Origin and significance of soft-sediment deformation in the Old Red Sandstone of central South Wales,UK

Vertically oriented water-escape cusps are the most common type of soft-sediment deformation structure in sandstone-rich intervals of the fluvial Brownstones and Senni Formations (Cosheston Subgroup, Daugleddau Group) of the Lower Old Red Sandstone in the central Brecon Beacons and eastern Black Mountains, South Wales. The structures are widely distributed and occur at several stratigraphical levels. They can be divided into two styles. (1) Small-scale (height less than a single bed), isolated water-escape cusps formed when loosely packed sediment deposited rapidly in flood events liquefied in advance of subsequent flood events or pulses, causing localised fluidization due to the escape of excess pore water. Inclined cusps higher in some beds confirm the relationship of this deformation style to active flood events. (2) Horizons of larger-scale (occupying the entire bed thickness), laterally continuous water-escape cusps and fold trains can be traced for hundreds of metres to kilometres and result from widespread liquefaction in response to earthquakes. A lack of overturning indicates that their formation did not coincide with active flow conditions. Further detailed mapping is needed to clarify the continuity and extent of such structures and their relationship to faults that may have been active during sedimentation. The occurrence of triggers capable of causing liquefaction in granular materials provides a greater control on the occurrence of soft-sediment deformation than do lithological controls such as grain size or interbedding of sandstone and mudstone. The findings are broadly consistent with interpretations of soft-sediment deformation in the Cosheston Subgroup in Pembrokeshire, SW Wales.     

Role of late glacial to mid-Holocene climate in catchment weathering in the central Tibetan Plateau

The lightness (L*) and concentrations of Rb, Sr and organic carbon (C_org) have been measured in the age-constrained lake sediment cores recovered from Co Ngoin in the central Tibetan Plateau. Dissolved Sr flux is a dominant control on the variation of Rb/Sr ratios in the sediments. Variations in color and geochemical proxies of Co Ngoin sediments display a continuous history of late glacial to mid-Holocene chemical versus physical weathering intensity in response to past climatic changes between approximately 13,500 and 4500 cal yr B.P. A lower chemical weathering under a late glacial climate was followed by a higher weathering during the Holocene Optimum. Weathering intensity in the central Tibetan Plateau catchment also responds to well-known climatic events, such as the Younger Dryas (YD), and possibly the Holocene Event 5 (HE-5). Although there are differences in time or duration of the climatic events, many of the well-known late glacial to mid-Holocene events occurred in high-elevation Co Ngoin where atmospheric circulation might play a hemispherical role in climatic forcing. The sediment hiatus since c. 4200 ¹⁴C yr B.P. in the Co Ngoin indicates a period of desiccation that was probably associated with a sharp decrease in summer monsoon strength. Our lascustrine results not only imply catchment weathering variations in response to late glacial to mid-Holocene climatic conditions in the central plateau, but also provide further evidence for global connections between regional climates.     

渤海西岸全新世气候演化与海陆变迁

应用第四纪地质学和海相生物等化石数量统计,以天津马棚口海岸带BQ1孔化石鉴定与统计结果,对古气候、古事件进行对比研究。通过岩芯编录,在岩性层中划分出4个海相层、5个过渡层、9个海面波动。结合研究区广泛分布的贝壳堤和牡蛎礁,利用其大量的测年资料,重现了6道海岸线;根据海相化石个体统计数,画出全新世气候演化曲线,与孢粉和物候所画的古气候演化曲线大体一致。研究历代海陆变迁,必然涉及到历史上长期争论不休的西汉大海侵等问题,谭其骧（1965）圈定的大海侵范围、海岸线分布以及考古结果几乎都能联系在一起,因此,大海侵之谜终于尘埃落定。考古界对河北平原自东汉—金的空白也有了初步答案,同时,发现中国朝代兴衰与气候冷暖有明显的对应,从而建立了气候分期。     

古生物化石的风化机理与保护研究进展

化石是研究地质历史、气候变迁、生物演化等的实证,有着极其重要的科学价值。一般情况下,化石经过成岩和化石化作用被无机矿物交代,有一定的抗风化能力,在经过常规清理加固处理即可稳定保存。然而在相对潮湿的环境中,部分化石因其组成成分容易发生物理化学变化,从而开裂粉化,严重威胁其保存。本文简要回顾了化石修理加固技术的发展历史,并从风化机理和保护两方面着重介绍了当前学界对化石中盐风化、黄铁矿氧化、干燥失水开裂等方面的研究进展,最后简要对化石保护与文物保护的关系进行论述,以期推动化石保护学科的深入发展。     

Evolution of the composition of seawater through geologic time, and its influence on the evolution of life

The redox state of the surface environment of the early Earth is still controversial, and a detailed and quantitative estimate is still lacking. We carried out in-situ analyses of major, trace, and rare-earth elements of carbonate minerals in rocks with primary sedimentary structures in shallow and deep sea-deposits, in order to eliminate secondary carbonate and contamination of detrital materials, and to estimate the redox condition of seawater through time. Based on the Ce content and anomalies of the carbonate minerals at given parameters of atmospheric CO₂ content (pCO₂) and Ca content of seawater, we calculated the oxygen contents of shallow and deep seawater, respectively. The results show that the oxygen content of the deep sea was low and constant until at least 1.9 Ga. The oxygen content of shallow seawater increased after 2.7 Ga, but fluctuated. It became quite high at 2.5 and 2.3 Ga, but eventually increased after the Phanerozoic. In addition, the calculation of a high pCO₂ condition shows that seawater was more oxic even in the Archean than at present, suggesting a relatively low pCO₂ through geologic time.Our detailed calculations from compositions of carbonate minerals in Three Gorge area, south China show a low oxygen content of seawater after the Snowball Earth until the late Ediacaran, an increase in the late Ediacaran, and a significant decrease around the Precambrian–Cambrian and Nemakit/Daldynian–Tommotian boundaries. These variations were possibly caused by global regression and dissolution of methane hydrates.     

Enigma variations: the stratigraphy,provenance, palaeoseismicity and depositional history of the Lower Old Red Sandstone Cosheston Group,south Pembrokeshire,Wales

The Lower Devonian (Lochkovian‐Emsian) Cosheston Group of south Pembrokeshire is one of the most enigmatic units of the Old Red Sandstone of Wales. It consists of a predominantly green, exceptionally thick succession (up to 1.8 km) within the red c. 3 km‐thick fill of the Anglo‐Welsh Basin, but occupies a very small area (27 km²). Four formations—Llanstadwell (LLF), Mill Bay (MBF), Lawrenny Cliff (LCF) and New Shipping (NSF)—group into lower (LLF + MBF) and upper (LCF + NSF) units on stratigraphical and sedimentological criteria. Two palynostratigraphic associations (Hobbs Point and Burton Cliff) are recognised in the LLF. Overall, the Cosheston succession comprises a fluvial, coarsening‐upward megasequence, mostly arranged in fining‐upward rhythms. It is interpreted as the fill of an east‐west graben bounded by faults to the north and south of the Benton and Ritec faults, respectively. Both ‘lower Cosheston’ formations were deposited by east‐flowing, axial river systems draining a southern Irish Sea landmass. Drainage reversal, early in the deposition of the LCF, resulted in ‘upper Cosheston’ lateral, SW‐flowing rivers which carried predominantly second‐ and multi‐cycle detritus. The ‘lower Cosheston’ is characterized by an abundance of soft‐sediment deformation structures, probably seismically triggered by movements along the graben's northern bounding fault. A minimum average (≥ mesoseismic) earthquake recurrence interval of c. 4000 yr is estimated for the MBF. This and the correlative Senni Formation of south‐central Wales form a regionally extensive green‐bed development that represents a pluvial climatic interval. Copyright © 2006 John Wiley & Sons, Ltd.     

Caledonide influences on the Old Red Sandstone fluvial systems of the Oslo Region,Norway

Red or buff‐coloured sandstones and siltstones of fluvial origin comprise approximately 80% of the Ringerike Group, a late Silurian Old Red Sandstone (ORS) sequence that crops out extensively in the Oslo Region of southern Norway. These fluvial sediments are lithostratigraphically ascribed to two laterally equivalent formations—the Stubdal Formation (to the north of Oslo) and the Skien Formation (to the south of Oslo). The fluvial strata of each of the two formations have a distinct style of sandbody geometry, facies, provenance, and palaeocurrent direction. Within the Stubdal Formation, shallow channelized sandbodies, low‐ to upper‐flow regime sedimentary structures, a Caledonide provenance and a palaeoflow toward the southeast are evident. Within the Skien Formation, sandbody geometry is entirely sheet form, with upper‐flow regime sedimentary structures, a provenance from Precambrian rocks to the northern and local parts of the Oslo Region and a palaeoflow toward the east. No stratal contact can be seen between the two fluvial formations, due to a 15 km break in exposure between the southernmost Stubdal Formation and the northernmost Skien Formation. Relationships with adjacent formations indicate that they are diachronous, lateral equivalents. Given the abrupt change in sedimentary style between the two formations, it is proposed that a barrier had developed within the foreland basin, diverting the ORS fluvial systems in southern Norway, from a southward (north of Oslo), to an eastward direction (south of Oslo). This diversion had implications for depositional gradient, fluvial regime and provenance, resulting in the differences visible in the deposits of those rivers. The barrier invoked is arguably a Caledonide blind thrust fault that developed a topographic high, running east–west through the vicinity of Oslo, during the late Silurian. Copyright © 2004 John Wiley & Sons, Ltd.     

Cenozoic tectonics and landform evolution of the coast and adjacent highlands of southeast New South Wales

The Upper Precambrian and Lower Palaeozoic Rocks in the Mt Lofty Ranges, South Australia, have been subjected to at least three phases of folding. The first involved the formation of inclined folds and less common reclined folds. These structures are overprinted by usually upright, moderately tight, second and third generation folds which may show a well developed axial plane crenulation cleavage.

The metamorphism commenced prior to the appearance of penetrative structures and continued in many areas until after the third phase of deformation. It appears to have had its greatest effect during the static period following the first phase of folding.

Mineral assemblages of the pelitic rocks indicate that the metamorphism is of the low pressure‐intermediate type and that there are at least four progressive zones of metamorphism, namely, chlorite, biotite, andalusite‐staurolite, and sillimanite. Cordierite occurs in the sillimanite zone and kyanite is sporadically distributed in the andalusite‐staurolite zone. In the Angaston‐Springton region separate andalusite and staurolite zone boundaries may be delineated which cross as they are traced towards Angaston. This relationship is considered to be due to higher pressures operating during metamorphism in the latter area.

The maximum pressure and temperature reached in the metamorphism of these rocks are discussed in the light of recent experimental data.     

Elucidating hydrological complexity and climate-influenced diagenesis during the early Carboniferous of South Wales

A revised age provided by conodonts from the Gilwern Oolite of the Clydach area of South Wales allows a clearer understanding of the palaeohydrology, palaeoclimatic history and diagenesis of previously correlated oolitic units. Earlier uncertainty over the apparent sub-regional differences in climate during the early Visean (Chadian—Arundian) lowstand is resolved. Previously a humid interval evidenced by prominent palaeo-epikarst capping the Gilwern Oolite along the northern outcrops of the South Wales synclinorium, was not recognized in what were regarded as correlative outcrops in the Chadian Gully Oolite in the southern part of the synclinorium. Conodont dating now shows that the Gilwern Oolite is much older (Courceyan) than the Chadian Gully Oolite, and during the prolonged exposure of the former there was an interval of weathering under a humid climate. This also explains the contrast between the diagenesis seen between the Gilwern and Gully oolites, which are no longer seen as correlatives.     

南海第四纪东亚季风演化的粘土矿物指标

南海作为西太平洋最大的边缘海,记录着东亚季风的演化历史。本文在过去十多年研究积累的基础上,综述粘土矿物是记录南海东亚季风演化历史的良好指标。大量表层样品和多个沉积岩芯的研究显示,南海第四纪以来的蒙脱石主要是形成于周边岛屿火山岩的快速化学风化作用,记录了同时期的东亚夏季风气候条件;伊利石和绿泥石形成于周边大陆和岛屿的机械侵蚀作用,与强烈降雨引发的侵蚀能力或东亚冬季风相对寒冷的气候条件有关;而高岭石形成于周边陆地表面的强烈化学风化作用,指示地质历史时期累积的或第四纪同时期的温暖潮湿气候条件,但由于强烈的差异沉降作用,高岭石在南海主要沉积在近海陆架区域,在深海记录中多指示海平面变化的古环境特征。因此,我们提出蒙脱石/（伊利石+绿泥石）比值是南海第四纪东亚夏季风演化的良好指标,比值高代表夏季风温暖潮湿气候条件下增强的化学风化作用,比值低指示冬季风相对寒冷气候条件下减弱的化学风化作用,或是强烈降雨气候条件下增强的机械侵蚀作用。南海东亚夏季风演化的强弱与北半球夏季日射量基本呈线性关系,表明东亚季风演化的天文驱动机制,第四纪以来的长期演化显示南海在1200~400ka期间盛行夏季风,可能是受到赤道太平洋厄尔尼诺-南方涛动（ENSO）的影响。

     

The arenig in South Wales: Sedimentary and volcanic processes during the initiation of a marginal basin

Marine clastic sediments and volcanics of Arenig (Ordovician) age crop out in South Wales. These were deposited after presumed late Tremadoc erosion and subsequent arc volcanicity. Arenig sedimentation was transgressive, and followed significant erosion of the arc volcanics. Arenig conglomerates, sandstones, and mudstones were deposited in deltaic and turbiditic systems. Storm and tidal processes influenced the shallow marine deposits. The minor rhyolitic volcanics extruded during the Arenig reflect the development of Ordovician marginal basin-type volcanics across Wales. Five sandstone petrofacies are defined and reflect differing proportions of these volcanics and of Cambrian and Precambrian basement material. Sedimentation patterns were controlled by intra-Arenig tectonism during an overall rise in sea level. Facies and petrofacies were ponded in small, interconnected, marine sub-basins. Earliest Arenig tectonism and sedimentation, also recognized in North Wales, reflects the initiation of a marginal basin in Wales.     

Global methane emission through mud volcanoes and its past and present impact on the Earth's climate

Mud volcanism is an abundant, global phenomenon whereby fluid-rich, low-density sediments extrude both on land and offshore. Methane, which generally exceeds 90 vol% of the gas phase, is emitted at high rates during and after emplacement of the mud domes and is known for its high global warming potential (GWP). This comprehensive estimate of the annual contribution of mud volcano degassing assesses the significance of mud volcanism for the accumulation of greenhouse gases in the atmosphere. A first-order estimate for the earlier, pre-anthropogenic volume of methane released through mud volcanoes further supports their profound effect on the Earth's climate since at least the Paleozoic (570 Ma).     

Research on quantitative assessment of climate change risk at an urban scale: Review of recent progress and outlook of future direction

Cities are not only major contributors to global climate change but also stand at the forefront of climate change impact. Quantifying and assessing the risk potentially induced by climate change has great significance for cities to undertake positive climate adaptation and risk prevention. However, most of the previous studies focus on global, national or regional dimensions, only a few have attempted to examine climate change risk at an urban scale and even less in the case of a recent literature review. As a result, a quantitative assessment of climate change risk for cities remains highly challenging. To fill this gap, the article makes a critical review of the recent literature on urban-scale climate change risk assessment, and classifies them into four major categories of studies which jointly constitute a stepwise modelling chain from global climate change towards urban-scale risk assessment. On this basis, the study summarizes the updated research progresses and discusses the major challenges to be overcome for the seamless coupling of climate simulation between different scales, the reproduction of compound climate events, the incorporation of non-market and long-lasting impacts and the representation of risk transmission insides or beyond a city. Furthermore, future directions to advance quantitative assessment of urban-scale climate change risk are highlighted, with fresh insights into improving study methodology, enriching knowledge of climate change impact on city, enhancing abundance and accessibility to data, and exploring the best practice to provide city-specific climate risk service.     

Research on quantitative assessment of climate change risk at an urban scale: Review of recent progress and outlook of future direction

Cities are not only major contributors to global climate change but also stand at the forefront of climate change impact. Quantifying and assessing the risk potentially induced by climate change has great significance for cities to undertake positive climate adaptation and risk prevention. However, most of the previous studies focus on global, national or regional dimensions, only a few have attempted to examine climate change risk at an urban scale and even less in the case of a recent literature review. As a result, a quantitative assessment of climate change risk for cities remains highly challenging. To fill this gap, the article makes a critical review of the recent literature on urban-scale climate change risk assessment, and classifies them into four major categories of studies which jointly constitute a stepwise modelling chain from global climate change towards urban-scale risk assessment. On this basis, the study summarizes the updated research progresses and discusses the major challenges to be overcome for the seamless coupling of climate simulation between different scales, the reproduction of compound climate events, the incorporation of non-market and long-lasting impacts and the representation of risk transmission insides or beyond a city. Furthermore, future directions to advance quantitative assessment of urban-scale climate change risk are highlighted, with fresh insights into improving study methodology, enriching knowledge of climate change impact on city, enhancing abundance and accessibility to data, and exploring the best practice to provide city-specific climate risk service.     

Research on quantitative assessment of climate change risk at an urban scale: Review of recent progress and outlook of future direction

Cities are not only major contributors to global climate change but also stand at the forefront of climate change impact. Quantifying and assessing the risk potentially induced by climate change has great significance for cities to undertake positive climate adaptation and risk prevention. However, most of the previous studies focus on global, national or regional dimensions, only a few have attempted to examine climate change risk at an urban scale and even less in the case of a recent literature review. As a result, a quantitative assessment of climate change risk for cities remains highly challenging. To fill this gap, the article makes a critical review of the recent literature on urban-scale climate change risk assessment, and classifies them into four major categories of studies which jointly constitute a stepwise modelling chain from global climate change towards urban-scale risk assessment. On this basis, the study summarizes the updated research progresses and discusses the major challenges to be overcome for the seamless coupling of climate simulation between different scales, the reproduction of compound climate events, the incorporation of non-market and long-lasting impacts and the representation of risk transmission insides or beyond a city. Furthermore, future directions to advance quantitative assessment of urban-scale climate change risk are highlighted, with fresh insights into improving study methodology, enriching knowledge of climate change impact on city, enhancing abundance and accessibility to data, and exploring the best practice to provide city-specific climate risk service.     

Research on quantitative assessment of climate change risk at an urban scale: Review of recent progress and outlook of future direction

Cities are not only major contributors to global climate change but also stand at the forefront of climate change impact. Quantifying and assessing the risk potentially induced by climate change has great significance for cities to undertake positive climate adaptation and risk prevention. However, most of the previous studies focus on global, national or regional dimensions, only a few have attempted to examine climate change risk at an urban scale and even less in the case of a recent literature review. As a result, a quantitative assessment of climate change risk for cities remains highly challenging. To fill this gap, the article makes a critical review of the recent literature on urban-scale climate change risk assessment, and classifies them into four major categories of studies which jointly constitute a stepwise modelling chain from global climate change towards urban-scale risk assessment. On this basis, the study summarizes the updated research progresses and discusses the major challenges to be overcome for the seamless coupling of climate simulation between different scales, the reproduction of compound climate events, the incorporation of non-market and long-lasting impacts and the representation of risk transmission insides or beyond a city. Furthermore, future directions to advance quantitative assessment of urban-scale climate change risk are highlighted, with fresh insights into improving study methodology, enriching knowledge of climate change impact on city, enhancing abundance and accessibility to data, and exploring the best practice to provide city-specific climate risk service.     

Research on quantitative assessment of climate change risk at an urban scale: Review of recent progress and outlook of future direction

Cities are not only major contributors to global climate change but also stand at the forefront of climate change impact. Quantifying and assessing the risk potentially induced by climate change has great significance for cities to undertake positive climate adaptation and risk prevention. However, most of the previous studies focus on global, national or regional dimensions, only a few have attempted to examine climate change risk at an urban scale and even less in the case of a recent literature review. As a result, a quantitative assessment of climate change risk for cities remains highly challenging. To fill this gap, the article makes a critical review of the recent literature on urban-scale climate change risk assessment, and classifies them into four major categories of studies which jointly constitute a stepwise modelling chain from global climate change towards urban-scale risk assessment. On this basis, the study summarizes the updated research progresses and discusses the major challenges to be overcome for the seamless coupling of climate simulation between different scales, the reproduction of compound climate events, the incorporation of non-market and long-lasting impacts and the representation of risk transmission insides or beyond a city. Furthermore, future directions to advance quantitative assessment of urban-scale climate change risk are highlighted, with fresh insights into improving study methodology, enriching knowledge of climate change impact on city, enhancing abundance and accessibility to data, and exploring the best practice to provide city-specific climate risk service.     

Research on quantitative assessment of climate change risk at an urban scale: Review of recent progress and outlook of future direction

Cities are not only major contributors to global climate change but also stand at the forefront of climate change impact. Quantifying and assessing the risk potentially induced by climate change has great significance for cities to undertake positive climate adaptation and risk prevention. However, most of the previous studies focus on global, national or regional dimensions, only a few have attempted to examine climate change risk at an urban scale and even less in the case of a recent literature review. As a result, a quantitative assessment of climate change risk for cities remains highly challenging. To fill this gap, the article makes a critical review of the recent literature on urban-scale climate change risk assessment, and classifies them into four major categories of studies which jointly constitute a stepwise modelling chain from global climate change towards urban-scale risk assessment. On this basis, the study summarizes the updated research progresses and discusses the major challenges to be overcome for the seamless coupling of climate simulation between different scales, the reproduction of compound climate events, the incorporation of non-market and long-lasting impacts and the representation of risk transmission insides or beyond a city. Furthermore, future directions to advance quantitative assessment of urban-scale climate change risk are highlighted, with fresh insights into improving study methodology, enriching knowledge of climate change impact on city, enhancing abundance and accessibility to data, and exploring the best practice to provide city-specific climate risk service.     

Research on quantitative assessment of climate change risk at an urban scale: Review of recent progress and outlook of future direction

Cities are not only major contributors to global climate change but also stand at the forefront of climate change impact. Quantifying and assessing the risk potentially induced by climate change has great significance for cities to undertake positive climate adaptation and risk prevention. However, most of the previous studies focus on global, national or regional dimensions, only a few have attempted to examine climate change risk at an urban scale and even less in the case of a recent literature review. As a result, a quantitative assessment of climate change risk for cities remains highly challenging. To fill this gap, the article makes a critical review of the recent literature on urban-scale climate change risk assessment, and classifies them into four major categories of studies which jointly constitute a stepwise modelling chain from global climate change towards urban-scale risk assessment. On this basis, the study summarizes the updated research progresses and discusses the major challenges to be overcome for the seamless coupling of climate simulation between different scales, the reproduction of compound climate events, the incorporation of non-market and long-lasting impacts and the representation of risk transmission insides or beyond a city. Furthermore, future directions to advance quantitative assessment of urban-scale climate change risk are highlighted, with fresh insights into improving study methodology, enriching knowledge of climate change impact on city, enhancing abundance and accessibility to data, and exploring the best practice to provide city-specific climate risk service.     

Holocene climate and landscape evolution East of the Pechora Delta, East-European Russian Arctic

This study presents a multiproxy record of Holocene environmental change in the region East of the Pechora Delta. A peat plateau profile (Ortino II) is analyzed for plant macrofossils, sediment type, loss on ignition, and radiocarbon dating. A paleosol profile (Ortino III) is described and radiocarbon dated. A previously published peat plateau profile (Ortino I) was analyzed for pollen and conifer stomata, loss on ignition, and radiocarbon dating. The interpretation of the latter site is reassessed in view of new evidence. Spruce immigrated to the study area at about 8900 ¹⁴C yr B.P. Peatland development started at approximately the same time. During the Early Holocene Hypsithermal taiga forests occupied most of the present East-European tundra and peatlands were permafrost free. Cooling started after 5000 ¹⁴C yr B.P., resulting in a retreat of forests and permafrost aggradation. Remaining forests disappeared from the study area around 3000 ¹⁴C yr B.P., coinciding with more permafrost aggradation. The retreat of forests resulted in landscape instability and the redistribution of sand by eolian activity. The displacement of the Arctic forest line and permafrost zones indicates a warming of at least 2–3°C in mean July and annual temperatures during the Early Holocene. At least two cooling periods can be recognized for the second half of the Holocene, starting at about 4800 and 3000 ¹⁴C yr B.P.