The contribution of Rob Westaway to the study of fluvial archives

Robert Westaway was a structural and hard-rock geologist who turned his attention to the study of Late Cenozoic fluvial archives, believing that the preservation of staircases of river terraces, particularly representing the Middle and Late Pleistocene, could only be explained in terms of crustal activity in response to surface processes, the latter affected by climatic change. His entry into this research area coincided with the realisation that such terrace sequences required surface or crustal uplift to have taken place over the time interval represented. Workers were unable to explain the observed amounts of uplift in terms of erosional isostasy, a process that could potentially have explained such one-way crustal movement. Westaway envisaged a mechanism by which mobile lower crust migrated to beneath uplifting areas, maintaining and reinforcing their uplift. The mechanism requires complex mathematics to explain it, as well as lending itself to mathematical modelling of the process, based on varying crustal properties and changes in the rates of surface processes in response to climatic fluctuation. Essentially the lower-crustal effect can be envisaged as a positive-feedback enhancement of erosional isostasy.It became apparent that Westaway's theories could explain geomorphological and sedimentary fluvial archives that were otherwise difficult to elucidate. Mantle-based erosional isostasy could not explain terrace staircases, for example. Many of these occur in regions that are tectonically inactive, and so cannot be attributed to neotectonic activity. A game-changer in terms of persuading the wider community came from the recognition of crustally ultrastable regions in which progressive long-timescale uplift has not occurred: Archaean cratons. Westaway's envisaged lower-crustal flow would not be expected in such regions, which have cold, brittle and immobile crust to its full depth. Ancient fluvial deposits are found close to modern valley-floor levels in such areas. Regions of younger Precambrian crust (Proterozoic) showing intermediate situations were subsequently identified. Other dilemmas could be resolved, such as the ‘back-tilting’ of the early-Middle Pleistocene Bytham River in the English Midlands, caused by its drainage crossing crustal blocks with different properties that have accordingly experienced differential uplift. Although glacio-isostasy, mostly seen in the effects of rebound since the Last Glacial Maximum (LGM), is largely accommodated in the mantle, and thus is reversed as a response to glacial loading and unloading, in areas of suitable crustal type there is evidently a small lower-crustal component that is less readily reversible.Westaway's important contribution has yet to be fully integrated into received wisdom in geomorphological and Quaternary circles, although much of it is now widely accepted and more will be explored and published in due course

A long Quaternary terrace sequence in the Orontes River Valley, Syria: a record of uplift and of human occupation

Mapping in the Homs region of Syria has revealed a hitherto unrecognized staircase of at least 12 gravel terraces of the upper Orontes River. The terrace gravels overlie Pliocene lacustrine marl and have been calcareously cemented into conglomerates, sometimes interbedded with cemented fine-grained alluvium. A tentative dating scheme, based on modelling the regional-scale surface uplift that has driven fluvial incision of ~ 400 m since the latest Miocene, and incorporating correlation with the dated terraces in the valley of the middle Orontes using height above the river, envisages terrace formation spanning at least the last 1.2 Ma

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

Quaternary rivers, tufas and mires of southern England: description of Geological Conservation Review sites

Southern England contains a wealth of sites, reviewed here, that contain evidence for past deposition in freshwater environments over a period of over 0.5 million years and have been designated as Geological Conservation Review sites for their representativeness of a range of such environments. They include nine sites from two complete terrace sequences (the Solent in Hampshire [Solent Cliffs West, Calshot Cliffs, Hillhead Cliffs, Dunbridge Pit, Wood Green Gravel Pit] and Stour in Kent [Fordwich Pit, Sturry Gravel Pits, Wear Farm Pit, Chislet, Bishopstone to Reculver Cliffs]), alongside a further fluvial gravel site at Aylesford, in the valley of the Medway in Kent. Sites from the Thames catchment, although geographically nearby, are not included, having been previously described by Bridgland (1994). Many of these sites contain abundant Palaeolithic artefacts and some also fossils of multiple groups. A further four sites record fluvial landforms (Mole Gap, Surrey) and ancient ‘high-level gravels’ that may relate to very Early Pleistocene river activity (Upper Common, Mountain Wood, Upper Hale). Tufa and mire sites are relatively rare in this region, making those which are preserved more significant. The tufa sites at Blashenwell Farm and Wateringbury provide context for adjacent archaeological sites and record landscape development in the early and mid Holocene. The mire deposits at Cranes Moor, Mark Ash Wood, Cothill Fen and Rimsmoor together record vegetation history from key regional ecosystems for the entirety of the Holocene

The record from British Quaternary river systems within the context of global fluvial archives.

Data amassed in the past decade on Quaternary fluvial archives has allowed comparison across widely separated regions of the world. Meanwhile there has been a new impetus for research on British sequences, as a result particularly of the Aggregates Levy Sustainability Fund (ALSF). In this context, the key British records (from the Thames, Severn–Avon, Trent, Wash system and Solent) are described briefly, with emphasis on the latest information. In the case of the Trent, sedimentary evidence, discovered during ALSF-funded work, appears to confirm the existence of a Middle Pleistocene ‘Trent–Ancaster’ River. In the case of the Solent, independent projects that sought to improve the age constraint for the sequence have produced complementary results; the first used luminescence dating, whereas the second made use of Palaeolithic evidence to calibrate numerical incision/uplift modelling. The overarching message is that the British fluvial archive can be readily understood within a global context; it typifies records from areas with relatively young crust that has been uplifting during the Quaternary and, being in the temperate latitudes and close to the Atlantic margin, it reflects strong climatic forcing. The combination of rich faunal and Palaeolithic artefact contents means that certain British records are of international significance