Transformation of phosphorus in the wadden sea: Apatite formation     

J. E. E. van Beusekom  V. N. de Jonge 《Ocean Dynamics》1997,49(2-3):297-305

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The relationship between glacial activity and sediment production: evidence from a 4450-year varve record of neoglacial sedimentation in Hector Lake, Alberta, Canada   总被引：3，自引：0，他引：3  

Eric M. Leonard 《Journal of Paleolimnology》1997,17(3):319-330

A 4450-year sequence of varves, spanning the entire Neoglacialinterval, has been recovered from Hector Lake, Alberta. The varve record is compared to records of regional glacial history toevaluate therelationship between alpine glacial activity and sediment production. Glacial controls on sediment production vary with the timescale considered. Long-term variations in sedimentation rate, of centuries to millennial duration, reflect changes in ice extent of the same timescale. Superimposed on these long-term changes is decadal-scale variability that is complexly related to upvalley ice extent. Over the short term, high sedimentation rates may be associated with glacier maximum stands, or with periods of glacier advance or recession. Overthe last millennium at least, highest sedimentation rates appear to have been associated with transitional periods, preceding or post-dating maximum ice stands, rather than with times of maximum ice extent.  相似文献   

Tectonic evolution of the Eastern Pilbara,Australia (extended abstract)     

White  S.H.  Zegers  T.E.  van Haaften  W.M.  Kloppenburg  A.  Wijbrans  J. 《Geologie en Mijnbouw》1997,76(4):343-347

Geologie en Mijnbouw -  相似文献   

Water-level changes in the Hammock River marsh palaeovalley, Connecticut between 13,000 and 6000 (C) yrs B.P.     

Orson van de Plassche  Sytze van Heteren  W. Roland Gehrels  Willem G. Mook 《Sedimentary Geology》1992,80(3-4):247-260

Detailed analysis of basal organic deposits underlying Hammock River marsh, Connecticut allowed documentation of water-level changes that occurred between 13,000 and 6000 yrs B.P. Four main periods of groundwater- and lake-level movements and related environmental changes can be identified.

1. (1) 12,500-10,200 yrs B.P. (lake stage): very rapid rise of the groundwater table of about 2 to 3 m, resulting in a shallow lake, followed by a more gradual rise of about 2.5 to 1.5 m.

2. (2) 10,200-7000 yrs B.P. (freshwater marsh, stage 1): slow overall rise of the water table interrupted by a drop of at least 1 m between about 9500 and 9000 yrs B.P. and of at least 0.8 m between about 8000 and 7500 yrs B.P., each event leading to oxidation and maceration of organic material.

3. (3) 7000-6400 yrs B.P. (complete desiccation of the swamp): rapid fall of the water table of at least 3.9 m. causing large-scale down-wasting of the accumulated peat.

4. (4) After 6400 yrs B.P. (freshwater marsh, stage 2): rapid rise of the water table.

The water-table rise of period 1 and the lowering of period 3 are attributed to predominantly local causes, while the groundwater fluctuations during period 2 are probably climate-related. The final water-level increase reflects the influence of Holocene relative sea-level rise.  相似文献   

Late glacial and Holocene vegetation history at Poets hill lake,western Tasmania     

Eric A. Colhoun 《The Australian geographer》1992,23(1):11-23

Pollen analysis of 3.25 m of late glacial and Holocene sediments gives a mid‐altitude (600 m) record of vegetation development after the last or Margaret Glaciation. Alpine herbfield, coniferous heath and Nothofagus gunnli scrub developed on the moraines until 11,400 BP. Wet montane forest and heath then developed with Phyllocladus aspleniifolius, Nothofagus cunninghamii and Eucalyptus until c. 10,000 BP. After 10,000 BP a mosaic of N. cunninghamii rainforest, Myrtaceae and Proteaceae scrub and Sprengelia incarnata heath occurred. The development of the vegetation from alpine communities to temperate rainforest, which is near its limit at 600 m, occurred under the influence of improving climatic conditions with rapid upslope migration or local expansion of taxa during the late glacial. Temperatures were warm enough for the development of rainforest at 600 m by 10,000 BP, if not earlier. The development of a mosaic of rainforest, scrub and heath vegetation rather than extensive rainforest after 10,000 BP reflects the influence of poor soils, bad drainage and fires. Comparison with similar pollen diagrams from western Tasmania suggests that the development of pollen/vegetation associations was time transgressive with altitude during the late glacial when climatic influences and migration rates were important, and that the mosaic of vegetation communities became more complex during the Holocene because of adjustment to or control by local ecological factors.  相似文献   

A New World Order (No Less)     

Herman van der Wusten 《The Professional geographer》1992,44(1):19-22

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Preface     

Eric F. Wood 《Surveys in Geophysics》1991,12(1-3):vii-viii

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Paleomagnetic evidence for a diachronic clockwise rotation of the Coastal Range, eastern Taiwan     

Teh-Quei Lee  Catherine Kissel  Eric Barrier  Carlo Laj  Wen-Rong Chi 《Earth and Planetary Science Letters》1991,104(2-4)

Paleomagnetic results obtained from over 2100 cores sampled at 132 early Pliocene to late Pleistocene sites in the Coastal Range of eastern Taiwan indicate that, since the late Pliocene, the margin of the Philippine Sea plate has undergone a clockwise rotation of about 30° as a direct consequence of the Plio-Pleistocene collision of this plate with the Chinese Continental plate. The rotation is diachronic and started between 3 and 4 Ma ago in the northern Coastal Range then propagated southward at an average speed of the order of 70 ± 10 km/Ma. This value is in very good agreement with estimates of the southward propagation of the collision between the Philippine Sea plate and the Eurasian margin in Taiwan. It is suggested that the rotation reflects the deformation of the Philippine Sea plate at depth and does not results from the shallow deformations involved in the building of the Coastal Range orogen.  相似文献   

Thematische Kartierung und Sensitivitätsraster im Deutschen Wattenmeer     

Karl-Heinz van Bernem 《Ocean Dynamics》1991,44(5-6):293-309

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The surface free energies of talc and pyrophyllite     

R. F. Giese  P. M. Costanzo  C. J. van Oss 《Physics and Chemistry of Minerals》1991,17(7):611-616

The components of the interfacial surface tension of talc and pyrophyllite were determined by measuring the rate of the capillary rise of a number of liquids through thin, sedimented deposits of the powdered minerals. The rate of capillary rise of a liquid in a powder is related to the contact angle between the liquid and the solid by the Washburn equation. The contact angles thus derived were used to determine the apolar (Lifshitzvan der Waals) component, γ ^LW , and the polar, electronacceptor and electron-donor parameters, γ ^⊕ and γ ^? respectively, of the Lewis acid/base component of the total interfacial surface energy using the Young equation. The values of γ ^LW for talc and pyrophyllite (31.5 and 34.4 mJ/m²) are slightly smaller than for smectite clay minerals (e.g., the value for hectorite is 39.9 mJ/m²), the electron donor parameter values are roughly comparable for talc and pyrophyllite (γ ^⊕ = 2.4 and 1.7 mJ/m²) as are the values of the electron acceptor parameter (γ ^? = 2.7 and 3.2 mJ/m²). The well-known hydrophobicity of these two minerals is due to the remarkably small value (for silicate minerals) of γ ^?(γ^⊕ is normally small or zero for silicates and many other oxides). The small values of both γ ^⊕ and γ ^? mean that the Lewis acid/base interactions between talc or pyrophyllite and highly polar water molecules are very weak. In contrast, low-charge smectites, the minerals most similar chemically and structurally to talc and pyrophyllite, have much greater values of γ ^? (≥ 30 mJ/m²) and are hydrophyllic.  相似文献