Middle Pleistocene lacustrine deposits in eastern Essex,England and their palaeogeographical implications

Investigations in quarry exposures in the Asheldham Gravel and related deposits of southeast Essex are described. Section logging, mapping and borehole investigations are supported by clast lithological, heavy and clay mineralogical determinations. The sediments are derived from reworking of local Thames basin materials, fine sediment being predominantly from the London Clay. The sequence is shown to represent an aggradation that began as the fluvial infilling of the River Medway valley. The River Thames, diverted into this valley by glaciation further west, overwhelmed the Medway, reworking the deposits. The valley was subsequently drowned and fine laminated lake sediment was initially deposited. This was during a period when the valley was drowned by the glacial lake ponded in the southern North Sea basin by the Anglian/Elsterian ice sheet. Progradation by a braid-delta complex advanced along the valley and subsequently fluvial deposition returned. Valley widening and straightening accompanied the delta progradation. The deposits were dissected by deep fluvial valleys infilled by Hoxnian interglacial sediments. The Asheldham Gravel is therefore placed in the Anglian/Elsterian Stage.     

A chronology for North Sea Lobe advance and recession on the Lincolnshire and Norfolk coasts during MIS 2 and 6

During the last (MIS 2) and older glaciations of the North Sea, a North Sea Lobe (NSL) of the British-Irish Ice Sheet flowed onshore and terminated on the lowlands of eastern England, constructing inset sequences of either substantial ice-marginal deposits and tills or only a thin till veneer, indicative of complex and highly dynamic glaciological behaviour. The glaciation limit represented by the Marsh Tills and the Stickney and Horkstow Moraines in Lincolnshire is regarded as the maximum margin of the NSL during MIS 2 and was attained at ∼19.5 ka as determined by OSL dating of overridden lake sediments at Welton le Wold. A later ice marginal position is recorded by the Hogsthorpe-Killingholme Moraine belt, within which ice-walled lake plains indicate large scale ice stagnation rapidly followed ice advance at ∼18.4 ka based on dates from supraglacial lake deposits. The NSL advanced onshore in North Norfolk slightly earlier constructing a moraine ridge at Garrett Hill at ∼21.5ka. In addition to the large ice-dammed lakes in the Humber and Wash lowlands, we propose that an extensive Glacial Lake Lymn was dammed in the southern Lincolnshire Wolds by the NSL ice margin at the Stickney Moraine. Previous proposals that older glacier limits might be recorded in the region, lying between MIS 2 and MIS 12 deposits, are verified by our OSL dates on the Stiffkey moraine, which lies immediately outside the Garrett Hill moraine and appears to be of MIS 6 age.     

The nature and origin of fissures in the East Anglian Coralline and Red Crags

Vertical or inclined planar fissures that may for the most part be classified as joints are commonly seen in exposures of both the Coralline and Red Crag in East Anglia. Measurements of fissure orientation reveal orthogonal patterns of alignment in both formations. The field relations of the fissures to the host Crag sediment suggest a tectonic rather than periglacial origin. It is proposed that the fissure system is the product of early Pleistocene tectonic flexuring in the area, on the western margin of the subsiding southern North Sea basin.     

Sea‐level changes,river activity,soil development and glaciation around the western margins of the southern North Sea Basin during the Early and early Middle Pleistocene: evidence from Pakefield,Suffolk, UK

This paper outlines evidence from Pakefield (northern Suffolk), eastern England, for sea‐level changes, river activity, soil development and glaciation during the late Early and early Middle Pleistocene (MIS 20–12) within the western margins of the southern North Sea Basin. During this time period, the area consisted of a low‐lying coastal plain and a shallow offshore shelf. The area was drained by major river systems including the Thames and Bytham. Changes in sea‐level caused several major transgressive–regressive cycles across this low‐relief region, and these changes are identified by the stratigraphic relationship between shallow marine (Wroxham Crag Formation), fluvial (Cromer Forest‐bed and Bytham formations) and glacial (Happisburgh and Lowestoft formations) sediments. Two separate glaciations are recognised—the Happisburgh (MIS 16) and Anglian (MIS 12) glaciations, and these are separated by a high sea level represented by a new member of the Wroxham Crag Formation, and several phases of river aggradation and incision. The principal driving mechanism behind sea‐level changes and river terrace development within the region during this time period is solar insolation operating over 100‐kyr eccentricity cycles. This effect is achieved by the impact of cold climate processes upon coastal, river and glacial systems and these climatically forced processes obscure the neotectonic drivers that operated over this period of time. © British Geological Survey/Natural Environment Research Council copyright 2005. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.     

The magnetic properties of Quaternary and Tertiary sediments in the southern North Sea

Cores from boreholes penetrating late Quaternary, glacial, interglacial and postglacial sediments and the underlying late Cenozoic delta complex of the southern North Sea have been examined for their magnetic properties. A magnetic polarity stratigraphy has been established as an aid to biostratigraphic dating of the sediments; the Kaena-Gauss and Gauss—Matuyama transitions and the base and top of the Olduvai subchron have been identified. The strength and stability of laboratory-induced isothermal remanent magnetisation display clear magneto-petrological variations, which match lithostratigraphic changes in the cores. Principal component analysis has picked out a basin-wide and palaeoenvironmental consistency in the magnetic data. Large, multi-domain magnetite grains predominate in the post-deltaic and fluvio-deltaic sediments, whereas smaller greigite or titanomagnetite grains are concentrated in the intertidal and marine deltaic facies. Since heavy mineral analysis indicates that most of the deltaic detritus derived from common source areas, the differences in magnetic mineralogy have probably been caused by the sediment transport processes operating within the delta complex.     

The Early and Middle Miocene transgression at the southern border of the North Sea Basin (northern Belgium)

The Lower–Middle Miocene Berchem Formation of northern Belgium is an essentially sandy sequence with a varying glauconite content and often abundant shelly intervals. The formation was deposited in a shallow marine environment and rests unconformably on stiff Rupelian clays or Chattian sands. The lithological recognition of the four members (Edegem Sands, Kiel Sands, Antwerpen Sands and Zonderschot Sands members) of the Berchem Formation solely based on lithological criteria proved to be difficult, especially in boreholes. The geometry of the Formation in the subsurface of northern Belgium remained largely unknown. Diverse and well preserved dinoflagellate cyst associations have been recovered from the four members in seven boreholes and two outcrops, and allow a refinement of the biostratigraphy of these deposits. A Miocene biozonation defined in mid‐latitude shallow marine deposits in the Atlantic Coastal Plain of the USA (Salisbury Embayment, Maryland) is readily applicable to this material, and has led to a detailed stratigraphic assessment of each member. Three detailed profiles depicting the distribution of the biozones in the subsurface of northern Belgium allow the reconstruction of the geometry and depositional history of the Berchem Formation. The oldest Miocene deposits are of early Burdigalian age and they testify to a transgression, which invaded Belgium from a north–northwestern direction. The maximum flooding took place during early Serravallian times. The upper boundary of the formation is a major erosional surface of late Serravallian or (slightly) younger age. Copyright © 2005 John Wiley & Sons, Ltd.     

Mesozoic (Late Jurassic) palynomorphs and charcoal from a sandstone pebble from Quaternary glacial deposits of the North Sea

The palynological contents as well as macroscopic charcoal fragments from a calcareous sandstone pebble from Quaternary glacial deposits of the North Sea (80 km SW of the Dogger Bank) are described. The taxonomic composition of the palynoflora points to a Late Jurassic (or Late Jurassic/Early Cretaceous) age of the sandstone. The charcoal is interpreted as direct evidence of palaeo‐wildfire occurring during this period in the source area of the sediments of this particular sandstone. This finding, together with already published data on Mesozoic deposits, allows to conclude that wildfires were obviously widespread during this period in the area of the modern day North Sea and adjacent areas. Copyright © 2012 John Wiley & Sons, Ltd.     

Holocene sedimentation on the North Norfolk barrier coast in relation to relative sea-level change

Fourteen distinct sedimentary environments have been recognised in the surface sediments of the intertidal zone of the North Norfolk coast. Nine of these can be distinguished in borehole samples on the basis of sedimentological and micro-palaeontological characteristics. They comprise: gravel; channel sand; intertidal sand; intertidal silty sand; intertidal mud and marsh creek; lower salt marsh; upper salt marsh; dune sand; and peat. Sediment accumulations have been penetrated to a depth of ?8 m OD and basal peats dated by ¹⁴C back to 8410 ± 50 years BP. An overall rate of sediment accumulation (and subsidence) of about 1 m per thousand years is indicated. There is considerable persistence of sedimentary environments in the same areas during up-building, but some erosion and roll-over of the coastal barrier system has occurred. Evidence of positive and negative sea-level tendencies are present in the record, but the main development of the tract is determined by sediment supply to the beach and marshes; positive sea-level tendencies occur at c. 6610, 5970, 4630 and 2790 BP, negative sea-level tendencies occur at 4520 to 4450 and (possibly) 3470 BP.     

Micromorphology of some North Sea till samples,a pilot study

In a pilot study three samples of diamictons from boreholes in the Dutch sector of the North Sea have been thin sectioned. In the thin sections the granulometry, structure and plasmic fabric of the diamictons have been studied. On the basis of this study two of the samples have been interpreted as flow tills, while one sample has been interpreted as a basal (lodgement) till.     

Dinoflagellate cyst biostratigraphy of the Upper Miocene Deurne Sands (Diest Formation) of northern Belgium,southern North Sea Basin

Diverse and well‐preserved palynomorph assemblages recovered from the Deurne Sands, a local member of the Upper Miocene Diest Formation near Antwerp, allow the recognition of dinoflagellate cyst biozones defined in the North Atlantic realm (East Coast, USA) and the North Sea region (Nieder Ochtenhausen well, northern Germany). Based on the dinoflagellate cyst assemblages and the calcareous microfossils, the deposition of the Deurne Sands took place at some time during middle to late Tortonian (Late Miocene). These sands can be correlated biostratigraphically with the Dessel Sands in the Campine area of northern Belgium. This correlation demonstrates the existence of two separate and contemporary depositional areas in northern Belgium during early Late Miocene times. Copyright © 2002 John Wiley & Sons, Ltd.     

Early and Middle Pleistocene river systems in eastern England: evidence from Leet Hill,southern Norfolk,England

Pleistocene sediments at Leet Hill, southern Norfolk are examined in terms of their sedimentary structures, palaeocurrent indicators, clast and heavy mineral lithology and litho- and morphostratigraphic position. Colour of the quartzite and vein-quartz clasts is used to differentiate the Bytham and the Kesgrave sands and gravels, with the Bytham sands and gravels having a significantly higher proportion of coloured material. The Kirby Cane sands and gravels are the lower sedimentary unit and were deposited by the Bytham river, which drained a catchment extending into central England. At Leet Hill, erosion of the Kesgrave Sands and Gravels by the Bytham river has given the Kirby Cane sands and gravels a distinctive lithological assemblage. Trace clast lithologies suggest that the Kesgrave Sands and Gravels in the region of Leet Hill were deposited in a coastal location with an input from northern sources as well as southern and Welsh sources diagnostic of the Thames catchment. The glaciofluvial Leet Hill Sands and Gravels were deposited by outwash from the Anglian Scandinavian ice sheet. Initially the flow direction of the outwash was determined by the Bytham river valley, but this changed to a southerly direction once the valley had been infilled. This paper provides the first indication of the location of the boundary (Early Pleistocene coastline) between the fluvial Kesgrave Sands and Gravels and the marine equivalent reworked by coastal processes, and demonstrates the way the pre-glacial relief initially controlled patterns of glaciofluvial sedimentation during the early part of the Anglian glaciation. Copyright © 1999 John Wiley & Sons, Ltd.     

Dinoflagellate cyst stratigraphy and palaeoenvironment of the marginal marine Middle and Upper Miocene of the eastern Campine area,northern Belgium (southern North Sea Basin)

A stratigraphical and palaeoenvironmental analysis with organic‐walled palynomorphs of the Bolderberg and Diest formations provides new insights in the depositional history during Miocene times at the southern border of the North Sea Basin. The Neogene transgression invaded Belgium from a north–northwestern direction and fully marine sediments were deposited in the northern part of Belgium. The age and the palaeoenvironment of the deposits at the very border of the southern North Sea Basin remained till a few decades ago incomplete. The recovered dinoflagellate cysts, acritarchs and green algae from the Bolderberg Formation in the Wijshagen Borehole indicate a marginal marine depositional environment during late Burdigalian and Langhian times in the eastern Campine area, in contrast to the deeper marine conditions prevailing to the north–northwest. The relative dating of the Bolderberg Formation confirms that maximum flooding occurred during Langhian to early Serravallian times. Deposition apparently took place during the Middle Miocene Climatic Optimum, and ended when the climatic deterioration set in at around 14 Ma. A hiatus spanning ca. 2 Ma separates the Middle Miocene Bolderberg Formation from the Upper Miocene Diest Formation in the eastern Campine area at the border of the North Sea Basin. Copyright © 2007 John Wiley & Sons, Ltd.     

阿拉斯加北坡盆地楚科奇海域层序格架

阿拉斯加北坡盆地经历了石炭纪—中侏罗世的被动大陆边缘阶段、中侏罗世—早白垩世的波弗特海裂谷阶段、早白垩世晚期—现今的布鲁克斯造山和前陆盆地阶段,盆山格局在古生代和现今发生了反转。盆地楚科奇海域可划分为4个一级层序与8个二级层序:4个一级层序为富兰克林巨层序、埃尔斯米尔巨层序、波弗特海裂谷巨层序、布鲁克林巨层序,层序界面分别为T_(100)、JU、K1;8个二级层序为下埃尔斯米尔超层序(SQ1)、中埃尔斯米超层序(SQ2)、上埃尔斯米尔超层序(SQ3)、下波弗特海裂谷超层序(SQ4)、上波弗特海裂谷超层序(SQ5)、下布鲁克林超层序(SQ6)、中布鲁克林超层序(SQ7)、上布鲁克林超层序(SQ8),层序界面分别为MU、PU、LCU、MAU、MBU。楚科奇海域的有利勘探区带为汉娜坳陷。     

Pleistocene stratigraphy in the Devils Hole Area,Central North Sea: Foraminiferal and amino-acid evidence

A detailed study of the foraminiferal assemblages from the 229.1-m-deep core 81/34 in the central North Sea has been combined with a series of measurements of the isoleucine epimerisation of foraminiferal tests. A total of 17 foraminiferal zones have been established and both the faunal compositions and the amino-acid values suggest that a major part of the sequence represents deposits of early and middle Pleistocene age. Only the uppermost zone is referred to the late Pleistocene. The sequence mainly comprises a series of marine zones from cold periods, but with some barren, possibly non-marine intervals in between. Only two of the foraminiferal zones can be referred to interglacial periods. The oldest one of these, defined here as the Devils Hole Interglacial, may belong to the latter part of the Cromerian Complex, while the upper warm interval is correlated with the Holsteinian of northwest Europe on the basis of its amino-acid values. A detailed stratigraphical correlation between core 81/34 and the neighbouring core 81/29 is suggested on the basis of their foraminiferal content, palaeomagnetic evidence and amino-acid measurements from both cores. A characteristic feature of both sequences is that most of the Quaternary record is missing. Similar episodic patterns of deposition and erosion have been reported previously from the North Sea area.     

北黄海东部次盆地下白垩统沉积环境及沉积充填

下白垩统是北黄海东部次盆地目前最重要的油气勘探层位,准确认识下白垩统的沉积特征,对下一步油气勘探战略选区及优化勘探部署具重要意义。依据钻测井、地震资料,利用古生物、地球化学、地球物理等手段,研究了下白垩统的沉积相类型,分析了古气候、古盐度、古水动力、古物源等沉积环境,最终探讨了三级层序地层格架内下白垩统的沉积充填及演化。结果表明,北黄海东部次盆地下白垩统发育扇三角洲-湖泊沉积体系。该时期以亚热带炎热半干旱气候为主,夹短暂温湿气候。古水体为淡水-半咸水性质,接受来自北部、东部、西南等多个方向的物源供给。早期地层分布局限,以滨浅湖亚相、扇三角洲相沉积为主;之后,湖泊水体范围扩大,发育扇三角洲平原-扇三角洲前缘-滨浅湖亚相沉积序列;中晚期地层受区域抬升作用的影响,仅残存于盆地西北部,以滨浅湖相沉积为主。     

北黄海盆地东部坳陷中新生代构造样式

北黄海盆地东部坳陷中新生代自下而上发育中侏罗统、上侏罗统、下白垩统、渐新统和新近系,划分为3个构造层,即下构造层、中构造层和上构造层,分别对应盆地的中生代断陷-反转阶段、古近纪断陷—反转阶段和区域沉降阶段3期构造演化阶段。不同的构造演化阶段造就了不同的构造样式,基于地震反射资料,结合盆地地质结构特征,总结了坳陷构造样式特征,即伸展构造、挤压构造、反转构造及扭动构造4种样式,以伸展构造样式为主,翘倾断块、滑动断阶及逆牵引背斜是研究区内有利于油气运聚成藏的主要构造样式。     

Provenance and depositional environments of Quaternary sediments from the western North Sea Basin

As the majority of the data on Quaternary sediments from the North Sea Basin are seismostratigraphical, we analysed the Elsterian Swarte Bank Formation, the Late Saalian Fisher Formation and the Late Weichselian (Dimlington Stadial) Bolders Bank Formation in order to determine genesis and provenance. The Swarte Bank Formation is a subglacial till containing palynomorphs from the Moray Forth and the northeastern North Sea, and metamorphic heavy minerals from the Scottish Highlands. The Fisher Formation was sampled from the northern and central North Sea. In the north, it is interpreted as a subglacial till, with glaciomarine sediments cropping out further south. These sediments exhibit a provenance signature consistent with the Midland Valley of Scotland, the Eocene of the North Sea Basin, the Grampian Highlands and northeast Scotland. The Bolders Bank Formation is a subglacial till containing palynomorphs from the Midland Valley of Scotland, northern Britain, and a metamorphic heavy‐mineral suite indicative of the Grampian Highlands, Southern Uplands and northeast Scotland. These data demonstrate that there was repeated glaciation of the North Sea Basin during the Middle and Late Pleistocene, with ice sheets originating in northern Scotland. There was no evidence for a Scandinavian ice sheet in the western North Sea basin. Copyright © 2011 John Wiley & Sons, Ltd.     

北黄海盆地东部坳陷中生界沉积特征及演化

北黄海盆地是我国近海勘探及研究程度均较低的中新生代叠合断陷盆地, 而东部坳陷是其内最具油气勘探前景的二级构造单元。通过岩芯观察与测井相分析, 结合三维地震资料, 认为东部坳陷中生界主要发育扇三角洲、辫状河三角洲、三角洲与湖泊沉积。受构造演化阶段的制约, 不同时期具有不同的沉积演化特征。其中中侏罗世处于湖盆的初期断陷期, 半深湖-深湖亚相发育, 仅在坳陷边缘见少量小规模的扇三角洲沉积。晚侏罗世处于断陷扩展期, 整体为一个完整的湖进-湖退旋回, 早期北部缓坡发育三角洲沉积, 南部及东部陡坡见扇三角洲沉积, 中后期则由于湖平面上升, 发育暗色泥岩为主的湖泊沉积, 晚期北部缓坡见小规模三角洲前缘沉积。早白垩世处于断陷萎缩期, 垂向发育2个正旋回沉积序列, 其中旋回下部以扇三角洲、辫状河三角洲相为主, 向上渐变为滨浅湖沉积。