Authigenic weddellite in sediments from the Coral Sea Basin     

GERRIT J. VAN DER LINGEN 《Sedimentology》1979,26(5):731-735

Euhedral, tetragonal, dipyramidal crystals of weddellite, an authigenic calcium oxalate, occur in samples from the topmost core of Deep Sea Drilling Project Site 210 in the Coral Sea Basin. Opinions in the literature differ as to whether weddellite is formed in situ or during sample storage. Comparison of smear-slides made of samples after a 4 year storage period with shipboard smear-slides made immediately after core retrieval, indicates that weddellite was formed in situ. Possible further growth during storage is not obvious. The presence of many corroded crystals, and the absence of weddellite in deeper cores, suggest that weddellite is formed soon after deposition, but dissolves again in time and with increased burial, due to changing geochemical parameters.  相似文献   

Need for an Iron-Formation Reference Sample*     

PETER W. UITTERDIJK APPEL 《Geostandards and Geoanalytical Research》1980,4(1):19-19

An international iron-formation reference sample is warranted as a basis for geochemical investigations of Precambrian iron-formations. A better knowledge of the geochemistry of iron formations will hopefully elucidate the long standing discussion on the genesis of iron-formations. The reference sample can furthermore be used in studies of deep-sea metalliferous deposits.  相似文献   

TRACING BY GRAVITY OF A NARROW BURIED GRABEN STRUCTURE,DETECTED BY SEISMIC REFRACTION,FOR GROUND-WATER INVESTIGATIONS IN NORTH CHILE*     

R.A. VAN OVERMEEREN 《Geophysical Prospecting》1980,28(3):392-407

In the Andes mountains of North Chile seismic refraction measurements revealed the existence of a buried graben structure. The special geological environment permitted the deduction, by detailed analyses of diffraction patterns and delayed arrival times, of a low velocity layer underneath a high velocity ignimbritic sheet. The gravity method was chosen as an economic secondary aid to trace the course of the buried structure. This unusual combination of detailed gravity measurements following a general seismic survey was not only successful in detecting and tracing a buried structure, but also provided complementary data about the deeper subsurface conditions.  相似文献   

THIN-SECTION SIZE ANALYSIS: A FURTHER NOTE     

PETER H. STAUFFER 《Sedimentology》1966,7(3):261-263

Criticisms by VAN DER PLAS (1962) of thin-section point counting as a method of size analysis appear to be based on confusion between number percent and volume percent. Points are samples of volume, and point counts yield volume percents. This is as much true of size classes as of other types of constituents, though distortions are caused in the distribution by the sectioning effect. The “ribbon” method advocated by Van der Plas counts individuals rather than points and hence yields number percents. The two types of statistic are fundamentally different.  相似文献   

Review     

PETER H. THOMPSON 《Journal of Metamorphic Geology》1986,4(2):231-233

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High-resolution stratigraphy of the northernmost concentric raised bog in Europe: Sellevollmyra, Andøya, northern Norway     

KARL-DAG VORREN  MAARTEN BLAAUW  STEFAN WASTEGÅRD  JOHANNES VAN DER PLICHT  CHRISTIN JENSEN 《Boreas: An International Journal of Quaternary Research》2007,36(3):253-277

From the Sellevollmyra bog at Andøya, northern Norway, a 440‐cm long peat core covering the last c. 7000 calendar years was examined for humification, loss‐on‐ignition, microfossils, macrofossils and tephra. The age model was based on a Bayesian wiggle‐match of 35 ¹⁴C dates and two historically anchored tephra layers. Based on changes in lithology and biostratigraphical climate proxies, several climatic changes were identified (periods of the most fundamental changes in italics): 6410–6380, 6230–6050, 5730–5640, 5470–5430, 5340–5310, 5270–5100, 4790–4710, 4890–4820, 4380–4320, 4220–4120, 4000–3810, 3610–3580, 3370–3340 (regionally 2850–2750; in Sellevollmyra a hiatus between 2960–2520), 2330–2220, 1950, 1530–1450, 1150–840, 730? and c. 600? cal. yr BP. Most of these climate changes are known from other investigations of different palaeoclimate proxies in northern and middle Europe. Some volcanic eruptions seemingly coincide with vegetation changes recorded in the peat, e.g. about 5760 cal. yr BP; however, the known climatic deterioration at the time of the Hekla‐4 tephra layer started some decades before the eruption event.  相似文献   

Anomalous luminescence of subglacial sediment at Haut Glacier d'Arolla,Switzerland – a consequence of resetting at the glacier bed?     

DARREL A. SWIFT  DAVID C. W. SANDERSON  PETER W. NIENOW  ROBERT G. BINGHAM  IAN C. COCHRANE 《Boreas: An International Journal of Quaternary Research》2011,40(3):446-458

Swift, D. A., Sanderson, D. C. W., Nienow, P. W., Bingham, R. G. & Cochrane, I. C. 2010: Anomalous luminescence of subglacial sediment at Haut Glacier d'Arolla, Switzerland – a consequence of resetting at the glacier bed? Boreas, Vol. 40, pp. 446–458. 10.1111/j.1502‐3885.2010.00196.x. ISSN 0300‐9483. Luminescence has the potential to elucidate glacial geomorphic processes because primary glacial sediment sources and transport pathways are associated with contrasting degrees of exposure to light. Most notably, sediment entrained from extraglacial sources should be at least partially reset, whereas sediment produced by glacial erosion of subglacial bedrock should retain substantial luminescence commensurate with a geological irradiation history. We set out to test the validity of this assumption at Haut Glacier d'Arolla, Switzerland using sediment sampled extraglacially and from the glacier bed. Contrary to our expectations, the subglacial samples exhibited natural signals that were substantially lower than those of other sample groups, and further (albeit limited) analyses have indicated no obvious differences in sample‐group luminescence characteristics or behaviour that could account for this observation. For glaciological reasons, we can eliminate the possibilities that the subglacial sediment has been extraglacially reset or exposed in situ to heat or light. We therefore advocate investigation of possible resetting processes related to subglacial crushing and grinding, and speculate that such processes, if more generally present, may enable the dating of subglacially deposited tills using luminescence‐based techniques.  相似文献   

The slope of isentropes constituting a frontal zone     

AARNOUT VAN DELDEN 《地球，A辑:动力气象学与海洋学》1999,51(5):603-611

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Real world and real time political geography     

PETER PERRY 《New Zealand geographer》1987,43(1):33-34

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Reefs ancient and modern     

PETER ELLIS 《Geology Today》1986,2(2):41-42

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