福建顺昌地区晋宁期溪东片麻岩的地质特征     

张开毕  黄宗林 《福建地质》2000,19(2):72-77

野外填图和室分析表明,福建顺昌北部溪东一带存在１种英云闪长质片麻岩体,并获得颗粒锆石Ｕ－Ｐｂ年龄７０５．９Ｍａ。它是中（酸）性深成岩体经受强烈变形变质作用改造的产物,属晋宁期侵入岩。它为研究福建省晋宁运动提供了重要资料。  相似文献   

Multi‐scale relief model (MSRM): a new algorithm for the visualization of subtle topographic change of variable size in digital elevation models          下载免费PDF全文

Hector A. Orengo  Cameron A. Petrie 《地球表面变化过程与地形》2018,43(6):1361-1369

Morphological analysis of landforms has traditionally relied on the interpretation of imagery. Although imagery provides a natural view of an area of interest (AOI) images are largely hindered by the environmental conditions at the time of image acquisition, the quality of the image and, mainly, the lack of topographical information, which is an essential factor for a correct understanding of the AOI's geomorphology. More recently digital surface models (DSMs) have been incorporated into the analytical toolbox of geomorphologists. These are usually high‐resolution models derived from digital photogrammetric processes or LiDAR data. However, these are restricted to relatively small areas and are expensive or complex to acquire, which limits widespread implementation. In this paper, we present the multi‐scale relief model (MSRM), which is a new algorithm for the visual interpretation of landforms using DSMs. The significance of this new method lies in its capacity to extract landform morphology from both high‐ and low‐resolution DSMs independently of the shape or scale of the landform under study. This method thus provides important advantages compared to previous approaches as it: (1) allows the use of worldwide medium resolution models, such as SRTM, ASTER GDEM, ALOS, and TanDEM‐X; (2) offers an alternative to traditional photograph interpretation that does not rely on the quality of the imagery employed nor on the environmental conditions and time of its acquisition; and (3) can be easily implemented for large areas using traditional GIS/RS software. The algorithm is tested in the Sutlej‐Yamuna interfluve, which is a very large low‐relief alluvial plain in northwest India where 10 000 km of palaeoriver channels have been mapped using MSRM. The code, written in Google Earth Engine's implementation of JavaScript, is provided as Supporting Information for its use in any other AOI without particular technical knowledge or access to topographical data. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

A diatom record of mid‐ to late Holocene palaeoenvironmental changes in the southern Okinawa Trough          下载免费PDF全文

DONGLING LI  HUI JIANG  KAREN LUISE KNUDSEN  SVANTE BJÖRCK  JESPER OLSEN  MEIXUN ZHAO  TIEGANG LI  JIALIN LI 《第四纪科学杂志》2015,30(1):32-43

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Storm‐dominated shelf‐edge delta successions in a high accommodation setting: The palaeo‐Orinoco Delta (Mayaro Formation), Columbus Basin,South‐East Trinidad     

Andrew P. Bowman  Howard D. Johnson 《Sedimentology》2014,61(3):792-835

Pliocene age deposits of the palaeo‐Orinoco Delta are evaluated in the Mayaro Formation, which crops out along the western margin of the Columbus Basin in south‐east Trinidad. This sandstone‐dominated interval records the diachronous, basinwards migration of the shelf edge of the palaeo‐Orinoco Delta, as it prograded eastwards during the Pliocene–Pleistocene (ca 3·5 Ma). The basin setting was characterized by exceptionally high rates of growth‐fault controlled sediment supply and accommodation space creation resulting in a gross basin‐fill of around 12 km, with some of the highest subsidence rates in the world (ca 5 to 10 m ka^?1). This analysis demonstrates that the Mayaro Formation was deposited within large and mainly wave‐influenced shelf‐edge deltas. These are manifested as multiple stacks of coarsening upward parasequences at scales ranging from tens to hundreds of metres in thickness, which are dominated by storm‐influenced and wave‐influenced proximal delta‐front sandstones with extensive, amalgamated swaley and hummocky cross‐stratification. These proximal delta‐front successions pass gradationally downwards into 10s to 100 m thick distal delta front to mud‐dominated upper slope deposits characterized by a wide variety of sedimentary processes, including distal river flood and storm‐related currents, slumps and other gravity flows. Isolated and subordinate sandstone bodies occur as gully fills, while extensive soft sediment deformation attests to the high sedimentation rates along a slope within a tectonically active basin. The vertical stratigraphic organization of the facies associations, together with the often cryptic nature of parasequence stacking patterns and sequence stratigraphic surfaces, are the combined product of the rapid rates of accommodation space creation, high rates of sediment supply and glacio‐eustasy in the 40 to 100 Ka Milankovitch frequency range. The stratigraphic framework described herein contrasts strikingly with that described from passive continental margins, but compares favourably to other tectonically active, deltaic settings (for example, the Baram Delta Province of north‐west Borneo).  相似文献   

The palaeo‐valley infilling glaciogenic Sarah Formation,an example from Rahal Dhab palaeo‐valley,Saudi Arabia     

《Sedimentology》2018,65(3):851-876

The Sarah Formation is a glaciogenic sedimentary unit deposited along the Gondwana margin during the latest Ordovician ice age and represents a major hydrocarbon reservoir in northern Saudi Arabia. Large‐scale glacial palaeo‐valleys cut into the Qasim Formation and were infilled by the Sarah Formation. Post‐glacial transgression in the earliest Silurian resulted in the deposition of the Qusaiba Shale Member and associated organic‐rich basal source rocks, which cap the Sarah Formation infilled palaeo‐valleys. This unique setting makes the Sarah Formation an important emerging exploration target in Saudi Arabia. This study focuses on the facies and depositional architecture in seismic‐scale outcrops of the Sarah Formation in north‐western Saudi Arabia. The Rahal Dhab palaeo‐valley provides a 100 km long dip‐oriented cross‐section which has been covered by 24 vertical sections, sedimentary architectural analyses at metre to kilometre scale and by three cored shallow boreholes. In the Rahal Dhab palaeo‐valley, the Sarah Formation was deposited in a proglacial setting that ranged from marginal marine to offshore prodelta and is made up of three units: (i) the Sarah Sandstone; (ii) the Sarah Shale; and (iii) the Uqlah Member. This study shows the relationships between these three units and architectural controls on reservoir quality in this system. This paper contributes to the regional understanding of the Sarah Formation, and the new depositional model of the Rahal Dhab palaeo‐valley provides an outcrop‐reservoir analogue for hydrocarbon exploration in adjacent areas.  相似文献   

Marine geophysical evidence for former expansion and flow of the Greenland Ice Sheet across the north‐east Greenland continental shelf     

Jeffrey Evans  Colm Ó Cofaigh  Julian A. Dowdeswell  Peter Wadhams 《第四纪科学杂志》2009,24(3):279-293

High‐resolution swath bathymetry and TOPAS sub‐bottom profiler acoustic data from the inner and middle continental shelf of north‐east Greenland record the presence of streamlined mega‐scale glacial lineations and other subglacial landforms that are formed in the surface of a continuous soft sediment layer. The best‐developed lineations are found in Westwind Trough, a bathymetric trough connecting Nioghalvfjerdsfjorden Gletscher and Zachariae Isstrøm to the continental shelf edge. The geomorphological and stratigraphical data indicate that the Greenland Ice Sheet covered the inner‐middle shelf in north‐east Greenland during the most recent ice advance of the Late Weichselian glaciation. Earlier sedimentological and chronological studies indicated that the last major delivery of glacigenic sediment to the shelf and Fram Strait was prior to the Holocene during Marine Isotope Stage 2, supporting our assertion that the subglacial landforms and ice sheet expansion in north‐east Greenland occurred during the Late Weichselian. Glacimarine sediment gravity flow deposits found on the north‐east Greenland continental slope imply that the ice sheet extended beyond the middle continental shelf, and supplied subglacial sediment direct to the shelf edge with subsequent remobilisation downslope. These marine geophysical data indicate that the flow of the Late Weichselian Greenland Ice Sheet through Westwind Trough was in the form of a fast‐flowing palaeo‐ice stream, and that it provides the first direct geomorphological evidence for the former presence of ice streams on the Greenland continental shelf. The presence of streamlined subglacially derived landforms and till layers on the shallow AWI Bank and Northwind Shoal indicates that ice sheet flow was not only channelled through the cross‐shelf bathymetric troughs but also occurred across the shallow intra‐trough regions of north‐east Greenland. Collectively these data record for the first time that ice streams were an important glacio‐dynamic feature that drained interior basins of the Late Weichselian Greenland Ice Sheet across the adjacent continental margin, and that the ice sheet was far more extensive in north‐east Greenland during the Last Glacial Maximum than the previous terrestrial–glacial reconstructions showed. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Palaeo‐oceanographical significance of Miocene deep‐sea ostracoda from the Kingfish 8 well,Gippsland Basin,southeastern Australia     

M. T. Warne  R. C. Whatley 《Australian Journal of Earth Sciences》2013,60(6):525-531

In the latest Early to Middle Miocene section of the Kingfish 8 well, offshore Gippsland Basin, the characteristically deep‐marine ostracod genus Zabythocypris is a conspicuous component of ostracod assemblages dominated by species of the genera Argilloecia, Krithe and Parakrithe. The taphonomy and taxonomic composition of the assemblages suggests that they accumulated in an upper bathyal environment (500–1000 m water depth) occurring in a lower continental slope setting. Supporting evidence for these deep‐marine ostracod assemblages occurring near the upper limit of their palaeobathymetrical range is the broadly coincident occurrence of the deep‐marine taxa Legitimocythere sp. and Neonesidea whatleyi Warne, in what would otherwise be considered an outer‐shelf (120–160 m) ostracod fauna at Fossil Beach, Mornington. Ostracod occurrences indicative of dysaerobic sea‐floor conditions in the Kingfish 8 well and Fossil Beach sections, when considered together, appear to record a shallowing of the oceanic oxygen‐minimum zone during the latest Early Miocene to earliest Middle Miocene transgressive phase of southeast Australia.  相似文献   

小凌河下游晚全新世地层与环境     

裴艳东  王宏  李建芬  Manfred FRECHEN  张玉发  范昌福  田立柱 《华北地质》2007,30(3):192-202

作为从出山口至入海河口直线距离仅约20 km的短途河流,小凌河下游地区及相邻潮间带表层发育了砾石质冲洪积扇、曲流河道滞留相-点状砂坝-泛滥平原与洼地、贝壳砾石海滩、盐沼、开放潮坪下部与中上部等一系列沉积环境。通过沉积地层学、年代地层学及新构造等方面的综合研究,1)将中、晚全新世地层划分为7个年代地层单元,2)发现了夏-西周、元末-明初两道年龄分别约为2 050～650 BC和1 350 AD的古海岸线,3)确立了春秋、中唐-北宋初、"小冰期"结束以来3次小凌河沉积期,最有可能发育的时间进一步限定在约650～400 BC(第1期)、约700～1 000 A(D第2期)和1 850 AD以来(第3期),4)提出了NW向与NE向构造加剧小凌河下游曲流发育的假说。  相似文献   

重庆巫山张家湾遗址2000年来的环境考古   总被引：15，自引：4，他引：15  

张强  朱诚  姜逢清  刘兴林  郭立新 《地理学报》2001,56(3):353-362

通过对重庆巫山张家湾西汉遗址T911剖面进行粒度、磁化率等环境替代指标的分析研究，结果表明，汉代该区发达的农业、手工业生产使人们盲目砍伐树木，使该区植被严重退化，使生态环境恶化，降水集中、坡地表面松散沉积丰富、缺乏植被保护等使流水侵蚀、坡地径流发育，导致水土流失严重，该区的人类文明因此而衰落，同时研究发现，该区在竺可桢划分的中国4次温暖期与4次寒期扣的第2次寒冷期（公元初至公元600年）仍为温暖期，这是由于该区西北面与东南面均有高大山脉包围，一定程度上阻挡了来自北方的冷空气进入本区的缘故，该区气候演变在一定程度上可能受西南季风的影响，至少该区在汉代气候演变与西南季风的强弱有某种相关关系，作为一个相对独立的气候变化单元，研究其气候变化与人类文明发展的耦合关系具有重要的理论意义与实际意义。  相似文献   

陕南镇旬矿田铅锌矿化特征及成因   总被引：1，自引：0，他引：1       下载免费PDF全文

李英  高福模 《地质找矿论丛》1989,(2):54-66

镇旬矿田属秦岭泥盆系铅锌一菱铁矿带,矿化在空间上分布于乾佑河南北向古断陷的两侧,产生于泥盆纪.铅锌矿化特征与凤太矿田的诸矿床及西成矿田的毕家山、邓家山等矿床相似.铅同位素组成是均匀的,模式年令略老于含矿地层年令,硫化物的硫同位素组成为海水硫酸盐型.矿体有沉积似层状和交代不规则状两种形态,主要围岩蚀变为硅化和铁白云石化.矿化与生物灰岩有密切空间和成因联系.因而说镇旬矿田与矿带中其余三个矿田的铅锌矿有相同的成因,成矿模式类似于E. D. Large(1981)和M. J. Russell(1983)提出的喷流成矿模式.  相似文献