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1.
Results are presented from a multidisciplinary study of fossiliferous interglacial deposits on the northern side of the Thames estuary. These fill a channel cut into London Clay bedrock and overlain by the Barling Gravel, a Thames–Medway deposit equivalent to the Lynch Hill and Corbets Tey Gravels of the Middle and Lower Thames, respectively. The channel sediments yielded diverse molluscan and ostracod assemblages, both implying fully interglacial conditions and a slight brackish influence. Pollen analysis has shown that the deposits accumulated during the early part of an interglacial. Plant macrofossils, particularly the abundance of Trapa natans, reinforce the interglacial character of the palaeontological evidence. A beetle fauna, which includes four taxa unknown in Britain at present, has allowed quantification of palaeotemperature using the mutual climatic range method (Tmax 17 to 26 °C; Tmin ?11 to 13 °C). A few vertebrate remains have been recovered from the interglacial deposits, but a much larger fauna, as well as Palaeolithic artefacts, is known from the overlying Barling Gravel. The age of the interglacial deposits is inferential. The geological context suggests a late Middle Pleistocene interglacial, part of the post‐diversion Thames system and therefore clearly post‐Anglian. This conclusion is supported by amino acid ratios from the shells of freshwater molluscs. The correlation of the overlying Barling Gravel with the Lynch Hill/Corbets Tey aggradation of the Thames valley constrains the age of the Barling interglacial to marine oxygen isotope stages 11 or 9. The presence of Corbicula fluminalis and Pisidium clessini confirms a pre‐Ipswichian (marine oxygen isotope substage 5e) age and their occurrence in the early part of the interglacial cycle at Barling precludes correlation with marine oxygen isotope stage 11, as these taxa occur only later in that interglacial at sites such as Swanscombe and Clacton. Thus by process of elimination a marine oxygen isotope stage 9 age would appear probable. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

2.
《Quaternary Science Reviews》2003,22(10-13):999-1010
The loess/palaeosol sequence of Kurtak, situated at the western bank of the upper Yenisei in Middle Siberia, represents one of the best developed Middle and Upper Pleistocene sediment records in Yenisei Siberia. More than 40 m thick loess and loess-like sediments intercalated by at least four pedocomplexes are exposed at a steep erosional slope at the bank of the Krasnoyarsk Water Reservoir. Infrared optically stimulated luminescence (IRSL) and thermoluminescence (TL) dating techniques have been applied on 38 fine grain samples from the upper 23 m of the profile, representing the penultimate and last interglacial–glacial cycle. The IRSL and TL age estimates are in good agreement with the geological estimates up to the last interglacial soil horizon (oxygen isotope substage (OIS) 5e). The luminescence ages show that the lowermost truncated palaeosol of kastanosjem-type is likely to have formed during the penultimate interglacial upon subaerial deposits. Three weak reddish brown palaeosols intercalated by reworked loess-like sediments correlate with early Upper Pleistocene interstadials (OIS5dion of -a), and a succession of humic horizons alternated by cryoturbation processes (Kurtak pedocomplex) is linked with OIS 3. Thick loess deposits between the pedocomplexes show now significant age increase with depth, indicating high accumulation rates at around 23 ka (OIS 2) and 60 ka (OIS 4).  相似文献   

3.
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   

4.
The Thame is one of the principal left-bank affluents of the Thames, the largest river in southern England; it joins the Upper Thames at Dorchester, ∼20 km downstream of Oxford. Its terraces include a younger group of four, which date from the late Middle Pleistocene and Late Pleistocene, are disposed subparallel to the modern river, and represent drainage within the modern catchment. At higher levels there are three older terraces, the Three Pigeons, Tiddington and Chilworth terraces, which are assigned to MIS 16, 14 and 12. With much gentler downstream gradients, these are fragmentary remnants of much more substantial fluvial deposits, indicating a much larger river that was disrupted by the Anglian (MIS 12) glaciation. This interpretation supersedes an earlier view that the glacigenic deposits in the Thame headwaters correlate with the Blackditch terrace, the highest of the younger group, which has hitherto provided an argument that the glaciation in this region occurred in MIS 10. It is suggested that the headwaters of the pre-Anglian ‘Greater Thame’ river were located near Northampton and that the Milton Sands of that area represent an upstream counterpart of the Chilworth terrace deposits. It is envisaged that this early Middle Pleistocene drainage geometry, located between the Jurassic limestone and Chalk escarpments, developed as a result of the increase in uplift rates that followed the Mid-Pleistocene Revolution (MPR). It is suggested that before this time, including during the Early Pleistocene, the modern Thame catchment and adjacent regions drained southeastward through the Chalk escarpment, but these small rivers lacked the erosional power to cut through the Chalk in pace with the faster uplift occurring in the early Middle Pleistocene, and so became diverted to the southwest, subparallel to the Chalk escarpment, to form the pre-Anglian ‘Greater Thame’ tributary of the Upper Thames. The post-MPR uplift is estimated to decrease northwestward from 90 m in the Middle Thames to 75 m near the Thame-Thames confluence and to 65 m upstream of Oxford. The post-Anglian (post-450 ka) component of uplift decreases northward from 33 m near the Thame-Thames confluence to an estimated ∼20 m in the Northampton area; the relative stability of the latter area makes feasible the proposed correlation between the Milton Sands and the pre-Anglian River Thame. Limited post-Anglian uplift in the Northampton area is also inferred from the upstream convergence of the terraces of the modern rivers Nene and Great Ouse. These observed lateral variations in vertical crustal motions reflect lateral variations in crustal properties (including heat flow, crustal thickness, and thickness of underplating at the base of the crust) that are known independently. This study thus provides, for the first time, an integrated explanation of the Pleistocene drainage development across a large region of central-southern England.  相似文献   

5.
Quaternary marine stratigraphy and geochronology in central West Greenland   总被引:1,自引:0,他引:1  
A new stratigraphic framework is proposed for the Quaternary of a portion of central West Greenland, based primarily on faunal and geochronologic studies of shallow shelf deposits. Twenty-four occurrences of pre-Holocene deposits were already known in West Greenland and data from 18 new sites are presented, together with new information on some of the previously described localities. Four pre-Holocene marine events are described. The interglacial Ivnaarssuit and Nordre Laksebugt marine events are considered to be Middle Pleistocene in age. The interstadial Laksebugt marine event is considered to be late Middle Pleistocene, whereas the Svartenhuk marine event is correlated with the last interglacial. For the last glacial period an extensive ice shelf is proposed west of Disko. The oldest postglacial deposits are dated at 10,470 ± 130 14C-years BP.  相似文献   

6.
The northern part of the West Siberian geosyneclise is characterized by a thick sedimentary cover and widespread Triassic sedimentary and volcanosedimentary rocks and Paleozoic platform structures. New targets have been recognized in the basement and deeply buried horizons of the geosyneclise cover. Reservoirs might be found in the following formations: Paleozoic cover deposits, weathering crusts, zones of Paleozoic rock deconsolidation, Triassic sedimentary and volcanosedimentary deposits, buried structures in the lower part of the cover, Lower and Middle Jurassic basal layers, pinch-outs of Jurassic horizons, Upper Jurassic bituminous shales and cavernous carbonates. Exploration of these potential structures will change the structure of the existing resource base toward the long-term replenishment of hydrocarbon resources and a stable rate of production replacement.  相似文献   

7.
For much of the Middle and all of the Upper Pleistocene the Upper Thames valley has remained outside the limit of ice advance. The main agents of landform evolution have been the River Thames and its tributaries, which have cut down episodically and in so doing have abandoned a series of river terraces. This study reports the findings of an investigation into exposures in the deposits underlying the Floodplain Terrace at Cassington, near Oxford, England. The sequence exposed reveals a stratigraphy of basal, predominantly fine-grained, lithofacies overlain by coarser gravel lithofacies. The fluvial architecture of these deposits indicates a major change in fluvial style from a low-energy (meandering) to a high energy (braided) channel system. The flora and fauna from the lower fine-grained lithofacies display a marked change from temperate at the base, to colder conditions towards the top, indicating a close association between deteriorating climate and changing fluvial depositional style. Amino acid and luminescence geochronology from the basal fine-grained lithofacies suggest correlation with Oxygen Isotope Stage 5 and hence it is argued that the major environmental change recorded at the site relates to the Oxygen Isotope Stage 5–4 transition. Deposition of much of the overlying gravel sequence probably occurred during Oxygen Isotope Stage 4, suggesting that the latter half of the Devensian may be less significant, in terms of fluvial landscape evolution in the Upper Thames valley, than was believed previously. © 1998 John Wiley & Sons, Ltd.  相似文献   

8.
吐哈盆地西南缘铀成矿的层位标定   总被引:3,自引:1,他引:2  
吐哈盆地是中国最近发现的核资源基地,但在2000年以前,这里的地层问题一直困扰着铀矿的勘探和生产。针对目标地层的时代判别与对比,作者除了运用传统的生物地层学和岩石地层学方法外,还成功地将泥岩矿物学和元素地球化学作为辅助标志应用其中。研究结果认为,目标地层形成于早侏罗世晚期至中侏罗世早期,属于水西沟群,主要由八道湾组、三工河组、西山窑组下段、西山窑组中段和西山窑组上段5个地层单位构成。铀矿化主要发育于西山窑组,其下段和上段是最主要的含矿层,中段为次要含矿层。八道湾组和三工河组基本上无矿化。  相似文献   

9.
River-channel and colluvial deposits, near Marsworth, Buckinghamshire, record a temperate-periglacial-temperate sequence during the late Middle Pleistocene. The deposits of a lower channel contain tufa clasts bearing leaf impressions that include Acer sp., and Sorbus aucuparia and containing temperate arboreal pollen attributed to ash-dominated woodland. The tufa probably formed at the mouth of a limestone spring before being redeposited in a small river whose deposits contain plant remains, Mollusca, Coleoptera, Ostracoda and vertebrate bones of temperate affinities. The sediments, sedimentary structures and limited biological remains above the Lower Channel deposits indicate that fluvial deposition preceded climatic cooling into periglacial conditions. Fluvial deposition recurred during a later temperate episode, as shown by the mammalian bone assemblage in stratigraphically higher channel deposits. The Upper Channel deposits are confidently attributed to Oxygen Isotope Sub-Stage 5e (Ipswichian) on the basis of their vertebrate remains. However, the age of the Lower Channel deposits is less clear. The mammalian and coleopteran remains in the Lower Channel strongly suggest correlation with Oxygen Isotope Stage 7 on the basis of their similarities to other sites whose stratigraphy is better known and the clear difference of the Lower Channel assemblage from well-established faunas of Ipswichian or any other age. By contrast, U–Th dating of the tufa clasts suggests an age post 160 ka BP, while Aile/Ile ratios on Mollusca point to an Ipswichian age and younger. Four ways of interpreting this age discrepancy are considered, the preferred one correlating the Lower Channel deposits with Oxygen Isotope Stage 7.  相似文献   

10.
Pleistocene fluvial sediments of the Northmoor Member of the Upper Thames Formation exposed at Latton, Wiltshire, record episodic deposition close to the Churn–Thames confluence possibly spanning the interval from Marine Isotope Stages (MIS) 7 to 2. The sequence is dominated by gravel facies, indicating deposition by a high‐energy, gravel‐bed river. A number of fine‐grained organic sediment bodies within the sequence have yielded palaeoenvironmental and biostratigraphical data from Mollusca, Coleoptera, vertebrates, pollen and plant macrofossils. The basal deposit (Facies Association A) contains faunal material indicating temperate conditions. Most of the palaeontological evidence including a distinctive small form of mammoth (Mammuthus cf. trogontherii), together with the U‐series age estimate of >147.4 ± 20 kyr suggest correlation with MIS 7. The overlying deposits (Facies Associations B and C) represent deposition under a range of climatic conditions. Two fine‐grained organic deposits occurred within Association B; one (Association Ba) in the northern part of the pit as a channel fill and the other (Association Bb) in its southern part as a scour‐fill deposit. The coleopteran assemblages from Ba, indicate that it accumulated under temperate oceanic conditions, while Bb, which also yielded a radiocarbon age estimate of 39 560 ± 780 14C yr BP, was formed under much colder and more continental climatic conditions. The sequence is considered to represent deposition within an alluvial fan formed at the Churn–Thames confluence; a depositional scenario which may account for the juxtaposition of sediments and fossils of widely differing age within the same altitudinal range. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

11.
Sedimentary kaolin deposits in the Lote 18 area (Santa Cruz Province, Patagonia, Argentina) have been mined since 1951. They constitute 30% of the country's production and are mainly used in the ceramic whiteware industry. The deposits belong to the Baqueró Formation (Lower Cretaceous) and unconfomably overlie either the ash-flow tuffs of the Chon-Aike Formation (Middle Jurassic), which are altered to kaolinite and minor illite, or the ash-fall tuffs of Bajo Grande Formation (Upper Jurassic-Lower Cretaceous), which are altered mainly to smectites. The presence of illite or smectite, as well as the kaolinite crystallinity, depends on the stratigraphic position of the kaolin horizons within the Lower Member of the Baqueró Formation and on the lithology of the underlying rocks. Kaolin beds composed of well-crystallized kaolinite at the base of the sequence overlaying Chon-Aike rocks are the purest. Kaolinite becomes less well cystallized with transport. Edge-to-face and swirl SEM textural patterns indicate the compaction of flocculated clays and clay movement during drainage and compaction. Mineralogical, petrological, and physico-structural evidence (i.e., form, extent, thickness) indicates that the kaolin deposits are sedimentary, formed by the transportation and deposition of previously formed kaolinite. Kaolin beds are ovoidal in plan and lenticular in profile, with thickness ranging from centimeters to 11 meters, and the culmination of fining-upward clastic sequences. Sedimentary facies analysis indicates that the kaolin deposits were formed in a fluvial environment from currents with a high suspended-load/bed-load ratio, as would result from deposition in ox-bow lakes.  相似文献   

12.
Sun Hole, a small fissure cave on the north side of Cheddar Gorge, Somerset, is best known as the site where late Upper Palaeolithic artefacts are associated with human and other mammal remains that immediately pre-date the Lateglacial interstadial. These remains from the upper levels (Unit I) overlie sediments (Unit II) that are thought to have accumulated during a full glacial period, below which are sediments (Unit III) attributed to an interglacial stage. The extinct land snail Retinella (Lyrodiscus) sp., which in Britain was only known from the Hoxnian Stage, had previously been recovered from Unit III. The interglacial at the base of the sequence was therefore assigned to the Hoxnian Stage (Marine Isotope Stage (MIS) 11, 424–374 kyr). Here we provide additional analyses of samples from Unit III, which as well as containing further Retinella (Lyrodiscus), also yielded a specimen of Monachoides incarnatus, its first record from the British Pleistocene. An associated assemblage of small mammals included a few that are rare in the British Pleistocene, such as birch mouse (Sicista cf. betulina) and garden dormouse (Eliomys quercinus). The vole Lasiopodomys gregaloides and the shrew Sorex (Drepanosorex) savini do not occur as late as the Hoxnian and therefore suggest an older age in the early Middle Pleistocene. The record from Sun Hole therefore has parallels with the well-known sequence from the upper Calcareous Member in the nearby cavern system at Westbury-sub-Mendip.  相似文献   

13.
Interpretation of weathered glacial and interglacial deposits in the lower King Valley suggests that the Early Pleistocene Thureau Formation is conformably overlain by the Regency Formation. Pollen analysis of the Regency Formation provides evidence of a new climatic stage, the Regency Interglacial. The interglacial deposit consists of humified peat overlain by drifted wood and leaves. The pollen analysis shows a transition from montane scrub rainforest to lowland temperate rainforest dominated by Lagarostrobos franklinii, Nothofagus cunninghamii and Phyllocladus aspleniifolius. Trace quantities of the species Quintinia psi-latispora and Gothanipollis perplexus , now both extinct in Tasmania, were also recorded. On the basis of intense chemical weathering and correlation with sediments that have a reversed magnetization the weathered glacial deposits of the Thureau Formation are thought to be older than 730,000 B.P. The eroded interglacial deposit rests on the weathered deposits and is buried by outwash gravels of the David Formation, which was deposited during an ice advance of the Middle Pleistocene Henty Glaciation (c. 150,000 B.P.). Comparison of the Regency site with a site 2 km to the south at Baxter Rivulet shows that the unconformity between the interglacial deposit and the overlying outwash gravel represents the erosion of the evidence for the Middle Pleistocene Moore Glaciation.  相似文献   

14.
青海聚乎更矿区是全球陆域中纬度地区天然气水合物的首要发现地,水合物储存层位主要为该矿区三露天井田的中侏罗世含煤岩系。依据钻孔岩心及测井曲线,对该矿区三露天井田含煤岩系进行沉 积环境分析,在单孔沉积相及沉积相断面图分析的基础上,重建研究区的岩相古地理格局。木里组下段岩性主要为细砾岩、含砾粗砂岩及粗砂岩等粗粒岩石,以辫状河为主的沉积环境;木里 组上段岩性以厚层砂岩与厚层煤层互层为特征,反映了水体逐渐加深的过程中发育三角洲为主的沉积环境;江仓组下段以细粒砂岩及泥岩互层夹薄煤层为特征,反映水体进一步加深过程中的三角洲前缘和滨浅湖环境;江仓组上段以油页岩、暗色泥岩为主,含有瓣鳃类化石,反映湖泊为主的沉积环境。  相似文献   

15.
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   

16.
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   

17.
Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 °C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed.  相似文献   

18.
Pleistocene deposits containing the disarticulated skeleton of a mammoth, and associated faunal and floral remains, were discovered in July 1990 at Upper Strensham, Worcestershire. The environmental evidence from the fauna and flora together with limited geological evidence, indicates that the deposits accumulated within a low energy fluvial environment with a surrounding marsh and restricted tree cover on, or close to, the floodplain. The patchy occurrence of trees in a species-rich grassland is discussed, and the climatic significance of the fauna and flora is considered. The Strensham site lies within the valley of the River Avon, which is known to contain at least five altitudinally distinct river terraces. The deposits at Strensham lie beneath a terraced surface that cannot be accommodated within the existing framework of terrace development in the valley, and evidence is presented which may suggest that these deposits form a previously unrecognised fluvial unit, the Strensham Member of the Avon Valley Formation. Amino-acid age estimates from shells taken from the fossiliferous sediments of the Strensham Member suggest a correlation with Oxygen Isotope Stage 7. This correlation suggests that the temperate deposits at this site should be correlated with the temperate phase recorded at Marsworth, Buckinghamshire and Stoke Goldington in the valley of the Great Ouse.  相似文献   

19.
The occurrence of the freshwater genus Tanousia Servain 1881 (Hydrobiidae) in the Middle Pleistocene lacustrine succession of the Piànico-Sèllere Basin (Bergamo, Northern Italy) represents a significant biostratigraphical discovery. The Tanousia were recovered from the basal part of the carbonate varved bed (BVC), in siltysandy slump sediments, and from the lower and middle parts of the La Palazzina Member (MLP) of the Piànico formation. The BVC unit, in which a dated tephra layer occurs, accumulated during an interglacial phase, as shown by pollen analyses. The MLP Tanousia-bearing layers have been laid down during cool–temperate climate oscillation. The Piànico population of Tanousia displays great morphological variability but is similar to T. runtoniana (Sandberger, 1880), T. stenostoma (Nordmann, 1901) and T. cf. T. stenostoma (Nordmann, 1901), from the Bavelian and Cromerian interglacial deposits of late Early and early Middle Pleistocene age in Northern Europe. As for these species, the Tanousia population from Piànico appears to indicate fluvial conditions under a fully temperate climate.  相似文献   

20.
This study presents an overview of Middle Pleistocene loess–palaeosol sequences (LPS) in northern France and discusses the palaeoclimatic significance of the pedosedimentary record in the context of western European LPS and of global climatic cycles for the last 750 ka. In this area, the oldest loess deposits (early Middle Pleistocene) are preserved in sedimentary traps (leeward scarps of fluvial terraces and dissolution sinkholes). They result from local deflation processes reworking Pleistocene sandy fluvial deposits or relicts of Tertiary sands. A large extension of typical calcareous loess over the landscape, the Loess Revolution, is then observed during MIS 6, with heavy mineral assemblages testifying to long-distance transport from the polar desert area of the dried eastern Channel. A correlation scheme is proposed between the global records of northern France in continental environments and both global palaeoclimatic records and other main western European LPS. After 30 years of research, northern France LPS stand as a fundamental archive of the impact of interglacial–glacial climatic cycles as well as millennial events. Finally, these works provide a robust chronoclimatic framework for the study of the western European Late Acheulean and Middle Palaeolithic and for the relative dating of the various fluvial terraces that they fossilise.  相似文献   

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