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1.
Evidence from the Trent terrace archive, Lincolnshire, UK, for lowland glaciation of Britain during the Middle and Late Pleistocene 总被引：1，自引：1，他引：0
Tom S. White Andy J. Howard 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):141-153
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. 相似文献
2.
Andy J. Howard John N. Carney Malcolm T. Greenwood David H. Keen Tim Mighall Charlotte O’Brien Emma Tetlow 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(3):419-431
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. 相似文献
3.
D.R. Bridgland R. Westaway A.J. Howard A.J. Long M.J. White 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):113-127
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. 相似文献
4.
Martin R. Bates Carl Champness Andrew Haggart Richard I. Macphail Simon A. Parfitt Jean-Luc Schwenninger 《Proceedings of the Geologists' Association. Geologists' Association》2014
This paper discusses the results of the investigation of Pleistocene sediments at the Royal Oak Portal (ROP) site on the new Crossrail scheme near Paddington Station, London. The site was sampled and recorded in May 2011 by archaeologists from Oxford Archaeology commissioned by Crossrail Ltd. The investigation revealed a sedimentary sequence associated with cool climate waterlain deposition towards the edge of the River Westbourne floodplain. During excavation an assemblage of around 100 identifiable large mammal bones was recovered, dating to the Late Pleistocene. The major concentration of bones, from bison and reindeer, was located and excavated from a shallow sequence of sediments. Analysis of the bones indicates that they represent a natural death assemblage, scavenged and subsequently disarticulated, transported by water, exposed and further dispersed and broken by trampling. The site is of regional and national importance because the assemblage derives from a well-constrained geological context, with associated dating evidence suggesting accumulation during the later parts of Marine Isotope Stage (MIS) 5 and continuing within MIS 4. The site is also of significance because it is one of a growing number of recently discovered sites away from the main fluvial archive for the British Middle and Upper Pleistocene. These sites have the potential to add significantly to our understanding of parts of the Pleistocene record that remain difficult to document through the investigation of the more active systems associated with major rivers such as the Thames, Severn or Trent. 相似文献
5.
ROB WESTAWAY 《Boreas: An International Journal of Quaternary Research》2009,38(2):261-284
Prior to its disruption during the Anglian glaciation (MIS 12), the Ingham or Bytham River used to flow eastwards across central England and East Anglia into the southern North Sea. It thus had a much larger catchment than any extant river system in Britain; its headwaters may well have been as far away as North Wales and/or NW England. Terrace deposits of this former river system crop out across East Anglia and, as for any other river, can be used to investigate uplift, landscape evolution and the physical properties of the underlying continental crust. However, such an investigation has hitherto been hampered by inconsistencies between different authors' terrace schemes; furthermore, and controversially, one such scheme has formed the basis for the inference that the region was affected by a pre‐Anglian (MIS 16) glaciation. By re‐examining the raw data, the Ingham River deposits are shown to be disposed in three terraces, inferred to date from MIS 16, 14 and 12. The evidence previously attributed to pre‐Anglian glaciation is associated with the youngest of these terraces, and thus marks the MIS 12 (i.e. Anglian) glaciation; the argument for glaciation of the region in MIS 16 is thus an artefact of previous miscorrelation of the terrace deposits. It is inferred that development of the very large Ingham River was synchronous with decapitation of the former ‘Greater Thames’, or ‘High‐level Kesgrave Thames’ river, some time between MIS 18 and MIS 16. Uplift histories at representative localities across East Anglia have been modelled using composite data sets, combining the terrace deposits of the Ingham River and of the post‐Anglian rivers Lark and Waveney. The sites modelled are typefied by much faster uplift in the early Middle Pleistocene than in the late Middle Pleistocene; this effect is shown to be a consequence of the relative thinness (no more than ～7–8 km thick) of the mobile lower‐crustal layer, itself a consequence of the low surface heat flow in the London Platform crustal province. The post‐Early Pleistocene uplift tapers eastward, consistent with the observed downstream convergence of the Ingham and Waveney terraces, and is close to zero near the modern coastline around Lowestoft and Great Yarmouth. Stratigraphic relationships between the Ingham terrace deposits and temperate‐stage marine and terrestrial deposits in this coastal area allow sites to be dated; thus, Pakefield and Corton date from MIS 15, whereas Norton Subcourse dates from MIS 17. The oldest known Lower Palaeolithic sites in the region, characterized by flake artefacts, are Pakefield (MIS 15) and Hengrave (?MIS 14); younger pre‐Anglian sites that have yielded handaxes and/or fossil material of the water vole Arvicola cantiana date from MIS 13. The minimal vertical crustal motion in this coastal area, where temperate‐stage deposits from different climate cycles crop out close to present‐day sea level, does not imply high crustal stability; instead, it indicates a ‘hinge zone’ between the uplifting hinterland and the subsiding depocentre in the southern North Sea. 相似文献
6.
对山西娘子关绵河不同阶地上沉积的泉钙华进行了高精度的230Th定年和碳氧稳定同位素组成测定。结果发现,绵河II级阶地沉积的娘子关泉钙华的最老年龄在407～466ka,远老于早前通过钙华中的石英砂热发光法(TL)获得的年龄,即绵河II级阶地上的娘子关泉钙华是在中更新世MIS12/11阶段形成的,而非原来认为的是晚更新世的产物。由此推测,绵河III级阶地娘子关泉钙华形成的年代更早,可能是中更新世的MIS14/13阶段。230Th测年获得的绵河I级阶地顶部的钙华形成于5ka前,即是在全新世中期以前形成的。结合钙华规模及其碳氧稳定同位素组成分析进一步发现,上述绵河三级阶地上的娘子关泉钙华均主要是湿热气候下的产物。然而,自II级阶地钙华形成至今,气候总体上在向干冷方向发展,泉域植被则呈现退化的趋势。 相似文献
7.
António A. Martins Pedro P. Cunha Luiz Osterbeek Stefano Grimaldi Jan-Pieter Buylaert João Matos 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):128-140
This paper aims to provide insight into human occupation and landscape change during the Pleistocene in a central area of the Lower Tejo basin (Portugal). Detailed geomorphological mapping, coupled with lithostratigraphy, sedimentology and luminescence dating, supports the identification of a complete terrace staircase sequence. It consists of six gravely terraces located below the culminant (Pliocene) basin unit. A chronological framework for the sedimentary sequences and associated human industries is proposed and correlated with marine oxygen isotope stages (MIS): T1 terrace, not dated; T2, not dated; T3, >300 ka; T4, ∼300-160 ka (MIS8, MIS7 and MIS6); T5, ∼136-75 ka (MIS5); T6, ∼62-30 ka (MIS3); colluvium and aeolian sands, ∼30-14 ka (MIS2); valley fill deposits, ∼14 ka to present (MIS1). The oldest artefacts were found at the base of the T4 terrace, with the local stratigraphic level dated to ≥175 ± 6 ka (Middle Pleistocene). The lithic assemblages collected from distinct stratigraphic levels (T4, T5 top, T6 terraces and colluvium) are characterized by the predominance of opportunistic technological choices, a feature that can be attributed partly to the preferential exploitation of the available raw material, dominated by local-sourced quartzites and quartz pebbles. The adaptation to local raw material (texture and volume), together with subsistence patterns and behaviours, could explain the rarity of Acheulian types (handaxes and cleavers) and picks in the T4 terraces of the Tejo tributaries; this is in contrast to the same terrace of the Tejo valley, in which these types are found. Interpretation of the environmental conditions (controlled by climate and glacio-eustatic sea-level changes) affecting the hunter-gatherer human groups is also presented. 相似文献
8.
Stéphane Cordier Manfred Frechen Dominique Harmand 《Boreas: An International Journal of Quaternary Research》2014,43(2):450-468
This paper focuses upon the youngest terraces of the Moselle and its tributary the Meurthe (NE France and SW Germany). It includes research on several sections, in particular the key sections of Golbey‐Pré Droué and Thörnich‐Hochrech (located in the vicinity of the Vosges Massif and in the Rhenish Massif, respectively), and the use of the Optically Stimulated Luminescence (OSL) dating method. Our investigations made it possible to obtain a more robust chronostratigraphical framework and to update the previous model of fluvial response to climate change. The results demonstrate that the Moselle terrace M3 (first terrace formed after the capture of the Upper Moselle by the Palaeo‐Meurthe) has the same age from the Vosges to the Rhenish Massif. The formation of this terrace included two main periods of sedimentation attributed to the Late Saalian (MIS 6) and the Early Weichselian (MIS 5), respectively. They were separated by a major episode of fluvial erosion that may be allocated to the MIS 6–5 transition on the basis of chronological and sedimentological evidence. This erosion led to the removal of most of the MIS 6 deposits, whereas the MIS 5 deposits have been widely preserved following the subsequent (MIS 5–4) terrace incision. This evolution somewhat contrasts with that observed in the Sarre valley, the main tributary of the Moselle, and with many fluvial systems in western Europe, which show better preservation of deposits from cold periods. This atypical behaviour is explained by the relationship between the fluvial evolution and the glaciers covering the upper Moselle catchment (Vosges Massif) during the Pleistocene cold periods. 相似文献
9.
眉山阶地第四系剖面地处番禺断隆区的边缘,毗邻狮子洋断陷区,是珠江三角洲第一次海侵所到达的区域,附近的断裂包括文冲断裂、化龙—黄阁断裂、新会—市桥断裂等三角洲内典型断裂。发育于网纹红土基座上的堆积阶地,自下而上大致分为杂色砂层、白色砂层、淤泥质层3层,构成一个完整的从动水环境到静水环境的沉积旋回。野外调查及14C测年和光释光（OSL）测年结果表明,眉山第四系剖面年龄约在70～30 ka B.P.之间,相当于深海O同位素4—2阶段。结合前人的研究资料,认为阶地面与沉降区的下旋回原本在同一高度,但自晚更新世以来,在断块差异升降中被错开,垂直距离在20 m以上,直观地指示了断隆区与断陷区的运动特征。 相似文献
10.
Rob Westaway 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(3):383-396
Lower Palaeolithic artefacts have been reported at Happisburgh, north Norfolk, in sediments that have been assigned to the late Early Pleistocene, in either marine isotope stage (MIS) 25 or 21, using magnetostratigraphy, biostratigraphy and clast lithology. However, the proposal that these sediments were deposited by the ancestral River Thames is inconsistent both with the established late Early Pleistocene palaeogeography of the region and with the dispositions of the contemporaneous Thames terraces. The Happisburgh deposits were evidently emplaced by a local river, which reworked older sediments that from their lithology had been derived largely from the Bytham River rather than the Thames catchment. Nonetheless, the potential significance of this sedimentary succession for early human dispersal and behaviour requires a conservative assessment of its youngest possible age. Although its basal part is clearly Early Pleistocene, there is nothing to preclude an early Middle Pleistocene age for the overlying sediments that have yielded the artefacts and the mammalian biostratigraphic evidence. It is indeed arguable that these sediments date from the cooling transition at the end of MIS 15c, and are thus younger than the artefact-bearing succession at Pakefield. Pending the availability of additional dating evidence, future discussion of the Happisburgh site should be qualified with respect to any claim for an Early Pleistocene age for the human occupation indicated. 相似文献
11.
R.M. Briant A.A. Kilfeather S. Parfitt K.E.H. Penkman R.C. Preece H.M. Roe J.-L. Schwenninger F.F. Wenban-Smith J.E. Whittaker 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(1):87-108
Late Middle Pleistocene Thames-Medway deposits in eastern Essex comprise both large expanses of Palaeolithic artefact-bearing river sands/gravels and deep channels infilled with thick sequences of fossiliferous fine-grained estuarine sediments that yield valuable palaeoenvironmental information. Until recently, chronological control on these deposits was limited to terrace stratigraphy and limited amino-acid racemisation (AAR) determinations. Recent developments in both this and optically stimulated luminescence (OSL) dating make them potentially powerful tools for improving the chronological control on such sequences. This paper reports new AAR analyses and initial OSL dating from the deposits in this region. These results will help with ongoing investigation of patterns of early human settlement.Using AAR, the attribution by previous workers of the interglacial channel deposits to both MIS 11 (Tillingham Clay) and MIS 9 (Rochford and Shoeburyness Clays) is reinforced. Where there are direct stratigraphic relationships between AAR and OSL as with the Cudmore Grove and Rochford Clays and associated gravels, they agree well. Where OSL dating is the only technique available, it seems to replicate well, but must be treated with caution since there are relatively few aliquots. It is suggested on the basis of this initial OSL dating that the gravel deposits date from MIS 8 (Rochford and Cudmore Grove Gravels) and potentially also MIS 6 (Dammer Wick and Barling Gravels). However, the archaeological evidence from the Barling Gravel and the suggested correlations between this sequence and upstream Thames terraces conflict with this latter age estimate and suggest that it may need more investigation. 相似文献
12.
The Early and early Middle Pleistocene archaeological record in Britain from c. 900 to 500 ka marks a critical shift in human occupation of northwest Europe, from occasional pioneer populations with simple core and flake technology to more widespread occupation associated with the appearance of Acheulean technology. Key to understanding this record are the fluvial deposits of the extinct Bytham River in central East Anglia, where a series of Lower Palaeolithic sites lie on a 15 km stretch of the former river. In this paper we present the results of new fieldwork and a reanalysis of historical artefact collections of handaxes and scrapers to: 1) establish the chronostratigraphic context of the Bytham archaeological record; 2) examine variability in lithic artefact typology and technology through time; and 3) explore the implications for understanding variation in lithic technology in the European record. Six phases of occupation of Britain are identified from at least marine isotope stage (MIS) 21 to MIS 13, with the last three phases characterised by distinctive lithic technology. We argue that this relates to the discontinuous occupation of Britain, where each phase represents the arrival of new groups derived from different European populations with distinctive material culture. 相似文献
13.
Beccy Scott Nick Ashton Kirsty E. H. Penkman Richard C. Preece Mark White 《第四纪科学杂志》2010,25(6):931-944
The late Middle Pleistocene sites in the Ebbsfleet Valley, Kent, UK, have yielded archaeological assemblages critical to understanding the early Middle Palaeolithic of northwestern Europe. Despite a long history of research, the nature and context of these assemblages are still poorly understood. This paper clarifies the stratigraphic, environmental and archaeological records at Ebbsfleet. These reflect a cold–warm–cold sequence of climatic events, preserved within part of the Taplow/Mucking Formation of the Thames (Marine Isotope Stage (MIS) 8/7/6). Levallois artefacts are shown to be restricted to the lower part of the Ebbsfleet Channel sequence (Phases I and II) and are assigned to late MIS 8/early MIS 7. This material is associated with fauna indicative of open environments during both cool and temperate conditions. Handaxe assemblages are recorded from higher up the sequence (Phases III–V), but have been redeposited from higher terrace units nearby. No primary context archaeology is apparent during these later phases of aggradation. This may indicate that humans abandoned the site once available raw material became inaccessible, and may also reflect a decline in human presence in Britain during the latter part of MIS 7. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
Danielle C. Schreve 《Proceedings of the Geologists' Association. Geologists' Association》2009,120(1):58-64
A new Pleistocene vertebrate assemblage from fluvial deposits of the River Severn in Gloucester, England, has yielded the remains of hippopotamus (Hippopotamus amphibius), a new record for this terrace system, with additional material from probable bison (cf. Bison priscus) and elephant (Elephantidae sp.). The presence of these taxa indicates fully temperate climatic conditions and the occurrence of hippopotamus, a significant biostratigraphical indicator for the British Late Pleistocene, suggests an age for the assemblage within MIS 5e (the Last Interglacial). This would contradict the older MIS 7-6 age for the gravel body that is currently accepted on the basis of deposit mapping and imply a more complex mode of deposition than presently envisaged in the valley. 相似文献
15.
The lithic record from the Solent River and its tributaries is re‐examined in the light of recent interpretations about the changing demography of Britain during the Lower and early Middle Palaeolithic. Existing models of the terrace stratigraphies in the Solent and its tributary areas are reviewed and the corresponding archaeological record (specifically handaxes) for each terrace is assessed to provide models for the relative changes in human occupation through time. The Bournemouth area is studied in detail to examine the effects of quarrying and urbanisation on collection history and on the biases it introduces to the record. In addition, the effects of reworking of artefacts from higher into lower terraces are assessed, and shown to be a significant problem. Although there is very little absolute dating available for the Solent area, a cautious interpretation of the results from these analyses would suggest a pre‐Marine Isotope Stage (MIS) 12 date for the first appearance of humans, a peak in population between MIS 12 and 10, and a decline in population during MIS 9 and 8. Owing to poor contextual data and small sample sizes, it is not clear when Levallois technology was introduced. This record is compared and contrasted to that from the Thames Valley. It is suggested that changes in the palaeogeography of Britain, in particular land connections to the continent, might have contributed to differences in the archaeological records from the Solent and Thames regions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
16.
Denis-Didier Rousseau Natalia Gerasimenko Zhanna Matviischina George Kukla 《Quaternary Research》2001,56(3):349
The Vyazivok loess sequence from the Dnieper Plain, Ukraine, documents regional environmental changes during the late Pleistocene and Holocene. Pedological and palynological analyses and low-field magnetic susceptibility document changes from dense temperate forest during the last interglacial maximum to open, harsh, loess–steppe during the latest Pleistocene. The Vyazivok section overlies hillwash derived from a lower Pleistocene terrace and consists of two stratified soil complexes (Kaydaky and Pryluky; marine isotope stage [MIS] 5 equivalent) separated by a layer of eolian dust (Tyasmyn silt). The lower soils in both complexes formed within forest. These soils are overlain by the Uday (MIS4) and Bug (MIS2) loess units, which are separated by boreal soils of the Vytachiv (MIS3) complex. The coldest conditions within the record occurred in the youngest loess. Holocene soils cap the Bug loess. The Vyazivok section shows remarkable similarities with other classical loess sequences in western Europe, the Czech Republic, and Austria. The Kaydaky, Pryluky, and Vytachiv deposits, correlate with the PKIII, PKII, and PKI soil complexes, respectively, of the Czech Republic. The Tyasmyn and Prylyky silt layers correspond to marker horizons from central Europe. 相似文献
17.
Clark E. Sherman Charles H. Fletcher Ken H. Rubin Kathleen R. Simmons Walter H. Adey 《Quaternary Research》2014
In situ Pleistocene reefs form a gently sloping nearshore terrace around the island of Oahu. TIMS Th–U ages of in situ corals indicate that most of the terrace is composed of reefal limestones correlating to Marine Oxygen Isotope Stage 7 (MIS 7, ~ 190–245 ka). The position of the in situ MIS 7 reef complex indicates that it formed during periods when local sea level was ~ 9 to 20 m below present sea level. Its extensiveness and geomorphic prominence as well as a paucity of emergent in situ MIS 7 reef-framework deposits on Oahu suggest that much of MIS 7 was characterized by regional sea levels below present. Later accretion along the seaward front of the terrace occurred during the latter part of MIS 5 (i.e., MIS 5a–5d, ~ 76–113 ka). The position of the late MIS 5 reefal limestones is consistent with formation during a period when local sea level was below present. The extensiveness of the submerged Pleistocene reefs around Oahu compared to the relative dearth of Holocene accretion is due to the fact that Pleistocene reefs had both more time and more accommodation space available for accretion than their Holocene counterparts. 相似文献
18.
Danielle Schreve Andy Howard Andrew Currant Stephen Brooks Simon Buteux Russell Coope Barnaby Crocker Michael Field Malcolm Greenwood James Greig Phillip Toms 《第四纪科学杂志》2013,28(2):118-130
This paper reports the discovery of a rare partial skeleton of a woolly rhinoceros (Coelodonta antiquitatis Blumenbach, 1799) and associated fauna from a low Pleistocene terrace of the River Tame at Whitemoor Haye, Staffordshire, UK. A study of the sedimentary deposits around the rhino skeleton and associated organic‐rich clasts containing pollen, plant and arthropod remains suggests that the animal was rapidly buried on a braided river floodplain surrounded by a predominantly treeless, herb‐rich grassland. Highlights of the study include the oldest British chironomid record published to date and novel analysis of the palaeoflow regime using caddisfly remains. For the first time, comparative calculations of coleopteran and chironomid palaeotemperatures have been made on the same samples, suggesting a mean July temperature of 8–11 °C and a mean December temperature of between ?22 and ?16 °C. Radiocarbon age estimates on skeletal material, supported by optically stimulated luminescence ages from surrounding sediments, indicate that the rhino lived around 41–43 k cal a BP. The combined geochronological, stratigraphic and palaeoenvironmental evidence places the assemblage firmly within the Middle Devensian (Marine Oxygen Isotope Stage 3). This would agree with other regional evidence for the timing of aggradation for the lowest terrace of the Trent and its tributary systems. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
19.
David R. Bridgland Mark J. White 《Boreas: An International Journal of Quaternary Research》2014,43(2):543-555
With the adoption of an ‘expanded chronology’ for the Middle Pleistocene, based on the greater number of warm and cold episodes evident in the marine oxygen isotope record from deep ocean cores, has come the recognition of a meaningful progression of artefact types, something that could not be achieved with reference to the previous ‘compressed chronology’. In Britain, at least, it has been established that Levallois knapping techniques appeared in MIS 9–8, that bout coupé handaxes are indicative of MIS 3 and, rather more tentatively, that assemblages with twisted ovate handaxes in significant numbers represent MIS 11 occupation. Added to these key markers, it is now possible to suggest that further tool types occur preferentially in deposits of particular age: assemblages with significant proportions of cleavers and ‘ficron’ handaxes appear to be correlated with deposits formed at around the time of the MIS 9 interglacial. This newly recognized patterning within the Lower and Middle Palaeolithic record differs markedly from the previous use, in the mid‐20th century, of archaeological typology as a means of dating Pleistocene sequences, which was based on a relative refinement of tool making that is now recognized to be unrelated to age. Indeed, the authors would wish to emphasize that, even with reference to the new scheme presented here, the archaeological record should only be seen as dating evidence ‘of last resort’. 相似文献
20.
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。 相似文献