Age determination of Quaternary deposits as indicated by ionium method applied to relics of bones

The ages of the first and third floodplain terraces at Igarka, on the Yenisey river, were found to be 42,000 and 100,000 years (table 2), using as test materials petrified bones from permafrost rocks in positions where neither adsorbtions nor losses of radioactive elements could have significantly altered their original concentrations in the samples, as happened elsewhere. —V.P. Sokoloff.     

Paleoclimatic implications of late quaternary lacustrine sediments in Western Nubia, Sudan

Owing to the hypercontinental location of Western Nubia, secular fluctuations of climate have been filtered and wet phases can be considered as representative of conditions throughout the southeastern Sahara. The study area is crossed by the 20-mm isohyet; between 9300 and about 4000 yr B.P., however, there were widespread lake and swamp environments with freshwater molluscs, ostracods, and diatoms, and a species-rich savanna mammal fauna. The center of the West Nubian Basin (approx. 18°N), an area of about 20,000 km², was occupied by a semiaquatic landscape which was situated at the same latitude as Paleolake Chad. From extensive lake carbonates up to about 4 m thick, a long-term rise of the groudwater table is inferred. Environments developed that now exist at about latitude 13°N. Radiocarbon dates from lake sediment sequences cluster between 30,000 and 21,000 yr B.P., indicating a Pleistocene wet phase. A gap in radiocarbon dates between 21,000 and 11,000 yr B.P. signals a phase of hyperaridity, similar to the present hyperarid phase, with eolian deflation and deposits of sand being the dominant forms of erosion and accumulation.     

塔河油田溶洞充填物的元素地球化学特征及环境意义

塔河油田位于塔里木盆地塔北隆起阿克库勒凸起的西南部,加里东-海西期强烈抬升导致的大气淡水岩溶作用、早石炭世发生的广泛海侵以及二叠纪大规模的火山活动,对奥陶系岩溶储层产生了不同程度的改造。对塔河地区的地质演化特征以及塔河油田地区溶洞砂泥质充填物镓、铷、锶、钡等微量元素和稀土元素的研究表明,大部分样品表现出淡水岩溶特征,仅T615井等4口井的溶洞充填物却表现出海水成因特征,充填物的元素地球化学特征表现出与早期大气淡水岩溶作用的叠加效应;此外,还有少量样品具有能反映热液作用特征的Eu正异常,说明该区碳酸盐岩地层也受热水溶蚀作用的影响。通过溶洞方解石和溶洞方解石胶结物碳、氧同位素值分布特征的分析也证实了塔河地区除了发育大气淡水岩溶作用外,还存在海水-淡水混合水溶蚀作用和热液溶蚀作用。     

A diatom maximum horizon in upper quaternary deposits

Diatom maxima have been observed in three sediment cores, two from the Skagerrak/Norwegian Sea area and one from the Fram Strait. The maxima occur between 11.000 B.P. and 9.000 B.P. in the Skagerrak/Norwegian Sea and between about 9.000 B.P. and 4.500 B.P. in the Fram Strait. It is thus likely that high diatom productivity as reflected by the diatom maximum horizons are time transgressive and follow the movements of the oceanic polar front. The occurrence of diatom maximum horizons can therefore be used as a signal indicating the presence of the polar front at the time of deposition. In both the Skagerrak and Norwegian Sea cores the maximum consist of two distinct peaks; the oldest characterized by cold water species (Thalassiosira antarctica), the youngest characterized by temperate species reflecting the present diatom flora.

---

Zusammenfassung In drei Sediment-Kernen, zwei davon aus dem Skagerrak-Nordsee-Gebiet und einem von der Fram-Straße, wurden Anhäufungen von Diatomeen beobachtet. Für das erste Gebiet wird das Maximum auf 11.000 bis 9.000 Jahren datiert, während in der Fram-Straße die größte Häufigkeit vor 9.000 bis 4.500 Jahren auftritt. Man kann daher annehmen, daß die erhöhte Produktion von Diatomeen, wie sie aus den Horizonten mit häufigerem Auftreten ersichtlich ist, sich mit der Zeit verschiebt und der Ausbreitung der Polarfront auf dem Meer folgt. So kann die Lage der Polarfront zur Zeit der Sedimentablagerung aus dem Auftreten von Horizonten mit der größten Diatomeenhäufigkeit ersehen werden.In den Proben vom Skagerrak und der Nordsee zeichnet sich das Maximum der Diatomeenhäufigkeit durch zwei Ausschläge aus, wobei der ältere davon vor allem durch die für kälteres Wasser spezifischen Arten (Thalassiosira antarctica), und der jüngere von Warmwasserarten, entsprechend der heutigen Diatomeenflora, geprägt wird.

---

Résumé Des maxima de la teneur en diatomées ont été observés dans trois carottes dont deux proviennent de la région Skagerrakmer du Nord et une du détroit de Fram. Ces maxima se présentent entre 11000 et 9000 ans BP au premier site et entre 9000 et 4500 ans BP au second. Il est donc admissible que la production élevée de diatomées reflétée par ces maxima est diachronique et suit le mouvement du front polaire océanique. Un horizon a teneur en diatomées maximale peut être ainsi utilisé comme un indicateur de la présence d'un front polaire au moment du dépôt. Dans les deux carottes du Skagerrak et de la Mer du Nord, le maximum comporte deux pics caractérisés, le plus ancien par des espèces d'eau froide (Thalassiosira antarctica), le plus récent par des espèces d'eau tempérée reflétant la flore des diatomées actuelles.

---

, — , . 11000 9000 , — 9000 4500 . , , , . , . : Thalassiosira antarctica, , - , .

     

Joints as fingerprints of stress in the quaternary carbonate deposits along coastal Saurashtra,Western India

Coastal cliffs and shore platforms are important geomorphic features of coastal areas of Saurashtra. These features are composed of medium to coarse grained carbonate sand and are designated as “Miliolitic limestones” that range in age from Middle to Late Pleistocene. Significant jointing has been observed in the Middle Pleistocene Miliolite Formation as well as in the younger shell limestone that comprises Chaya Formation of Late Pleistocene. Along with NE-SW trend which is the direction of maximum horizontal compressive stress [S_Hmax] for Indian sub-continent, other trends recorded are NNE-SSW, N-S, NW-SE and E-W. When compared with other regional studies, neotectonic episode in Saurashtra peninsula appears to be younger than at least 125ky. The present study on joint sets also indicates that they are important to understand stresses associated with anticlockwise rotation of the Indian plate.     

Climatic changes during the last 35,000 years as indicated by land, sea, and air data

Detailed climatic records from land (glaciation curves, fossil records, etc.), sea (eustatic changes, deep-ses date), and air (Greenland 0¹⁸ curve) are almost identical for the last 35,000 years. This cannot be a mere coincidence: it indicates that even minor fluctuations are caused by global climatic changes. The various records seem to be easily correlated with each other. The Last Ice Age is characterized by drastic changes between colder and warmer periods. The Present (Flandrian) Interglacial (Holocene Epoch) is also characterized by climatic fluctuations, although of minor amplitude. Analysis of peaks and bottoms in six Atlantic deep-sea cores gives a climatic sequence identical to the eustatic transgression/regression sequence, indicating the recording of global short-term warm/cold fluctuations. From these fluctuations, the climatic cyclicity was calculated. Two drastically frequency-changing cycles were found, one varying from 230 to 1,000 years and one from 1,000 to 3,600 years. A third cycle of 21,000 years was also estabished. The transition from the Last Ice Age to the Present Interglacial is marked by three major steps towards interglacial conditions; viz. at 12,7000, 10,000 and 9,300 radiocarbon years B. P. The 10,000 boundary has earler been suggested as the Pleistocene/Holocene boundary.     

贵州荔波董哥洞3号石笋的同位素年龄及古气候信息

石笋是岩溶记录中最全面、最系统的古气候环境信息库,研究表明,洞穴内、外环境变化,都不同程度地显示在石笋的组成、结构构造、沉积 (生长 )纹层及其层面构造、沉积速率和古气候环境变化等方面。利用洞穴石笋保存的信息重建古环境,是近 2 0年来的热门课题之一。当前全球气候变化预测研究中,洞穴石笋的高分辨率定年和碳、氧同位素组成的变化规律,为这个领域的突破和填补空白作出了重大贡献。本文通过对荔波董哥洞 3号石笋进行热电离质谱 (TIMS)U-系测年及碳氧同位素分析,获得了距今 16.33万年至 9.13万年的古气候信息。石笋在大于 16.33万年前开始生长,9.13万年后停止生长,平均沉积速率为 2.87mm/ 100a(未扣出间断时间 ),属中更新世的产物。其年龄与δ18O的变化可与深海岩芯V2 8～ 2 38同位素记录所揭示的第五和第六阶段以及与北方离石黄土层 (L2 )和下马兰黄土第一古土壤层 (S1)进行对比。它反映此阶段区内经历了寒冷和温暖 (间夹冷期 )等气候变化,与全球古气候变化波动基本一致,同时也存在地区性的气候变化。     

安徽蓬莱仙洞不同滴水点差异PCP作用及其古气候记录研究意义

正石笋由于分布广泛、定年准确,并且具有丰富的气候和环境代用指标(如氧碳稳定同位素~([1,2])、微层厚度~([3])、微量元素~([4~6])等),因而受到古气候学家广泛关注。其中,微量元素和稳定碳同位素常被用来间接地反映局地干湿变化。当降水减少时,洞穴滴水在洞顶储存时间较长,使岩溶水在补给石笋之前已经发生了方解石沉积作用。由于Mg,Sr和Ba在方解石和溶液中的分配系数远小于1~([7,8]),从而使Ca优先于Mg,Sr和Ba沉积出来,使得溶液(渗流水及其所形成的滴水)和现代次生碳酸盐沉积物中的Mg,Sr和Ba富集,进而导致Mg/Ca,Sr/Ca和Ba/Ca比值增大~([4,5,9]),这种现象被称为方解石前期沉积作用(Prior Calcite Precipitation,简称PCP)。此外,当降水减少,洞穴滴水滴率变慢(即PCP作用增强)时,CO_2脱气时间增长也会导致石笋碳同位素偏     

22-Ma eolian deposits in China and long-term climate changes

The history of eolian dust deposition in northern China has been traced back to 22 million years ago （Ma） and the combination of different eolian formations provides a nearly continuous terrestrial climate record since the early Neogene. The spatial distribution of environmental indicators define a roughly EW zonal climate pattern in Asia throughout the Paleogene, attributable to a circulation pattern dominated by a Planetary Wind System （PWS）. A major rearrangement occurred near the Miocene/Oligocene boundary, characterized by a replacement of the zonal PWS by a monsoon circulation similar to that of the present day. This event is also marked by the onset of loess deposition in northern China. The Asian summer monsoon was likely rather weak during the Paleogene. The loess deposition and formation of numerous well-developed paleosols since the Early Miocene indicate that the following features of the modem-day circulation already existed 22 Ma ago： sizeable deserts in the Asian inlands as dust sources, the winter monsoon as dust carrier, and an energetic summer monsoon as a supply of moisture. Uplift of the Himalayan-Tibetan complex and changes in land-sea distribution were likely responsible for these joint changes in circulation and aridity. From 22 to 6 Ma, loess accumulation rates were much lower, suggesting moderate levels of ar/dity and winter monsoon strength. Evolution of the aridity was not strongly correlative with the cooling trends indicated by marine oxygen isotope records, suggesting a smaller impact of global cooling on drying of the Asian interior during this time interval. However, the general aridification history since about 6 Ma matches the ongoing high-latitude cooling and the consequent expansion of Arctic sea-ice/ice sheets. Some increases in aridification also coincide with proposed uplift of portions of the Tibetan Plateau.     

大连开发区炮台山土洞形成与预防研究

季节性天然降水在补给区内聚集 ,沿着渗透通道逐渐形成一定规模的土洞 ,它受特殊的地形地貌单元、地层结构补给与排泄条件制约 ,其淘蚀效应对附近地表构筑物产生潜在的不安全因素     

Soil quality changes in land degradation as indicated by soil chemical, biochemical and microbiological properties in a karst area of southwest Guizhou, China

Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (C_org), extractable extracellular carbon (C_ext), total soil nitrogen (N_t), alkali-hydrolyzable nitrogen (N_ah), total phosphorus (P_t), available phosphorus (P_a) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-C_mic, and by calculation from substrate-incubation respiration, SIR-C_mic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of C_mic/C_org and BR/C_mic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as C_org and C_ext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-C_mic, SIR, and SIR-C_mic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation.     

Origins and genesis of loess deposits in central Spain,as indicated by heavy mineral compositions and grain‐size variability

The formation of loess deposits strongly depends on the availability of deflatable dust‐sized material. Identification of source areas and mechanisms of dust production is essential for an appropriate characterization of related palaeoenvironmental conditions. So far, little research has been done on loess deposits in the Mediterranean region and information about mechanisms of dust production is very rare. In this context, it is not clear from where the loess deposits from the upper Tagus Basin in central Spain originated. The main objective of this study was to find out whether these loess deposits were formed primarily by mountain processes and fluvial comminution, or whether they have their origin in the weathering of Tertiary marls in the centre of the Madrid Basin. A further concern was to link the determined source areas with loess formation mechanisms and concomitant environmental contexts. Following a comprehensive approach using heavy minerals and grain‐size data, together with information on stratigraphic features and geomorphic positions, different local loess sources could be identified. This study shows that during the last 35 kyr a major proportion of the Tagus loess deposits was deflated from river floodplains, while the mountain region of the Iberian Range was identified as a significant source of respective floodplain sediments. Based on heavy mineral compositions and dating results, it was found that during Heinrich Stadial 3, sediment supply from the Iberian Range strongly increased, suggesting an environmental shift from initially warmer towards colder temperatures in late Marine Isotope Stage 3. Furthermore, it was found that grain‐size patterns clearly indicate maximum wind strengths during Heinrich Stadial 3, followed by Heinrich Stadial 2 and Heinrich Stadial 1. These results demonstrate that the formation of dust‐sized particles in this part of the Mediterranean operated similar to many other places in temperate and continental regions, and that weathering processes linked to hot and dry environments were only of minor importance.     

Pleistocene oceanographie changes indicated by deep sea benthic foraminifera in the northern Indian Ocean

An attempt has been made to understand the Pleistocene bottom water history in response to the paleoclimatic changes in the northern Indian Ocean employing quantitative analyses of deep sea benthic foraminifera at the DSDP sites 219 and 238. Among the 150 benthic foraminifera recorded a few species show dominance with changing percent frequencies during most of the sequence. The dominant benthic foraminiferal assemblages suggest that most of the Pleistocene bottom waters at site 219 and Early Pleistocene bottom waters at site 238 are of North Indian Deep Water (NIDW) origin. However, Late Pleistocene assemblage at site 238 appears to be closely associated with a water mass intermediate between North Indian Deep Water (NIDW) and Antarctic Bottom Water (AABW). Uvigerina proboscidea is the most dominant benthic foraminiferal species present during the Pleistocene at both the sites. A marked increase in the relative abundance ofU. proboscidea along with less diverse and equitable fauna during Early Pleistocene suggests a relative cooling, an intensified oceanic circulation and upwelling of nutrient rich bottom waters resulting in high surface productivity. At the same time, low sediment accumulation rate during Early Pleistocene reveals increased winnowing of the sediments possibly due to more corrosive and cold bottom waters. The Late Pleistocene in general, is marked by relatively warm and stable bottom waters as reflected by low abundance ofU. proboscidea and more diverse and equitable benthic fauna. The lower depth range for the occurrence ofBulimina aculeate in the Indian Ocean is around 2300 m, similar to that of many other areas.B. aculeata also shows marked increase in its abundance near the Pliocene/Pleistocene boundary while a sudden decrease in the relative abundance ofStilostomella lepidula occurs close to the Early/Late Pleistocene boundary.     

Fluid regime in the Austrian Moldanubian Zone as indicated by fluid inclusions

Summary Petrographic and fluid inclusion studies were carried out on amphibolites, metapelites and calc-silicate rocks from the Varied Group and the Gföhl Unit of the Austrian Moldanubian Zone. Thermobarometric calculations yield 670–770°C and 7–10 kbar as highest grade conditions for the studied samples. Four fluid inclusion types were identified and measured by microthermometry and Raman analysis: CO₂-(±H₂O) rich, aqueous, CH₄- and N₂-rich inclusions. The oldest fluid, seen as mixed CO₂-H2O inclusions in quartz, infiltrated the Moldanubian rocks at temperatures between 650 and 400°C, causing widespread retrograde metamorphism, as a consequence of thrusting of the Moldanubian rocks over those of the Moravian Zone. During successive uplift stages, fluids continuously evolved to CO₂-richer compositions and lower densities by selective water leakage and density re-equilibration mechanisms. Finally, low salinity aqueous and CH₄- and N₂-rich fluids were trapped during the very late retrograde stage of Variscan metamorphism.

---

Fluid-Regime im Niederösterreichischen Moldanubikum abgeleitet aus Flüssigkeitsein-schluß-Untersuchungen

Zusammenfassung An Metabasiten, Metapeliten und Kalksilikatgesteinen der Gföhler Einheit und Bunten Serie des Niederösterreichischen Moldanubikums wurden petrographische und Flüssigkeitseinschluß-Untersuchungen durchgeführt. Thermobarometrische Berechnungen ergaben 670–770°C und 7–10kbar als maximale Metamorphosebedingungen für die untersuchten Gesteine.Vier verschiedene Typen von Flüssigkeitseinschlüssen wurden identifiziert (CO₂-reiche, wäßrige, CH₄,- sowie N₂-reiche Einschlüsse), sowie mittels Mikrothermometrie und Raman-Untersuchungen analysiert. Das älteste Fluid (gemischte CO₂-H₂O Flüssigkeitseinschlüsse) wurde im Zuge der Moravischen Überschiebung aus dem Moravikum freigesetzt und infiltrierte zwischen 650 und 400°C die darüberliegenden moldanubischen Gesteinspakete, woraus umfassende retrograde Umwandlungen resultierten. Während der sukzessiven Abkühlung und Hebung der Gesteine entwickelten sich diese Einschlüsse infolge selektiven Wasserverlustes und kontinuierlicher Dichteanpassung zu wasserärmeren Zusammensetzungen und geringeren Dichten. Die gering salinaren wäßrigen und die CH₄,- and N₂-reichen Einschlüsse sind einem sehr späten retrograden Stadium der Variszischen Metamorphose zuzuordnen.[]

---

Abbreviations

Mineral names ab albite - alm almandine - am amphibole - an anorthite - and andradite - bi biotite - cpx clinopyroxene - ga garnet - grs grossularite - Kfsp potassium feldspar - ky kyanite - mu muscovite - or orthoclase - pl plagioclase - pyp pyrope - q quartz - sil sillimanite - sps spessartine - T temperature (°C) - T _h homogenization temperature (to liquid) - T _m melting temperature - P pressure (kbar) - Ma 10⁶ years - MG Monotonous Group - VG Varied Group - GU Gföhl Unit With 4 Figures     

Lithofacial complexes of quaternary deposits in the central and southeastern baltic sea

Geological and seismic profiling data (more than 25000 km of seismic profiles and about 1000 sediment sampling stations) collected during the last 30 yr by research vessels of the Shirshov Institute of Oceanology, Russian Academy of Sciences are summarized. Seismic records are directly correlated with sediment cores. The distribution map (scale 1 : 500000) of Quaternary lithofacial complexes corresponding to certain stages of the Baltic Sea evolution is compiled. The following four complexes are distinguished (from the base to the top): (I) moraine, with maximum thicknesses 60 and 170 m in valleys and ridges respectively: (II) varved clay of periglacial basins and from the Baltic Ice Lake (BIL), up to 25 m thick in depressions; (III) lacustrinemarine homogeneous clay with a thickness up to 4–8 m in depressions; (IV) marine sediments (mud, aleurite, coarse-grained deposits) accumulated in environments with intense bottom currents activity (thickness 2–4 m in the Gotland Basin, 4–6 m in the Gdansk Basin, and 10–20 m in fans and prodeltas). The Quaternary sequence is cut through by inherited valleys, where the thickest Holocene sediments are noted. Today, these valleys serve as routes of sediment transport to slope bases and central parts of basins. Outblows of deep gas (through faults and fractures) and diagenetic gas (from sediments) to the bottom surface also occur in the valleys. Sedimentation rates are higher in the Gdansk Basin (up to 100–120 cm/ka). Thick sand, aleurite, and mud bodies are accumulated here (about 15–20 m in the Visla River prodelta). The sedimentation rate is slower in the Gotland Basin (up to 50–60 cm/ka), where thin (2–4 m) sections of more fine-grained mud occur     

The Late Pleistocene clastic deposits in the Romito Cave,southern Italy: a proxy record of environmental changes and human presence

Clastic sediments deposited in caves and rock shelters bear peculiar sedimentological characteristics and have seldom been considered as a high‐resolution proxy record of climatic or environmental changes. The Romito Cave has its entrance at 275 m above sea level, about 25 km from the Tyrrhenian coast of Calabria, southern Italy. New archaeological excavation performed since 2000 has revealed a sedimentary succession spanning the record of Gravettian to Late Epigravettian cultures (Late Pleistocene). The present study focuses on the lower part (2.5 m thick) of the succession, where three main unconformity‐bounded stratigraphic units have been recognised (labelled RM1–3). Each unit consists of water‐lain deposits indicating high‐ to low‐competence flow, capped with anthropogenic deposits. The gradual deactivation and reactivation of the water drainage between 23 475 ± 190 and 16 250 ± 500 cal. a BP is correlated with regional precipitation changes due to the onset of dry climatic conditions of the Last Glacial Maximum. However, the deactivation of cave drainage after the deposition of unit RM3, around 15 400 ± 500 cal. a BP, deviates from the regional hydrological trend of progressively increasing water discharges and is attributed to the drainage cut‐off by probable cave wall collapses. Copyright © 2008 John Wiley & Sons, Ltd.     

Late Pleistocene environmental changes indicated by fossil insect faunas of the English Midlands

Twenty-five fossil insect assemblages are described from discrete lenses of or-ganic material in a gravel sequence at Four Ashes. The youngest date of 30,500 years B.P. obtained on the organic materialhas confirmed that the till overlying the gravels is Late Devensian (Weichselian) in age. The analyses of the insect faunas have shown conclusively for the first time the existence of climatic changes in one geographic area during the Early and Middle Devensian in Britain. Some of the earliest insect faunas can be correlated with the Brorup Interstadial, when boreal forests existed in the English Midlands. It is suggested that a cold period prior to 43,000 years ago (but post-Brorup) may have caused the elimination of the trees, because around 40,000 years ago the insects indicate that there was a rapid climatic amelioration when it was warm enough for trees to grow again in that area. Around 36,000 years ago there was another climatic deterioration when the thermophilous insect species were replaced by a large number of arctic stenotherms and a tundra type of environment. This cold period lasted for at least 6,000 years and probably became increasingly severe with the approach of the main Devensian ice advance sometime after 30,500 years B.P.