Paleoclimatic record of a long deep sea core from the eastern Mediterranean

A deep-sea core over 16 m long from the crestal area of the Mediterranean Ridge has been investigated with different techniques, including quantitative micropaleontology, stable isotopes (measured on the epipelagic species Globigerinoides ruber and on the mesopelagic species Globorotalia inflata), and clay mineralogy. The resulting record of climatic fluctuations can be cross correlated to other Mediterranean cores by means of isochronous lithologies (tephra layers and sapropels). The climatic record of the Mediterranean is similar in character, phase, and chronology to the records investigated in the equatorial Pacific and in the Caribbean. Isotope stages 1 to 17 have been recognized. Cyclically repeated stagnant cycles resulting in sapropel deposition complicate both the isotopic and the faunal signal. The isotopic investigations reveal that the temperature change in the surface layers of the eastern Mediterranean was no greater than 8°C in the late “glacial” Pleistocene. The chronostratigraphic and biostratigraphic interpretation of Core KS09 indicate that the mean sedimentation rate was 2.4 cm/1000 years, a value very close to the 2.5 cm/1000 years calculated for the entire Quaternary section at DSDP Site 125, also located in the crestal area of the Mediterranean Ridge in the Ionian Basin. The base of KS09 is likely to be very close to the Brunhes/Matuyama boundary dated at 0.7 my.     

A new Middle Pleistocene interglacial record from Denmark: Chronostratigraphic correlation,palaeovegetation and fire dynamics

Previously only three terrestrial interglacial periods were known from southern Scandinavia, all of which could be relatively easily correlated within the central European stratigraphical framework. Here, we present a new interglacial–interstadial pollen, plant macrofossil and charcoal record from Trelde Klint, Denmark, and analyse its biostratigraphy, correlation with other European records, vegetation development, fire dynamics and absolute dating. Except for a slight truncation of the early part of the record, the pollen stratigraphy exhibits a full interglacial succession, including temperate trees (Quercus, Ulmus and Tilia) during its mesocratic stage. Macrofossil analysis allowed identification to species level for Quercus robur, Picea abies and two mosses. Conifers (Pinus and Picea) dominate the pollen record of the interglacial sequence, and the occurrence of Larix pollen in the top part of the interglacial record as well as in the interstadial sediments is especially indicative of this interglacial. The overall diversity of tree genera is rather low. These biostratigraphical features suggest that Trelde Klint is unique among Danish records, but it is similar to records from northern Germany. Numerical analyses (REVEALS and DCA) indicate that forests during the temperate stage were dense and that vegetation openness increased only towards the end of the interglacial, accompanied by increased fire occurrence. A short interstadial sequence with a dominance of Pinus and Betula and the presence of Larix is present above the interglacial deposit. We argue that lack of attention to differences in fire regimes may hamper understanding of between‐site correlations of interglacial pollen records. OSL dating, using a novel feldspar technique, yields an average age of 350±20 ka for the sandy sediments above the interglacial layers at Trelde Klint, suggesting that the whole interglacial–interstadial succession belongs to Marine Isotope Stage 11.     

The Piànico tephra: an early Middle Pleistocene record of intraplate volcanism in the Mediterranean

ABSTRACT Distal tephra are a valuable record of the volcano-tectonic evolution of an area under study. Here, we document the case of the Early Middle Pleistocene rhyolitic tephra of Piànico, discovered in the Southern Italian Alps. The geochemical characteristics of Piànico are unique among the distal tephra outcropping in Italy and indicate an intraplate volcanism at the source. The alkali composition and trace elements show a striking resemblance with the rhyolitic complex of the Euganean Hills, located 170 km from Piànico. However, these rhyolites are much older (Oligocene). Alternatively, the source of this intraplate volcanic episode could be located in the southern Tyrrhenian Sea.     

Electron microprobe correlation of tephra layers from Eastern Mediterranean abyssal sediments and the Island of Santorini

Five widespread tephra layers are found in late Quaternary sediments (0–130,000 yr B.P.) of the Eastern Mediterranean Sea. These layers have been correlated among abyssal cores and to their respective terrestrial sources by electron-probe microanalysis of glass and pumice shards. Major element variations are sufficient to discriminate unambiguously between the five major layers. Oxygen isotope stratigraphy in one of the cores studied was used to data four of the five layers. Two of the widespread layers are derived from explosive eruptions of the Santorini volcanic complex: the Minoan Ash (3370 yr B.P.) and the Acrotiri Ignimbrite (18,000 yr B.P.). An additional layer, found in one core only, is most likely correlated to the Middle Pumice Series of Santorini (approximately 100,000 yr B.P.). Two layers are correlated to deposits on the islands of Yali and Kos and date to 31,000 and 120,000 yr B.P., respectively. One layer originated from the Neapolitan area of Italy 38,000 yr B.P.     

The Upper Pleistocene to Holocene sediments on the Mediterranean island of Lampedusa (Italy)

The island of Lampedusa lies on the northern edge of the African continental shelf, but during some Quaternary marine lowstands it was joined to the African continent. The study and dating of the aeolian, alluvial, detrital sediments, calcareous crusts and speleothems have established that the climatic–environmental variations recorded on the island can be related chronologically to those known for northern Libya, Tunisia and the Italian peninsula. During the Last Glacial Maximum, phases of Saharan dust accumulation on Lampedusa occurred, and were coeval with dust accumulation in crater lakes and on high mountains in central‐southern Italy, and with phases of glacial advance in the Apennines and in the Alps. During the late Holocene, accumulation of Saharan dust on Lampedusa occurred but there was little accumulation of dust on the northern side of the Mediterranean Sea. With the new data from Lampedusa, it is possible to envisage two different scenarios of atmospheric circulation relating to the Last Glacial Maximum and to the late Holocene. During the Last Glacial Maximum, southerly atmospheric circulation brought rainfall to the southern slopes of the Alps and to the Apennines. During the late Holocene, a prevalent westerly atmospheric circulation became established in the northern Mediterranean. Copyright © 2004 John Wiley & Sons, Ltd.     

Magnetic properties of urban topsoils and correlation with heavy metals: a case study from the city of Xuzhou, China

Heavy metals in urban topsoils have been shown to be very useful tracers of environmental pollution. Thus, their detailed studies are of great importance. Apart from expensive and time-consuming chemical methods, several simple, rapid and cheap proxy methods have been developed recently, one of them being based on rock-magnetic parameters. This examines the use of rock-magnetic methods designed to assess the degree of heavy-metal pollution of urban topsoils from the city of Xuzhou (China). The aim was to identify the magnetic properties and to link the “magnetic pollution” to the concentrations of the heavy metals. Since a strong correlation has been found between saturation isothermal remanent magnetization (SIRM) and the heavy metals, namely, Fe, Se, Ti, Sc, Ba, Bi, Pb, Cu, Zn, Cr and Mo, an anthropogenic contamination origin is thought to be the cause. The present study shows that SIRM is a fast, inexpensive and non-destructive method for the detection and mapping of heavy-metal-contaminated urban topsoils.     

A mid to late Holocene record of palaeoclimatic changes from Nal Sarovar: a palaeodesert margin lake in western India

With a view to obtain palaeoclimatic data from a climatically sensitive region we have studied core samples from Nal Sarovar, a large shallow lake lying within the palaeodesert margin of Thar in western India. A combination of C/N ratios and δ¹³C on a radiocarbon-dated core section have been used as climatic proxies. A high-resolution record extending back to ca. 6.6 ka BP has been reconstructed. The data indicate that, in the past, climate has varied from drier to wetter than present on time-scales of few hundreds to few thousands of years. There are, however, significant differences on the timing of these wet and dry periods, when compared with the available data from lakes farther north, in Rajasthan. Further, it looks unlikely that during the 6.6 ka the catchment areas of Nal Sarovar experienced such a significant increase in rainfall as has been suggested for the Rajasthan lakes. Interestingly, drier periods in Nal Sarovar data appear to correlate well with periods of glacier expansion in Eurasia indicating that the palaeoclimatic variations recorded in Nal Sarovar are a regional feature. © 1997 John Wiley & Sons, Ltd.     

爪哇犀(Rhinoceros sondaicus,Rhinocerotidae)化石在中国更新统的首次发现

犀类是我国华南地区更新世地层中最为常见的化石哺乳动物类群之一。本文对广西崇左三合大洞中发现的犀牛化石材料进行了形态特征描述,并与我国华南地区第四纪相关属种以及东南亚地区所发现的化石和现生种进行了比较,从牙齿形态特征和大小等方面来看,认为三合大洞中的标本应该归入爪哇犀(Rhinoceros sondaicus)。此次所发现的爪哇犀(Rhinoceros sondaicus)化石根据相关文献记录,应该是爪哇犀化石在我国更新世地层中的首次报道,并且是我国有关爪哇犀的最早记录。形态学研究表明,该地区早更新世早期的扶绥岩亮洞、鲤鱼山百孔洞以及泊岳山巨猿洞发现的扶绥犀(Rhinoceros fusuiensis)可能是爪哇犀的直接祖先。三合大洞中爪哇犀的发现进一步丰富了我国华南地区独角犀的种类,填补了该种类在我国更新世地层中缺乏化石记录的空白。     

First record of Bison antiquus from the Late Pleistocene of southern Mexico

In Mexico, just 54% of the reported Pleistocene Bison material has been identified to species. Current paleontological research in northwestern Oaxaca, southern Mexico, has allowed collection of several specimens of Bison antiquus that are part of the Viko Vijin Local Fauna. B. antiquus had a very wide geographic distribution, from lowlands to mountainous landscapes of North and Central America. The B. antiquus record from southern Mexico links their former records from central Mexico and middle Central America and confirms this wide geographic distribution. The univariate mesowear score of the B. antiquus specimens from Oaxaca is in the lower extreme of grazers and the upper end of mixed-feeders, suggesting that they had a less abrasive diet than the modern plains Bison, as has been observed in other samples of this species from diverse parts of North America. The presence of B. antiquus in the Viko Vijin L. F. constrains the age of this fossil assemblage within a range from 60 Ka to 11.7 Ka.     

Deep sea rock record exhumed on oceanic volcanic islands: the Cretaceous sediments of Maio,Cape Verde

Revising the deep water stratigraphy exposed on Maio offers a key section recording the sedimentary evolution in the distal domain of the Central Atlantic and the related North West African Atlantic margin (NWAAM). The oceanic volcanic island is one of nine islands in the Cape Verde archipelago, and is unique to the Central Atlantic due to the exposures of ophiolites and the overlying Mesozoic deep water sediments uplifted during the Cenozoic. This provides the opportunity to assess at outcrop, the exhumed sediments, stratigraphy and palaeo-environments of the early Central Atlantic and contribute towards the knowledge of passive margin evolution along the NWAAM, part of the largest continental remnant of Gondwana.Combined with the previous recording of calpionellids, the first collection of lower Valanginian ammonites from the lowest sedimentary succession provides conclusive evidence that Jurassic sediments are not present on Maio. Bed-by-bed sampling and ensuing micro-palaeontological analysis of these 71 samples, together with a re-interpretation of Stahlecker's remaining historical palaeontological collection providing a comprehensive dataset to build a high-resolution stratigraphic framework for the Mesozoic sediments. This reveals pelagic deep water limestones of the Morro Fm. were deposited until the upper Barremian. A major lithological change from carbonate- to siliciclastic-dominated facies, corresponding to the Morro-Carquiejo Fm. boundary is recognised as a regional hiatus spanning part of the Aptian identified across the Central Atlantic. The overlying Albian and younger Carquiejo Fm. is seen as an equivalent to the Albian-Cenomanian black shales of DSDP Leg 41, yet organic content is absent due to degradation. Future studies can build on this multi-disciplinary investigation revising the stratigraphy of Maio.     

Loess—palaeosol sequence in Kashmir: Correlation of mineral magnetic stratigraphy with the marine palaeoclimatic record

In this paper we use the mineral magnetic data (χ and χ_fd) to stratigraphically correlate different loess-palaeosol profiles in Kashmir Valley. The two available thermoluminescence (TL) chronologies on the Kashmir loess profiles have been reinterpreted to identify the soil of the Last Interglacial (ca. 125 000 yr BP). We show that the mineral magnetic data correlates well with the global marine δ¹⁸O record. This correlation has revealed the well-known Milankovich periodicities of 40 ka and 20 ka in the loess-palaeosol record. On the basis of this study, we conclude that loess deposition in the Kashmir Valley started around 200 ka and not 350 ka ago as suggested by earlier workers, and that magnetic susceptibility variations provide a tool to decipher climatic changes from loess-palaeosol sequences.     

Magnetic properties of light and dark sediment layers from the japan sea: Diagenetic and paleoclimatic implications

Rock magnetic/paleoclimatic/diagenetic relationships of sediments spanning the last 0.78 Ma have been investigated using samples collected from light and dark layers recovered at ODP Sites 794 (Yamato Basin) and 795 (Japan Basin). Rock-magnetic parameters (K, K_fd, ARM, SIRM, S-ratio) are shown to reflect diagenetic processes and climate-related variations in the concentration, mineralogy and grain-size of the magnetic minerals contained within the sediments. The magnetic mineralogy is dominated by ferrimagnetic (magnetite-type) minerals with a small contribution made by hematite and iron sulphides such as pyrrhotite and/or greigite. Magnetic mineral concentration and grain size vary between light and dark layers with the former characterized by a higher magnetic content and a finer magnetic grain size. Magnetite dissolution, related to sulfate reduction due to bacterial degradation of organic matter, is the process responsible for the magnetic characteristics observed in the dark layers, testifying to the reducing conditions in the basin. Variations in the rock magnetic properties of the sediments are strongly correlated with global oxygen isotope fluctuations, with glacial stages characterized by a lower magnetic mineral content and a coarser magnetic grain size relative to interglacial stages. Major downcore changes in the magnetic properties observed at Site 794 can be related to changes in the oceanographic conditions of the basin associated with the flow of the warm Tsushima Current into the Japan Sea at about 0.35–0.40 Ma ago.     

Magnetic characterisation and correlation of a Younger Dryas tephra in North Atlantic marine sediments

A technique for identifying non‐visible basaltic tephra‐rich horizons of Younger Dryas (YD)/Greenland Stadial (GS) 1 age in northeast Atlantic sediments using rapid, non‐destructive magnetic measurements is presented. Three high‐resolution marine sediment cores have been studied in an E–W transect across the Hebridean margin: St Kilda Basin (MD95‐2007), Barra Fan (MD95‐2006) and Rockall Trough (MD04‐2822). Magnetic susceptibilities and remanent magnetisations were measured at contiguous 1 cm resolution on bulk sediments. In all three cores, an interval with higher proportions of hard magnetic minerals coincides with a clearly defined peak in basaltic tephra shard (>250 µm) counts, which can be constrained to the early part of the YD/GS1 based on faunal climate proxies. Electron microprobe analyses of the magnetically distinct basaltic tephra interval, in all three cores, displays the same major element geochemistry as published for the Vedde basaltic (I Tab. 1), i.e. sourced from the Icelandic volcano Katla. The identification of transitional alkalic basaltic tephras within marine sediments could potentially be facilitated by magnetic analysis as a useful chronostratigraphic screening tool. Copyright © 2009 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.     

Land–sea correlation of Middle Pleistocene temperate sub-stages using high-precision uranium-series dating of tufa deposits from southern England

High-precision U-series dating allows a direct correlation to be made between terrestrial records of the penultimate interglacial (Marine Oxygen Isotope Stage 7 (MIS 7)) in Britain and sub-stage climate forcing in the marine oxygen isotope sequence. U-series ages of surficial tufa deposits are of sufficient precision to correlate discrete episodes of temperate conditions with individual warm sub-stages within MIS 7. Furthermore, detailed biostratigraphy allows periods of faunal turnover to be correlated with cold climates and lowered sea level. Ecological and environmental conditions in Britain during MIS 7 are therefore driven by the short-lived, sub-stage climate forcing that is observable in the marine isotope record. It is clear that interglacial climates are highly dynamic, producing multiple climatic optima and a diverse range of environments within single warm episodes. Consequently sub-stage records of climate forcing are crucial frameworks for reconstructing terrestrial records of environmental change.     

Holocene lake sediments from the Faiyum Oasis in Egypt: a record of environmental and climate change

The Qarun Lake in the Faiyum Oasis (Egypt) provides a unique record of Holocene environmental and climate change in an arid area largely devoid of fossil proxy records. Multiple lithological, palaeontological and geochemical proxies and 32 radiocarbon dates from the 26‐m‐long core FA‐1 provide a time series of the lake's transformation. Our results confirm that a permanent lake appeared in the Holocene at c. 10 cal. ka BP. The finely laminated lake sediments consist of diatomite, in which diatoms and ostracods together with lower concentrations of ions indicate a freshwater environment at the end of the early and middle Holocene. This freshwater supply was closely associated with regular inflows of the Nile water during flood seasons, when the Intertropical Convergence Zone (ITCZ) migrated northwards in Africa, although it has probably never reached the Faiyum Oasis. Local rainfall, possibly connected with a northern atmospheric circulation, may have been important during winter. Several phases in the lake's evolution are recognized, represented by oscillations between deep open freshwater conditions during more humid climate and shallow fresh to brackish water during drier episodes. After a long freshwater phase, the lake setting has become more brackish since c. 6.2 cal. ka BP as indicated by diatoms and increasing contents of evaporite ions in the sediment. This clearly shows that since that time the lake has occasionally become partly desiccated. This is a result of reduced discharge of the Nile. In the late Holocene the lake was mostly brackish and then gradually turned into a saline lake. This natural process was interrupted about 2.3 cal. ka BP when a man‐made canal facilitated water inflow from the Nile. The examined FA‐1 core can be used as a reference age model of climate change in the Holocene and its impact on the development and decline of ancient civilizations in northeastern Africa.     

Palaeomagnetic correlation and dating of Plio/Pleistocene sediments at the southern margins of the North Sea Basin

A series of discontinuous sediment sequences, of Plio/Pleistocene age, occur onshore around the southern North Sea margins, notably in the East Anglian region of Britain. Intensive lithological and palaeontological analyses of these sediments have shown that they record both major and minor oscillations in climate, sea level and environmental conditions. However, significant uncertainties exist regarding the absolute and relative chronostratigraphies of many of these sequences, hindering understanding of the relative impacts of climatic, eustatic and tectonic changes on the palaeogeographic development of the southern North Sea basin. Here, a number of key East Anglian Plio/Pleistocene sites are subjected to robust palaeomagnetic and mineralogical examination, in order to determine those sediments which display reliable, syn‐depositional magnetic polarities, which are thus of use in ascribing a palaeomagnetically determined age from comparison with the Geomagnetic Polarity Timescale (GPTS). Based on a range of palaeomagnetic and complementary mineralogical methods, reliable palaeomagnetic directions were obtained from eight sites, with reversed polarities displayed by sediments from three sites. These polarity determinations can be used to infer absolute ages and test published, between‐site correlations. Copyright © 2005 John Wiley & Sons, Ltd.     

The record of tidal cycles in mixed silici–bioclastic deposits: examples from small Plio–Pleistocene peripheral basins of the microtidal Central Mediterranean Sea

The Pliocene–Pleistocene peripheral marine basins of the Mediterranean Sea in southern Italy, from Basilicata and western Calabria to northern and eastern Sicily, represent tectonically formed coastal embayments and narrow straits. Here, units of cross‐stratified, mixed silici–bioclastic sand, 25 to 80 m thick, record strong tidal currents. The Central Mediterranean Sea has had a microtidal range of ca 35 cm, and the local amplification of the tidal wave is attributed to tides enhanced in some of the bays and to the out‐of‐phase reversal of the tidal prism in narrow straits linking the Tyrrhenian and Ionian basins. The siliciclastic sediment was generated by local bedrock erosion, whereas the bioclastic sediment was derived from the contemporaneous, foramol‐type cool‐water carbonate factories. The cross‐strata sets represent small to medium‐sized (10 to 60 cm thick) two‐dimensional dunes with mainly unidirectional foreset dip directions. These tidalites differ from the classical tidal rhythmites deposited in mud‐bearing siliciclastic environments. Firstly, the foreset strata lack mud drapes and, instead, show segregation of siliciclastic and bioclastic sand into alternating strata. Secondly, the thickness variation of the successive silici–bioclastic strata couplets, measured over accretion intervals of 2 to 3 m and analysed statistically, reveal only the shortest‐term, diurnal and semi‐diurnal tidal cycles. Thirdly, the record of diurnal and semi‐diurnal tidal cycles is included within the pattern of neap‐spring cycles. Differences between these sediments and classical tidal rhythmites are attributed to the specific palaeogeographic setting of a microtidal sea, with the tidal currents locally enhanced in peripheral basins. It is suggested that this particular facies of mud‐free, silici–bioclastic arenite rhythmites in the stratigraphic record might indicate a specific type of depositional sub‐tidal environment of straits and embayments and the shortest‐term tidal cycles.     

安徽龙河口水库沉积物磁性特征及其环境意义

对龙河口水库建库以来代表性沉积物柱样（ALE）进行了磁性参数测量和粒度分析，探讨了各磁性参数随深度变化的特点及与粒度参数的关系。同时通过与流域降水量曲线的比较，认为库区沉积物受降水量影响显著，cARM/c可作为反映流域降水量变化的一个间接指标。     

Magnetic properties of bottom sediments from Meromectic Shira Lake (Siberia,Russia)

Magnetic properties were studied in bottom sediments of saline meromictic Shira Lake by the methods of static magnetometry and resonance Mössbauer spectroscopy for the first time. All layers of bottom sediments contain nanosized single-domain magnetite particles produced by magnetotactic bacteria. The concentration of magnetite in bottom sediments decreased with depth, reaching a local minimum in the layer corresponding to the minimal level of the lake observed in 1910–1930. It is demonstrated that biogenic magnetite may indicate climate-related changes in the level of Shira Lake, in addition to the other biological and geochemical characteristics.