments relates to variations in sea-level, with black sands being deposited during lower sea level stands and clays at the lowest. It is suggested that fine marine sediments, exposed during low sea-level stands, may also be the dominant source of silty or clayey units in other coastal eolian deposits in the subtropical Atlantic and Mediterranean.

The sequence spans from 200,000–300,000 years ago up to the 20th century. Sedimentation was discontinuous and often rapid; erosional hiatuses are present. During the Holocene, eolian sands started accumulating at 8200 yr B.P. during a transgressive phase and stopped at 4500 yr B.P. as sea level approached its present height. Colluviation increased dramatically following the first human settlement of the island in the 15th century and continued up to the 20th century, as dated by amino acid epimerization analysis of land snails. Earlier periods of colluviation were identified from the age distribution of land snail shells redeposited in younger colluvium.

Paleoenvironmental reconstruction was based mainly on soil and sediment features (including rhizolith morphology) and land snail faunas but also on stable isotope variations (¹³C, ¹⁸O) in land snails and secondary carbonates, pollen (generally not well preserved), and phytoliths. Most of the portion of the Middle Pleistocene represented in the sequence was characterized by moderately dry conditions, in comparison to the late Pleistocene and Holocene. During the last interglacial, relatively wet conditions occurred, wetter than during the Holocene interglacial. Moderately moist conditions were present during the accumulation of the thick unit dating to ca. 80,000 yr B.P. As sea level fell subsequent to this period, conditions appear to have become drier. Starting ca. 50,000–55,000 yr B.P., conditions were especially wet, but prior to the last glacial maximum, markedly arid conditions ensued. Toward the end of the last glacial, wet conditions returned and produced the best-developed soil preserved in the sequence. Moderately moist conditions occurred during the early to middle Holocene but apparently become slightly drier after 4500 yr B.P. The impact of human settlement can be seen in the loss of woody vegetation and enhanced gullying and colluviation during the last ca. 500 years.     

许家窑遗址74093地点1977年出土石制品研究

许家窑遗址74093地点位于泥河湾盆地中部, 发现于1974年, 出土了早期智人化石以及大量的石制品和动物化石。该地点进行过多次发掘, 其中1977年在U3等探方共出土石制品共1765件, 类型包括石核、石器、完整石片、不完整石片和断块等。石制品原料取自梨益沟流水带来的河卵石, 以石英岩和脉石英为主。石制品以小型居多, 锤击法为主要剥片方法, 砸击法应用较少。石器毛坯以片状居多, 占63.6%; 石器类型多样, 以刮削器和石球为主; 石器由锤击法加工而成, 加工部位多集中分布在毛坯的单侧或者单端, 单向加工占72.4%, 且以正向为主; 双向加工占27.6%, 多以复向加工为主。年代测定表明古人类在该地点活动的时间大致发生在晚更新世早期。石器组合属于华北小石器工业传统, 大量石球的发现对于研究早期人类的剥片技术和生存行为具有重要意义。     

Ages for hominin occupation in Lushi Basin, middle of South Luo River, central China

A newly discovered Paleolithic site in loess deposits in the Lushi Basin, South Luo River, central China, is dated using pedostratigraphic analysis, optically stimulated luminescence (OSL) and magnetostratigraphic analysis. This region is regarded as an important place for hominin occupation and settlement during the early to middle Pleistocene. Results indicate that the archaeological site dates from 600 ka to 620 ka, reinforcing the view that Homo erectus had occupied a large area of eastern Asia by 620 ka. The lithic assemblages of Lushi Basin is a flake and core technology, typical for this time period in north-central China. It may be compared with that at the Zhoukoudian locality 1 in north China and some sites in the Luonan Basin, and provides important data for understanding the behavior and stone tool technology of early Chinese hominins.