福建平潭岛晚第四纪沉积序列 及MIS 5海侵旋回特征

选择位于福建平潭岛北部芦洋埔海积平原的PT01钻孔,岩芯长度28.3 m,采用加速器碳同位素（AMS 14C）和光释光（OSL）测年建立地层年代框架,认为晚更新世富含有孔虫等海相生物化石的地层应归属于MIS 5高海面期,即MIS 5e的潮下带滨海相沉积。结合岩性特征、古生物化石、沉积物色度、粒度分析及其参数等指标,进行了沉积单元的划分,重建了MIS 6末期以来的沉积相变化过程,揭示出MIS 5期间的多次海平面波动变化,即MIS 5高海面期沉积环境仍存在滨海、潮坪、潟湖、风成砂等沉积相之间的转换,并可能存在短暂的陆相或风化过程。而该区整个末次冰期的沉积缺失或较薄,上部全新世沉积也不发育,厚度仅为3.79 m,以沼泽相―风成砂相为主。     

Climate fluctuations during the Holocene in NW Iberia: High and low latitude linkages

High resolution benthic foraminiferal stable isotopes (δ¹⁸O, δ¹³C) and molecular biomarkers in the sediments are used here to infer rapid climatic changes for the last 8200 years in the Ría de Muros (NW Iberian Margin). Benthic foraminiferal δ¹⁸O and δ¹³C potentially register migrations in the position of the hydrographic front formed between two different intermediate water masses: Eastern North Atlantic Central Water of subpolar origin (ENACW_sp) and subtropical origin (ENACW_st). The molecular biomarkers in the sediment show a strong coupling between continental organic matter inputs and negative δ¹³C values in benthic foraminifera. The rapid centennial and millennial events registered in these records have been compared with two well known North Atlantic Holocene records from the subtropical Atlantic sea surface temperatures (SST) anomalies off Cape Blanc, NW Africa and the subpolar Atlantic (Hematite Stained Grains percentage, subpolar North Atlantic). Comparison supports a strong link between high- and low-latitude climatic perturbations at centennial–millennial time scales during the Holocene. Spectral analyses also points to a pole-to-equator propagation of the so-called 1500 yr cycles. Our results demonstrate that during the Holocene, the NW Iberian Margin has undergone a series of rapid events which are likely triggered at high latitudes in the North Atlantic and are rapidly propagated towards lower latitudes. Conceivably, the propagation of these rapid climatic changes involves a shift in atmospheric and oceanic circulatory systems.     

BOOK REVIEWS

Book reviewed is the article: Small-State Security in the Balkans . Aurel Braun. South American Development: A Geographical Introduction . Rosemary D. F. Bromley and Ray Bromley. Interregional Migration, National Policy and Social Justice . Gordon L. Clark. Marketing Architectural and Engineering Services . Weld Coxe. A Geography of the Third World . J. P. Dickenson, C. G. Clarke, W. T. S. Gould, R. M. Prothero, D. J. Siddle, C. T. Smith, E. M. Thomas-Hope, and A. G. Hodgkiss. Wildlife and Man in Texas: Environmental Change and Conservation . Robin W. Doughty. At the Sea's Edge . William T. Fox. Englewood Cliffs Geography and Ecology . I. P. Gerasimov. Urbanization in Contemporary Latin America. Critical Approaches to the Analysis of Urban Issues . Alan Gilbert in association with Jorge E. Hardoy and Ronaldo Ramírez, eds. The Coming of the Transactional City . Jean Gottmann. College Park Visions of City and Country: Prints and Photographs of Nineteenth-Century France . Bonnie L. Grad and Timothy A. Riggs. Worcester Soviet Geography Today: Physical Geography . N. A. Gvozdetskiy, ed. Adaptive Responses of Native Amazonians . Raymond B. Hames and William T. Vickers, eds. Urban and Regional Industrial Research: The Changing UK Data Base . Michael Healey, ed. Cuando se Acaban los Montes . Stanley Heckadon Moreno. A Panama Forest and Shore: Natural History and Amerindian Culture in Bocas del Toro . Burton L. Gordon. Pacific Grove Mozambique: From Colonialism to Revolution, 1900–1982 . Allen Isaacman and Barbara Isaacman. Soviet Natural Resources in the World Economy . Robert G. Jensen, Theodore Shabad, and Arthur W. Wright, eds. The Changing Geography of the United Kingdom . R. J. Johnston and J. C. Doornkamp, eds. Pluralism and Political Geography—People, Territory and State . Nurit Kliot and Stanley Waterman, eds. Landmarks Preservation and the Property Tax . David Listokin. Irrigation Horticulture in Highland Guatemala: The Tablón System of Panajachel . Kent Mathewson. Her Space, Her Place: A Geography of Women . Mary Ellen Mazey and David R. Lee. Man, A Geomorphological Agent . Dov Nir. Dordrecht The Book of America: Inside the 50 States Today . Neal R. Peirce and Jerry Hagstrom. Rivers . Geoffrey E. Petts. Proceedings, United States/Australia Workshop on Design and Implementation of Computer-Based Geographic Information Systems . Donna Peuquet and John O'Callaghan, eds. Outdoor Recreational and Resource Management . John Pigram. Remaking the City: Social Science Perspectives on Urban Design . John S. Pipkin, Mark La Gory and Judith R. Blau, eds. The Crust of Our Earth: An Armchair Traveler's Guide to the New Geology . Chet Raymo. Englewood Cliffs Concepts and Themes in the Regional Geography of Canada J. Lewis Robinson. Vancouver Secondary Cities in Developing Countries: Policies for Diffusing Urbanization . Dennis A. Rondinelli. Beverly Hills Legal Foundations of Environmental Planning , Vol 1. J. G. Rose. Can We Delay a Greenhouse Warming? Stephen Seidel and Dale Keyes. Mobilizing Human Resources in the Arab World . R. Paul Shaw. Prairie Mosaic: An Ethnic Atlas of Rural North Dakota . William C. Sherman. The Future of Conflict in the 1980s . William J. Taylor, Jr. and Steven A. Maaranen, eds. The Visual Display of Quantitative Information . Edward R. Tufte. U.S. 40 Today: Thirty Years of landscape Change in America . Thomas R. Vale and Geraldine R. Vale. Madison Silent Violence: Food, Famine and Peasantry in Northern Nigeria . Michael Watts. Readings in Historic Preservation: Why? What? How? Norman Williams Jr., Edmund Kellogg and Frank Gilbert, eds.     

THE KUROSHIO MEANDER/SOUTHERN OSCILLATION CONNECTION AND DROUGHT/FLOOD CYCLES IN THE CHANGJIANG RIVER

In response to a suggestion that the large meander of the Kuroshio is a good predictor of droughtsin the Changjiang River Valley, it is argued that more recent inceptions of the meander lend statisticalweigh to the belief that the large meander is itself a consequence of E1 Nino, and hence of the SouthernOscillation. The meander usually lags. Thus, if the meander reliably predicts droughts, the Tahiti componentof the Southern Oscillation will usually give six months' extra warning.     

Atlantic ocean heat piracy and the bipolar climate see‐saw during Heinrich and Dansgaard–Oeschger events

The millennial‐scale asynchrony of Antarctic and Greenland climate records during the last glacial period implies that the global climate system acts as a bipolar see‐saw driven by either high‐latitudinal and/or near‐equatorial sea‐surface perturbations. Based on the results of recent modelling of generic Heinrich and Dansgaard–Oeschger scenarios, we discuss the possibility that oscillations of the deep‐ocean conveyor may have been sufficient to cause this bipolar see‐saw. The bipolar climate asynchrony in our scenarios is caused by the toggle between North Atlantic heat piracy and South Atlantic counter heat piracy. Ocean circulation has an enhanced sensitivity to the northern deep‐water source as the North Atlantic Deep Water (NADW) cannot enter the Southern Ocean at depths shallower than the bottom of the Drake Passage. Any shoaling of the NADW can, therefore, increase the northward incursion of Antarctic Bottom Water (AABW), and trigger an interhemispheric climate oscillation. As hundreds of years are required to warm the respective high latitudes, the observed climate lead and lags between the two hemispheres can be explained entirely by the variability of the meridional overturning and by the corresponding change in the oceanic heat transport. Accordingly, it is entirely feasible for the global climate to work like a pendulum, which theoretically could be controlled by pushing at either of the deep‐water sources. Our model scenarios suggest that it is entirely feasible for the bipolar climate see‐saw to be controlled solely by variations in NADW formation. Copyright © 2001 John Wiley & Sons, Ltd.     

中等质量星演化中的蓝拐和CNO双循环

天体物理学家第一次成功地计算中等质量恒星演化到中心氦燃烧阶段 ,就发现蓝拐现象 ,它是赫罗图上形成黄巨星分支的重要理论条件。但由于蓝拐对很多输入物理 ,如对流的混合长理论 ,对流超射 ,初始元素丰度等都十分敏感稍稍不同就会抑制或触发蓝拐 ,因此蓝拐的激发机制一直没有满意的理论。本文回顾了蓝拐的研究历史 ,并对中等质量恒星在演化过程中的蓝拐的激发机制问题进行理论分析 ,给出一个蓝拐整个过程的物理图象。本文探寻了氢燃烧核反应的CNO循环过程对蓝拐的影响 ,用两种不同的方法处理CNO循环 ,在第一种模型中保持14N丰度不变 ;而在第二种模型中计算了16 O向14N的转化过程。结果模型一中出现了蓝拐而模型二中没有蓝拐。在对两种模型的比较中 ,我们进一步研究蓝拐的触发机制。我们注意到蓝拐的一个重要特征 ,恒星内部的核反应产能增加决定了蓝拐光度的上升 ;同时对于一个内部产能恒定的恒星 ,恒星外壳的膨胀和收缩将决定恒星表面的有效温度。根据这点 ,对恒星内部和外壳的各种物理量进行了研究 ,并着重注意了恒星外壳对内部产能变化的反应。我们发现RGB阶段产生的氢丰度不连续区的跳变是恒星光度上升的一个关键因素 ,当氢壳层的外边缘接触到氢跳变的时候 ,突然增加的氢丰度使氢燃烧壳层变宽 ,产能     

Carbon dioxide emission and carbon accumulation in coastal wetlands

Direct measurements of CO₂ fluxes were made in salt, brackish and freshwater marshes and parallel adjacent open water areas in Barataria Basin, Louisiana. Vertical flux density was determined by monitoring the accumulation of CO₂ in aluminum chambers placed over the water or sediment surfaces. Annual CO₂ fluxes were 418, 180 and 618 g Cm^?2 from the salt, brackish and freshwater marsh, respectively. Water bodies adjacent to the marsh evolved 103, 54 and 242 g CO₂-Cm^?2yr^?1 to the atmosphere from saline, brackish and freshwater lakes, respectively. The role these marshes play in serving as a major carbon sink was determined from the carbon content of the sediment, vertical accretion rates and the bulk density of the sediment. Accretion rates were calculated from the depth in the sediment of the 1963 horizon, the year of peak ¹³⁷Cs fallout. Net carbon accumulation was essentially the same in all three marshes; 183, 296 and 224 g Cm^?2yr^?1 from the salt, brackish and fresh marsh, respectively. Data presented suggest a limited net export of carbon from these coastal marshes. A large percentage of fixed carbon remained on the marsh, being immobilized in accretionary processes or lost to the atmosphere as CO₂.     

Sequence in Australian coal seams

An embedded Markov model is used to test microlithotype analyses of subsections of a wide range of Australian coal seams for the presence of nonrandom sequences of lithologies. The data for individual seams, transformed to give five states (four states if dirt bands are excluded),were summed into geologically and geographically distinct groupings. The results suggest that dirt bands form an essential part of the sequences and that partial or complete cyclicity is present in many seam groupings. The cyclicity is either asymmetric or partially symmetric with the vitrite +clarite content of the coal decreasing upwards within each cycle. A new cycle is marked either by a sharp reversion, or by a slightly gradational reversion, to a vitrite +clariterich lithology. This reversion may or may not be preceded by a dirt band. In virtually all groupings, a vitrite +clarite-rich lithology is the most likely type after a dirt band. The sequences are similar to those that have been described in European coals and it seems probable that the presence of intraseam, cyclic sequences is a normal, rather than an unusual condition, within coal seams. This cyclicity is a response to changes in the sedimentation balance. These changes are probably due in large part to processes originating within the peat-forming environment but processes external to this environment are also likely to produce cyclic sequences of coal lithologies.     

Influence of wetting–drying cycles on swell–shrink behaviour of GPA-reinforced expansive clay beds

ABSTRACT

Granular pile-anchor (GPA) technique is an innovative tension-resistant foundation technique which can effectively ward off the dual swell–shrink problem posed by expansive clays. The other tension-resistant foundation techniques are drilled piers, belled piers and under-reamed piles. Laboratory scale model studies and field scale experiments on GPAs revealed that swelling of expansive clay beds could be effectively controlled by GPA technique. This paper presents results obtained from laboratory scale model studies on GPA-reinforced expansive clay beds subjected to alternate cycles of wetting and drying. Swelling and shrinkage of the clay beds were monitored for three wetting–drying cycles (N) spanning a time period of 300 days. The clay beds were reinforced with varying number of GPAs (n = 0, 1, 2 and 3). Swelling (mm) and shrinkage (mm) of the clay beds in a given wetting–drying cycle decreased with increasing number of GPAs. Further, swelling (mm) and shrinkage (mm) significantly decreased with increasing number of wetting–drying cycles (N) also. For a given number of GPAs (n), swelling and shrinkage decreased with increase in depth from the top of the clay bed too.