Mammalian biostratigraphy of the later Middle Pleistocene in Britain

This study explores and develops the potential of fossil mammals to differentiate between the various climatic episodes of the post-Anglian Middle Pleistocene in Britain. Mammalian fossils are particularly valuable as biostratigraphic indicators on account of their morphological evolution and rapid turnover, through origination and extinction of species. Furthermore, the large-scale climatic fluctuations that affected north-west Europe during the Quaternary produced major shifts in the geographical distributions of many species, resulting in discernible patterns of presence and absence in the fossil record of a particular region. The development of a globally-applicable climatostratigraphic framework, based on the oxygen isotope record from deep-ocean sediments, has provided a new and challenging scheme for the interpretation of the British Quaternary record. Long fluvial sequences in Britain have been related to this record with considerable success, thereby providing a detailed archive of climatic change through the Pleistocene. The Thames valley was selected as a framework for the relative dating of the various climatic fluctuations, since it has been claimed to have the most reliably-dated long terrestrial sequence in the later Middle Pleistocene. The Thames model was therefore adopted as a testable hypothesis against which the mammalian evidence could be compared. The findings of this study confirm the presence of four complete climatic cycles between the Anglian and the Holocene, each with its own distinctive mammalian suite. In addition, it has been possible to identify subdivisions within these temperate stages, probably representing smaller-scale climatic fluctuations within an interglacial, and perhaps corresponding to isotopic substages. It has been possible to resolve a longstanding controversy concerning the age of the British type Hoxnian Interglacial. Amino acid geochronology had suggested that sediments at Hoxne belonged to a later interglacial than deposits from the first post-Anglian temperate episode in the Thames valley, such as Swanscombe. The results of the present study reveal close similarity between the mammalian fauna from Hoxne and that from Swanscombe, suggesting that there was indeed a single Hoxnian Interglacial, and that it directly post-dated the Anglian (i.e. Stage 11). Sediments of this age can be distinguished from those attributable to two other late Middle Pleistocene interglacials, all of them distinct from and older than, the Ipswichian. It has been suggested that distinctive mammalian assemblages can be identified from interglacials equivalent to oxygen isotope stages 9 and 7; moreover, it is apparent that the assemblages from warm Substages 7c and 7a differed from one another in species composition. Certain useful characters have also been determined, which can permit useful separation of some of the late Middle Pleistocene cold episodes, although in comparison with the interglacials, the evidence from these is scanty. The present study has provided a new biostratigraphic framework that may be both tested and refined as new sites become available in Britain, and also compared with the evidence from continental north-west Europe

Fossils from Quaternary fluvial archives : sources of biostratigraphical, biogeographical and palaeoclimatic evidence.

Fluvial sedimentary archives have the potential to preserve a wide variety of palaeontological evidence, ranging from robust bones and teeth found in coarse gravel aggradations to delicate insect remains and plant macrofossils from fine-grained deposits. Over the last decade, advances in Quaternary biostratigraphy based on vertebrate and invertebrate fossils (primarily mammals and molluscs) have been made in many parts of the world, resulting in improved relative chronologies for fluviatile sequences. Complementary fossil groups, such as insects, ostracods and plant macrofossils, are also increasingly used in multi-proxy palaeoclimatic and palaeoenvironmental reconstructions, allowing direct comparison of the climates and environments that prevailed at different times across widely separated regions. This paper reviews these topics on a regional basis, with an emphasis on the latest published information, and represents an update to the 2007 review compiled by the FLAG-inspired IGCP 449 biostratigraphy subgroup. Disparities in the level of detail available for different regions can largely be attributed to varying potential for preservation of fossil material, which is especially poor in areas of non-calcareous bedrock, but to some extent also reflect research priorities in different parts of the world. Recognition of the value of biostratigraphical and palaeoclimatic frameworks, which have been refined over many decades in the 'core regions' for such research (particularly for the late Middle and Late Pleistocene of NW Europe), has focussed attention on the need to accumulate similar palaeontological datasets in areas lacking such long research histories. Although the emerging datasets from these understudied regions currently allow only tentative conclusions to be drawn, they represent an important stage in the development of independent biostratigraphical and palaeoenvironmental schemes, which can then be compared and contrasted

A Levallois Knapping Site at West Thurrock, Lower Thames, UK: its Quaternary Context, Environment and Age

Levallois knapping debris is present beneath the sides of a disused tramway cutting connected to Lion Pit, West Thurrock, Essex. This occurrence, first recorded during the early 20th century, is in the basal gravel of the Taplow/Mucking Formation, which dates from the end of Marine Oxygen Isotope Stage (MIS) 8. The relatively undisturbed nature of this knapping debris is confirmed by the incidence of refitting material, although finer debitage is absent, presumably winnowed out. The Levallois character of the assemblage is demonstrated by the occurrence of characteristic ‘tortoise’ cores and flakes with faceted striking platforms. The artefact-bearing gravel is overlain by &gt;10 m of predominantly fine-grained sediments, including fossiliferous sands and massive clayey silt, as well as laminated silts, clays, and sands of possible estuarine origin. These are attributed to deposition under temperate conditions during MIS 7. To the south, a younger fluvial gravel, attributed to MIS 6, has been incised into the interglacial sequence. The top of the estuarine sequence has been affected by pedogenesis, both before and after its burial by an unbedded solifluction gravel.</jats:p

Correlation of English and German Middle Pleistocene fluvial sequences based on mammalian biostratigraphy

AbstractIn this paper interglacial mammalian assemblages from key Middle Pleistocene fluvial sites in Germany are compared to Mammal Assemblage-Zones (MAZs) recently established in the post-Anglian/Elsterian sequence of the Lower Thames, U.K. It is believed that four separate interglacials are represented by the Lower Thames MAZs, correlated with oxygen isotope stages (OIS) 11, 9, 7 and substage 5e (although the last of these is Late Pleistocene). Nowhere in Germany can a full sequence of these interglacials be identified from mammalian evidence in a single terrace staircase, as is the case in the Lower Thames, although further research on the Wipper terraces at Bilzingsleben may identify such a sequence. It is also possible that the sequence of overlapping fluvial channels in the lignite mine at Schöningen will eventually produce a comparable mammalian story. Excellent correspondence has been recognized between the mammalian assemblages at Steinheim an der Murr and Bilzingsleben II and the Swanscombe MAZ from the Thames. These three sites are attributed to the Hoxnian/Holsteinian interglacial and are thought to correlate with OIS 11. Close comparison can also be made between the mammalian sequence from the celebrated travertine locality at Weimar-Ehringsdorf and two separate MAZs from Aveley, in the Thames, attributed to separate substages of OIS 7. An equivalent to the Purfleet MAZ of the Thames, which is believed to correlate with OIS 9, has yet to be identified in Germany.</jats:p

VERTEBRATE RECORDS | Late Pleistocene Megafaunal Extinctions

During and after the last glaciation (i.e., during the last 100. 000 years), many large-bodied vertebrate species (the so-called Pleistocene megafauna) died out. This megafaunal extinction reduced by more than half the number of large-bodied mammals in the world, including large herbivores, predators, and scavengers. Australia lost 86% of its Pleistocene megafauna, mostly between 50. 000 and 40. 000 years ago, about the time that people arrived there. South America lost 80% of its megafauna, mostly during the Late Glacial interval. North America lost 73% of its megafauna, also during the Late Glacial interval. The timing of New World human habitation is controversial, but the most widely accepted view is that most of the New World megafaunal extinctions took place just as people arrived in the Americas.The principal two opposing views concerning the cause of these extinctions are that (1) human predation was the most important element in the megafaunal demise, or that (2) environmental change was responsible for these extinctions. We suggest a third possibility, that environmental change (especially in the New World) had diminished megafaunal populations during the Late Glacial, and that human predation may have delivered the coup de grâce that precipitated the extinctions.</p

Implications of new Quaternary uplift models for correlation between the Middle and Upper Thames terrace sequences, UK.

Modelling of uplift histories in the Upper and Middle Thames valleys has revealed an important difference, in the form of additional early post-Anglian uplift in the Middle Thames, attributed to an Anglian (~440 ka) glacio-isostatic effect. Terraces in the Upper Thames around Oxford seem unaffected by glacio-isostasy and their heights show regional uplift of ~35–40 m since the Anglian. The result of the glacio-isostasy is that Anglian terraces are significantly higher above the valley floor in the Middle Thames (up to 55 m) than in the Upper Thames. Recognition of this displacement of Middle Thames terraces has solved long-standing problems of correlation between this area and the Upper Thames: the pre-Anglian (Cromerian Complex) age of the Sugworth Channel deposits, indicated by biostratigraphy, is no longer a difficulty, whereas the Hanborough Terrace is now thought to be of Anglian age, albeit incorporating pre-Anglian faunal remains and perhaps with a significant early post-Anglian component. These findings have implications for the understanding of the effects of Middle Pleistocene glacio-isostasy and of landscape evolution on the periphery of glaciated regions