Direct terrestrial-marine correlation demonstrates surprisingly late onset of the last interglacial in central Europe

An interdisciplinary study of a small sedimentary basin at Neumark Nord 2 (NN2), Germany, has yielded a high-resolution record of the palaeomagnetic Blake Event, which we are able to place at the early part of the last interglacial pollen sequence documented from the same section. We use this data to calculate the duration of this stratigraphically important event at 3400 ± 350 yr. More importantly, the Neumark Nord 2 data enables precise terrestrial-marine correlation for the Eemian stage in central Europe. This shows a remarkably large time lag of ca. 5000 yr between the MIS 5e ‘peak’ in the marine record and the start of the last interglacial in this region.     

Coastal paleogeography and human occupation of the Western Alaska Peninsula

Geological and archaeological investigations on the western Alaska Peninsula establish relationships between postglacial sea level changes and regional settlement patterns, which are linked to the spatial and temporal distribution of marine and estuarine resources. Isostatic emergence dominated relative sea‐level changes since deglaciation, but erosional landforms and gaps in the archaeological record suggest that site preservation has varied because of the interplay of eustatic sea level rise, isostatic uplift, and tectonic deformation. Coastal subsidence associated with a major earthquake about 2200 yr B.P. is linked with a 300‐year hiatus in the regional archaeological record. A shift from estuarine to littoral and offshore resources following this period demonstrates the impact of such dynamic sea level fluctuations on the shape and biological productivity of the coastal zone. However, changes in village organization, house form, and subsistence base that define several archaeological phases arise from both environmental and sociopolitical instability. Models of culture change should accommodate local and regional geological boundary conditions in the North Pacific and similarly dynamic settings. © 2000 John Wiley & Sons, Inc.     

Geoarchaeology and late glacial landscapes in the western lake superior region,Central North America

The transition from full glacial to interglacial conditions along the southern margin of the Laurentide ice sheet resulted in dramatic changes in landscapes and biotic habitats. Strata and landforms resulting from the Wisconsin Episode of glaciation in the area directly west of Lake Superior indicate a context for late Pleistocene biota (including human populations) connected to ice margins, proglacial lakes, and postglacial drainage systems. Late Glacial landscape features that have the potential for revealing the presence of Paleoindian artifacts include abandoned shorelines of proglacial lakes in the Superior and Agassiz basins and interior drainages on deglaciated terrains. The linkage between Late Pleistocene human populations and Rancholabrean fauna has yet to be demonstrated in the western Lake Superior region, although isolated remains of mammoth ( Mammuthus) have been documented, as well as fluted points assigned to Clovis, Folsom, and Holcombe‐like artifact forms. Agate Basin and Hell Gap (Plano‐type) artifacts also imply the presence of human groups in Late Glacial landscapes associated with the Agassiz and Superior basins. © 2007 Wiley Periodicals, Inc.     

北美东部被动大陆边缘盆地的分段性与油气勘探

北美东部被动大陆边缘是世界上最古老的完整被动大陆边缘之一,是研究被动大陆边缘发育演化的天然实验室。本文在大量国外研究成果的基础上,应用盆地构造解析方法,深入研究了北美东部被动大陆边缘盆地群的地质结构和构造演化特征,并揭示了盆地群的油气地质规律。研究认为,北美东部盆地群沉积充填和不整合面发育具有明显的分段性和差异性。以区域不整合面为界,不同段盆地可划分为不同的构造层:南段盆地可划分为两套构造层;中段南部盆地可划分为3套构造层;中段北部盆地可划分为4套构造层;而北段盆地可划分为5套构造层。盆地群整体经历了陆内裂谷—陆间裂谷—被动大陆边缘的演化过程,但不同段盆地的构造演化具有明显的分段性和迁移性:晚三叠世沉降中心位于南段盆地;早侏罗世初期迁移至中段盆地,南段大陆开始裂解;中侏罗世逐渐迁移至北段盆地,中段大陆开始裂解;早白垩世晚期,北段大陆开始裂解。受持续的抬升剥蚀及大西洋岩浆活动省的联合作用,南段盆地和中段大多数盆地缺乏油气保存条件;斯科舍盆地和大浅滩盆地是主要的含油气盆地,以上侏罗统烃源岩为主,主要发育断层—背斜圈闭和盐体刺穿圈闭,整体表现为“自生自储”和“下生上储”的特征。     

Structure Styles of Mesozoic-Cenozoic U-bearing Rock Series in Northern China

In Northern China, sandstone-type uranium (U) deposits are mostly developed in Mesozoic-Cenozoic basins. These U deposits are usually hosted in unvarying horizons within the basins and exhibit typical U-forming sedimentary associations, which is referred to as U-bearing rock series. This study describes the structural features of U-bearing rock series within the main Mesozoic-Cenozoic U-producing continental basins in Kazakhstan, Uzbekistan, and Russia in the western segment of the Central Asian Metallogenic Belt (CAMB), and Northern China in the eastern segment of the CAMB. We analyze the basic structural conditions and sedimentary environments of U-bearing rock series in Northern China and classify their structural styles in typical basins into river valley, basin margin, and intrabasin uplift margin types. The intrabasin uplift margin structural style proposed in this study can be used to indicate directions for the exploration of sandstone-type U deposits hosted in the center of a basin. At the same time, the study of structural style provides a new idea for exploring sandstone-type U deposits in Mesozoic-Cenozoic basins and it is of great significance to prospecting of sandstone-type uranium deposits.     

Syn‐rift sequence development in a fault‐controlled embayment (Early Permian Irwin River Coal Measures,Northern Perth Basin,Western Australia)

Stratigraphic patterns and sequence development in tectonically active extensional basins remain poorly documented in comparison with passive‐margin settings. Rift basin fills are generally characterized by coarsening‐upward trends in response to the rapid creation of accommodation by extensional faulting, and the progressive filling of graben during more quiescent periods. The Early Permian Irwin River Coal Measures in the Northern Perth Basin (Western Australia) record a complex stratigraphic arrangement of conglomerate, sandstone, mudstone and coal, and have been attributed to delta plain depositional environments that developed in a cool–temperate climatic setting during syn‐rift activity. Sedimentary analysis of outcrop and core data from the fault‐bounded Irwin Terrace is used to distinguish nine facies associations reflecting deposition in braided rivers, fixed‐anastomosed channel belts, tide‐influenced coastal environments and storm‐affected distal bays. The broader depositional system is interpreted as a morphologically asymmetrical tide‐dominated embayment with a fluvial and wave influence. The stratigraphic architecture of the Irwin River Coal Measures was strongly influenced by the evolving rift basin margin. Fault reactivation of the major basin‐bounding Darling Fault in the early syn‐rift phase caused footwall uplift and the inception of transverse palaeo‐valleys occupied by braided fluvial systems. Fault block subsidence during the subsequent balanced, backstepping and drowning phases resulted in a dominantly retrogradational stacking pattern indicating progressive flooding of marginal‐marine areas and culminating in deposition of distal marine elements. In the active rift basin, it is proposed that preservation of a shallow‐marine syn‐rift sequence was promoted by the geomorphological confinement of the embayed system increasing tidal current acceleration and hampering transgressive ravinement. The proposed sequence model demonstrates that transgressive successions can develop in the early syn‐rift phase in response to footwall uplift and tectonic subsidence. The syn‐rift sequence recording the filling of an embayment on a rift basin margin may be applied in similar tectonic and/or depositional contexts worldwide.     

Quaternary paleoenvironments and potential for human exploitation of the Jordan plateau desert interior

The physical, chemical, numerical, and radiometric analyses of a 31‐m sediment core from the Qa'el‐Jafr basin provide an important record of Quaternary paleoenvironments for the Jordan Plateau and evidence for several significant changes in climate regime. Cluster and PCA analyses of the geochemical data support the designation of major sedimentation regimes identified by stratigraphic and sediment analyses. Multiple cycles of alluvial deposition, lacustrine units, and erosional unconformities characterize the deepest sediments, followed by a period(s) of intense evaporation. Radiocarbon ages of charcoal in the uppermost 7 m place the aeolian/alluvial phase between 16,030 ± 140 yr B.P. and 24,470 ± 240 yr B.P. Deflation processes may explain the lack of a Holocene sequence. Despite lacking radiometric ages for the lower sediments, the thickness and degree of calcium‐carbonate cementation suggest considerable age for the basal sediments, which suggests that a very long terrestrial record of Quaternary climate changes has been preserved in the Jafr basin. This new record of paleoenvironments provides important context to the archaeological record of the Jordan Plateau during the Quaternary. Several archaeological surveys demonstrate extensive human exploitation of lakes and springs of the major wadis along the western margin of the Rift Valley. However, little is known of human exploitation of the desert interiors. Qa'el‐Jafr sediments demonstrate significant lacustrine and high moisture phases sufficient for human exploitation of the eastern desert during the Pleistocene. © 2005 Wiley Periodicals, Inc.     

14,000 Years of Sediment, Vegetation, and Water-Level Changes at the Makepeace Cedar Swamp, Southeastern Massachusetts

Data from a transect of four cores collected in the Makepeace Cedar Swamp, near Carver, Massachusetts, record past changes in deposition, vegetation, and water level. Time series of palynological data provide a 14,000-yr record of regional and local vegetation development, a means for biostratigraphic correlation and dating, and information about changes in water level. Differences in records among cores in the basin show that water level decreased at least 1.5 m between 10,800 and 9700 cal yr B.P., after which sediment accumulation was slow and intermittent across the basin for about 1700 yr. Between 8000 and 5600 cal yr B.P., water level rose 2.0 m, after which slow peat accumulation indicates a low stand about the time of the hemlock decline at 5300 ± 200 cal yr B.P. Dry conditions may have continued after this time, but by 3200 cal yr B.P., the onset of peat accumulation in shallow cores indicates that water level had risen to close to its highest postglacial level, where it is today. Peat has accumulated across the whole basin since 3200 cal yr B.P. Data from Makepeace and the Pequot Cedar Swamp, near Ledyard, Connecticut, indicate an early Holocene dry interval in southern New England that began 11,500 yr ago near the end of the Younger Dryas interval. The dry conditions prevailed between 10,800 and 8000 cal yr B.P. and coincide with the arrival and later rise to dominance of white pine trees (Pinus strobus) both regionally and near the basins. Our results indicate a climatic cause for the “pine period” in New England.     

A highstand oolitic sequence and associated facies from a Late Triassic lake basin, south-west England

High energy, lake‐shoreline carbonate sequences are rarely documented in the geological record. However, one example occurs in the Upper Triassic Mercia Mudstone Group (MMG) of southern Britain. The MMG is one of a number of thick, non‐fossiliferous mudstone deposits associated with North Atlantic Mesozoic rift basins. The origin of the MMG mudstones is the subject of current debate, with marine, playa‐lacustrine and alluvial–aeolian models having been proposed. Shoreline features have been documented from the northern margin of the basin, but the rarity of such features elsewhere in the MMG has led many workers to doubt a lacustrine origin for the mudstones. Wave‐dominated, lake‐shoreline deposits have been recognized in several sections from the southern basin margin in the Clevedon area of the Bristol Channel in south‐west England. These deposits provide evidence for the development of a sizeable perennial to semi‐perennial hypersaline lake in which the MMG mudstones accumulated. Shoreline sediments overlie alluvial stream and sheet‐flood deposits, and pass from transgressive gravel–conglomerate beach units with bioclasts, influenced by shore‐normal waves (deposited under semi‐humid conditions), to lower gradient, highstand oolitic sands affected by more varied wave approach (deposited under progressively more arid conditions), which culminated in lowstand, oolitic strand‐plain deposits overlain by a playa‐mudflat unit. Shoreline deposits record a simple shallowing‐upward transgressive–highstand–lowstand sequence. However, a change from a reflective (transgressive) to dissipative (highstand) shoreline is believed to represent a climatically induced change in prevailing wind direction. Shoreline features recognized in the MMG are similar to those of recent playa‐lacustrine basins of the western United States. Ooids display a variety of size, fracture and dissolution features in addition to beachrock fabrics, suggesting that they were originally composed of radial aragonite, similar to modern ooids from the Great Salt Lake, Utah.     

鄂尔多斯盆地东缘构造-水文地质控气特征

基于大量野外地质工作,结合钻孔抽水试验资料分析,探讨了鄂尔多斯盆地东缘构造、水文地质条件及其对煤层气 保存的控制特征。结果显示,盆地边界近NS 向的压性断裂和褶皱构造发育,构造变形程度向盆地内部逐渐减弱,即盆地边 缘和内部的构造条件均有利于煤层气保存。依据构造、地下水补给及排泄条件和地貌等特征,研究区可划分为5 个水文地 质单元,西南部韩城单元的水动力条件强于东部各水文地质单元,东部各单元中又以柳林泉流域水动力条件最强,这种差 异在构造背景上的叠加,导致煤层气保存条件发生分异。中部黄河东断凹单元煤层含气量随埋藏深度的加深而增高,北部 柳林单元在柳林泉以西发育有利煤层气保存的地下水动力场条件,中南部龙门山单元北部的地下水动力条件可能有利于煤 层气保存,西南部韩城单元西北段地下水处于滞流环境而使煤层气保存条件较好。     

The Pleistocene Cape Kidnappers section in New Zealand: orbitally forced controls on active margin sedimentation?

High sedimentation rates in Pleistocene active margin basins can provide a very detailed record of tectonic and climatic controls on sediment preservation. A 500 m thick, Pleistocene rock section exposed in northeastern North Island of New Zealand (Kidnappers Group), provides the opportunity to discuss these controls. The section is composed of conglomerate, sandstones, siltstones and minor shales, interbedded with tephra layers. The sediments were deposited in alluvial to shallow marine environments and preserved in stacks of depositional units decimetres to hundreds of metres thick as a result of base‐level changes through time. The correlation of base‐level changes in the section with the deep sea oxygen isotope stratigraphy shows that the sequences at 10 m and 80 m scales can correlate, respectively, to the 20 and 100 kyr changes in eustatic sea‐level, but that the 80‐m‐thick sequences correlate also to changes in tectonic uplift rates. A major change in the stratigraphical architecture occurs at the Mid‐Pleistocene Transition (MPT) when the 40 kyr ice volume variations shifted to a dominant 100 kyr variation. This change includes an increase in the amplitude of the shifts in depositional environments and an overall simplification of the stacking pattern of the depositional units through the MPT. This study illustrates that active margin basins can record orbitally forced sedimentary cycles and points to a possible leading influence of eustasy on the pattern of sediment preservation in tectonically active areas. Copyright © 2004 John Wiley & Sons, Ltd.     

A paleoclimatic review of southern South America during the late Paleozoic: A record from icehouse to extreme greenhouse conditions

This paper provides a review of the Late Mississippian to Permian paleoclimatic history for southern South America based on lithologic indicators, biostratigraphic information, and chronostratigraphic data. The region is divided into three major types of basins: 1. Eastern intraplate basins (e.g., Paraná Basin), 2. Western retroarc basins (e.g., Paganzo Basin) and 3. Western arc-related basins (e.g., Río Blanco Basin). Four major types of paleoclimatic stages are recognized in these basins: 1. glacial (late Visean–early Bashkirian), 2. terminal glacial (Bashkirian–earliest Cisuralian) 3. postglacial (Cisuralian–early Guadalupian), and 4. semiarid–arid (late Guadalupian–Lopingian). The glacial stage began in the late Visean and continued until the latest Serpukhovian or early Bashkirian in almost all of the basins in southern South America. During the Bashkirian–earliest Cisuralian (terminal glacial stage), glacial deposits disappeared almost completely in the western retroarc basins (e.g., Paganzo Basin) but glaciation persisted in the eastern basins (e.g., Paraná and Sauce Grande Basins). A gradual climatic amelioration (postglacial stage) began to occur during the earliest Permian when glacial deposits completely disappeared across all of South America. During this interval, glacial diamictites were replaced by thick coal beds in the Paraná Basin while north–south climatic belts began to be delineated in the western basins, which were likely controlled by the distribution of mountain belts along the Panthalassan Margin of South America. Towards the late Permian, climatic belts became less evident and semiarid or arid conditions dominated in the southern South America basins. Eolian dunes, playa lake deposits, and mixed eolian–fluvial sequences occur in the Paraná Basin and in the western retroarc basins. Volcanism and volcaniclastic sedimentation dominated along the western margin of South America at that time. The stratigraphic record obtained in southern South America supports a long duration transition from icehouse to extreme greenhouse conditions.     

Basin fill evolution and paleotectonic patterns along the Samfrau geosyncline: the Sauce Grande basin–Ventana foldbelt (Argentina) and Karoo basin–Cape foldbelt (South Africa) revisited

As integral parts of du Toit’s (1927) “Samfrau Geosyncline”, the Sauce Grande basin–Ventana foldbelt (Argentina) and Karoo basin–Cape foldbelt (South Africa) share similar paleoclimatic, paleogeographic, and paleotectonic aspects related to the Late Paleozoic tectono-magmatic activity along the Panthalassan continental margin of Gondwanaland. Late Carboniferou-earliest Permian glacial deposits were deposited in the Sauce Grande (Sauce Grande Formation) and Karoo (Dwyka Formation) basins and Falkland–Malvinas Islands (Lafonia Formation) during an initial (sag) phase of extension. The pre-breakup position of the Falkland (Malvinas) Islands on the easternmost part of the Karoo basin (immediately east of the coast of South Africa) is supported by recent paleomagnetic data, lithofacies associations, paleoice flow directions and age similarities between the Dwyka and the Lafonia glacial sequences. The desintegration of the Gondwanan Ice Sheet (GIS) triggered widespread transgressions, reflected in the stratigraphic record by the presence of inter-basinally correlatable, open marine, fine-grained deposits (Piedra Azul Formation in the Sauce Grande basin, Prince Albert Formation in the Karoo basin and Port Sussex Formation in the Falkland Islands) capping glacial marine sediments. These early postglacial transgressive deposits, characterised by fossils of the Eurydesma fauna and Glossopteris flora, represent the maximum flooding of the basins. Cratonward foreland subsidence was triggered by the San Rafael orogeny (ca. 270 Ma) in Argentina and propogated along the Gondwanan margin. This subsidence phase generated sufficient space to accommodate thick synorogenic sequences derived from the orogenic flanks of the Sauce Grande and Karoo basins. Compositionally, the initial extensional phase of these basins was characterized by quartz-rich, craton-derived detritus and was followed by a compressional (foreland) phase characterized by a paleocurrent reversal and dominance of arc/foldbelt-derived material. In the Sauce Grande basin, tuffs are interbedded in the upper half of the synorogenic, foldbelt-derived Tunas Formation (Early–early Late? Permian). Likewise, the first widespread appearance of tuffs in the Karoo basin is in the Whitehill Formation, of late Early Permian (260?Ma) age. Silicic volcanism along the Andes and Patagonia (Choiyoi magmatic province) peaked between the late Early Permian and Late Permian. A link between these volcanics and the consanguineous airborne tuffs present in the Sauce Grande and Karoo basins is suggested on the basis of their similar compositions and ages.     

Differences in the Tectonic Evolution of Basins in the Central‐Southern South China Sea and their Hydrocarbon Accumulation Conditions

To reveal the causes of differences in the hydrocarbon accumulation in continental marginal basins in the centralsouthern South China Sea,we used gravity-magnetic,seismic,drilling,and outcrop data to investigate the tectonic histories of the basins and explore how these tectonic events controlled the hydrocarbon accumulation conditions in these basins.During the subduction of the Cenozoic proto-South China Sea and the expansion of the new South China Sea,the continental margin basins in the central-southern South China Sea could be classified as one of three types of epicontinental basins:southern extensional-foreland basins,western extensional-strike slip basins,and central extensional-drift basins.Because these basins have different tectonic and sedimentary histories,they also differ in their accumulated hydrocarbon resources.During the Cenozoic,the basin groups in the southern South China Sea generally progressed through three stages:faulting and subsidence from the late Eocene to the early Miocene,inversion and uplift in the middle Miocene,and subsidence since the late Miocene.Hydrocarbon source rocks with marine-continental transitional facies dominated byⅡ-Ⅲkerogen largely developed in extremely thick Miocene sedimentary series with the filling characteristics being mainly deep-water deposits in the early stage and shallow water deposits in the late stage.With well-developed sandstone and carbonate reservoirs,this stratum has a strong hydrocarbon generation potential.During the Cenozoic,the basin groups in the western South China Sea also progressed through the three developmental stages discussed previously.Hydrocarbon source rocks with lacustrine facies,marine-continental transitional facies,and terrigenous marine facies dominated byⅡ2-Ⅲkerogen largely developed in the relatively thick stratum with the filling characteristics being mainly lacustrine deposits in the early stage and marine deposits in the late stage.As a reservoir comprised of self-generated and self-stored sandstone,this unit also has a high hydrocarbon generation potential.Throughout those same three developmental stages,the basin groups in the central South China Sea generated hydrocarbon source rocks with terrigenous marine facies dominated byⅢkerogen that have developed in a stratum with medium thicknesses with the filling characteristics being mainly sandstone in the early stage and carbonate in the late stage.This reservoir,which is dominated by lower-generation and upper-storage carbonate rocks,also has a high hydrocarbon generation potential.     

Evolution and palaeoenvironment of the Bauru Basin (Upper Cretaceous,Brazil)

The Bauru Basin was one of the great Cretaceous desert basins of the world, evolved in arid zone called Southern Hot Arid Belt. Its paleobiological record consists mainly of dinosaurs, crocodiles and turtles. The Bauru Basin is an extensive region of the South American continent that includes parts of the southeast and south of Brazil, covering an area of 370,000 km². It is an interior continental basin that developed as a result of subsidence of the central-southern part of the South-American Platform during the Late Cretaceous (Coniacian–Maastrichtian). This sag basin is filled by a sandy siliciclastic sequence with a preserved maximum thickness of 480 m, deposited in semiarid to desert conditions. Its basement consists of volcanic rocks (mainly basalts) of the Lower Cretaceous (Hauterivian) Serra Geral basalt flows, of the Paraná-Etendeka Continental Flood Basalt Province. The sag basin was filled by an essentially siliciclastic psammitic sequence. In lithostratigraphic terms the sequence consists of the Caiuá and Bauru groups. The northern and northeastern edges of the basin provide a record of more proximal original deposits, such as associations of conglomeratic sand facies from alluvial fans, lakes, and intertwined distributary river systems. The progressive basin filling led to the burial of the basaltic substrate by extensive blanket sand sheets, associated with deposits of small dunes and small shallow lakes that retained mud (such as loess). Also in this intermediate context between the edges (more humid) and the interior (dry), wide sand sheet areas crossed by unconfined desert rivers (wadis) occurred. In the central axis of the elliptical basin a regional drainage system formed, flowing from northeast to southwest between the edges of the basin and the hot and dry inner periphery of the Caiuá desert (southwest). Life in the Bauru Basin flourished most in the areas with the greatest water availability, in which dinosaurs, crocodiles, turtles, fish, amphibians, molluscs, crustaceans, and charophyte algae lived. The fossil record mainly consists of transported bones and other skeletal fragments. In the northeastern and eastern marginal regions fossils are found in marginal alluvial fan deposits, broad plains of braided streams and ephemeral alkaline water lakes. In the basin interior the fossil record is related to deposits in sand sheets with braided streams, small dunes, and shallow lakes. In the great Caiuá inner desert a few smaller animals could survive (small reptiles and early mammals), sometimes leaving their footprints in dune foreset deposits. The aim of this article is to present and link the basin sedimentary evolution, palaeoecological features and palaeontological record.     

The geometry of fan‐deltas and related turbidites in narrow linear basins

The sediment distribution in three narrow, linear basins, two modern and one ancient, in Greece and Italy, was studied and related to changes in basin configuration. The basins are the Plio‐Quaternary Patras–Corinth graben, the Pliocene–Quaternary Reggio–Scilla graben and the middle Tertiary Mesohellenic piggy‐back basin. These basins were formed at different times and under different geodynamic conditions, but in each case, the tectonic evolution produced a narrow area in the basin where the water depth decreased dramatically, forming a strait with a sill. This strait divided the basin into major and minor sub‐basins, and the strait has a similar impact on sedimentary environments in all three basins, even though different depositional environments were formed along the initial basin axis. Predictions for the development of depositional environments in the two modern basins, especially in their straits, are based on the studied ancient basin. In the straits, powerful tidal flows will transport finer sediments to sub‐basins and trapezoidal‐type fan‐deltas will gradually fill up and choke the strait through time. In sub‐basins, according to basin depth, either deltaic (in the shallow minor sub‐basin) or turbiditic (in the deep major sub‐basin) deposits may accumulate. Moreover, an extensive shelf is likely to develop between the strait and major sub‐basin. This shelf will be cross‐cut by canyons and characterized by thin fine‐ to coarse‐grained deposits. These sediment models could be applied to analogous basin geometries around the world. Copyright © 2003 John Wiley & Sons, Ltd.     

Flow dynamics,sedimentation and erosion of glacial lake outburst floods along the Middle Pleistocene Scandinavian Ice Sheet (northern central Europe)

During the Middle Pleistocene late Saalian glaciation of northern central Europe numerous pro‐glacial lakes formed along the southwestern margin of the Scandinavian Ice Sheet. Little is known about the drainage history of these lakes, the pathways of glacial lake outburst floods and their impacts on erosion, sedimentation and landscape evolution. This study investigated the impact of the late Saalian Weser and Münsterland Lake (Germany) outburst floods. In particular, we reconstructed the routing and flow dynamics of the lake outburst flood and analysed the flood related sediments. We employed one‐dimensional hydraulic modelling to calculate glacial lake outburst flood hydrographs. We modelled the flow pathway and local flow conditions along the pathway based on the boundary conditions of two different hydrographs and two different ice‐margin positions. The modelling results were compared with geomorphological and sedimentological field data in order to estimate the magnitude and impact of the flood on erosion and sedimentation. Two major lake drainage events are reconstructed for the study area, during which approximately 90–50 km³ of water was released. Modelling results indicate that the lake outburst floods created a high‐energy flood wave with a height of 35–50 m in confined valley areas that rapidly spread out into the Lower Rhine Embayment eventually flowing into the North Sea basin. The sedimentary record of the outburst floods comprises poorly sorted coarse‐grained gravel bars, long‐wavelength bedforms and sandy bedforms deposited by supercritical and subcritical flows. Some parts of the sandy flood deposits are rich in reworked mammoth bones or mammoth and horse teeth, pointing to reworking of older fluvial sediments, hydraulic concentration and subsequent re‐sedimentation of vertebrate remains. These deposits are preserved in sheltered areas or at high elevations, well above the influence of postglacial fluvial erosion. The flood‐related erosional features include up to 80‐m‐deep scour pools, alluvial channels and streamlined hills.     

Continental margin basins in East Asia: tectonic implications of the Meso‐Cenozoic East China Sea pull‐apart basins

The East China Sea basins, located in the West Pacific Continental Margin (WPCM) since the late Mesozoic, mainly include the East China Sea Shelf Basin (ECSSB) and the Okinawa Trough (OT). The WPCM and its adjacent seas can be tectonically divided into five units from west to east, including the Min‐Zhe Uplift, ECSSB, the Taiwan–Sinzi Belt, OT, and the Ryukyu Island Arc, which record regional tectonic evolution and geodynamics. Among those tectonic units, the ECSSB and the OT are important composite sedimentary pull‐apart basins, which experienced two stages of strike‐slip pull‐apart processes. In seismic profiles, the ECSSB and the OT show a double‐layer architecture with an upper half‐graben overlapping on a lower graben. In planar view, the ECSSB and the OT are characterized by faulted blocks from south to north in the early Cenozoic and by a zonation from west to east in the late Cenozoic. The faulted blocks with planar zonation and two‐layer vertical architecture entirely jumped eastward from the Min‐Zhe Uplift to the OT during the late Cenozoic. In addition, the whole palaeogeomorphology of the ECSSB changed notably, from pre‐Cenozoic highland or mountain into a Late Eocene continental margin with east‐tilting topography caused by the eastward tectonic jumping. The OT opened to develop into a back‐arc basin until the Miocene. Synthetic surface geological studies in the China mainland reveal that the Mesozoic tectonic setting of the WPCM is an Andean‐type continental margin developing many sinistral strike‐slip faults and pull‐apart basins and the Cenozoic tectonic setting of the WPCM is a Japanese‐type continental margin developing dextral strike‐slip faults and pull‐apart basins. Thus, the WPCM underwent a transition from Andean‐type to Japanese‐type continental margins at about 80 Ma (Late Cretaceous) and a transition in topography from a Mesozoic highland to a Cenozoic lowland, and then to below sea‐level basins. Copyright © 2013 John Wiley & Sons, Ltd.     

藏北羌塘盆地与西亚特提斯盆地构造比较及其油气远景

羌塘盆地是中国西部除塔里木、柴达木、准噶尔盆地外，又一大型古生代一中新生代盆地。与其具有相似构造背景的西亚特提斯带盆地群是目前世界上油气最富集的地区。通过对西亚特提斯带含油气盆地的形成、构造演化背景的分析，探讨了盆地油气富集的地质条件，认为羌塘盆地的形成演化与特提斯西段阿富汗地块具有相似性，侏罗纪的沉积演化和构造格局与中亚的长拉库姆油气盆地类似，故具备形成油气的基本条件。然而，羌塘盆地距喜马拉雅褶皱带较近，新近纪以来构造改造十分强烈。逆冲推覆作用一方面可以产生构造圈闭，但也使烃源岩的成熟度偏高，不利于油气的保存，这与中东地区含油气盆地油气大量聚集的油气田具有显著差异。为此羌塘盆地的油气勘探应寻找保存条件与生油条件相匹配的地区。     

被动大陆边缘碳酸盐生长序列与盆山转换耦合

碳酸盐作为盆地堆积物整体的一部分，剖析达到碳酸盐清水环境的先决条件、保持条件和中止消亡条件就可判别盆地中碳酸盐沉积与其他堆积作用之间的关系，恢复盆地性质、演化历史和盆转山的过程。碳酸盐生长的４个边界条件：碳酸盐生长的基座、碳酸盐沉积前后的转换面、碳酸盐生长序列的内部结构和碳酸盐中止和消亡方式、不同板块部位的盆地和盆转山过程，这４个边界条件均不相同。在被动大陆边缘转为前陆盆地过程中，碳酸盐生长发育的４个边界条件也随之而变化。其过程为：早期裂谷充填；晚期裂谷、碎屑岩陆架形成；碳酸盐陆架；热沉降和镶边碳酸盐台地