Modelling the influence of glacial isostasy on Late Weichselian ice‐sheet growth in the Barents Sea     

Daniel Howell  Martin J. Siegert  Julian A. Dowdeswell 《第四纪科学杂志》2000,15(5):475-486

A fully integrated ice‐sheet and glacio‐isostatic numerical model was run in order to investigate the crustal response to ice loading during the Late Weichselian glaciation of the Barents Sea. The model was used to examine the hypothesis that relative reductions in water depth, caused by glacio‐isostatic uplift, may have aided ice growth from Scandinavia and High Arctic island archipelagos into the Barents Sea during the last glacial. Two experiments were designed in which the bedrock response to ice loading was examined: (i) complete and rapid glaciation of the Barents Sea when iceberg calving is curtailed except at the continental margin, and (ii) staged growth of ice in which ice sheets are allowed to ground at different water depths. Model results predict that glacially generated isostatic uplift, caused by an isostatic forebulge from loads on Scandinavia, Svalbard and other island archipelagos, affected the central Barents Sea during the early phase of glaciation. Isostatic uplift, combined with global sea‐level fall, is predicted to have reduced sea level in parts of the central Barents Sea by up to 200 m. This reduction would have been sufficient to raise the sea floor of the Central Bank into a subaerial position. Such sea‐floor emergence is conducive to the initiation of grounded ice growth in the central Barents Sea. The model indicates that, prior to its glaciation, the depth of the Central Deep would have been reduced from around 400 m to 200 m. Such uplift aided the migration of grounded ice from the central Barents Sea and Scandinavia into the Central Deep. We conclude that ice loading over Scandinavia and Arctic island archipelagos during the first stages of the Late Weichselian may have caused uplift within the central Barents Sea and aided the growth of ice across the entire Barents Shelf. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Observations of flexure and the rheology of oceanic lithosphere   总被引：2，自引：0，他引：2  

A. B. Watts  S. Zhong 《Geophysical Journal International》2000,142(3):855-875

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Crustal underplating and its implications for subsidence and state of isostasy along the Ninetyeast Ridge hotspot trail     

Ingo Grevemeyer  & Ernst R. Flueh 《Geophysical Journal International》2000,142(2):643-649

Recent seismic field work has revealed high lower-crustal velocities under Ninetyeast Ridge, Indian Ocean, indicating the presence of crustal underplating ( Grevemeyer et al . 2000 ). We used results from Ocean Drilling Program (ODP) drill cores and cross-spectral analysis of gravity and bathymetric data to study the impact of the underplating body on the subsidence history and the mode of isostatic compensation along Ninetyeast Ridge. Compared with the adjacent Indian basin, the subsidence of Ninetyeast Ridge is profoundly anomalous. Within the first few millions of years after crustal emplacement the ridge subsided rapidly. Thereafter, however, subsidence slowed down significantly. The most reliable model of isostasy suggests loading of a thin elastic plate on and beneath the seafloor. Isostatic compensation of subsurface loading occurs at a depth of about 25 km, which is in reasonably good agreement with seismic constraints. Subsurface loading is inherently associated with buoyant forces acting on the lithosphere. The low subsidence may therefore be the superposition of cooling of the lithosphere and uplift due to buoyant material added at the base of the crust. A model including prolonged crustal growth in the form of subcrustal plutonism may account for all observations.  相似文献   

龙门山断裂系及邻区地壳重力均衡效应与汶川地震   总被引：11，自引：2，他引：9       下载免费PDF全文

王谦身  滕吉文  张永谦  杨辉 《地球物理学进展》2008,23(6):1664-1670

龙门山断裂系位于松潘-甘孜山地与成都盆地平原之间,地形高差达3500±500 m.根据重力资料给出四川中西部成都盆地、龙门山、邛崃山区、松潘等川西山地(102°E～105°E,30°N～33°N)的地壳厚度(Moho界面深度)分布.为了探究汶川大地震孕育与发生的原因,将其与据艾里(Airy)大陆均衡理论给出的理论均衡地壳厚度进行对比分析,以探讨该地区的地壳均衡状态.研究结果表明:龙门山断裂带系及以西地区深部地壳是处于很不均衡的状态.为了深化认识重力均衡与大地震的相关性,尚需对该地区深部结构与地壳重力均衡效应作精细研究.同时,本文上述研究结果亦有益于震后确定城镇布局和为不同类型建筑物重建选址方面提供深部要素.  相似文献   

地壳均衡与海平面变化   总被引：6，自引：0，他引：6  

杨学祥 《地球科学进展》1992,7(5):22-30

提要:在全球海面变化的近期研究中，无论是均衡模式、还是重力模式，写考虑到冰川均衡作用和水力均衡作用。本文认为，绝对均衡表示地壳均街的最终结果，相对均衡表示地壳均衡中一系列中间过程。这两种均衡之间的差别，往往被人们所忽视。
    定量计算的结果表明，冰盖的吸引不仅使周围的海面升高，而且使内核在外核中产生定向运动。由于参加相对均衡的大陆壳数量不同、宕石圈的强度不同，陆壳与陆充、陆克与洋壳之间将产生不同幅度的垂直运动。这为解释全球海面变化不一致性提供了另一个新思路。
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Geomorphological development of the eastern margin of the Australian Craton   总被引：1，自引：0，他引：1  

C. R. Twidale  E. M. Campbell 《地球表面变化过程与地形》1992,17(4):419-431

The denudation chronologies of five uplands of contrasting geological structure located at the eastern margin of the Australian Craton are examined. They are the Isa Highlands, MacDonnell Ranges and Flinders Ranges (fold mountains, orogenic setting); the Arcoona Plateau (dissected plateau, platform setting); and the Gawler Ranges (massif of old silicic volcanics, cratonic setting). In each, surfaces of Mesozoic age, many of them exhumed and of pre-Cretaceous age, are preserved. Each also appears to have been uplifted recurrently. Each was either overwhelmed or bordered by the Early Cretaceous (Neocomian-Aptian) sea. Tectonism associated with the break-up of Gondwana probably allowed this important marine transgression. Thereafter, thalassostatic and erosional/depositional isostatic responses have maintained the uplands as uplands and the intervening basins as negative topographic and structural units; the pattern of topography has been constant for the last 60–100 Ma.  相似文献   

桃村拆离断层及其与金矿成矿作用的探讨     

黄贤芳  仉宝聚  刘德长  陈平田  王志刚  李永甫 《铀矿地质》1993,(6)

本文运用伸展构造理论,通过野外实地观察结合遥感影像判读和室内综合研究,提出了桃村断裂为一条拆离断层。并进一步剖析了与其伴生的变质核杂岩的构造特点;分析了拆离断层和变质核杂岩的影像特点;探索了它与该区成矿作用的关系。这对认识我国东部普遍存在的先压后张断层的成因和演化,了解我国东部与铀矿及其它矿产有关的区域拉张构造背景的关系,开拓新的找矿思路是有启迪的。  相似文献   

On the growth and collapse of wide orogenic belts   总被引：1，自引：0，他引：1  

Jichun Sun  Stanley A. F. Murrell 《Geophysical Journal International》1994,118(1):255-268

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衡山变质核杂岩体西缘剥离断层及其对铀成矿的控制作用   总被引：6，自引：1，他引：6  

张进业 《铀矿地质》1994,10(3):144-149,185

衡山变质核杂岩体是由元古界深变质岩和燕山期复式花岗岩体组成，其西缘的界版剥离断层是区域深断裂的一部分，在断裂下盘山现糜棱岩－混合岩带具韧性变形特征，沿断裂已发现一些有意义的铀矿化，根据剥离断层控矿模式，提出在断裂上盘王冲－谢马冲地段寻找陡倾正断层与离断层交切处的隐伏铀矿的设想。  相似文献   

Denudation,isostasy and landscape evolution     

A. R. Gilchrist  M. A. Summerfield 《地球表面变化过程与地形》1991,16(6):555-562

The idea that the isostatic response to progressive denudational unloading can be episodic over cyclic timescales is widely cited in the geomorphological literature. We demonstrate, however, that this notion, which has been regarded as a possible mechanism of widespread landscape rejuvenation, is based on a fundamental misunderstanding of the principles of flexural isostasy. Rather than a discontinuous response, in cases where the half-width of the applied load is greater than a few tens of kilometres the lithosphere experiences a continuous compensation which is dependent upon the wavelength of the applied load rather than upon a lateral, or vertical, threshold of unloading which has to be exceeded before isostatic recovery is initiated. Although a flexural isostatic response cannot account for episodic uplift during a denudational cycle, it can explain the growth and persistence of significant marginal upwarps along passive margins across which there is a marked contrast in denudation rates. Such marginal upwarps, in turn, probably play a critical role in the long-term evolution of drainage systems and landscapes in adjacent continental hinterlands.  相似文献