A critical review of the glaciomarine model for Irish sea deglaciation: evidence from southern Britain,the Celtic shelf and adjacent continental slope

In support of their ‘glaciomarine’ model for the deglaciation of the Irish Sea basin, Eyles and McCabe cited the occurrence of distal glaciomarine mud drapes onshore in the Isles of Scilly and North Devon, and of arctic beach‐face gravels and sands around the shores of the Celtic Sea. Glacial and sea‐level data from the southern part of the Irish Sea in the terminal zone of the ice stream and the adjacent continental slope are reviewed here to test this aspect of the model. The suggestion that the glacial sequences of both the Isles of Scilly and Fremington in North Devon are glaciomarine mud drapes is rejected. An actively calving tidewater margin only occurred early in the deglacial sequence close to the terminal zone in the south‐central Celtic Sea. Relative sea‐levels were lower, and therefore glacio‐isostatic depression less, than envisaged in the glaciomarine model. Geochronological, sedimentological and biostratigraphical data indicate that the raised beach sequences around the shores of the Celtic Sea and English Channel were deposited at, or during regression soon after, interglacial eustatic highstands. Evidence for ice‐rafting at a time of high relative sea‐levels is restricted to a phase(s) earlier than the Late Devensian. These data indicate that the raised beach sequences have no bearing on the style of Irish Sea deglaciation. Copyright © 2001 John Wiley & Sons, Ltd.     

A critical review and re-investigation of the Pleistocene deposits between Cranfield Point and Kilkeel,Northern Ireland: Implications for regional sea-level models and glacial reconstructions of the northern Irish Sea basin

The coastline of County Down includes sites that are pivotal to understanding the history of the last glaciation of the northern Irish Sea Basin in relation to relative sea level and regional glacial readvances. The cliff sections display evidence that has been used to underpin controversial models of glaciomarine sedimentation in isostatically-depressed basins followed by emergent marine and littoral environments. They also provide crucial evidence claimed to constrain millennial-scale ice sheet oscillations associated with uniquely large and rapid sea-level fluctuations. This paper reviews previous work and reports new findings that generally supports the ‘terrestrial’ model of glaciation, involving subglacial accretion and deformation of sediment beneath grounded ice. Deep troughs were incised into the till sheet during a post Late Glacial Maximum draw-down of ice into the Irish Sea Basin. Ice retreat was accompanied by glaciomarine accretion of mud in the troughs during a period of high relative sea level. The trough-fills were over-ridden, compacted, deformed and truncated during a glacial re-advance that is correlated with the Clogher Head Readvance. Grounding-line retreat accompanied by rapid subaqueous ice-proximal sedimentation preserved a widespread subglacial stone pavement. Raised beach gravels cap the sequence. The evidence supports an uninterrupted fall in relative sea level from c. 30?m that is consistent with sea level curves predicted by current glacio-isostatic adjustment modelling. Critical evidence previously cited in support of subaerial dissection of the troughs, and hence rapid fall and rise in relative sea level prior to the deposition of the glaciomarine muds, is not justified.     

5万年来杭州地区同位素古温度与海平面变化的研究

用稳定同位素地球化学古温度测定方法，对杭州地区临安瑞晶洞穴石笋的同位素古温度进行了研究，获得距今5-1万a间该区的古气候变化的记录，并与杭州湾海平面变化曲线进行了对比。     

Mid‐ to late Holocene relative sea‐level change in Poole Harbour,southern England

A foraminiferal transfer function for mean tide level (MTL) is used in combination with AMS radiocarbon dated material to construct a record of relative sea‐level (RSL) change from Poole Harbour, southern Britain. These new data, based on multiple cores from duplicate sites, indicate four phases of change during the last 5000 cal. (calendar) yr: (i) rising RSL between ca. 4700 cal. yr BP and ca. 2400 cal. yr BP; (ii) stable to falling RSL from ca. 2400 cal. yr BP until ca. 1200 cal. yr BP; (iii) a brief rise in RSL from ca. 1200 cal. yr BP to ca. 900 cal. yr BP, followed by a period of stability; (iv) a recent increase in the rate of RSL rise from ca. 400–200 cal. yr BP until the present day. In addition, they suggest that the region has experienced long‐term crustal subsidence at a rate of 0.5 mm C¹⁴ yr^?1. Although this can account for the overall rise in MTL observed during the past 2500 yr, it fails to explain the changes in the rate of rise during this period. This implies that the phases of RSL change recorded in the marshes of Poole Harbour reflect tidal range variations or ‘eustatic’ fluctuations in sea‐level. Copyright © 2001 John Wiley & Sons, Ltd.     

南极海冰变化异常与全球海平面变化(英)

In this paper, the long-term variation trend of the Antarctic sea ice in 1973～1994 and the inter-decade variation rule of the global sea level are analyzed. It is foundthat, the Antarctic sea ice area in 1980's was significantly less than in 1970's but with regional difference:decreasing in Regions Ⅰ, Ⅱ, and Ⅲ, and increasing in Region Ⅳ, the average global sea levelheightvalue in 1980's was also significantly higher than in 1970's but also with very large regional difference.Connecting variation of both to analyze their physical mechanism, it is pointed that, the accumulated seaice anomaly value in 1980's less than in 1970's means a global climate warming, the sea watertemperature and air temperature rising, sea water volume expanding, and more icebergs transportingfrom the ice cover on the Antarctic continent to ocean in the warmer years. As a result, the global sealevel raised significantly with the global average sea level value in 1980's was 22 mm higher than in 1970's. The Sea Level Raising (SLR) distributed uneven. It is especially true in the Pacific Ocean andAtlantic. This kind of uneven SLR distribution closely relates to, or is introduced by the uneven sea ice change of the Antarctic Regions.     

Tertiary Sea Level Changes and Sequence Stratigraphic Framework in East China Sea Shelf Basin

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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.     

Sea‐level change in the Irish Sea since the Last Glacial Maximum: constraints from isostatic modelling

Models of glacio‐hydroisostatic sea‐level change have been published for the British Isles that are broadly consistent with the observational evidence, as well as with glaciological constraints. It has been argued, however, that the models fail to represent sea‐level change along the Irish Sea margins and in southern Ireland for the post‐deglaciation period. The argument rests on the interpretation of the depositional environment of the elevated ‘Irish Sea Drift’ on both sides of the Irish Sea: whether this is terrestrial or glaciomarine. The isostatic models for the British Isles are consistent with the former interpretation in that sea‐levels on either side of the Irish Sea, south of about the Isle of Man, are not predicted to have risen above present sea‐level at any time since the deglaciation of the Irish Sea. This implies that ice over both the Irish Sea and Ireland was relatively thin (ca. 600–700 m over Ireland). If the glaciomarine interpretation of the elevated Irish Sea Drift is correct, then the maximum ice thickness over central and southern Ireland would have to reach 2000 m, exceeding that over Scotland. Furthermore, for the resulting sea‐level change to be consistent with the Holocene evidence, this thick ice sheet could not have extended to the eastern side of the Irish Sea. Nor could it have been very thick at its northern and western limits. If such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the Irish Sea Drift as terrestrial in origin. Copyright © 2001 John Wiley & Sons, Ltd.     

滨岸-浅海混合沉积对海平面与气候变化的响应--以塔里木盆地巴麦地区石炭系为例

陆源碎屑-碳酸盐混积作用发生的环境特征尚不明确,导致对混积岩分布规律认识不足。以塔里木盆地巴麦地区石炭系为例,通过薄片观察、矿物组成分析、主微量元素分析,对沉积环境和古环境特征参数进行了研究。研究区混积岩发育在障壁滨岸、碳酸盐岩局限台地和开阔台地。利用与混积强度相关性极好的Ti、Rb、K和Al的含量,将混积岩定量划分为4级。利用Na/Ca比值、Na含量分析了古盐度特征,Mn/Fe比值和Sr含量分析了古水深,用V/（V+Ni）比值反映了氧化还原条件,并利用Ti/Al,Mg/Sr反映了古气候特征。研究结果表明Ⅱ级以上混积均发生在湿润气候下,而干旱气候无明显混积,并且混合沉积大部分发生在海平面下降阶段。碳酸盐岩开阔台地的混积强度仅达I级,障壁滨岸和碳酸盐岩局限台地的混积强度较高,发育Ⅲ级和IV级高度混积岩。不同沉积环境的混合沉积均对古气候变化与相对海平面变化具有良好的响应,是详细的古环境变化记录。     

A late Ordovician (Hirnantian) karstic surface in a submarine channel,recording glacio‐eustatic sea‐level changes: Meifod,central Wales

The growth and decay of the end‐Ordovician Gondwanan glaciation is globally reflected by facies changes in sedimentary sequences, which record a major eustatic fall and subsequent rise in the Hirnantian Stage at the end of the Ordovician. However, there are different reported estimates of the magnitude and pattern of sea‐level change. Particularly good evidence for end‐Ordovician sea‐level change comes from a sequence at Meifod in central Wales, which has a karstified limestone unit within a channel incised into marine shelf sediments. Pre‐glacial (Rawtheyan) mudstones have a diverse fauna suggesting a mid‐to‐deep‐shelf water depth of c. 60 m. The channel, 20 m deep, was incised into these mudstones and partially filled with a mixture of fine sand and detrital carbonate. The taphonomy of bioclasts and intraclasts indicates that many had a long residence time on the sea floor or suffered diagenesis after shallow burial before being resedimented into the channel. The presence of carbonates on the Welsh shelf is atypical and they are interpreted as having accumulated as patches during a minor regression prior to the main glacio‐eustatic fall. Comparison of the carbon stable‐isotopic values of the bioclast material with the global isotopic record confirms that most of the material is of Rawtheyan age, but that some is Hirnantian. The resedimented carbonates lithified rapidly and formed a limestone, several metres thick, in the deepest parts of the channel. As sea‐level fell, this limestone was exposed and eroded into karstic domes and pillars with a relief of over 2 m. The overall, glacio‐eustatic, sea‐level fall is estimated to be in excess of 80 m. A succeeding sea‐level rise estimated to be 40–50 m is recorded in the laminated crust that mantles the karstic domes and pillars. The crust is formed of encrusting bryozoans, associated cystoids, crinoid holdfasts and clusters of the brachiopod Paromalomena, which is normally associated with mid‐shelf environments. Fine sands buried the karst topography and accumulated to fill the channel. In the sandstones at the base of the channel there is a Hirnantia fauna, while in the sandstones high in the channel‐sequence there is cross‐stratification characteristic of mid‐shoreface environments. This would indicate a fall of sea‐level of c. 30 m. The subsequent major transgression marking the end of the glaciation is not recorded at the Meifod locality, but nearby exposures of mudstones suggest a return to mid‐to‐deep‐shelf environments, similar to those that prevailed before the Hirnantian regression. The Meifod sequence provides strong evidence for the magnitude of the Hirnantian sea‐level changes and by implication confirm larger estimates for the size of the ice sheets. Smaller oscillations in relative sea‐level seen at Meifod may be local phenomena or may reflect eustatic changes that have not been widely reported elsewhere. Copyright © 2005 John Wiley & Sons, Ltd.     

Glaciomarine deposition around the Irish Sea basin: some problems and solutions

Reconstructing the depositional processes and setting (marine or terrestrial depositional environment) of late Devensian age glacigenic sediments around the Irish Sea basin (ISB) is critical for developing an all‐embracing and consistent glacial model that can account for all observed field evidence. Identifying episodes of marine and terrestrial glacial deposition from field data is considered the first step in achieving this goal. Criteria for distinguishing marine and terrestrial glacial environments in the ISB include the geomorphology, sedimentology and faunal content (biofacies) of the associated deposits. Exposures of glacigenic sediments around the ISB are very diverse in terms of their morphosedimentary characteristics and associated biofacies, and thus inferred depositional processes and setting. Possible reasons for the diverse geological record include the differing geometry of eastern and western ISB coasts, time‐transgressive ice retreat, and differential land rebound effects as a result of forebulge collapse and neotectonics. Poor geochronometric control on ice sheet events has not helped the correlation of ISB events with glacial and climatic events elsewhere. Future investigations of glacial sites around the ISB should use an integrated methodological approach involving a range of geomorphological, sedimentary and biofacies data, and dating control where possible. This will help in developing a more precise and holistic late Devensian glacial model that is constrained rigorously by field geological evidence. Copyright © 2001 John Wiley & Sons, Ltd.     

黔西南二叠纪早期陆源碎屑沉积体系对冈瓦纳冰川发育的响应

通常认为黔西南和黔南地区二叠纪栖霞组之下的一套陆缘碎屑岩地层,是石炭纪-二叠纪冈瓦纳大陆冰盖发育鼎盛时期大幅度海平面下降期间的沉积。最新研究表明,石炭纪-二叠纪冈瓦纳冰川是由多次不连续的冰川事件构成的。因此恢复该套以陆源碎屑岩为主地层的形成环境和堆积过程,探讨其成因与冈瓦纳冰川发育的关系,具有非常重要的科学意义。本研究查明了黔西南地区该套陆源碎屑岩的地层厚度和砂泥比值空间变化规律。在此基础上,选取碎屑岩发育最好的普安龙吟剖面开展沉积体系与成因研究。结果表明,沙子塘组主要是碳酸盐沉积体系,龙吟组和包磨山组主要为浅海陆棚三角洲沉积体系,梁山组以滨岸陆源碎屑沉积体系为主;二叠纪早期黔西南地区的陆棚相泥岩形成于冰川消融导致的海平面快速上升期间,三角洲沉积体系形成于海平面晚期高位域期间,而不是形成于冈瓦纳冰川增长期间的低位域沉积。冈瓦纳冰川的推进和消融是龙吟剖面二叠纪早期地层发育样式的主控因素。     

塔里木盆地巴楚地区石炭系高频旋回层序分析

高频旋回层序是海平面高频振荡的结果和产物。通过对塔里木盆地巴楚地区石炭系地面、钻井剖面的详细解析,首次总结出7个高频旋回层序类型,识别出50余个五级（或六级）高频旋回层序,它们在纵向上有规律地组合、叠加,组成8个四级旋回层序,3个三级旋回层序及2个二级旋回层序,构成了塔里木盆地巴楚地区石炭系的层序地层格架,同时也反映了该区石炭纪海平面的变化规律及其沉积响应。     

Triassic Sequence Stratigraphy and Sea-Level Changes in Qomolongma Area, Southern Tibet,China: From Epicontinental Sea to Rift Basin

INTRODUCTIONThe Qomolongm a area was paleogeographically situatedon the northern margin of the Indian plate and was part of theGondwana continent in the Mesozoic.In the latest MiddlePermian(late Capitanian) due to the formation of the Pangeasupercontinent,the area was uplifted significantly,resultingin an overall regression and an eminentdisconformity atca2 5 8Ma.During mosttim e of the L ate Perm ian,the Qomolongm aarea was subject to erosion and free of deposit (Shi et al.,1996 ;L …     

Oxygen Isotope Records of Core 8KL of the South China Sea and Sea - level Change

Based on a comparison between the oxygen isotope records of benthic and plank tonic foraminifers from core 8KL of the South China Sea and sea-level change records derived from the Huon Peninsula, New Guinea, it is found that both records are very similar from 72 K a B.P. to the present, especially for the benthic oxygen isotope record. The linear regression shows that δ18O changes (0.9995‰ for benthic foraminifers and 1.022‰ for planktonic foraminifers) are equal to 100 m in sea-level fluctuation. After making temperature correction in the δ18O record of benthic foraminifers from 72 to 120 Ka B.P., the curve of sea-level oscillation of the South China Sea since 186 Ka B.P. has been reconstructed. The lowermost sea - level that occurred in the last glacial maximum and oxygen isotope stage 6 is approximately - 130 m.     

Geomorphological evidence from the Lleyn Peninsula constraining models of the magnitude and rate of isostatic rebound during deglaciation of the Irish Sea Basin

A stepped series of sand and gravel terraces on the Lleyn peninsula of North Wales is used to test the magnitude and rate of isostatic depression required by the recently proposed glacimarine model of deglaciation of the Irish Sea Basin. A relative sea-level fall of 70 m is required while the ice remained pinned at the north Lleyn coast. Even taking the maximum known rate of isostatic uplift, the margin would have to remain stationary for 1400 years. It seems more reasonable to interpret the Lleyn terraces, and similar features around the Irish Sea Basin, as glacifluvial and glacilacustrine.     

Sea level change: a philosophical approach

The present Cenozoic era is an icehouse episode characterized by a low sea level. Since the beginning of the industrial revolution, the human race has been emitting greenhouse gases, increasing the global atmospheric temperature, and causing a rise in sea level. If emissions continue to increase at the present rate, average global temperatures may rise by 1.5°C by the year 2050, accompanied by a rise of about 30 cm in sea level. However, the prediction of future climatic conditions and sea level is hampered by the difficulty in modelling the interactions between the lithosphere, kryosphere, biosphere and atmosphere; in addition, the buffering capacity of our planet is still poorly understood. As scientists cannot offer unambiguous answers to simple questions, sorcerer's apprentices fill in the gaps, presenting plans to save planet without inconveniencing us.The geological record can help us to learn about the regulation mechanisms of our planet, many of which are connected with or expressed as sea level changes. Global changes in sea level are either tectono-eustatic or glacioeustatic. Plate tectonic processes strongly control sea levels and climate in the long term. There is a strong feed-back mechanism between sea level and climate; both can influence and determine each other. Although high sea levels are a powerful climatic buffer, falling sea levels accelerate climatic accentuation, the growth of the polar ice caps and will hence amplify the drop in sea level. Important sources of fossil greenhouse gases are botanic CO₂ production, CO₂ released by volcanic activity, and water vapour. The latter is particularly important when the surface area of the sea increases during a rise in sea level (maritime greenhouse effect). A volcanogenic greenhouse effect (release of volcanogenic CO₂) is possibly not equally important, as intense volcanic activity may take place both during icehouse episodes as well as during greenhouse episodes. The hydrosphere, land vegetation and carbonate platforms are major CO₂ buffers which may both take up and release CO₂. CO₂ can be released from the ocean due to changes in the pCO₂ caused by growth of coral reefs and by uptake of CO₂-rich freshwater from karst provinces. Efficient sinks of CO₂ are the weathering products of silicate rocks; long-term sinks are organic deposits caused by regional anoxic events which preferrably develop during sea level rises and highstands; and coal-bearing strata. Deposition of limestone also removes CO₂ from the atmospheric-hydrospheric cycle at a long term. Biotic crises are often related to either sea-level lows or sea-level highs. Long-term sea-level lows, characteristic of glacial periods, indicate cooling as major cause of extinction. During verly long-lasting greenhouse episodes the sea level is very high, climate and circulation systems are stable and biotic crises often develop as a consequence of oxygen depletion. On land, niche-splitting, complex food web structures and general overspecialization of biota will occur. Whether the crisis is caused by a single anoxic event (e.g. in the Late Devonian) or a disturbance by an asteroid impact (e.g. the Cretaceous/Tertiary boundary), it will only trigger total collapse of an ecosystem if a large part of it was already in decline. The regulatory mechanisms and buffers are thermodynamically extremely efficient if they are given sufficient time in which to deploy their power. However, after major catastrophes the re-establishment of successful ecosystems will take millions of years. The present rate of sea level and associated temperature rise is much too fast to be compensated and buffered by the network of natural controls. It is likely that the transitional time towards a new steady state will be an extremely variable and chaotic episode of unpredictable duration. Correspondence to: H. Seyfried     

海平面升降对海相临滨储层宏观非均质性控制机理——以塔里木盆地哈得逊东河砂岩储层为例

本文研究海平面变化对海相单一亚相储层宏观非均质性的影响。以经典层序地层学理论为指导,应用岩心测试、测井数据,对哈得油田东河砂岩段临滨亚相储层宏观非均质性进行了分析,提出了海平面升降对临滨亚相储层宏观非均质性控制机理,确定了海平面相对变化控制的储层宏观非均质性分布模式。结果表明,准层序、准层序组及体系域内不同级次的海平面变化,对沉积物形成的水动力条件及沉积后所处表生环境产生较大影响,各项储层宏观非均质参数表现出明显的规律性,使准层序内单一临滨亚相储层宏观非均质性表现为向上减弱的变化趋势;准层序组内由于准层序堆砌特征差异,使退积式准层序组内临滨亚相储层宏观非均质性呈向上变强的特征,而进积式准层序组内表现为由强到弱的趋势;高位体系域内单一临滨亚相储层宏观非均质性总体表现为向上逐渐减弱。     

造礁生物群落演化在海平面变化研究中的运用-以中扬子台地下奥陶统红花园组生物礁为例

中扬子台地下奥陶统红花园组造礁生物群落主要有五种 :蓝绿藻群落 (S群落 )、Calathium 蓝绿藻群落 (C S群落 )、Batostoma-Calathium群落 (B C群落 )、Archaeoscyphia-Calathium群落 (A C群落 )和Batostoma-Calathium 蓝绿藻群落 (B C S群落 )。群落的演化模式有两种 :①A C群落 /B C群落→C S群落 /B C S群落→S群落;②S群落→C S群落 /B C S群落→A C群落 /B C群落,它们分别对应于上下两期生物礁。群落最大的生态差别可能是其最适合的水深,说明其演化的主要动力可能是相对海平面的变化,根据各群落适应的水深特征,可推测红花园建礁期为一个海平面下降到上升的一个过程,相对海平面变化的最大幅度约为 15m。生物礁内生物群落的演化是海平面变化的灵敏示踪剂,可识别 5m左右的相对海平面的变化.