The British Pleistocene fluvial archive: East Midlands drainage evolution and human occupation in the context of the British and NW European record

This paper reviews the Pleistocene evolution and human occupation of the River Trent, the major fluvial artery draining Midland Britain, and places it within a modern Quaternary context. In contrast to the sedimentary records of the River Thames and the erstwhile Bytham system, which extend back to the early Pleistocene, present knowledge of the terrace sequence of the Trent, its tributary systems and associated ancestral courses extends back only to the Anglian glaciation (Marine Isotope Stage (MIS) 12), although the regional pre-Anglian drainage configuration is demonstrably complex. The post-Anglian sequence is well developed, with major terrace sand and gravel aggradations associated with each subsequent cold stage. Temperate-climate sediments correlating with MIS 7 and 5e have been recorded, although deposits relating to earlier interglacials during MIS 11 and 9 have yet to be identified. Evidence for human occupation in the form of Lower and Middle Palaeolithic artefacts has been recorded from terrace sediments correlated with MIS 8 and MIS 4, but the majority of this material is heavily rolled and abraded, suggesting significant reworking from older deposits. This review demonstrates that there is a rich palaeo-environmental record from the Trent but the lack of a high-resolution chronostratgraphic framework raises issues about correlation with other systems.     

Resolving the Holocene alluvial record in southeastern Australia using luminescence and radiocarbon techniques

A previous assessment of radiocarbon (¹⁴C) dates from alluvial units in southeastern Australia revealed a gap in the geochronological record that coincides with the Holocene climatic optimum. This gap in the alluvial record can be further refined using optically stimulated luminescence (OSL). The chronology of Holocene river terraces on Widden Brook, a sandy alluvial stream in southeastern Australia, was established using ¹⁴C and OSL techniques. Combined use of these independent techniques allows for a more rigorous assessment of the alluvial record. The robust chronology, consisting of 38 ¹⁴C and 11 OSL samples, permitted identification of significant depositional variation within the catchment, resulting from localised geomorphic processes. The three terrace sequences identified yielded distinct chronologies, suggesting alluvial deposition at different times. The sequences exhibited a continuous chronology, which indicated continuous deposition throughout the Holocene. The chronology of terrace sequences within this catchment suggests that terrace formation can be attributed to localised geomorphic processes rather than climatic forcing. Copyright © 2010 John Wiley & Sons, Ltd.     

The Holme Pierrepont sand and gravel and the timing of Middle and Late Devensian floodplain aggradation in the English Midlands

This paper provides the first detailed, multi-proxy environmental record for the character of Lateglacial conditions in the lowest Pleistocene terrace of the main valley floor of the River Trent at Holme Pierrepont near Nottingham. The analysis of pollen, plant, insect and mollusc remains preserved within organic channels near the base of the terrace, named the Holme Pierrepont Sand and Gravel by the British Geological Survey (historically known as the Floodplain Terrace), provided evidence of cool, though not fully arctic climatic conditions and a largely treeless landscape, roamed by large herbivores. Radiocarbon dating indicates that these sediments were deposited during the Loch Lomond Stadial (Younger Dryas GS-1). Comparison of these dates from Holme Pierrepont with those from morphostratigraphically similar deposits in the wider Trent catchment suggests that the Holme Pierrepont Sand and Gravel may have been laid down in two separate pulses of braidplain aggradation either side of the ‘Last Glacial Maximum’. It has been demonstrated from historical documentation and riverine archaeological evidence that the middle Trent has been particularly sensitive to changing flood frequency and magnitude associated with climatic oscillations during the late Holocene; this study demonstrates that such sensitivity appears to extend back into the late Pleistocene. The timing of fluvial aggradation recorded at Holme Pierrepont agrees broadly with that recorded from other sites across England and north-west Europe.     

Pleistocene fluvial terraces from northern France (Seine,Yonne, Somme): synthesis,and new results from interglacial deposits

The Seine, Yonne and Somme are the main rivers draining northwestern France and flowing into the Channel. During Pleistocene cold stages they were tributaries of the “Fleuve Manche”. They are characterised by well-developed stepped terrace systems showing up to 10 incision steps for the last 1 Ma. After 15 years of research and the synthesis of stratigraphical, sedimentological, bioclimatical data and numerical dating, these terrace systems are interpreted as the response of the fluvial environments to climatic cyclicity, superimposed on a background of slow tectonic uplift. The comparison of these three terrace systems shows that the incision budget is similar within the studied area (about 55–65 m/1 Ma), implying relative homogeneity of uplift. In the main part of the area, beyond marine influence, the analysis of each stepped alluvial formation shows regular sediment balance generally composed of coarse periglacial gravels (pleniglacial), covered by fine-grained sediments locally overlain by calcareous tufa (interglacial). However, in the Lower Seine valley, close to the present coast, the low terrace includes two estuarine interglacial units interbedded within periglacial gravel units. Nevertheless, until recently evidence of full interglacial conditions remained elusive in fluvial contexts, especially in the Somme. To address these issues a new research programme has been launched on tufa deposits that are the best candidate to register the climatic optimum. Initial results from la Celle (Seine), Saint-Acheul and Caours (Somme) allow palaeoenvironmental reconstructions of MIS 11 and 5e, and thus confirm the importance of calcareous tufa to define a reference record of Pleistocene Interglacials for northern France. Moreover, it has been previously demonstrated that the main incision leading to terrace formation can be attributed to the transition between interglacial and glacial (during early glacial phases). The new results from interglacial records have important implications concerning the precise occurrence of the major incision phases within the climatic cycle as they provide the starting point immediately preceding downcutting.     

Evidence from the Trent terrace archive, Lincolnshire, UK, for lowland glaciation of Britain during the Middle and Late Pleistocene

The late Middle Pleistocene fluvial terrace sequence of the lower Trent system, Lincolnshire (eastern England), provides an excellent record of environmental change, including evidence for the last two interglacial episodes. It also provides important stratigraphical evidence for the timing and extent of three separate glaciations. Two of these, the Anglian and Devensian, are well-established correlatives of Marine Isotope Stages (MIS) 12 and 2 respectively; the third is a hitherto un-named post-Anglian-pre-Devensian glaciation in eastern England that has been the subject of much previous speculation, but can now be attributed with some confidence to MIS 8. Crucially, the recognition of MIS 7 interglacial deposits within the Balderton-Southrey terrace of the proto-Trent indicates that the underlying Wragby Till, which is ascribed to this additional glaciation, was emplaced no later than MIS 8. The oldest terrace preserved within the lower Trent staircase, the Eagle Moor-Martin Terrace, is considered to be a complex glacial outwash terrace related to the Wragby Till glaciation. It is suggested that deposits representing MIS 11-9, which are conspicuously absent throughout the Trent system, were removed by this glaciation. This is a departure from previous interpretations, which have suggested MIS 10 or MIS 6 as the most likely stages in which an extensive post-Anglian-pre-Devensian lowland glaciation might have occurred in Britain. However, the widespread preservation of undisrupted post-MIS 8 fluvial sequences throughout the Trent valley and in neighbouring systems, within which MIS 7 interglacial deposits have now been recognized at a number of localities, indicates that ice sheets are unlikely to have advanced further into this catchment during MIS 6 than during the Devensian (MIS 2). Recognition of a British glaciation during MIS 8 corresponds with widespread evidence in Europe, which suggests that glacial deposits classified as ‘Saalian’ represent both MIS 8 and MIS 6; in many areas, distinguishing these remains controversial, as confident correlation with either stage is often only possible where glacial sediments interdigitate with well-constrained fluvial records.     

Sediment provenance of late Quaternary morainic,fluvial and loess‐like deposits in the southwestern Verkhoyansk Mountains (eastern Siberia) and implications for regional palaeoenvironmental reconstructions

A provenance analysis of late Quaternary deposits from tributaries of the Aldan and Lena rivers in Central Yakutia (eastern Siberia) was carried out using analysis of heavy minerals and clay mineralogy. Cluster analysis revealed one assemblage that is characterized by relatively high proportions of amphibole, orthopyroxene and garnet as well as pedogenic clay minerals, reflecting a sediment provenance from the wide catchment area of the Lena and Aldan rivers. In contrast, the three other clusters are dominated by stable heavy minerals with varying amounts of clinopyroxene, apatite and garnet, as well as high percentages of illite and chlorite that are indicative of source rocks of the Verkhoyansk Mountains. Glacial moraines reveal the local mountain source signal that is overprinted by the Lena‐Aldan signal in the oldest moraines by reworking processes. Alluvial sediments in the Verkhoyansk Foreland show a clear Lena source signal through intervals of the middle and late Pleistocene, related to a stream course closer to the mountains at that time. Loess‐like cover sediments are characterized by the dominant Lena provenance with increasing proportions of local mountain sources towards the mountain valleys. Aeolian sands in an alluvial terrace section at the mountain margin covering the time between 30 ka and 10 ka BP reflect temporarily dominant inputs of aeolian materials from the Lena Plains. Copyright © 2007 John Wiley & Sons, Ltd.     

The Quaternary history of the Wash fluvial network, UK

This paper appraises and compares the Middle-Upper Pleistocene sedimentary sequences preserved in the fluvial systems draining into the Fenland Basin and the Wash estuary. Of the main Fenland rivers the longest records, which extend back to the initial Anglian (glacial) formation of the basin, are found in the Great Ouse and its tributaries, particularly the Cam and the Nar. These sequences preserve sediments representing all four post-Anglian interglacials. The Nene also has an extensive post-Anglian history, with evidence for a Hoxnian estuary that is presumed to have been the precursor of the Wash. North of the Nene, however, the Welland and Witham (proto-Trent) have relatively short sequences, which are thought to commence with a later (post-Anglian-pre-Devensian) glaciation that affected Lincolnshire and fed the previously-recognized Tottenhill outwash delta south of Kings Lynn. Prior to Devensian deglaciation the Witham valley was occupied by the Trent, which was the trunk river of the late Middle Pleistocene Wash system. During periods of low sea level the river would have extended north-eastwards across what is now the floor of the North Sea, possibly via the Inner Silver Pit. Several of the central Fenland sequences show evidence of infrequent terrace formation during the late Quaternary, although this might in part be due to poor vertical separation between terraces, so that differentiating them has been difficult; this has been exacerbated by mixed biostratigraphical signals due to the preservation of sediments representing more than one interglacial beneath a single terrace surface. In several of the systems there is evidence for valley rejuvenation to the lowest terrace or valley-floor level during the MIS 4-3 transition. The observed differences within what, during the predominant periods of lower sea level, would have been a single Wash river system are difficult to explain.     

Fluvial networks of the Iberian Peninsula: a chronological framework

Knowledge of the evolution of Spanish fluvial networks has improved during recent years as more river systems have been studied and more geochronological data has become available. However, the chronological framework is a major issue as the range of applications is limited by methodological constraints and spatial coverage is sparse. Integration of ‘absolute’ dating methods with biostratigraphy and palaeomagnetism permits the recent evolution of these river systems to be reviewed. The timing of incision from the Late Neogene to the present varies between the major Iberian fluvial systems, depending on the substrata and tectonic settings. Early Pleistocene and older fluvial sequences in the core areas of the Iberian Peninsula provide a more extensive record of fluvial evolution and are better preserved than the terrace flights in the coastal lowlands. Middle Pleistocene sequences are well developed in most of the major river systems in Iberia, particularly those of the Tajo, Guadalquivir and Aguas River, and frequently represent the principal climatic cycles of that period, although tectonic and sea-level effects can also be seen. For Late Pleistocene to Holocene times, the scheme becomes more complex. Our review suggests that each river system has responded differently to local and regional climate control, glacial and periglacial processes in headwaters in high mountain areas, glacio-eustatic sea-level changes and local and regional tectonic patterns.     

Terrace reconstruction and long profile projection: a case study from the Solent river system near Southampton,England

River terrace sequences are important frameworks for archaeological evidence and as such it is important to produce robust correlations between what are often fragmentary remnants of ancient terraces. This paper examines both conceptual and practical issues related to such correlations, using a case study from the eastern part of the former Solent River system near Southampton, England. In this region two recent terrace schemes have been constructed using different data to describe the terrace deposits: one based mainly on terrace surfaces; the other on gravel thicknesses, often not recording the terrace surface itself. The utility of each of these types of data in terrace correlation is discussed in relation to the complexity of the record, the probability of post-depositional alteration of surface sediments and comparison of straight-line projections with modern river long profiles. Correlation using age estimates is also discussed, in relation to optically stimulated luminescence dating of sand lenses within terrace gravels in this region during the PASHCC project. It is concluded that the need for replication at single sites means that this approach has limited use for correlative purposes, although dating of sediments is important for understanding wider landscape evolution and patterns of human occupation.     

Reconstructing historical trends in metal input in heavily-disturbed,contaminated estuaries: studies from Bilbao,Southampton Water and Sicily

Estuaries may be important reservoirs for contaminants as they tend to act as sinks for fine, contaminant-reactive sediments, and, historically, they have acted as centres for industrial and urban development. Analysis of dated sediment cores from these areas may allow historical trends in heavy metal input to be reconstructed, and recent and historical inputs of metal contaminants to be compared. Undisturbed saltmarsh settings have been used widely in the reconstruction of historical trends in metal input as saltmarshes provide a stable, vegetated substrate of dominantly fine sediments, and are less prone to erosion and reworking than adjacent mudflat areas. In comparison, much less research on historical pollution trends has been undertaken at estuarine sites which are prone to severe local disturbance, such as intertidal areas which are routinely dredged or where sedimentary processes have been modified by human activities such as shipping, salt working, port activities, land claim etc. This paper assesses the usefulness of ²¹⁰Pb and ¹³⁷Cs dating, combined with geochemical studies, in reconstructing historical trends in heavy metal input and sediment accretion in 3 heavily-modified, industrialised estuarine areas in Europe: the Bilbao estuary (Spain), Southampton Water (UK), and the Mulinello estuary (Sicily). Of these sites, only a salt marsh core from the Mulinello estuary provides a high-resolution record of recent heavy metal inputs. In Southampton Water only a partial record of changing metal inputs over time is retained due to land-claim and possible early-diagenetic remobilisation, while at Bilbao the vertical distribution of heavy metals in intertidal flats is mainly controlled by input on reworked sediment particles and variations in sediment composition. Where ¹³⁷Cs and ²¹⁰Pb distributions with depth allow a chronology of sediment deposition to be established, and early-diagenetic remobilisation has been minimal, mudflat and saltmarsh cores from even the most heavily-disturbed estuarine sites can provide useful information on variations in historical contaminant input. When the sediments have been vigorously mixed or reworked, large-scale compositional variations are present, or significant early-diagenetic remobilisation has occurred, however, only general information on the scale of contamination can be obtained.     

The role of glacio-isostasy in the formation of post-glacial river terraces in relation to the MIS 2 ice limit: evidence from northern England

In recent years it has been demonstrated that the formation of long-timescale river terrace sequences, which are generally found in areas beyond the extent of most if not all of the Middle and Late Pleistocene ice sheets, has invariably been a response to uplift during the Late Cenozoic and especially the Quaternary. Climatic fluctuation at a Milankovitch timescale has driven the alternations of aggradation and incision recorded in such terraces. It has been widely observed, however, that fluvial terraces also occur in areas glaciated during the Last Glacial Maximum (LGM), which coincides with marine oxygen isotope stage (MIS) 2. This paper, in seeking to compare records from inside and outside of the LGM ice limit, concentrates on a single English river system, that of the Humber. The Humber estuary is shared by the largely Pennine-derived drainage of the Yorkshire Ouse, to the north and entirely within the MIS 2 glacial limit, and, to the south, the Trent, which is almost wholly outside the LGM limit. Thus the Trent has a terrace sequence extending back to the Middle Pleistocene, whereas in the component rivers of the Ouse system, records begin with the melting of the last glacial ice. Importantly, there is considerable difference in the disposition of the post-LGM fluvial deposits in these two subsystems. In the Ouse system there are modest terrace staircases, commencing with full glacial deposits that stand up to 30 m above the modern floodplain. In the Trent, in contrast, last glacial gravels form the foundation of the modern floodplain, with Holocene sediments emplaced directly above them. Thus there is little or no post-LGM incision in the Trent, whereas in the Ouse several incision events are recorded, continuing into the later stages of the Holocene. Wider comparison reveals that the Ouse system is an exemplar for other sequences within the MIS 2 limit, whereas systems beyond this glaciation typically have last glacial sediments beneath their modern floodplains and show little evidence of Holocene incision. The various possible explanations of these differences are discussed, with emphasis placed on glacio-isostatic uplift of areas glaciated during MIS 2 as the main reason for the significant post-glacial incision that typifies valleys in such regions. A new approach to modelling glacio-isostatic adjustment is outlined, from which it is concluded that lower-crustal flow plays a significant role in this process in regions of relatively hot and dynamic crust, like northern England, in addition to the mantle flow that is considered in conventional analyses of glacio-isostasy. Lower-crustal flow has a significant effect due to the combination of the small spatial scale of the glaciated region of northern England and the high mobility of the lower-crustal layer beneath it, due to the heating effect of the widespread Palaeozoic granite in the area.     

Climatic deterioration and the end of the Gortian Interglacial in sediments from Derrynadivva and Burren Townland,near Castlebar,County Mayo,Ireland

Pollen and macrofossil analyses of two sequences of organic sediment in western Ireland have allowed the recognition of the latter parts of the Gortian Interglacial, a Middle Pleistocene temperate stage. The palaeobotanical information from the two sites identifies the preservation of partial sequences from the Gortian Interglacial (believed to be the equivalent of the Hoxnian Stage of Britain and the Holsteinian of Europe). The pollen and macrofossil data from one of the sites, Derrynadivva, span the middle and latter parts of the temperate stage. The results show that fire influenced the vegetation throughout the middle part of the temperate stage, and the termination of the organic depositional sequence appears to have been due to environmental deterioration. The former is identified through the abundant occurrence of charcoal in the sediments, whereas the latter is apparent in the sediment sequence and in the reworking of thermophilous pollen types into the upper part of the deposit. The second site, Burren Townland, records only part of the later zones of the interglacial, but the ericaceous assemblages of the latter part of the Gortian Interglacial are well developed and well preserved. Macrofossil analyses and scanning electron microscopy work on the pollen at the latter site has allowed the recognition of Rhododendron ponticum, adding to previous records of this species, which now has a very disjunct European distribution.     

Terraced fills of Pleistocene and Holocene age in the Rheidol Valley,Wales

The legacy of repeated Pleistocene glaciations has endowed many Welsh river valleys with locally thick successions of glacial and alluvial sediments. Investigations of a well-preserved flight of terraced sediments with good exposures at Capel Bangor, on the Afon Rheidol, mid-Wales, has allowed its Quaternary valley fill stratigraphy to be examined in detail. Study has revealed five terraced fills consisting of seven distinct sedimentary units. These range from Late Devensian ice-contact and ice-marginal deposits, to Holocene high-sinuosity stream sediments with episodes of man-induced accelerated deposition of fine-grained alluvium, and to aggradation and subsequent incision associated with historic metal mining. Examination of general sedimentary properties (e.g., granulometry, sedimentary structures, terrace surface morphology) show both differences in the pattern and controls of deposition and also progressive changes over Late Devensian and Holocene times. The sediments of the Rheidol Valley record the response and subsequent recovery of a drainage basin to glaciation, and the increasing influence of man on sediment yields, channel processes, and sediment quality.     

Interpreting the response of a dryland river system to Late Quaternary climate change

A U-series calcrete chronology has been constructed for three Late Quaternary terrace units, termed the D1, D2 and D3 terraces in age descending order, from the Rio Aguas river system of the Sorbas basin, southeast Spain. The D1 terrace formed between 30,300±4400 year BP and 12,140±360 year BP, correlating well with the Last Glacial Maximum when rates of sediment supply would have increased greatly, because of higher rates of weathering, reduced vegetation cover and weak soil development. The D2 terrace formed between 12,800±1100 year BP and 9,600±530 year BP, correlating well with the Younger Dryas event. The D3 terrace could only be poorly constrained to the early Holocene and no unequivocal cause could be assigned to this period of aggradation. The sedimentology and geomorphology of the D2 terrace suggests, however, that the aggradation of this unit was a response to diapirism/karstic processes occurring within the underlying Messinian gypsum strata and the subsequent damming of the Aguas system. Therefore, despite its coincident occurrence with the Younger Dryas, aggradation of the D2 terrace is unrelated to climate change. The style of this response, controlled predominantly by the characteristics of the underlying bedrock, makes correlating the terrace record of the Aguas with other systems in the Mediterranean unreliable. This study, therefore, highlights the problems of correlating fluvial sequences in regions of variable tectonics, climatic history and bedrock geology and emphasises the need to properly understand the main controls on individual fluvial systems before any attempt is made to correlate their depositional histories.     

Recent sedimentary processes in Scoresby Sund, East Greenland

The fjord system of Scoresby Sund on the east coast of Greenland has been the subject of two research cruises by RV Polarstern in 1988 and 1990. Most of the year, the fjord is covered by sea-ice. Sediment input takes place mostly via drifting icebergs during the short summer period. Depending on the distance to glaciers, surface sediments carry varying proportions of coarse ice-rafted debris (IRD). The degree of sediment reworking by scouring icebergs is controlled by the depth of the fjord, with the most intense reworking in areas shallower than about 450 m depth. Both IRD contribution and intensity of sediment scouring clearly control the distribution pattern of benthic organisms.     

Fashion and phases of late Pleistocene aggradation and incision in the Alaknanda River Valley, western Himalaya, India

We study the aggradation and incision of the Alaknanda River Valley during the late Pleistocene and Holocene. The morphostratigraphy in the river valley at Deoprayag shows the active riverbed, a cut terrace, and a fill terrace. The sedimentary fabric of the fill terrace comprises four lithofacies representing 1) riverbed accretion, 2) locally derived debris fan, 3) the deposits of waning floods and 4) palaeoflood records. The sedimentation style, coupled with geochemical analysis and Optically Stimulated Luminescence (OSL) dating, indicate that this terrace formed in a drier climate and the river valley aggraded in two phases during 21–18 ka and 13–9 ka. During these periods, sediment supply was relatively higher. Incision began after 10 ka in response to a strengthened monsoon and aided by increase of the tectonic gradient. The cut terrace formed at ~ 5 ka during a phase of stable climate and tectonic quiescence. The palaeoflood records suggest wetter climate 200–300 yr ago when the floods originated in the upper catchment of the Higher Himalaya and in the relatively drier climate ~ 1.2 ka when locally derived sediments from the Lesser Himalaya dominated flood deposits. Maximum and minimum limits of bedrock incision rate at Deoprayag are 2.3 mm/a and 1.4 mm/a.     

青海唐古拉沱沱河地区晚更新世河流阶地沉积特征及意义

青海沱沱河地区水系密布、河网交织,沿主干水系河流阶地发育。对沱沱河沿岸不同地段河流阶地进行物质成分及古植物孢粉进行研究,确定了自63.1 kaB.P.(ESR)以来的晚更新世草本植物与木本植物两个古植被演化阶段,相应气候由温凉较干向温和较湿转变。详细的测年(TL、ESR)数据显示,位于基座阶地之上的阶地堆积物为晚更新世97.78 KaB.P.以来堆积而成,推断长江水系在研究区的形成与外泄地质时期为晚更新世早期。     

Sedimentary record from Lake Hovsgol, NW Mongolia: Results from the HDP-04 and HDP-06 drill cores

The Hovsgol Drilling Project retrieved Pleistocene sediment section with the basal age of ca. 1 Ma from the Hovsgol rift basin, NW Mongolia. Detailed lithologic data on drill cores is presented and compared with analogous sediment facies in the radiocarbon-dated records of the last glacial–interglacial transition. Drill cores from two sites, presently in 239 m and 235 m water depth, represent somewhat different depositional settings. The shorter HDP-06 drill core (26 m) at the base of the gentler SE slope of the rift basin contains lithologic evidence for several recent lake lowstands on the order of −200 m. The longer HDP-04 drill core (81 m) some 8 km away at the base of the steep NW underwater slope is composed of finer sediments and contains at least 10 characteristic transitions from calcareous to carbonate-free (diatomaceous) layers. These lithologic transitions are interpreted here as signals of repeated Pleistocene lake transgressions in the Hovsgol basin. Transgressions appear to have been associated with lower sedimentation rates and with the deposition of thin turbidite beds at the drill site. Comparison of drill core lithology with the available seismic data shows reasonable agreement in terms of the number of lowstand events and the general trends of changing lake level. HDP-04 drill core retrieved shallow-water facies containing sand and carbonate oolites deposited at the time of the most dramatic mid-Pleistocene regression of the lake. At ca. 24 m core depth, this interval corresponds to a major basinwide angular unconformity apparent in the seismic pattern. Lake Hovsgol, a smaller sister rift lake of the grand Lake Baikal, has a confined local catchment, which makes it very sensitive to regional variations in the effective moisture. Consisting primarily of calcareous mud, the sedimentary record of Lake Hovsgol provides a unique regional sedimentary archive. Future multi-proxy studies of the Hovsgol sedimentary records will allow constraint of the mid-late Pleistocene history of the hydrologic budget in the Baikal region of continental interior Asia.     

Coastal Evolution Over the Past 3000 Years at Conrads Beach,Nova Scotia: the Influence of Local Sediment Supply on a Paraglacial Transgressive System

Many coastlines are retreating in response to sea level rise, compounded by glacial–isostatic subsidence in areas marginal to former ice sheets. The resulting barrier and estuarine deposits are dominated by transgressive stratigraphy. Where supplied primarily from relict glacial deposits, this “paraglacial” sediment input may rise and fall, increasing as a new source such as a drumlin headland is exposed to erosion but declining as the source becomes exhausted. Conrads Beach, on the Atlantic coast of Canada, has experienced a succession of barrier growth and reworking as sediment supply from several drumlin sources has varied over the past 3000 years. In the context of long-term regional transgression, there have been intervals of years to centuries characterized by local stability or progradation. Ground-penetrating radar profiles and refraction seismic data were used to image the facies architecture of Conrads Beach to depths of 6–8 and 10–24 m, respectively. Thirteen vibracores provided a record of lithofacies characteristics and geometry. Results show evidence of an estuarine basin at ~2800 years BP. As the outer coast retreated, erosion of drumlins provided multi-century sediment pulses to adjacent beaches and embayments. Locally increased sediment supply fed a prograding beach ridge complex from >600 to ~150 years BP and tidal channels feeding sediment to back-barrier flood delta deposits. This study documents the complexity of coastal adjustment to time- and source-varying sediment supply under long-term rising sea level. It expands and refines previous models, providing guidance required for effective management and hazard mitigation on transgressive paraglacial coasts.