Late Pleistocene Deposits Research Articles

A robust feldspar luminescence dating method for Middle and LatePleistocene sediments

Luminescence dating is used extensively to provide absolute chronologies for LatePleistocene sediments. Nowadays, most optical dates are based on quartz optically stimulated luminescence (OSL). However, the application of this signal is usually limited to the last ∼100 ka because of saturation of the quartz luminescence signal with dose. In contrast, the feldspar infrared stimulated luminescence (IRSL) dose–response curve grows to much higher doses; this has the potential to extend the datable age range by a factor of 4–5 compared with quartzOSL. However, it has been known for several decades that thisIRSLsignal is unstable, and this instability often gives rise to significant age underestimation. Here we test against independent age control the recently developed feldspar post‐IR IRSLapproach to the dating of sediments, which appears to avoid signal instability. A physical model explaining our observations is discussed, and the method is shown to be accurate back to 600 ka. The post‐IR IRSLsignal is reduced by exposure to daylight more slowly than that from quartz and low‐temperatureIRSL, preventing its general application to young (e.g.Holocene) sediments. Nevertheless, this new approach is widely applicable (feldspar of appropriate luminescence behaviour is even more ubiquitous than quartz). These characteristics make this a method of great importance for the dating of Middle and LatePleistocene deposits.

Plio-Pleistocene Climate and Faunal Change in Central Eastern Australia

Understanding the responses of Plio-Pleistocene terrestrial vertebrates to long-term trends in climate change in central eastern Australia has advanced considerably in recent years following the recovery and documentation of a series of remarkable fossil assemblages. The middle Pliocene Chinchilla Local Fauna of SE Queensland preserves a diverse suite of vertebrate taxa suggestive of a paleoenvironment consisting of wetlands, closed wet forest, open woodlands, and grasslands. Local extinctions of numerous arboreal and terrestrial woodland species suggest that significant faunal and habitat reorganization occurred between the Pliocene and Pleistocene, in part, reflecting the expansion of open woodlands and grasslands. Middle Pleistocene deposits in the Mt Etna region of central eastern Queensland contain extensive fossil assemblages of rainforest-adapted vertebrates dated >500–280 ka. Such faunal assemblages show remarkable long-term stability despite being subjected to numerous glacial-interglacial climatic shifts. However, sometime between 280–205 ka, a major faunal turnover/ extinction event occurred, where the previously dominant rainforest-adapted faunas gave way to xeric-adapted forms. Independent paleoclimatic records suggest that this shift was a result of increased climatic variability and weakened northern monsoons. Late Pleistocene deposits of the Darling Downs, SE Queensland, provide an important temporal extension to the Mt Etna region. Recent studies have demonstrated minimally, a three stage extinction of local megafauna (giant land mammals, birds and lizards). Associated radiometric and optical dating indicates that the progressive loss of megafauna from the region was initiated at least 75 kyr before the continental colonisation of humans. The progressive changes in megafaunal community dynamics were most likely driven by intense climatic changes (i.e., increased aridity) associated with the last glacial cycle. The potential role of humans in the final extinctions (posthuman colonisation) is unclear. However, if humans did

New developments in the Upper Pliocene–Pleistocene stratigraphic units of the Dacian Basin (Eastern Paratethys), Romania

Abstract As a result of multidisciplinary investigations carried out, in the last two decades, the knowledge of the Pliocene and Quaternary stratigraphy from Dacian Basin has increased considerably. New lithostratigraphic units were revealed, for example: Trajkovo Fm (Romanian), Vlǎdeni Fm, Vânǎtori Fm (Pleistocene), and other units have been reassessed: Izvoarele Fm, Tulucesti Fm (Romanian). A new biozonation based on molluscan fauna from the Late Pliocene ( NSM11 , NSM12 ) and Pleistocene ( QM1-QM9 ) deposits made possible a more accurate subdivision and cronostratigraphical assignments and correlations. Many localities with Romanian mammal associations (Lupoaia, Drǎnic, Podari, Tetoiu, Leu etc.) were reviewed, adding new taxa in the faunal list, with implications for accurately establishing host deposit ages. These studies, together with bio-magnetostratigraphic investigations led to revision of the Romanian Stage boundaries and subdivisions (Pelendavian, Valahian) and to outline several new Pleistocene chronostratigraphic units: the Argedavian, Dinogetian, Ilfovian stages and Milcovian, Uzunian, Netindavian, Musaisian substages. Finally, one major achievement consisted in the Pliocene/Pleistocene boundary relocation in the Dacian Basin, in agreement with its new position at ∼2.6 Ma in the Mediterranean realm.

Late Quaternary weathering, erosion, and deposition in Nahal Yael, Israel: An "impact of climatic change on an arid watershed"?

In their seminal paper in 1979, Bull and Schick proposed a conceptual model for the geomorphic response to Pleistocene to Holocene climate change, based on the hyperarid Nahal Yael watershed in the southern Negev Desert. In this model, the change from semiarid late Pleistocene to hyperarid early Holocene climates reduced vegetation cover, increased the yield of sediment from slopes, and accelerated aggradation of terraces and alluvial fans. The model is now over 30 yr old, and during this time, chronologic, paleoenvironmental, and hydrogeomorphic research has advanced. Here, we reevaluate the model using data acquired in Nahal Yael over the 30yr since the original model was proposed. Recent studies indicate that the late Pleistocene climate was hyperarid, and a transition from semiarid to hyperarid climates did not occur. The revised chronology reveals a major 35–20 ka episode of accelerated late Pleistocene sediment production on slopes (with lower rates probably already at ca. 50ka) due to increased frequency of wetting-drying cycles caused by frequent extreme storms and floods between 35 and 27 ka. Without lag time, these sediments were transported and aggraded in depositional landscape components (fluvial terraces and alluvial fans). This intensified sediment production and delivery phase is unrelated to the Pleistocene-Holocene transition. The depositional landforms were rapidly incised between 20 and 18 ka. Since and/or soon after this Last Glacial Maximum (LGM) incision, most material leaving the basin originated from sediments stored in depositional landforms and was not produced from bedrock. Using these new data, we propose a revision to the Bull and Schick model in this hyperarid environment. Our revision suggests that the model should include the frequent storms and floods responsible for a late Pleistocene pulse of intense weathering due to numerous cycles of wetting and drying on slopes and coeval sediment transport to fluvial terraces and alluvial fans. We also discuss the common use and pitfalls of using the Bull and Schick conceptual model to explain observations in diverse arid environments, usually without sufficient data on basin-specific stratigraphic, chronologic, paleoenvironmental, and paleoclimatic information.

The taxonomic status of Lymnaea subscalariformis Suter, 1917 (Mollusca: Pulmonata: Lymnaeidae) (Note)

The definitive shell characteristics of Lymnaea subscalariformis Suter, 1917, described from late Pleistocene deposits in the Upper Awatere Valley, Marlborough, are shown to be erosional artefacts. The species is synonymised with the extant Australasian Lymnaea tomentosa (Pfeiffer, 1855).

LB1 and LB6 Homo floresiensis are not modern human (Homo sapiens) cretins

Excavations in the late Pleistocene deposits at Liang Bua cave, Flores, have uncovered the skeletal remains of several small-bodied and small-brained hominins in association with stone artefacts and the bones of Stegodon. Due to their combination of plesiomorphic, unique and derived traits, they were ascribed to a new species, Homo floresiensis, which, along with Stegodon, appears to have become extinct ∼17 ka (thousand years ago). However, recently it has been argued that several characteristics of H. floresiensis were consistent with dwarfism and evidence of delayed development in modern human (Homo sapiens) myxoedematous endemic (ME) cretins. This research compares the skeletal and dental morphology in H. floresiensis with the clinical and osteological indicators of cretinism, and the traits that have been argued to be associated with ME cretinism in LB1 and LB6. Contrary to published claims, morphological and statistical comparisons did not identify the distinctive skeletal and dental indicators of cretinism in LB1 or LB6 H. floresiensis. Brain mass, skeletal proportions, epiphyseal union, orofacial morphology, dental development, size of the pituitary fossa and development of the paranasal sinuses, vault bone thickness and dimensions of the hands and feet all distinguish H. floresiensis from modern humans with ME cretinism. The research team responsible for the diagnosis of ME cretinism had not examined the original H. floresiensis skeletal materials, and perhaps, as a result, their research confused taphonomic damage with evidence of disease, and thus contained critical errors of fact and interpretation. Behavioural scenarios attempting to explain the presence of cretinous H. sapiens in the Liang Bua Pleistocene deposits, but not unaffected H. sapiens, are both unnecessary and not supported by the available archaeological and geochronological evidence from Flores.

Late Quaternary geology of the Tunka rift basin (Lake Baikal region), Russia

The objective of this research is to obtain a better understanding of the evolution of the Tunka rift basin, part of the Baikal rift zone, and how it relates to the overall geologic history of the region, particular for the Quaternary period. The tectonically active Baikal rift zone began forming over 50million years ago and continues today. In the Tunka basin, during the Oligocene and Middle Pliocene, relatively weak tectonic disturbances took place and thick accumulations of organic-rich sands, silts, and clays were deposited in lacustrine–marshy subtropical environments. Tectonism increased between the Miocene and Pliocene and thick units of coarse alluvium and floodplain sediments were deposited. During the Late Pliocene–Quaternary, tectonism formed basins that are now filled with a variety of coarse clastic materials. Early and Middle Pleistocene sediments are poorly exposed, covered by widespread Late Pleistocene deposits. Three Late Pleistocene sedimentary facies dominate: boulder–pebble gravels (proluvial, glacial fluvial, and alluvial sediments), alluvial sand, and loess-like sediments with associated slope deposits altered by post-depositional wind erosion. The relationship between these complexes, including radiocarbon and other chronological data and fauna and flora remains, indicates that they began forming c. 70000yr ago. Paleosols, glacial deposits and cryogenic material indicate that at times the climate was cool or cold. During the early Late Pleistocene renewed tectonism took place causing increased deposition of coarse sediments. The middle Late Pleistocene deposits consist mostly of sandy, floodplain alluvium. By the end of the Late Pleistocene–Holocene, alluviation was reduced and replaced by a high degree of erosion and aeolian deposition.

Magnetic characterization and paleoclimatic significances of late Pliocene-early Pleistocene sediments at site 882A, northwestern Pacific Ocean

Aeolian dust, a primary terrigenous component of ocean sediments, has been widely used to reconstruct the paleoclimatic evolution because its transported distance, grain size and concentration are sensitive to climate changes. To further characterize the aeolian dust, the deposits at site Ocean Drilling Program (ODP) 882A in northwestern Pacific Ocean are divided into four grain-size fractions ( 64 μm) using the gravitative differentiation method. Detailed rock magnetism results show that magnetite and hematite are dominant magnetic minerals for the dust components. In addition, the aeolian dust ( 64 μm) contributes little to the magnetic enhancement of the sediments at 2.73 Ma. These new results greatly improve our understanding of paleoenvironmental evolution during late Pliocene-early Pleistocene in this area.

Mechanical stratigraphy and (palaeo-) karstification of the Murge area (Apulia, southern Italy)

Abstract The Cretaceous Apulia Platform, exposed in the Murge area (southern Italy), suffered intense (palaeo)karstification. This study focuses on the controlling factors of karstification with emphasis on fracturing. Mechanical stratigraphy was used to calculate the fracture density within different sedimentary sequences. Several mechanical units were defined and a characteristic relationship was found between unit thicknesses and fracture density, that is, fracture density increases if layer thickness decreases. In some of the quarries studied, sedimentary cycles are clearly present that are also reflected in the fracture density logs. The degree of karstification within a mechanical unit is proportional to the mean fracture spacing. Based on fracture orientation data extracted from LIDAR scans, different orientation clusters were observed between fractures that are karstified and fractures that are not karstified, post-dating karstification. The clusters of karstified fractures are related to the compression of the southern Apennines. The fractures became dissolution enlarged during the Pleistocene uplift caused by bulging of the Apulia Platform. This main karstification phase occurred prior to Late-Pleistocene deposition and before the formation of orthogonal fracture sets.

Unravelling the Late Pleistocene habitat of the southernmost woolly mammoths in Europe

The southernmost record of woolly mammoths ( Mammuthus primigenius) in Europe has been found in Late Pleistocene sediments from ‘El Padul’ peat-bog, in the Granada Basin (southern Spain). In this paper we discuss a plausible habitat based on stable isotopic analyses of these specimens, dated ∼40–30 cal ky BP, probably corresponding with the beginning of Heinrich Stadial 4 (HS4) and the end of Heinrich Stadial 3 (HS3). Woolly mammoth remains preserve an accurate isotopic register of past climatic conditions because they needed to ingest large amount of resources daily (water and fresh food), whose isotopic signature, influenced by the environmental conditions, was recorded in their tissues. The δ 18O w values of the past meteoric waters (−5.4‰ to −6.7‰ vs V-SMOW), calculated from the isotopic composition of teeth enamel, suggest moderate temperatures in comparison with those of similar age recovered in central and northern Europe. Due to its geographic position in southern Europe, our samples recorded the highest δ 18O w values of past meteoric waters deduced from mammoth remains in Europe. The difference between these values and those of δ 18O w of current mean annual precipitation are minimal, contrasting with those of higher latitudes during the end of the last glaciation (∼50 to ∼20 cal ky BP). The isotopic values of nitrogen (10.1‰ to 13.2‰ vs AIR) and carbon (−20.7 to −21.8‰ vs V-PDB) of collagen show a dry habitat, which occasionally could have been extreme. Taken as a whole, the isotopic results suggest that the studied specimens lived in a very dry steppic area, with moderately cold conditions, contrasting with the wet environment of ‘El Padul’ peat-bog, and its colder temperatures, due to the influence of glacial conditions of the Sierra Nevada, the highest peninsular mountain range. The described habitat may be sited in a more westerly position than the ‘El Padul’ peat-bog, and it was warmer and drier than those of contemporaneous European woolly mammoths.

Piston-core based biostratigraphic constraints on Pleistocene oscillations of the West Antarctic Ice Sheet in western Ross Sea between North Basin and AND-1B drill site

New diatom-biostratigraphic age data derived from piston core were used to constrain the chronology for a seismic-based interpretation of West Antarctic Ice Sheet (WAIS) advance and retreat from the North Basin outer shelf in western Ross Sea. The data demonstrates that grounded ice occupied the outer shelf on at least ten occasions during the last 2.0 Ma of the Pleistocene. Although the biostratigraphic resolution is low, the constraints permit correlations to coeval section recently drilled in South McMurdo Sound at the AND-1B drill site. Our interpretation of regional-scale correlations suggests that the Pleistocene dynamics of the WAIS involved grounding-line translations in excess of 600 km. However, the data also suggests that only two major advances of grounded ice occurred since ~ 0.71 Ma. In other words, several of the late Pleistocene sediment cycles at AND-1B must represent only minor advance and retreat of grounded ice to and from South McMurdo Sound. The results prove false the long-standing tacit assumption that the WAIS experienced major advances in association with peak glacials and eustatic lowstands during the last 700 ka of the Pleistocene. These results show that piston cores can be used to constrain the timing of pre-Holocene grounding events. These data also highlight the need for regional-scale correlations to distinguish between major versus minor grounding-line translations of grounded ice in the marine setting.

Unexpected finding of a newEquusspecies (Mammalia, Perissodactyla) belonging to a supposedly extinct subgenus in late Pleistocene deposits of Khakassia (Southwestern Siberia)

A new species of Equus, E. (Sussemionus) ovodovi n. sp., was excavated in Proskuriakova Cave (Khakassia, Southwestern Siberia) in deposits carbon dated at 40 000 BP. This slender, middle-sized equid was first considered as related to E. hydruntinus Stehlin & Graziosi, 1935 but biomolecular analyses showed that it actually belonged to a group hitherto unknown of Equus. Indeed, a more detailed study of the fossils evidenced features characteristic of the subgenus Sussemionus Eisenmann, 2010, common during the middle Pleistocene but supposed extinct after. The current article describes this new species.

Preservation potential of ancient plankton DNA in Pleistocene marine sediments

Recent studies have shown that ancient plankton DNA can be recovered from Holocene lacustrine and marine sediments, including from species that do not leave diagnostic microscopic fossils in the sediment record. Therefore, the analysis of this so-called fossil plankton DNA is a promising approach for refining paleoecological and paleoenvironmental information. However, further studies are needed to reveal whether DNA of past plankton is preserved beyond the Holocene. Here, we identified past eukaryotic plankton members based on 18S rRNA gene profiling in eastern Mediterranean Holocene and Pleistocene sapropels S1 (~9 ka), S3 (~80 ka), S4 (~105 ka), and S5 (~125 ka). The majority of preserved ~400- to 500-bp-long 18S rDNA fragments of microalgae that were studied in detail (i.e. from haptophyte algae and dinoflagellates) were found in the youngest sapropel S1, whereas their specific lipid biomarkers (long-chain alkenones and dinosterol) were also abundant in sediments deposited between 80 and 124 ka BP. The late-Pleistocene sediments mainly contained eukaryotic DNA of marine fungi and from terrestrial plants, which could have been introduced via the river Nile at the time of deposition and preserved in pollen grains. A parallel analysis of Branched and Isoprenoid Tetraethers (i.e. BIT index) showed that most of the organic matter in the eastern Mediterranean sediment record was of marine (e.g. pelagic) origin. Therefore, the predominance of terrestrial plant DNA over plankton DNA in older sapropels suggests a preferential degradation of marine plankton DNA.

Paleomagnetic record in the Late Pleistocene loess-soil deposits of the Pekla section in the time interval 425–50 Ka

The composition, granulometry data, and concentration of grains that carry the natural remanent magnetization (NRM) are studied in the bottom 6.5 meters of the loess-soil deposits of the Pekla section (Azov coast, Krasnodar region). It was shown that these strata, which correspond to the 9th–11th marine oxygen isotope stages (MIS) and cover the time interval ∼425–300 ka, are suitable for further paleomagnetic investigation. The deposits in the upper portion of the Inzhavino paleosoils (Likhvin Interstadial) contain the records of anomalous deviations of the direction of magnetization from the dipole field at the sampling site. The studied interval was sampled by taking two hand blocks from four sampling levels, which minimizes the errors due to the specimen cutting. This anomaly dated ∼300 ka possibly corresponds to the Biva-II geomagnetic excursion. However, the studies of implications of anisotropy in magnetic susceptibility (AMS) for the direction of natural remanent magnetization (NMR) have shown that parts of the samples from the Inzhavino paleosoils and the underlying loess horizon are magnetically anisotropic, which is characteristic for biogenic magnetite grains, while other parts of the samples exhibit plane anisotropy typical for natural sedimentary structures. A weak correlation between the time series of averaged curves of relative paleointensity, NRM20/ARM20 (and NRM20/K) for the loess horizons of the Pekla section and the global composite reference curve of relative paleointensity, Sint-800, in the time intervals 200–130 ka and 370–320 ka indicates that the paleomagnetic records have been imprinted not only on the detritic magnetic grains but also on the grains produced by chemical reactions and the life processes of bacteria.

Horns of the woolly rhinoceros Coelodonta antiquitatis (Blumenbach, 1799) in the Ice Age Museum collection (Moscow, Russia)

The Ice Age Museum (Moscow, Russia) houses the most representative collection of woolly rhinoceros horns in the world. It consists in about 30 complete and fragmentary specimens from the Late Pleistocene deposits of Northern Yakutia and Chukotka. This collection includes five complete sets of nasal and frontal horns of the same individual (two sets with their own proper skull); series of horns of different individual age: from juvenile to old; horns of specific structure; a series of horns of a different stage of preservation from a relatively good one to a rather poor one, displaying various stages of organic matter decay. The most interesting specimens from this collection are described in brief. The horn collection of Ice Age Museum has important significance for the understanding of the woolly rhinoceros adaptive biology and ecology in the Ice Age period.

Bos primigenius Bojanus, 1827 from the Early Late Pleistocene Deposit of Avetrana (Southern Italy) and the Variation in Size of the Species in Southern Europe: Preliminary Report

Very abundant remains of Bos primigenius have been recovered in the early Late Pleistocene site of Avetrana (southern Italy). The site is characterized by a karst filling originated from a series of almost coeval depositional events. This discovery represents a rare record in the early Late Pleistocene of southern Europe. Biometrical analysis of the metapodial bones of aurochs from Avetrana gave the cue to examine the evolutive trend of the species in southern Europe, from the Middle Pleistocene to Holocene. This trend is characterized by an increase in size of the metapodial bones from Middle Pleistocene to early Late Pleistocene and to a decrease in size of the same during the late Late Pleistocene and Holocene. Also, the variations in size are competed by change in shape of the metapodial bones. These variations seem to be related with climatic fluctuations and competitions with Homo and Bison. At least, five evolutive stages are recognized; they constitute an important tool for the biochronological correlations among the Pleistocene sites of southern Europe.

New stratigraphic and structural evidence for Late Pleistocene surface faulting along the Monte Olimpino Backthrust (Lombardia, N Italy).

We summarize some preliminary results achieved during the investigations conducted for the CARG Project, geological sheet n. 75 Como, i.e. the analysis of the Quaternary evolution of the Monte Olimpino Backthrust and the evaluation of its seismogenic activity. Cross-border field mapping between Ticino (CH) and Lombardia (IT) resulted in the finding of new outcrops (Borgo Vico site, in the north-western sector of the urban area of Como) located along the front of the Monte Olimpino Backthrust, that allowed to recognize evidence for Late Pleistocene reverse surface faulting along this structure.At Borgo Vico, a clastic Tertiary unit, the Villa Olmo Conglomerate, intercalated in the Chiasso Fm. of Early Oligocene age, is thrust over a Late Pleistocene fluvioglacial and glacio-lacustrine sequence (Comerci et alii, 2007).Until now, the Monte Olimpino Backthrust was supposed by most authors to have been active until Tortonian times. Sileo et alii (2007) inferred a Pliocene activity and proposed, based on geomorphic evidence, that fault displacement was still taking place during Pleistocene. However, this is the first time that Pleistocene activity along the Monte Olimpino Backthrust has been documented by unequivocal tectonic offset of late Pleistocene deposits. Paleoseismological analyses are in progress in order to distinguish potential coseismic movement from fault creep during the observed recent displacement.

A reappraisal of the dwarfed mammoth Mammuthus lamarmorai ( ) from Gonnesa (south-western Sardinia, Italy)

The Gonnesa Quaternary deposits have been cited since the end of the 19th century due to the discovery, during the construction of a railway, of an incomplete postcranial skeleton belonging to an endemic dwarfed elephant, afterward described by Major as a new species (“Elephas lamarmorae”Major, 1883). Although the remains have since been reported in the literature as coming from the aeolian deposits outcropping at Funtana Morimenta, the precise provenance of the findings and their chronostratigraphical setting remained uncertain. Taking into account the route of the now disused railway, the stratigraphical successions of the Morimenta area, and the fact that the elephant bones were actually collected during a number of excavations spanning several decades, the location of the fossiliferous site is most likely on the northeast end slope of Guardia Pisano hill (Gonnesa), where aeolianites correlate with the Funtana Morimenta Formation (FMF) outcrop. The FMF is supposed to predate the onset of the MIS 5e climatic event and the Tyrrhenian “Panchina” overlies equivalent deposits cropping out along the Gonnesa Gulf coast. Therefore, the hypothesis that the elephant remains found in the “Morimenta” area were retrieved from late Middle Pleistocene deposits cannot be ruled out. The anatomical features of the bones suggest they represent a single individual, perhaps partially exposed and damaged before the discovery. New evidence, including a thus far unpublished tusk fragment from the Guardia Pisano hill (Gonnesa), whose Schreger angles fall within the range of Mammuthus, supports the systematic attribution of the incomplete Morimenta skeleton to a dwarfed mammoth. The size reduction of this Sardinian dwarfed mammoth is discussed in light of body-mass changes undergone by insular endemic elephants.

Late Quaternary (24–10 ka BP) environmental history of the Neotropical lowlands inferred from ostracodes in sediments of Lago Petén Itzá, Guatemala

We inferred late Pleistocene and early Holocene (24–10 ka BP) environmental conditions in and around Lago Peten Itza, Guatemala from ostracode remains in the lake sediments. Multivariate statistics were run on autecological information for 29 extant ostracode species collected in 63 aquatic ecosystems on the Yucatan Peninsula along a steep, increasing NW–S precipitation gradient and across a large altitudinal range. Conductivity and water depth are the most important factors that shape ostracode communities. Transfer functions were developed and applied to fossil ostracode assemblages in a ~76-m sediment core (PI-6, ~85 ka) taken in 71 m of water from Lago Peten Itza, to infer past shifts in conductivity and water level. Results suggest climate was cold and wet during the Last Glacial Maximum (LGM). Alternating dry and wet conditions characterized the deglacial. Early Holocene climate was warmer and wetter. The LGM was characterized by low ostracode species richness (4 spp.) and abundance (<940 valves g−1), dominance of benthic over nektobenthic taxa, abundant Physocypria globula, conductivity as low as 190 µS cm−1, and clay-rich sediments with relatively high total organic carbon and low C/N ratios (<14), suggesting relatively deeper water at the core site associated with abundant precipitation. Greatest water depth at the core site during the LGM occurred late in the period and was ~50 m. The deglacial was characterized by drier conditions, higher ostracode species richness (6 spp.) and abundances up to 18,115 valves g−1, dominance of nektobenthic species, and presence of shallow-water and littoral-zone indicators such as Heterocypris punctata and Strandesia intrepida, conductivity up to 550 µS cm−1, C/N ratios as high as 37, and gypsum deposition. Lowest inferred lake depth at the core site during the deglacial was ~20 m. The early Holocene was characterized by high numbers of ostracode remains, up to 25,500 valves g−1, and the presence of L. opesta and P. globula. Cytheridella ilosvayi was absent from late Pleistocene sediments, suggesting it colonized northern Central America during the Holocene.

The dating and interpretation of a Mode 1 site in the Luangwa Valley, Zambia

Flake based assemblages (Mode 1) comprise the earliest stone technologies known, with well-dated Oldowan sites occurring in eastern Africa between ∼ 2.6-1.7 Ma, and in less securely dated contexts in central, southern and northern Africa. Our understanding of the spread and local development of this technology outside East Africa remains hampered by the lack of reliable numerical dating techniques applicable to non-volcanic deposits. This study applied the still relatively new technique of cosmogenic nuclide burial dating ( 10Be/ 26Al) to calculate burial ages for fluvial gravels containing Mode 1 artefacts in the Luangwa Valley, Zambia. The Manzi River, a tributary of the Luangwa River, has exposed a 4.7 m deep section of fluvial sands with discontinuous but stratified gravel layers bearing Mode 1, possibly Oldowan, artefacts in the basal layers. An unconformity divides the Manzi section, separating Mode 1 deposits from overlying gravels containing Mode 3 (Middle Stone Age) artefacts. No diagnostic Mode 2 (Acheulean) artefacts were found. Cosmogenic nuclide burial dating was attempted for the basal gravels as well as exposure ages for the upper Mode 3 gravels, but was unsuccessful. The complex depositional history of the site prevented the calculation of reliable age models. A relative chronology for the full Manzi sequence was constructed, however, from the magnetostratigraphy of the deposit (N>R>N sequence). Isothermal thermoluminescence (ITL) dating of the upper Mode 3 layers also provided consistent results (∼78 ka). A coarse but chronologically coherent sequence now exists for the Manzi section with the unconformity separating probable mid- or early Pleistocene deposits below from late Pleistocene deposits above. The results suggest Mode 1 technology in the Luangwa Valley may post-date the Oldowan in eastern and southern Africa. The dating programme has contributed to a clearer understanding of the geomorphological processes that have shaped the valley and structured its archaeological record.