关于奥陶系最上部赫南特(Hirnantian)亚阶全球层型的建议   总被引：10，自引：4，他引：6  

戎嘉余  陈旭  哈帕尔 《地层学杂志》2000,24(3):176-181

在对鄂西宜昌王家湾和分乡、黔北桐梓红花园、黔东北松桃陆地坪 4条剖面的相关地层和主要门类化石做了新的无间断采集和重新鉴定笔石和腕足动物这两个重要化石门类的基础上 ,发现奥陶纪最末期—志留纪最早期的完整笔石序列与腕足动物等新的化石材料 ,初步了解奥陶纪末集群灭绝后生物幸存的基本特征。经过选择 ,特推荐宜昌王家湾公路旁穿越奥陶 -志留纪界线地层剖面作为建立国际赫南特亚阶的首位候选 (leading candidate)层型 ,并推荐桐梓红花园相关剖面作为辅助候选 (auxiliary candidate)层型。对建立全球赫南特亚阶界线层型的基本条件和国外相关剖面的优缺点作了分析。本文所识别的赫南特亚阶相当于两个笔石带 :下部 N ormalograptus ex-traordinarius- N.ojsuensis带和上部 N.persculptus带。典型的 H irnantia动物群的整体地质历程为奥陶纪最末期 ,相当于 N ormalograptus extraordinarius- N.ojsuensis带和 N.persculptus带的一部分。  相似文献   

Mass extinctions: Processes and evidence edited by S. K. Donovan,Belhaven Press 1989. No. of pages: 266. Price: £32.00 (hardback). ISBN 1–85293–059–4     

D. A. T. Harper 《Geological Journal》1991,26(2):185-186

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Chemical depletion of sediment under the Greenland Ice Sheet          下载免费PDF全文

Joseph A. Graly  Neil F. Humphrey  Joel T. Harper 《地球表面变化过程与地形》2016,41(13):1922-1936

The chemical composition of sediment sampled from a network of ice boreholes contacting the bed of the ablation zone of the Greenland Ice Sheet is compared to the composition of intact bedrock clasts. This sediment is enriched in silica and depleted in reactive cations compared to the underlying bedrock. In order to test whether these differences result from grain size biases either in sample collection or due to natural sorting, sediment samples were analyzed by grain size aliquots. Enrichment of silicon and depletion of cations is consistent across grain size classes and the compositions of bedrock and subglacial sediment are statistically separate. The difference in composition between subglacial sediment and rock aligns closely with the composition of dissolved solutes in waters sampled from the same field sites and is dissimilar to the composition of the sites' suspended sediment. This implies that chemical weathering rather than disproportionate physical removal of friable minerals is responsible for the compositional differences between rock and sediment. Mass balance analysis implies 3–10% of the sediment's mass is lost to solute dissolution, with approximately double that amount precipitated as clay minerals (a large portion of which may have been physically expelled). This result implies that temperate ice sheet subglacial environments may be more chemically active than previously realized. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Coordinated Ocean-ice Reference Experiments (COREs)     

Stephen M. Griffies  Arne Biastoch  Claus Böning  Frank Bryan  Gokhan Danabasoglu  Eric P. Chassignet  Matthew H. England  Rüdiger Gerdes  Helmuth Haak  Robert W. Hallberg  Wilco Hazeleger  Johann Jungclaus  William G. Large  Gurvan Madec  Anna Pirani  Bonita L. Samuels  Markus Scheinert  Alex Sen Gupta  Camiel A. Severijns  Harper L. Simmons  Jianjun Yin 《Ocean Modelling》2009,26(1-2):1-46

Coordinated Ocean-ice Reference Experiments (COREs) are presented as a tool to explore the behaviour of global ocean-ice models under forcing from a common atmospheric dataset. We highlight issues arising when designing coupled global ocean and sea ice experiments, such as difficulties formulating a consistent forcing methodology and experimental protocol. Particular focus is given to the hydrological forcing, the details of which are key to realizing simulations with stable meridional overturning circulations.The atmospheric forcing from [Large, W., Yeager, S., 2004. Diurnal to decadal global forcing for ocean and sea-ice models: the data sets and flux climatologies. NCAR Technical Note: NCAR/TN-460+STR. CGD Division of the National Center for Atmospheric Research] was developed for coupled-ocean and sea ice models. We found it to be suitable for our purposes, even though its evaluation originally focussed more on the ocean than on the sea-ice. Simulations with this atmospheric forcing are presented from seven global ocean-ice models using the CORE-I design (repeating annual cycle of atmospheric forcing for 500 years). These simulations test the hypothesis that global ocean-ice models run under the same atmospheric state produce qualitatively similar simulations. The validity of this hypothesis is shown to depend on the chosen diagnostic. The CORE simulations provide feedback to the fidelity of the atmospheric forcing and model configuration, with identification of biases promoting avenues for forcing dataset and/or model development.  相似文献   

Silurian of the Midland Valley of Scotland and Ireland          下载免费PDF全文

Euan N.K. Clarkson  David A.T. Harper 《Geology Today》2016,32(5):195-200

The Silurian rocks and fossils of the Midland Valley of Scotland, and its extension across the northern parts of Ireland, have fascinated and challenged geologists for over 150 years. The spectacular diversity of facies and faunas, displayed in a series of inliers, is matched by contrasts in scenery from the rugged Atlantic coast of western Ireland to the undulating hills and heather moors on the northern margin of the Southern Uplands. Here, tectonic events near the climax of the Caledonian orogenic cycle served to fashion a mosaic of dynamic sedimentary environments on the Laurentian margin, at an exciting time in Earth history, as life established its foothold on the land.  相似文献   

Eye in the Sky     

Dorothy Harper 《国际地球制图》2013,28(2)

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Heliospheric coordinate systems     

M. Fränz  D. Harper 《Planetary and Space Science》2002,50(2):217-233

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Late Glacial beech forest: an 18,000–5000-BP pollen record from Auckland, New Zealand     

A. K. Lancashire  J. R. Flenley  M. Harper 《Global and Planetary Change》2002,33(3-4)

Australia, New Zealand and South America are the main sources of terrestrial climate change records for midlatitudes in the Southern Hemisphere. The advantage of studying the New Zealand record is that its vegetation has been subject to human influence for only the last thousand years. Vegetation records for Auckland are important because earlier work indicates that during the Last Glacial Maximum, the boundary between scrubland and forest lay in the Auckland region. Auckland is situated in a volcanic field and the coring site was in the crater of a small extinct volcano (Crater Hill, formed about 29 ka BP). The 4-m long core contained sediment dating from c. 5 to c. 18 ka BP. We present pollen and diatom records from this core.The pollen records from basal clays indicate southern beech forest (mainly Nothofagus menziesii) was present in the region around Crater Hill from 18 to 14.5 ka BP. At this time, there were areas of scrub in the crater surrounding a hardwater lake. The southern forest limit could well have been close to the site. Records from overlying peat indicate beech forest was replaced by Podocarp broadleaf forest as the Last Glacial ended. Metrosideros spp. (coastal forest trees) peak in the early Holocene. This coincides with an impoverished diatom flora which indicates drier conditions in the basin. When the lake reformed in the Holocene on peat its water was more acidic.  相似文献   

Oxygen isotope geochemistry of the Omeo Metamorphic Complex,Victoria: Implications for metamorphic fluid flow,mineralisation and anatexis     

I. Cartwright  S. Harper 《Australian Journal of Earth Sciences》2013,60(6):963-969

Metamorphosed turbidites from the Omeo Metamorphic Complex show only minor changes in δ¹⁸O values with increasing metamorphic grade from 13.4 ± 1.7% in the chlorite and biotite zones to 12.3 ± 1.0% in the sillimanite + K‐feldspar zone. Rocks within 5 km of the S‐type granite at Hume Dam have δ¹⁸O values of 6.8–8.1% that probably reflect interaction with heated meteoric‐igneous fluids. Interaction with igneous fluids has also occurred close to other I‐ and S‐type granites in this region. However, pervasive metamorphic fluid‐rock interaction in this terrain did not occur, which limits the region's potential for hydrothermal mineralisation. Anatexis at high grades was probably via dehydration‐melting reactions that consumed muscovite and biotite, which is consistent with there being little fluid present during metamorphism. Small (kilometre scale or less) S‐type granites in the sillimanite + K‐feldspar zone have δ¹⁸O values similar to those of the surrounding metasediments and probably formed by melting of those rocks. By contrast, larger (tens of kilometres scale) Ca‐rich, peraluminous, S‐type granites have lower δ¹⁸O values than the surrounding metasediments, and may represent melts of underlying middle to lower crust.  相似文献   

Plate dynamics: Caribbean map corrections and hotspot push     

J. F. Harper 《Geophysical Journal International》1990,100(3):423-431

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