Palaeoclihlatic Indicators of China's Quaternary Saline Lake Sediments and Hydrochemistry

In this paper the authors classify saline lake sediments into the cold, warm and eurythermal phases, reveal the consistency between the zoning of hydrochemical types of modern saline lake water and climatic zoning and give climatic parameters under the conditions of typical cold phase (mirabilite and natron), warm phase (thenar-dite) and slightly warm phase (bloedite) saline lake deposition.     

国外海洋气水合物研究的一些新进展

海洋水合物是未来的新型海洋天然气能源,文中简要介绍近年来国际大洋钻探项目在北美陆坡布莱克海岭和由德国Ｓｕｅｓｓ教授等人在东太平洋水合物海岭对海洋气水合物的勘察、取样和多学科的综合研究方面所取得的一些主要新进展和成果。１９９５年ＯＤＰ１６４航次在北美陆坡的布莱克海岭的９９７站位通过钻探取到３块块状气水合物和一些气水合物小碎块。德国Ｅ．Ｓｕｅｓｓ教授和他的同事们在东太平洋的水合物海岭于１９９６年和１９９年在约８００ｍ水深下的海底浅表深积物取到了大量的层块状气水合物。他们的研究表明,布莱克海岭和东太平水合物海岭的气水合物中的甲烷气体均来自细菌对ＣＯ２的分解结果,１６４航次９９５,９９７两上站位较明显的ＢＳＲ均与其下浮沉积物来自细菌对ＣＯ２的分解结果。１６４航次９９５,９９７两个站位较明显的ＢＳＲ均与其下伏沉积物中所饱     

江汉平原江陵湖泊沉积物粒度特征及气候环境意义

以江汉平原江陵湖泊沉积物为研究对象,结合沉积物岩性、粒度组成、孢粉和有机碳同位素等,分析了江陵湖泊沉积物粒度组成特征及该区域近9 000 a来的气候环境变化。研究发现,江陵湖泊沉积物记录了该区湖泊水体逐渐减小直至消亡的过程,气候环境变化大致可分为以下5个阶段：（1）8 900～6 300 a B.P.为水体较深、面积较大的开阔湖阶段,气候暖湿;（2）6 300～4 700 a B.P.为面积较小、水体较浅的潴水湖阶段,气候干旱;（3）4 700～3 400 a B.P.为面积更小、水体更浅的洼地湖阶段,气候偏暖偏湿;（4）3 400～2 500 a B.P.为湖沼泥炭发育阶段,气候暖湿;（5）2 500 a B.P.以来,由湖泊及湖沼堆积转化为洪水漫滩堆积,古云梦泽开始萎缩,气候变干。江陵湖泊沉积物粒度所记录的区域气候干湿变化与国内邻近区域（特别是鄱阳-洞庭湖区）显示出较好的一致性,沉积物粒度研究是恢复区域古降水等气候环境变化的有效途径。     

海底沉积物在应力-应变过程前后的微区变化特征

自1925年太沙基提出的“蜂窝状结构”概念以来,有关土和沉积物微结构分类研究取得了一系列重大成果[1-3].高国瑞[4]则研究分析了我国沿海海相沉积物的微结构类型和工程性质,梁元博等[5]提出典型堆垒结构和颗粒孔隙取向的海洋沉积物微结构模式,卢博等[6-7]对南海海底沉积物微结构影响物理力学性质以及提出的微结构分类研究,丰富了我国海底沉积物结构和微结构的微区分析研究.本文试图通过沉积物在应力一应变过程中的微区变化特征分析研究,为海底工程地质实践服务.     

New palaeomagnetic result from Vendian red sediments in Cisbaikalia and the problem of the relationship of Siberia and Laurentia in the Vendian

A palaeomagnetic study of Vendian red sediments from the Lena River section on the western margin of Lake Baikal in the region of Cisbaikalia (54°N, 108°E) has isolated a stable remanence with direction D = 296.3°, I = −27.7° (high-temperature component) and a corresponding pole of 2.7°S, 168.2°E. The primary nature of this remanence is confirmed from a positive fold test, dual polarities and the presence of detrital haematite. This result, together with all late Precambrian–Early Cambrian palaeomagnetic data from Siberia, indicates that Siberia occupied low latitudes during that time. It has been proposed on the basis of palaeomagnetic data that Laurentia occupied high latitudes during the Vendian, so it would appear that there cannot have been any Laurentia–Siberia connection at that time. A review of Vendian to Cambrian Laurentian palaeomagnetic data shows that such an interpretation is ambiguous. An alternative interpretation places Laurentia in low latitudes and confirms the Laurentia–Siberia fit of Hoffman (1991 ) and Pelechaty (1996 ). However, the lack of Late Vendian palaeomagnetic data for Siberia still allows the possibility that it could have occupied high latitudes during that time.     

白令海表层沉积物中的放射虫与海洋环境

通过对白令海 1 2个表层沉积物中微体生物化石放射虫的分析 ,共鉴别放射虫 2 4 72枚 ,计36属、45种。表层沉积物中放射虫的分布特点为 :1 .浅水陆架 -陆坡上部区的粉砂、细砂沉积物中放射虫化石数量少且属种单调。2 .陆坡下部区的火山碎屑及浊流沉积物中放射虫化石亦不丰富。3.海盆区粘土沉积物中的放射虫化石丰度高且分异度高。本区陆架放射虫化石的优势种为Spongotrochus glacialis.影响放射虫分布的主要因素为海流、地形、水深、水温等。另外 ,该区沉积物的物源主要为陆源沉积物、生物源沉积物和火山源沉积物 ,它们主要来源于俄罗斯东部的勘察加半岛、美国的阿拉斯加半岛及阿留申群岛     

Mechanisms of pore water organic matter adsorption to montmorillonite

The extent and mechanisms of adsorption of marine pore water organic matter to montmorillonite were studied in a series of batch and sequential adsorption experiments. Pore water natural organic matter (pNOM) and easily extracted natural organic matter (eNOM) were collected from Liberty Bay (Puget Sound, WA, USA) sediments. The pNOM and eNOM were each divided into two size fractions using a 1000 D ultrafilter. Batch adsorption isotherms were approximately linear, and the >1000 D fractions of both pNOM and eNOM had larger partition coefficients (K_d) than the <1000 D fractions. A two-component fit of the sequential adsorption data indicated that pNOM and eNOM contained a similar amount of NOM (30%) that was not surface reactive toward montmorillonite. After correcting the batch adsorption K_ds for the non-reactive components, the K_ds estimated by batch and sequential adsorption were identical (2.7 l/kg for >1000 D pNOM and eNOM, and 1.6 l/kg for <1000 D pNOM and eNOM). Mechanisms of adsorption were investigated by systematically changing conditions (pH, temperature and ionic composition) of >1000 D fractions during batch isotherm experiments. Adsorption of NOM was found to decrease with increased temperature, suggesting that hydrophobic effects were not the dominant adsorption mechanisms in this system. Ion exchange was also not an important adsorption mechanism because adsorption increased with ionic strength. The observed enhancement in adsorption with ionic strength indicated that van der Waals interactions were important in the adsorption of NOM. Ligand exchange was found to be a significant mechanism since the presence of SO₄²⁻ in solution reduced the amount of NOM adsorbed. Ca²⁺ enhanced adsorption slightly more than Na⁺, suggesting that cation bridging was involved. The relative contributions of van der Waals interactions, ligand exchange and cation bridging were estimated to be approximately 60%, 35% and 5%, respectively, for adsorption of NOM in a CaCl₂ solution.     

The magnetic properties of the recent sediments of Brothers Water, N W England

The magnetic properties of recent sediments from five short cores from Brothers Water in the English Lake District are compared with those from a set of catchment soil samples. From the comparison, it is concluded that bacterial magnetosomes have made a significant contribution to the magnetic properties of the sediments of the last five decades. This contribution is superimposed on a continuing erosive input of haematite-rich sediment from the parent materials of the catchment and may obscure any possible increase in surface soil input during recent times. The results highlight the difficulty of making sediment-source linkages where biogenic contributions to the magnetic properties of the sediment are important relative to the input of magnetic minerals from catchment erosion.     

Geochemical record of the Holocene Jomon transgression and human activity in coastal lagoon sediments of the San'in district, SW Japan

Coastal lagoon muds were analyzed to evaluate changes in sedimentary environments by the Jomon transgression from the lower to middle Holocene age and human activities. Core samples from Lake Shinji, Southwest Japan were utilized, which cover the entire Holocene Nakaumi Formation (ca. 23-m thick), and comprise the Lower, Middle, Upper and Uppermost members. Total sulfur (TS) contents and Fe₂O₃/Al₂O₃ ratios increase from the boundary of Middle and Upper members, which is 1 m below the Kikai-Akahoya (K-Ah) volcanic ash of 6300 years BP. This change coincides to the pollen flora zone boundary of the Pinus–Abies and the Cyclobalanopsis–Castanopsis, suggesting transition to a warming climate. Chemical index of alteration (CIA) values [(ratio of Al to Al+Ca+Na+K)×100] and Rb/K ratios also show gradual increase from the middle part of the Upper member, due to its derivation from highly weathered source material probably formed under warming and rainy condition. Al₂O₃/TiO₂ and SiO₂/TiO₂ show little variation from the Lower to the Upper members, probably related to consistent feldspar composition in the source rocks, and homogeneously mixed clays. In the Uppermost member (from 1500 years), sharp increases in Ti/Zr and decreases in both Nb/Y and Zr/Y occurred, suggesting heavy mineral fractionation. This change was caused by iron sand processing called Kannanagashi and charcoal-making in the most mountainous regions. Soil erosion by these processes brought changes in mud composition, shown by the enrichment in Al₂O₃, and depletion in Zr and Cr. Human activities thus had severe impacts on sedimentary environments compared with the natural changes since the Jomon transgression.