Racetrack and Bonnie Claire: southwestern US playa lakes as analogs for Ontario Lacus, Titan

We note the geomorphological and meteorological processes at Racetrack Playa, Death Valley National Park, as analogs for those at Ontario Lacus on Titan. Although Ontario is ∼50× larger, the planforms of the two features are nearly identical, both are extremely flat, and are in environments where infrequent rainfall occurs against a climate, where evaporation exceeds precipitation. While the famous moving rocks on the Racetrack Playa may be exceptional on the Earth, the lower gravity and thicker atmosphere may render wind-induced rock transport comparatively common on Titan. Nearby Bonnie Claire Playa also provides field insights into the interpretation of remote sensing data from Titan.     

Isotope geochemistry of Swan Lake Basin in the Nebraska Sandhills,USA: Large 13C enrichment in sediment-calcite records

This study presents isotope geochemical analyses conducted on water column samples and core sediments collected from the Swan Lake Basin. Water analyses include the dissolved methane (CH₄) content and the ratio of carbon-13 to carbon-12 (δ¹³C) in dissolved inorganic carbon (DIC). The core sediments – sandy muds containing inorganic calcite, organic matter, and opal phases ± ostracods – were examined by X-ray diffraction, dated by radiocarbon (¹⁴C), analyzed for wt% organic carbon, wt% organic nitrogen, wt% organic matter, wt% calcite, δ¹³C of bulk-sediment insoluble organic matter (kerogen), ¹⁸O:¹⁶O ratio (δ¹⁸O) and δ¹³C of bulk and ostracod calcite. Of particular significance is the large enrichment in carbon-13 (δ¹³C = +4.5 to +20.4‰ V-PDB) in the calcite of these sediments. The ¹³C-enriched calcite is primarily formed from DIC in the water column of the lake as a result of the following combined processes: (i) the incorporation of ¹³C enriched residual carbon dioxide (CO₂) after partial reduction to CH₄ in the sediments and its migration into the water column-DIC pool; (ii) the preferential assimilation of ¹²C by phytoplankton during photosynthesis; (iii) the removal of ¹³C-depleted CH₄ by ebullition and of organic matter by sedimentation and burial. The ¹³C enrichment was low between 3624 and 2470 yr BP; high between 2470 and 1299 yr BP; and moderate since 1299 yr BP. Low ¹³C enrichment was formed under low water-column carbon levels while higher ones were formed under elevated rates of biomass and calcite deposition. These associations seem to imply that biological productivity is the main reason for carbon-13 enrichments.     

Assessing landscape change in Waterton Lakes National Park,Canada, using multitemporal composites constructed from terrestrial repeat photographs

The objective of this paper is to investigate landscape level changes that have occurred in Waterton Lakes National Park (WLNP), Canada between the years 1914 and 2005 using digital image processing techniques usually associated with satellite image analysis. Multitemporal colour composites, image classification, and principal components analysis were used to process registered images of the montane ecotone from photographic pairs of Bellevue Hill, Horseshoe Basin and Lakeview Ridge. The resulting digital images offered insight into the spatial nature of the vegetation changes that have occurred over the last 90 years at these sites. Changes observed included increased forest cover through vertical migration and the infill of conifers and aspen both on the slopes and the valley bottoms of WLNP.     

Paleohydrology of the upper Laurentian Great Lakes from the late glacial to early Holocene

Between 10,500 and 9000 cal yr BP, δ¹⁸O values of benthic ostracodes within glaciolacustrine varves from Lake Superior range from − 18 to − 22‰ PDB. In contrast, coeval ostracode and bivalve records from the Lake Huron and Lake Michigan basins are characterized by extreme δ¹⁸O variations, ranging from values that reflect a source that is primarily glacial ( − 20‰ PDB) to much higher values characteristic of a regional meteoric source ( − 5‰ PDB). Re-evaluated age models for the Huron and Michigan records yield a more consistent δ¹⁸O stratigraphy. The striking feature of these records is a sharp drop in δ¹⁸O values between 9400 and 9000 cal yr BP. In the Huron basin, this low δ¹⁸O excursion was ascribed to the late Stanley lowstand, and in the Lake Michigan basin to Lake Agassiz flooding. Catastrophic flooding from Lake Agassiz is likely, but a second possibility is that the low δ¹⁸O excursion records the switching of overflow from the Lake Superior basin from an undocumented northern outlet back into the Great Lakes basin. Quantifying freshwater fluxes for this system remains difficult because the benthic ostracodes in the glaciolacustrine varves of Lake Superior and Lake Agassiz may not record the average δ¹⁸O value of surface water.     

高邮湖、南四湖和东平湖有色可溶性有机物来源组成特征

高邮湖、南四湖和东平湖作为南水北调东线枢纽湖泊,其水质状况对保障调水安全起到关键性作用本文运用三维荧光光谱平行因子分析法(EEMs-PARAFAC)分析了3个湖泊在不同水文情景下有色可溶性有机物(CDOM)吸收、荧光光谱特征以及荧光组分与主要水质参数的相关性,以探究3个湖泊CDOM来源组成特征结果表明,平行因子分析法解析CDOM三维荧光图谱,得到陆源类腐殖质C1、类色氨酸C2和类酪氨酸C3不同水文情景对高邮湖CDOM来源与结构组成影响较明显,丰水期其类腐殖质荧光强度显著大于枯水期(t-test,P<0.01),并且与a(254)呈正相关(R²=0.85,P<0.01),表明类腐殖质是CDOM主要部分,该荧光组分贡献率可达50%[F_maxC1/(F_maxC1+F_maxC2+F_maxC3)×100%],高邮湖受到入湖河流来水的影响较大,丰水期入湖口附近荧光强度明显高于其他水域东平湖和南四湖CDOM来源组成特征相似,丰水期东平湖和南四湖组分C2和C3显著低于枯水期(t-t...     

BOOK REVIEWS

Book Reviewed in this article: The Rice Economy of Asia . Randolph Barker and Robert W. Herdt with Beth Rose. Using Microcomputers: A Guidebook for Writers, Teachers, and Researchers in the Social Sciences . Blaine A. Erie—the Lake that Survived . Noel M. Burns. Geology and Society . Donald R. Coates. Caves and Karst of Kentucky . Percy H. Dougherty, ed. Altered Harvest: Agriculture, Genetics, and the Fate of the World's Food Supply . Jack Doyle. The Middle East and North Africa, A Political Geography . Alasdair Drysdale and Gerald H. Blake. Clamor at the Gates. The New American Immigration . Nathan Glazer, ed. Development and the Landowner: An analysis of the British experience . Robin Goodchild and Richard Munton. Discovering Landscape in England and Wales . Andrew Goudie and Rita Gardner. The Modern Plantation in the Third World . Edgar Graham and Ingrid Floering. Social Relations and Spatial Structures . Derek Gregory and John Urry, eds. The World Food Problem 1950–1980 . David Grigg. Costa Rica: A Geographical Interpretation in Historical Perspective . Carolyn Hall. The Urbanization of Capital: Studies in the History and Theory of Capitalist Urbanization . David Harvey Consciousness and the Urban Experience: Studies in the History and Theory of Capitalist Urbanization . David Harvey. Reviving Main Street . Deryck Holdsworth, ed. Rural Roads and Poverty Alleviation . John Howe and Peter Richards, eds. Uneven Development in Southern Europe: Studies of Accumulation, Class, Migration and the State . Ray Hudson and Jim Lewis, eds. Karst Geomorphology . J. N. Jennings. The Geomorphology of North-west England . R. H. Johnson, ed. Climate Impact Assessment: Studies of the Interaction of Climate and Society . Robert Kates, Jesse Ausubel, Mimi Berberian, eds. Public Service Provision and Urban Development . Andrew Kirby, Paul Knox, and Steven Pinch, ed. State and Market: The Politics of the Public and the Private . Jan-Erik Lane, ed. Living Cities . Twentieth Century Fund Task Force on Urban Preservation Policies. World Climatic Systems . John G. Lockwood. Urban Ethnicity in the United States. New Immigrants and Old Minorities . Lionel Maldonaldo and Joan Moore, eds. Culture and Conservation: The Human Dimension in Environmental Planning . Jeffrey A. McNeely and David Pitt, eds. The Andean Past. Land, Societies, and Conflicts . Magnus Mörner. Gaia: An Atlas of Planet Management . Norman Myers, ed. Progress in Industrial Geography . Michael Pacione, ed. Progress in Political Geography . Michael Pacione, ed. Rivers and Landscape . Geoff Petts and Ian Foster. Urbanization and Planning in the 3rd World: Spatial Perceptions and Public Participation . Robert B. Potter. One Island, Two Nations? A Political Geographical Analysis of the National Conflict in Ireland . D. G. Pringle. Circulation in Third World Countries . R. Mansell Prothero and Murray Chapman. The Ozarks Outdoors: A Guide for Fishermen, Hunters, and Tourists . Milton D. Rafferty. Suburban Burglary: A Time and a Place for Everything . George Rengert and John Wasilchick. Geomorphology and Soils . K.S. Richards, R.R. Arnett, and S. Ellis, eds. The Homes and Homeless of Post-War Britain . Frederick Shaw. Indochinese Refugees in America . Paul J. Strand and Woodrow Jones, Jr. Wild Horses and Sacred Cows . Richard Symanski. Forever Wild: Environmental Aesthetics and the Adirondack Forest Preserve . Philip G. Terrie. The Regional Economic Impact of Technological Change . A.T. Thwaites and R.P. Oakey, eds. The Good Life . Yi-Fu Tuan.     

烧失量分析在湖泊沉积与环境变化研究中的应用

烧失量分析是一种便捷的测定湖泊沉积物有机碳与碳酸盐含量的方法。由于沉积物烧失量主要受区域气温、有效降水等气候环境条件的控制,因此烧失量反映湖泊气候环境特征,成为指示区域气候环境变化的重要指标,该项指标在环境变化研究中具有重要作用。     

华北克拉通甘陶河群南寺组碎屑岩锆石U-Pb年龄、Hf同位素组成及构造意义

甘陶河群是华北克拉通前寒武纪典型地层之一,主要出露在河北省西北部。本文报道了甘陶河群南寺组碎屑岩地球化学、锆石U-Pb年龄和Hf同位素特征,主要认识如下:样品均属长石砂岩或石英砂屑岩,具有Nb、Ta、Zr、Hf亏损特征和负Sr异常;碎屑锆石U-Pb年龄主要分为三组:1800~2400Ma、2400~2600Ma和2600~3100Ma;甘陶河群南寺组最年轻的碎屑锆石年龄为1861 Ma,结合甘陶河群上覆地层东焦群形成于约1.83Ga之后的地质事实,制约甘陶河群南寺组沉积上限范围1861~1830Ma。所有样品均具有约2.5Ga年龄峰值,记录了华北克拉通前寒武纪基底强烈构造岩浆热事件的时代,证明了华北克拉通前寒武纪基底主要由约2.5Ga岩石组成;中部带大陆地壳增生主要发生在约2.5Ga。     

Factors affecting seasonality of lithogenic and biogenic particle flux in a large estuarine ecosystem

Seasonal patterns of vertical flux over two years (2001–2003) at two stations in the Bras d'Or Lakes, a large estuary in Cape Breton Island, Nova Scotia, were determined using aluminum and organic carbon in settled particles collected in moored traps to calculate lithogenic (terrigenous) and marine biogenic fractions. On an annual basis, lithogenic material comprised 53% and 81% of dry weight and 48% and 66% of organic carbon in settled particles at the deep- (128 m) and shallow-water (41 m) locations, respectively. Peaks in runoff, inferred from rain and snowfall precipitation, ice cover and possible horizontal transport of resuspended sediment coincided with maximum sedimentation rates of lithogenic material during unstratified periods between October and March. Biological factors correlated with phytoplankton and ice algal primary production and seasonal changes in zooplankton grazing inferred from phaeopigments controlled biogenic particle fluxes under stratified conditions between June and September and during winter. Year-to-year variations in deposition of lithogenic and marine biogenic material depended on seasonal differences in stratification, precipitation, freeze/melt conditions and the extent of ice cover.     

青藏高原微生物甘油醚类化合物古气候指标研究进展

由微生物产生的甘油醚类化合物是有机地球化学领域的研究热点之一。这些大分子化合物能够敏感的响应环境参数的变化,因而在古气候重建中具有重要意义。我国青藏高原地区甘油醚类化合物的研究起步较晚但发展很快。本文综述了该地区甘油醚类化合物气候代用指标的现代过程和古环境研究方面的一些进展,以期为青藏高原地区古环境研究工作提供一些启示。