Middle Pleistocene Interglacials Research Articles

Late Middle Pleistocene pollen biostratigraphy in Britain: pitfalls and possibilities in the separation of interglacial sequences

Recent work on late Middle Pleistocene interglacials in Britain has shown that sites formerly attributed to the Hoxnian include representatives of two different interglacials, which have been correlated with Oxygen Isotope Stages 11 and 9. Palynology has long been used to characterize and correlate temperate sequences in Britain. However, the quality of the palynological record is considerably better in lacustrine sequences than in fluvial and estuarine sediments; the former have longer sequences and higher resolution, whereas more rapid deposition in fluvial and estuarine environments leads to sequences representing only fragments of interglacials. The latter type of site, however, is more likely to have multi-proxy evidence and to be readily fitted into a stratigraphical framework. The problems are reviewed in the light of new work in the West Midlands, where some of the most complete British late Middle Pleistocene lacustrine sequences are preserved. Lacustrine sites here have a strong affinity with ‘Hoxnian’ sites of the ‘type’ area in East Anglia. A critical question remains as to whether the two interglacials conflated under the term Hoxnian can be separately characterized in terms of their pollen assemblages. Details of lacustrine sequences in the North Birmingham area and East Anglia show remarkable similarities, perhaps suggesting that the same interglacial is recorded in all of them. As many of these sites are thought to be kettle holes or glacially overdeepened basins, the first interglacial following the Anglian glaciation is the most likely to be represented, suggesting that all the lacustrine ‘Hoxnian’ sites might date from OIS 11. In areas not glaciated since the Anglian, interglacials after OIS 11 are likely to be represented only by fragmentary, non-lacustrine sequences, difficult if not impossible to separate using palynology alone.

Differentiation of the British late Middle Pleistocene interglacials: the evidence from mammalian biostratigraphy

Acknowledgement of the climatic complexities of the marine oxygen isotope (δ 18O) record has inspired fresh investigations into methods of identifying and separating interglacial deposits on land. Biostratigraphical analysis of fossil mammalian assemblages, particularly those from long fluvial sequences, has proved to be a uniquely valuable technique in the differentiation of the various temperate episodes of the late Middle Pleistocene in Britain, thereby enabling a sequence of diagnostic mammalian assemblage-zones to be established. The scheme has provided an important means of correlation between geographically-distant localities and between different types of depositional environment. Using mammalian biostratigraphical information, this paper explores the evidence for three post-Anglian interglacials prior to the Last (Ipswichian) Interglacial, correlated with Stages 11, 9 and 7 of the oxygen isotope record, and presents the case for the recognition of much smaller-scale environmental and climatic oscillations within these interglacials, possibly corresponding to marine isotopic substages.

Pleistocene climate change, natural environments and palaeolithic occupation of the Altai area, west-central Siberia

Diversity of the relief and the Pleistocene environments of the mountain areas of SW Siberia played a major role in the history of the palaeolithic peopling of this territory. The geographical and contextual distribution of the cultural records reflects a climatic instability in the Altai area. Palaeoenvironmental proxy data indicate that the natural conditions during the earlier stages were generally more favourable for early human occupation than during the later stages. The cyclic nature of the glacial and interglacial periods led to periodic landscape transformations and generation of specific ecosystems adjusted to particular topographic settings and responding to climatic variations. The initial occupation of the broader Altai region associated with “pebble-tool” industries from alluvial formations likely occurred during some of the Middle Pleistocene interglacials accompanying the northern expansion of the temperate zone and biota. Mixed coniferous and broadleaf forests established in the tectonically active mountain zone with elevations of 1500–2000 m and parklands in the adjacent plains and continental basins provided a wide range of occupation habitats. There is limited evidence for persistence of Early Palaeolithic inhabitation during glacial stages due to inhospitable periglacial conditions. The last interglacial warming, indicated by re-colonization of southern Siberia by coniferous taiga forests, is linked with the appearance of the Mousterian tradition. Changes in the relief configuration influenced the local climate regime and opened new habitats for the Middle Palaeolithic population concentrated in the transitional zones of 500–1000 m elevation in the karstic area of the NW Altai foothills. Occupation of the central and southern Altai during the early last glacial was impeded by harsh, ice-marginal environments and expansion of glaciers in the valleys filled by large proglacial lakes. Progressive warming during the early mid-last glacial interstadial stage (59–35 ka BP) caused wasting of the ice fields accompanied by cataclysmic releases of ice-dammed lakes and large-scale erosional processes. Periodic outbursts of the glacial basins had a dramatic impact on the regional ecosystems, also obliterating the earlier cultural records. Appearance of the transitional early Late Palaeolithic stone industries reflects adaptation to mosaic interstadial habitats, including sub-alpine forest, dark coniferous forest, mixed parklands and open steppe. The identical geographical distribution of the Middle and Late Palaeolithic sites and the time-transgressive lithic technologies suggest a regional cultural (and biological?) continuity in the broader Altai area during the Late Pleistocene. Re-establishment of cold tundra–steppe and tundra–forest habitats correlates with the Late Palaeolithic horizon with developed stone industries dominated by blade-flaking techniques. These techniques possibly survived in more protected locations characterized by warm microclimates in the northern Altai throughout the last glacial maximum (20–18 ka BP). Emergence of the microlithic assemblages with wedge-shape cores is linked with a new cultural adjustment in the final stage of the Palaeolithic development responding to transformations of the former periglacial ecosystems towards the end of the Pleistocene.

Application of palynology in the stratigraphy of quaternary deposits of the U.S.S.R.

The analysis of the data on Pleistocene and Upper Pliocene forest floras in the territory of the U.S.S.R. showed that they can be subdivided into three successive age groups on the basis of the same criterion, the generic composition of geographical groups of dendroflora. Group I is characterized by the presence of American-East Asian and American-Mediterranean-Asian genera: prenemoral flora with similar composition throughout the continent. Group II is characterized by the presence of the only group of genera which is absent in the modern flora of the region: protonemoral flora in Europe and the Far East with American-Mediterranean-Asian genera and quaiboreal in Siberia and Kamchatka with American-Euro-Asian genera. Group III is characterized by the total absence of the genera which are not represented in the modern local flora: nemoral in Europe and the Far East and boreal in Siberia and Kamchatka. The stratigraphic position of the prenemoral flora corresponds to the Lower Pleistocene and the Upper Pliocene. Paleomagnetic evidence of the Ural and Middle Asia indicates that the prenemoral flora existed during the Matuyama epoch. The protonemoral flora in Europe and the Far East corresponds to the Middle Pleistocene interglacials. Nemoral and boreal floras correspond to the Upper Pleistocene and Holocene. Paleomagnetic data on the Kama region, Middle Asia and the Far East indicate that floras of groups II and III existed during the Brunhes epoch. For more detailed subdivision of the deposits other criteria should be used.

Quaternary landscape development of the Rio Magdalena basin between Neiva and Bogotá (Colombia): A reconstruction based on evidence derived from paleosols and slope deposits

The Quaternary landscape development of part of the middle Magdalena basin is reconstructed from evidence provided by paleosols and slope deposits preserved on glacis surfaces. The paleosols were formed during stable periods with tropical conditions which we have correlated with the Interglacials. The slope deposits were mainly formed during unstable periods with alternating very dry and very wet conditions which we have correlated with the Glacials. If these correlations are correct, it appears that, with the progress of the Quaternary, the (seasonal) variability of the Glacial climates became less pronounced and that of the Interglacial/Postglacial climates more pronounced, leading to a gradually diminishing amplitude of the Quaternary climatic fluctuations. The glacis were formed during periods of pronounced landscape instability (Phase 1, possibly Early or Middle Pleistocene Glacials). Next came a period of landscape stability which left a ferric hydromorphic soil formed in a humid climate (Phase 2, possibly Middle Pleistocene Interglacial(s)). This was followed by an unstable period during which the surfaces of the glacis were somewhat enlarged and covered by coarse slope deposits (Phase 3, presumably penultimate Glacial). After this, part of the area was raised by tectonic movements, streams incised into the glacis surfaces, and stream terraces were formed (Phase 4). During a stable period, plinthic hydromorphic soils and red ferrallitic soils were formed which show the effect of dry seasons (Phase 5, presumably last Interglacial). They were covered with slope deposits formed from shallow mass movements and soil erosion (Phase 6, presumably last Glacial). The sedimentation of volcanic materials began in this period and continued into the first part of the Holocene (Phase 7). Also continuing into the Holocene were (soil) erosion and the deposition of colluvium (Phase 8). During the Holocene, loss of clay due to alternating dry and wet conditions became a more important aspect of soil formation (Phase 9).