Sodium and strontium in mollusc shells: preservation,palaeosalinity and palaeotemperature of the Middle Pleistocene of eastern England

This paper revisits the utility of sodium (Na) content in aragonite and calcite mollusc shells as an indicator of palaeosalinity. The data come mainly from a related suite of Middle Pleistocene marine and freshwater fossils that have been subject to broadly similar diagenetic histories. Environmental salinity is re-affirmed as the primary factor in determining the sodium content of modern and ancient mollusc shells: values <2000 ppm Na are generally indicative of non-marine environments while values >2000 Na ppm are typically from marine shells. There is a positive relationship between Na (salinity) and Sr which is a helpful discriminator of palaeosalinity in the fossil data set. The Na and Sr data give confidence that the fossil shells have not suffered pervasive diagenetic alteration and that the marine fossils lived in fully marine conditions. Oxygen isotope values in the best-preserved, fully marine fossil shells, suggest Middle Pleistocene ‘eastern England’ seawater temperatures were broadly similar to those of the modern North Sea.     

Identification of last interglacial deposits in eastern Beringia: a cautionary note from the Palisades,interior Alaska

Last interglacial sediments in unglaciated Alaska and Yukon (eastern Beringia) are commonly identified by palaeoecological indicators and stratigraphic position ～2–5 m above the regionally prominent Old Crow tephra (124 ± 10 ka). We demonstrate that this approach can yield erroneous age assignments using data from a new exposure at the Palisades, a site in interior Alaska with numerous exposures of last interglacial sediments. Tephrochronology, stratigraphy, plant macrofossils, pollen and fossil insects from a prominent wood‐rich organic silt unit are all consistent with a last interglacial age assignment. However, six ¹⁴C dates on plant and insect macrofossils from the organic silt range from non‐finite to 4.0 ¹⁴C ka BP, indicating that the organic silt instead represents a Holocene deposit with a mixed‐age assemblage of organic material. In contrast, wood samples from presumed last interglacial organic‐rich sediments elsewhere at the Palisades, in a similar stratigraphic position with respect to Old Crow tephra, yield non‐finite ¹⁴C ages. Given that local permafrost thaw since the last interglaciation may facilitate reworking of older sediments into new stratigraphic positions, minimum constraining ages based on ¹⁴C dating or other methods should supplement age assignments for last interglacial sediments in eastern Beringia that are based on palaeoecology and stratigraphic association with Old Crow tephra. Copyright © 2011 John Wiley & Sons, Ltd.     

Morphostratigraphy and provenance of Plio‐Pleistocene terraces in the south‐eastern Alpine foreland: the Mislinja and Upper Savinja valleys,northern Slovenia

This study focuses on the Plio‐Pleistocene fluvial deposits preserved in the terrace staircases in the south‐eastern Alpine foreland of the Mislinja (MV) and Upper Savinja valleys (USV) in northern Slovenia. The area is located at the north‐eastern margin of the Adria microplate, where neotectonic activity is the prevailing driving force for the terrace formation. The aim of this study is to determine the morphostratigraphy and provenance of the Pliocene to Early Pleistocene gravels using geomorphic and clast lithological analysis. The established morphostratigraphic framework encompasses three terraces in the MV and five terraces in the USV. Due to the lack of age‐relevant data, the morphostratigraphy of the MV and USV is based on the results of geomorphic analysis, clast petrography and data from the literature. Low‐level, middle‐level and high‐level terrace groups were tentatively attributed to the Late and Middle Pleistocene, Early Pleistocene–Pliocene and Pliocene, and compared with the traditional Quaternary stratigraphy of the Alpine foreland. The results of the clast lithological analysis revealed major provenance areas. Moreover, the evolution of long‐term drainage from the Miocene onward was inferred, which suggests that the system reached conformity with the present‐day drainage pattern at the Miocene to Plio‐Pleistocene transition. Copyright © 2019 John Wiley & Sons, Ltd.     

Palaeoenvironmental interpretation of a Pleistocene alluvial succession in central Poland: sedimentary facies analysis as a tool for palaeoclimatic inferences

A Pleistocene valley-fill alluvial succession deposited in the Kleszczów Graben, central Poland, has been studied in the Belchatów openpit mine. The succession, palynologically documented to represent the Drenthe/Warthe interstadial, consists of three alluvial complexes whose component lithofacies associations indicate a fluvial system evolving from temperate-climate meandering river to transitional-type shallow braided network, to periglacial well-developed braided river influenced by aeolian sand supply. The study suggests that the abundance of fine-grained overbank deposits, occurrence of peats/palaeosols and fining-upward cyclothems are diagnostic attributes of perennial meandering river alluvium, which may indicate temperate climatic conditions. Periglacial braided river alluvium is recognizable by an admixture of wind-derived sand grains with aeolian surface textures and by the occurrence of ice-wedge features, indicative of cold climatic conditions. The distinction between the two basic types of alluvium is aided by the analysis of architectural elements and palaeocurrent directional data. The study demonstrates that sedimentological facies analysis can be a useful tool for the recognition of palaeoclimatic changes in Pleistocene alluvial successions.     

Geochemistry of Quaternary sediments of the Jeongokri archaeological site,Korea: implications for provenance and palaeoenvironments during the Late Pleistocene

The geochemical characteristics of an approximately 6‐m‐long sediment core collected from the Jeongokri archaeological site (Hantan River, Korea) were examined to determine the provenance of the sediments and to reconstruct the palaeoenvironment of the study area during the Late Pleistocene (200–127 ka). The core sediments were subdivided into two parts based on grain size: an upper (0–380 cm depth) and lower part (>380 cm depth). The lower part was deposited primarily by fluvial processes during an interglacial period [marine isotope stage (MIS) 7] with warm and humid conditions. Conversely, the upper part was mainly deposited by aeolian processes during a cold and dry glacial period (MIS 6). Geochemical characteristics, represented by major, trace and rare earth element (REE) compositions, and textures of the Jeongokri core sediments show distinct differences between the upper and lower parts. The mineralogy and major, trace and REE compositions indicate that the influence of felsic source rocks (e.g. granite) was dominant in the lower sediments, which were derived from the Hantan River. In contrast, increased quartz content and the very fine and homogeneous grain size in the upper sediments indicate an aeolian origin. REE ratios and distribution patterns, and geochemical signatures indicate that these sediments were derived predominantly from Chinese loess deposits and partially from local sediments from the Korean Peninsula; the possible source area of the upper sediments is the northern part of the Yellow Sea basin. The Yellow Sea basin, having mixed geochemical signatures between Chinese loess and Korean‐derived sediments, was exposed because of low sea levels during MIS 6. The exposed Yellow Sea basin was located in the path of winter‐monsoon winds, which may have carried a great deal of airborne sediments from the basin to the Jeongokri area. Copyright © 2011 John Wiley & Sons, Ltd.     

Provenance of Jurassic accretionary complex: Mino terrane, inner zone of south-west Japan – implications for palaeogeography of eastern Asia

Provenance and tectonic history of the Jurassic accretionary complex, Mino terrane, located in the Inner Zone of south‐west Japan, were studied using sandstone framework composition and mudrock geochemistry. Modal analysis of sandstones shows that the tectonic setting of the source area for the studied Mino terrane clastic rocks was uplifted basement, largely dominated by high‐grade metamorphic terrain composed of quartz and feldspar, especially plagioclase. The textural and mineralogical immaturity, extent of alkali and alkaline earth element leaching, low chemical index of alteration values and depleted rare earth element (REE) contents suggest rapid uplift and erosion within the source terrain and a relatively weak weathering intensity. Factor analysis revealed that grain‐size effects governed compositional heterogeneity in the studied sediments. Provenance of the sediments is interpreted as being plagioclase‐enriched felsic basement rock, such as granodiorite, within a continental margin and evolved arc tectonic setting rather than active volcanic arc. Lack of a contribution from active volcanic arcs may have resulted from the cessation of volcanism during the reorganization of the subducting plate system and/or erosion of arc volcanics and exposure of basement. Considering the previous studies on palaeogeography and palaeocurrent reconstruction, the north‐eastern part of the Yeongnam massif in the Korean Peninsula is interpreted as the most probable source area for the studied turbidites. The results of mixing calculation for Mino terrane sediments suggest that Precambrian leucocratic granite and the basement rock of the Cretaceous Gyeongsang Basin shed large amounts of sediments to the Mino trench, whilst Precambrian granitic gneiss and the Triassic pluton supplied lesser amounts. The results of this study reveal that, although active subduction–accretion processes were occurring, the Mino trench was bordered by continental basement rocks. This knowledge contributes to enhanced understanding of the Jurassic palaeogeography of the east Asia continental margin.     

Early Miocene stratigraphy of central west Anatolia,Turkey: implications for the tectonic evolution of the eastern Aegean area

Small‐mammalian faunas enable the discrimination and correlation of uppermost Lower Miocene lacustrine sedimentary units in central western Anatolia. On the basis of sequential stratigraphic relationships, early Early Miocene and latest Early Miocene relative ages are suggested for the older lacustrine mass‐flow deposits and younger paper shale units, respectively, which are devoid of age‐diagnostic fossils. In central western Anatolia, the sequential differences between the uppermost Lower Miocene successions delineate a deformation zone of NE–SW‐trending fault blocks separated by vertical faults. This deformation zone, inherited from Late Oligocene tectonics, underwent an early Early Miocene sinistral transtension leading to pull‐aparts that were emplaced by granitoids. Limited extension caused the late Early Miocene repetitive up‐ and down‐wards motions of the fault blocks, with variable magnitudes. This led to contrasting subsidence histories in the relevant basinal system. During the latest Early Miocene, fault blocks coalesced into a regional body characterized by uniform slow subsidence and non‐extensional deformation facies. The general trend of the above tectonic events can be explained by lateral slab segmentation and progressive asthenospheric wedging, in response to NE‐directed and decelerated palaeosubduction in the Aegean. Copyright © 2007 John Wiley & Sons, Ltd.     

陇东新近纪红粘土与第四纪黄土地球化学特征及其物源和风化指示意义

甘肃省平凉市灵台县邵寨镇剖面风尘堆积底界年龄大约为5.23 Ma B.P.,通过对该剖面新近纪红粘土与第四纪黄土-古土壤序列的常量元素、 微量元素、Nd同位素的测试,分析其在物源和风化方面的指示意义,发现新近纪红粘土与第四纪黄土具有相似的常量、 微量元素UCC标准化曲线和稀土元素球粒陨石标准化曲线,指示二者皆来自广阔的...     

A landslide database for Nicaragua: a tool for landslide-hazard management

A digital landslide database has been created for Nicaragua to provide the scientific community and national authorities with a tool for landslide-hazard assessment, emergency management, land-use planning, development of early warning systems, and the implementation of public and private policies. The Instituto Nicaragüense de Estudios Territoriales (Nicaraguan Geosciences Institute, INETER) began to compile the database in a digital format in 2003 as part of a comprehensive geographical information system for all types of geohazards. Landslide data have been obtained from a variety of sources including newspapers, technical reports, and landslide inventory maps. Inventory maps are largely based on fieldwork and aerial-photo analyses conducted by foreign development agencies in collaboration with INETER and other Nicaraguan institutions. This paper presents the sources of landslide information, introduces the database, and presents the first analyses of the data at national and regional scales. The database currently contains spatial information for about 17,000 landslides that occurred in mountainous and volcanic terrains. Information is mainly recorded for the period 1826–2003, with a large number of events that occurred during the disastrous Hurricane Mitch in October 1998. The oldest historical event is dated at 1570, some events are recorded as prehistorical, and other events have unknown dates of occurrence. Debris flows have been the most common types of landslides, both in volcanic and nonvolcanic areas, but other types, including rockfalls and slides, have also been identified. Intense and prolonged rainfall, often associated with tropical cyclones, and seismic and volcanic activity represent the most important landslide triggers. At a regional scale, the influence of topographic (elevation, slope angle, slope aspect) and lithologic parameters on the occurrence of landslides was analyzed. The development of the database allowed us to define the state of knowledge on landslide processes in the Nicaragua and to provide a preliminary identification of areas affected by landslides.     

Molecular fossils as a tool for tracking Holocene sea-level change in the Loch of Stenness,Orkney

Sediments deposited in the Loch of Stenness (Orkney Islands, Scotland) during the Holocene transgression, previously dated to between ~5939–5612 bp , were analysed for molecular fossils – lipids and chlorophyll pigments from primary producers – that complement conventional microfossil and lithological approaches for studying past sea-level change. While microfossil and lithological studies identified a transgression between 102 and 81 cm core depth, key molecular fossils fluctuate in occurrence and concentration between 118 and 85 cm, suggesting an earlier start to the transgression. Terrestrial lipid concentrations decreased and algal-derived, short-chain, n-alkanoic acid concentrations increased at 118 cm, indicating a disruption of the freshwater lake conditions associated with the early stages of the marine transgression. The lipid and pigment analyses provided information that complements and extends that from microfossil analysis, presenting a more complete record of Holocene sea-level changes and local vegetation changes in the Loch of Stenness. The isostatic stability of Stenness during the Holocene points towards other factors to explain the transgression, such as regional factors and/or melting of the Antarctic ice sheet (which occurred up to 3 ka).     

渭河盆地始新世-渐新世沉积物源变化的钻探样品Sr和Nd同位素证据

始新世暖期和始新世-渐新世降温阶段（EOT）在地球气候系统演化中具有代表性,对认识现代全球变暖过程和机制有参考价值。渭河盆地堆积了始新世以来连续的河湖相沉积序列,对其进行沉积物源示踪研究有助于重建渭河流域地貌演化、沉积过程和气候环境变化。本研究对渭河盆地新生代沉积中心固市凹陷荔参1井（钻探井深6535 m）下部的始新世红河组（6527~5529 m）和渐新世白鹿塬组（5315~4759 m）样品进行了Sr和Nd同位素分析,探索古近纪渭河盆地的物源变化过程。结果显示,红河组样品Sr和Nd同位素平均值分别是⁸⁷Sr/⁸⁶Sr=0.716127和ε_Nd=-13.5,白鹿塬组Sr和Nd同位素平均值分别是⁸⁷Sr/⁸⁶Sr=0.720461和ε_Nd=-12.4。分粒级（< 2 μm,2~64 μm和>64 μm）Sr和Nd同位素测试结果表明,粒度效应对渭河盆地始新世-渐新世沉积物硅酸盐矿物的Sr同位素值影响较大,而对Nd同位素影响较小,表明硅酸盐矿物Nd同位素值可作为渭河盆地沉积物物源的指示。结合潜在源区Sr和Nd同位素分布特征,发现渭河盆地始新世和渐新世沉积物主要来自于秦岭造山带和鄂尔多斯地块的贡献,其物源变化与构造抬升和气候演变密切相关。渭河盆地始新世和渐新世沉积物传输和堆积过程与晚新生代相似,具有相对稳定的两端元物源,为利用红河组和白鹿塬组沉积序列重建古气候古环境奠定了良好的基础。

     

SEM–EDS analysis of western Mediterranean obsidians: a new tool for Neolithic provenance studies

The contents of Na, Al, Si, K, Ca and Fe of 99 obsidians from the western Mediterranean islands of Lipari, Palmarola, Pantelleria and Sardinia were determined with the energy-dispersive spectrometer of a scanning electron microscope (SEM–EDS). The Na and in a lesser way other elements contents characterize any obsidian source-island. In Sardinia (80 samples), the four Monte Arci obsidian geochemical types can be discriminated from binary diagrams of element contents or by a discriminant analysis based on the six elements measured. It is concluded that SEM–EDS offers a new option for Neolithic obsidian provenance studies in this region. To cite this article: F.-X. Le Bourdonnec et al., C. R. Geoscience 338 (2006).     

An Australian provenance for the eastern Otago Schist protolith,South Island,New Zealand: evidence from detrital zircon age patterns and implications for the origin of its gold

Uranium–lead age patterns of detrital zircons in Otago Schist meta-sandstones from eastern Otago, including areas of orogenic gold mineralisation, are mostly consistent with a Rakaia Terrane (Torlesse Composite Terrane) accretionary wedge protolith. Southwest of the Hyde-Macraes and Rise & Shine shear zones the depositional age is regarded as Middle–Late Triassic. At the south and west margins, there are two areas in the Late Triassic Waipapa Terrane protolith. Northeast of the Hyde-Macraes Shear Zone, the schist protolith has Middle to Late Triassic and middle to late Permian depositional ages of Rakaia Terrane affinity. At the northeastern margin of the Hyde-Macraes Shear Zone, there is a narrow strip with a mid-Carboniferous protolith, which may be a counterpart of the Carboniferous accretionary wedge in the New England Orogen, eastern Australia. Ordovician–Silurian zircons are a minor but distinctive feature in many of the protolith age patterns and form significant age components at hard-rock gold locations. These constrain the provenance of Rakaia Terrane protolith sediments to Late Triassic time and within the Permian–Triassic magmatic arcs at the northeastern Australian continental margin and partly within the Ordovician–Silurian granitoids of the Charters Towers Province hinterland and environs. The latter have extensive gold mineralisation and thus upon exhumation might be the origin of Otago gold.     

Transport in a 2-D saturated porous medium: A new method for particle tracking

A new method for solving the transport equation based on the management of a large numbe of particles in a discretized 2-D domain is presented. The method uses numerical variables to represent the number of particles in a given mesh and is more complex than the 1-D problem. The first part of the paper focuses on the specific management of particles in a 2-D problem. The method also would be valid for three dimensions as long as the medium can be modeled similar to a layered system. As the particles are no longer tracked individually, the algorithm is fast and does not depend on the number of particles present. The numerical tests show that the method is nearly numerical dispersion free and permits accurate calculations even for simulations of low-concentration transport. Because each mesh is considered as a closed system between two successive time steps, it is easy to add adsorption phenomenon without any problem of numerical stability. The model is tested under conditions that are extremely demanding for its operating mode and gives a good fit to analytical solutions. The conditions in which it can be used to best advantage are discussed.     

西秦岭凤县北部罗汉寺岩组沉积时代和源区特征：来自LA- ICP- MS锆石U- Pb年龄证据

秦岭造山带罗汉寺岩组的形成时代长期存在争议。选择西秦岭东段凤县北部罗汉寺岩组凝灰岩和浅变质碎屑岩为研究对象，运用LA- ICP- MS锆石U- Pb同位素年代学方法，探讨罗汉寺岩组的形成时代和物源特征。结果显示，罗汉寺岩组下部a岩段中凝灰岩结晶年龄为407±10 Ma；上部碎屑岩段(c岩段)中千枚岩碎屑锆石年龄介于2658~420 Ma之间，主要包括490~420 Ma和997~639 Ma两个区间峰值年龄，其次为1557~1318 Ma、2484~1745 Ma，另有少量2650 Ma左右年龄值。结合区域地质资料，限定罗汉寺岩组主体形成时代为早—中泥盆世。研究同时表明，罗汉寺岩组物源具有明显的多元性，490~420 Ma年龄组的锆石主体来自于商丹洋俯冲作用形成的弧岩浆岩；997~639 Ma年龄组可进一步细分为843~639 Ma和997~867 Ma，前者主要来自于南秦岭构造带，后者主要来自于北秦岭构造带；2658~1318 Ma的中元古代—新太古代年龄组与北秦岭构造带、华北板块和扬子板块的岩浆活动相关。综合分析认为南秦岭和北秦岭地块早—中泥盆世时期尚未全面碰撞成陆，商丹洋为残留洋(海)盆。     

Geochronology and provenance of detrital zircons from late Palaeozoic strata of central Jilin Province,Northeast China: implications for the tectonic evolution of the eastern Central Asian Orogenic Belt

Here we present new U–Pb and Hf isotopic data for detrital zircons obtained from six samples of late Palaeozoic units from central Jilin Province, Northeast China, and use these data and sedimentary formations to constrain the late Palaeozoic tectonic evolution of the eastern segment of the southern margin of the Central Asian Orogenic Belt. The majority of the detrital zircons from the six samples are euhedral–subhedral and exhibit oscillatory zoning, indicating a magmatic origin. Zircons from sandstones in the Devonian Wangjiajie and Xiaosuihe formations yield seven main age populations (399, 440, 921, 1648, 1864, 1911, and 2066 Ma) and two minor age populations (384 and 432 Ma), respectively. Zircons from a quartz sandstone in the Carboniferous Luquantun Formation yield four age populations (~332, 363, 402, and 428 Ma), and zircons from quartz sandstones of the Permian Shoushangou, Fanjiatun, and Yangjiagou formations yield age populations of 265, 369, 463, 503, and 963 Ma; 264, 310, 337, 486, and 529 Ma; and 262, 282, 312, 338, 380, 465, and 492 Ma, respectively. These data, together with the ages of magmatic zircons from interbedded volcanics and biostratigraphic evidence, as well as analysis of formations, give rise to the following conclusions. (1) The Wangjiajie and Xiaosuihe formations were deposited in an extensional environment during Middle and Middle–Late Devonian time, respectively. The former was sourced mainly from ancient continental material of the North China Craton with minor contributions from newly accreted crust, while the latter was sourced mainly from newly accreted crust. (2) The Luquantun Formation formed in an extensional environment during early–late Carboniferous time from material sourced mainly from newly accreted crust. (3) The Shoushangou, Fanjiatun, and Yangjiagou formations formed during a period of rapid uplift in the late Permian, from material sourced mainly from newly accreted crust.     

A classification scheme for mantle-derived garnets in kimberlite: a tool for investigating the mantle and exploring for diamonds

A new empirical method has been devised for classification of mantle-derived garnets in kimberlite. Simple chemical screens have been developed to distinguish between garnets from different parageneses, based on Mg, Fe, Ca, Cr, Ti and Na values of published analyses of garnets from >2000 ultramafic xenoliths in kimberlite. Although crustal garnets are typically uncommon as xenocrysts in kimberlite, the first step in the classification is to screen these from the mantle population, using data from >600 garnet-bearing crustal rocks. Such a screen may also prove useful in evaluating the source (crust vs. mantle) of garnet in kimberlite exploration samples. Subsequent steps divide mantle garnets into eclogite, peridotite and Cr-poor megacryst groupings, and sub-groups of the peridotite (lherzolite, harzburgite, wehrlite) and eclogite (Groups I and II and A, B, C and grospydite) populations. Important features of this classification include the fact that it is based on distinctions between groups of fundamental geological significance (e.g., peridotite vs. eclogite) and it is based on a large, well-documented and well-understood xenolith database. As it utilizes oxide values and molar ratios of major and minor elements, the rationale for the screens is readily understood and it is simple to use.     

The use of simultaneous R- and Q-mode factor analysis as a tool for assisting interpretation of mineral magnetic data

The paper demonstrates both the potential and possible limitations of the use of simultaneous R-and Q-mode factor analysis for the detection of multivariate patterns in mineral magnetic data sets. Two examples are presented: correlation of Quaternary age glacial sediments from the Isle of Man within the Irish Sea Basin, and secondly, sediment-source linkages in recent lake sediments from Bar Mere, Cheshire, England. In both examples, the factor analysis offers useful insights into the environmental processes involved. Also, it seems to offer a suitable method by which qualitative interpretations of mineral magnetic data can be underpinned by a more objective approach. Plots of both variable and sample factor loadings provide a simple visual impression of the underlying multivariate trends in the data set. Given the simplicity with which the factor approach used here can be performed, it appears that it could become routine practice for the analysis of suitable mineral magnetic data sets.