Holocene lake-level fluctuations and beach-ridge development along the northern shore of Lake Michigan, USA

Geomorphology of a beach-ridge complex and adjacent lake basins along the northern shore of Lake Michigan records fluctuations in the level of Lake Michigan for the last 8000 to 10 000 ¹⁴C yr B.P. (radiocarbon years Before Present). A storm berm at 204.7–206 m (671.6–675.9 ft) exposed in a sandpit provides evidence of a pre-Chippewa Low lake level that is correlated with dropping water levels of Glacial Lake Algonquin (c. 10 300–10 100 ¹⁴C yr B.P.). Radiocarbon dates from organic material exposed in a river cutbank and basal sediments from Elbow Lake, Mackinac Co., Michigan, indicate a maximum age of a highstand of Lake Michigan at 6900 ¹⁴C yr B.P., which reached as high as 196.7 m (645 ft), during the early-Nipissing transgression of Lake Michigan. Basal radiocarbon dates from beach swales and a second lake site (Beaverhouse Lake, Mackinac Co.) provide geomorphic evidence for a subsequent highstand which reached 192.6 m (632 ft) at 5390±70 ¹⁴C yr B.P.Basal radiocarbon dates from a transect of sediment cores, along with tree-ring data, and General Land Office Surveyor notes of a shipwreck, c. A.D. 1846, reveal a late-Holocene rate for isostatic rebound of 22.6 cm/100 radiocarbon years (0.74 ft/100 radiocarbon years) for the northern shore of Lake Michigan, relative to the Lake Michigan-Lake Huron outlet at Port Huron, Michigan. Changes in sediment stratigraphy, inter-ridge distance, and sediment accumulation rates document a mid- to late-Holocene retreat of the shoreline due to isostatic rebound. This regression sequence was punctuated by brief, periodic highstands, resulting in progressive development over the past 5400 ¹⁴C yr of 75 pairs of dune ridges and swales each formed over an interval of approximately 72 years. Times of lake-level fluctuation were identified at 3900, 3200, and 1000 ¹⁴C yr B.P. based on changes in inter-ridge spacing, shifts in the course of Millecoquins River, and reorientation of beach-ridge lineation. Soil type, dune development, and selected pollen data provide supporting evidence for this chronology. Late-Holocene beach-ridge development and lake-level fluctuations are related to a retreat of the dominant Pacific airmass and the convergence of the Arctic and Tropical airmasses resulting in predominantly meridional rather than zonal air flow across the Great Lakes region.This is the 13th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.     

历史时期全球化作用下的城市空间转变——以1890s~1930s广州东山地区为例

世界城市历史研究作为新兴的研究领域,虽然突破了世界城市经典理论的“现代主义”视角,证明全球化对城市空间转变的作用具有长期性,但仍局限在“经济主义”的分析范畴之内,将经济因素视为决定性动力。20世纪初期,广州东山地区完成由“乡村地区”向“社会精英阶层居住地”的空间转变,促使城市空间格局由“东村西富”变为“东贵西富”。这场具有历史意义的空间转变是教会、华侨、政府、官僚4种动力相互作用、相继推动的结果。东山地区的发展历史表明,除经济联系外,城市的全球文化联系对空间转变同样具有重要推动作用。在一些特定的城市或城市中的特定地区,社会文化动力对城市空间转变具有决定性的作用。     

BOOK REVIEWS

Books reviewed in this article: Boundary Control and Legal Priniciples . Curtis M. Brown , Walter G. Robillard and Donald A. Wilson . Lost Initiatives: Canada's Forest Industries, Forest Policy, and Forest Conservation . R. Peter Gillis and Thomas R. Roach . The Navajo Atlas: Resources, People, and History of the Dine Bikeyah . James M. Goodman . The City and the Sign . M. Gottdiener AND Alexandros Ph . Lagopoulos , EDS. The Comfortable House: North American Suburban Architecture 1890–1930 . Alan Gowans . Arabic-Islamic Cities. Building and Planning Principles . Besim Salim Hakim . Contemporary Climatology . Ann Henderson -Sellers and Peter J. Robinson . A Trace of Desert Waters . Samuel G. Houghton . Geography, Resources and Environment. Vol. 1: Selected Writings of Gilbert F. White. Vol. 2: Themes from the Work of Gilbert F. White . Robert W. Kates AND Ian Burton , ED. Spatial Dimensions of Unemployment and Underemployment (A Case Study of Rural Punjab) . Gopal Krishan . Maps of the Holy Land: Cartobibliography of Printed Maps, 1475–1900 . Compiled by Eran Laor , assisted by Shoshana Klein . The Geography of Third World Cities . Stella Lowder . A Perspective on U.S. Farm Problems and Agricultural Policy . Lance Mc Kinzie , Timothy G. Baker AND Wallace E. Tyner . Soil Erosion and Its Control. R.P.C . Morgan , ED Geopolitics . Patrick O'Sullivan . Landscape, Meanings and Values . Edmund C. Penning -Rowsell AND David Lowenthal , EDS.     

BOOK REVIEWS

Book Reviewed in this article: Marine Resources of Kuwait: Their Role in the Development of Non-oil Resources . Fatimah H. Y. al -Abdul -Razzak Recollections of a Revolution: Geography as Spatial Science . Mark Billinge , Derek Gregory and Ron Martin Entre l'Eden et l'Utopie . Luc Bureau Developments in Political Geography . M. A. Busteed The Elements of Graphing Data . William S. Cleveland Rural Resource Management . Paul J. Cloke and Chris C. Park Third World Atlas . Ben Crow and Alan Thomas Exploitation, Conservation, Preservation: A Geographic Perspective on Natural Resource Use . Susan L. Cutter , Hilary Lambert Renwick, and William H. Renwick . Wine Regions of the Southern Hemisphere . Harm Jan de Blij Regional Development: Problems and Policies in Eastern and Western Europe . George Demko The Geographer at Work . Peter R. Gould Change in the Amazon Basin . John Hemming Geography Since the Second World War . R. J. Johnston and P. Claval Urbanization in China: Town and Countryside in a Developing Economy 1949–2000 A.D. , R. J. R. Kirkby Transport and Communications for Pacific Microstates: Issues in Organisation and Management . Christopher C. Kissling Fluvial Forms and Processes . David Knighton The Urban Millennium . Josef W. Konvitz Technological Transition in Cartography . Mark Stephen Monmonier Field Guide to Soils and the Environment: Applications of Soil Surveys . Gerald W. Olson Northern Australia: The Arenas of Life and Ecosystems on Half a Continent . Don Parkes A Killing Rain: The Global Threat of Acid Rain . Thomas Pawlick From the Family Farm to Agribusiness: The Irrigation Crusade in California and the West, 1850–1931 . Donald J. Pisani Hybrid Maize Diffusion in Kenya . Franz -Michael Rundquist Warning and Response to the Mount St. Helens Eruption . Thomas F. Saarinen and James L. Sell Coastal Geomorphology in Australia . B. G. Thom Tropical Rain Forests of the Far East , 2nd ed . T. C. Whitmore The Dark Side of the Earth . Robert Muir Wood Categorical Data Analysis for Geographers and Environmental Scientists , Neil Wrigley     

GEOGRAPHY AND THE LESSONS FROM EL NIÑO*

Recognized for years as a major environmental disruption, El Niño generated intense public interest in 1982–1983. During its last occurrence, this phenomenon, which develops in the tropical Pacific and usually affects rimlands of the Pacific basin, exceeded its boundaries and its effects were transmitted to continental North America, Europe, Africa and East Asia. Notwithstanding its vast areal extent, the interest of geographers in El Niño events, past and recent, has been comparatively less than that demonstrated by natural scientists and ecologists: little has been accomplished to place these climatic-ecological crises within global perspective. Lessons from El Niño include the acknowledgement of new concepts of climatic transitivity, ocean dynamics and energy exchanges that must find a place within the conceptual wealth of geography if this science intends to keep up with the rapid progress of other geosciences.     

梅州市名城文化景观的保护与开发研究

从名城文化内涵出发，着眼于作为客家人文中心和名城文化景观的集中的梅州市区，全面分析了其中丰富多样的文化景观资源的特征及其文化内蕴。揭示了梅州名城文化景观保护与开发过程中的成绩与存在问题。并从文化地理学的视觉，结合旅游开发和城市规划，论证了科学保护与开发梅州名城文化景观的下述对策与途径的必要性与可行性：提升名城办的职能并与相关部门共营名城文化氛围；强化名城轴线与标志性文化景观；抢救与保护“老字号”等一批文化景观景区；适度利用，以积极的开发促其效的保护。     

BP模型双样本训练方法

根据气象预报应用情况，分析ＢＰ模型训练人工神经元网络中存在的问题，并提出双样本训练方案。试验表明，采用双样本训练的网络，实际预报能力较高。     

微波消解—冷原子荧光光谱法测定植物样品中的汞

为了简化测量植物中汞含量的方法,提高灵敏度及结果的可信度,实验采用微波消解植物样品的办法,使样品经氯化亚锡还原,再用冷原子荧光测定出植物样品中汞的含量。确定了消解样品的方法和微波消解样品的条件,优化了仪器的最佳工作参数。方法检出限0.30×10-9(稀释因子100倍),精密度(n=12)在2.09%~6.05%,加标回收率94.1%~105.5%,方法经生物国家一级标准物质验证方法准确可靠。     

Overpressure within upper continental slope sediments from CPTU data,Gulf of Lion,NW Mediterranean Sea

Data from in situ piezocone tests (CPTU) and laboratory analyses are utilized for the interpretation of the stress history of Quaternary sedimentary sequences in the upper continental slope of the Gulf of Lion, northwestern Mediterranean Sea. A CPTU based preconsolidation pressure profile referenced to the current effective stress indicates that the deposit is underconsolidated from 12 meters below the seafloor (mbsf) down to at least 150 mbsf. Excess pore pressure below 12 mbsf is further supported by results from oedometer and dissipation tests. Subseafloor pockmarks and indications of free gas in seismic reflection profiles reveal four main overpressure sources (SI–SIV) with overpressure ratios >0.3 at subseafloor depths coinciding with levels where the dominantly silty-clayey sediment contains increased proportions of sand. We relate the excess pore pressure related to free gas due to gas exsolution processes and sea level variations driven by Pleistocene sea level changes.