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1.
MATTHEW R. BENNETT MICHAEL J. HAMBREY DAVID HUDDART JEAN FRANOIS GHIENNE 《第四纪科学杂志》1996,11(6):437-449
Traditionally, geometrical ridge networks are interpreted as the product of the flow of subglacial sediment into open basal crevasses at the cessation of a glacier surge (‘crevasse-fill’ ridges). They are widely regarded as a characteristic landform of glacier surges. Understanding the range of processes by which these ridge networks form is therefore of importance in the recognition of palaeosurges within the landform record. The geometrical ridge network at the surge-type glacier Kongsvegen in Svalbard, does not form by crevasse filling. The networks consist of transverse and longitudinal ridges that can be seen forming at the current ice margin. The transverse ridges form as a result of the incorporation of basal debris along thrust planes within the ice. The thrusts were apparently formed during a glacier surge in 1948. Longitudinal ridges form through the meltout of elongated pods of debris, which on the glacier surface are subparallel to the ice foliation and pre-date the surge. This work adds to the range of landforms associated with glacier surges. 相似文献
2.
MARTIN MARKGREN MAUNO LASSILA 《Boreas: An International Journal of Quaternary Research》1980,9(4):271-274
In Västerbotten County, Sweden, both Rogen moraine and Blattnick moraine are common in the inner part of the county. Rogen moraines are found primarily in basins and upslope positions, whereas the Blattnick type (first found in the Blattnicksele area in the county) mostly occurs in broader, more plain-like areas. Moreover, both types show a great variety of individual forms, due to topography, basal conditions and ice tectonics. Most Rogen moraine ridges are characterized by features due to active ice. The Blattnick moraine type is characterized by broader and more drumlinized ridges. They are often proximally higher and laterally-distally extended, thus merging into streamlined mounds or hills. The material composition of Rogen and Blattnick moraines is similar. The authors have found the following sequence of transitional forms from the Scandinavian mountains in the west towards the east: (1) Rogen moraines, (2) crescent ridges, (3) Blattnick moraines, (4) drumlins. 相似文献
3.
Besshi-type volcanic-associated massive sulfide deposits (VMSD) are associated with undifferentiated basaltic formations.
They form within the mid-ocean ridges near the continental margins, in back-arc spreading zones, and rarely in intracontinental
rift basins. They are characterized by a wide spread of turbidites in ore-bearing strata, Co-rich copper-zinc ores, the predominance
of subvolcanic sills, sheet-like ore bodies, an absence of clear structural control, relatively low Cu, Zn, Ag, and Au grades,
enrichment in Pb, and relatively large ore and metal reserves. 相似文献
4.
《Journal of Asian Earth Sciences》2006,26(6):859-881
Structural analysis in the well-exposed and well-preserved Neyriz ophiolite suggests that it is a relatively undisturbed piece of oceanic lithosphere. Detailed structural mapping of high-T deformation mantle flow revealed the presence of three elliptical shaped diapirs trending NW–SE. These diapirs are characterized by vertical mantle foliations associated with vertical plunging stretching lineations, which progressively incline toward parallelism with the gently NE-dipping Moho. The NW–SE direction of asthenospheric upwelling of diapirs is parallel with the orientations of the vertical sheeted dike complex. This suggests that the Neyriz ophiolite was created by two NW–SE palaeo-ridge axes. These palaeo-ridges are classified as fast-spreading ridges. These ridges are segmented by a dextral palaeo-transform fracture zone. This is consistent with fast-spreading ridges. Comparison between the Neyriz and Oman ophiolites reveals that they show similar characteristics. Most of the Oman palaeo-ridge systems are oriented NW–SE and NNW–SE. They also display similar sheeted dike complex orientations and crustal thickness variations. These two ophiolites originally were part of the Neo-Tethyan oceanic lithosphere and afterwards were separated by the Oman line during continental collision of the Iranian micro-continent and Afro-Arabian continent. 相似文献
5.
NELSON R. HAM JOHN W. ATTIG 《Boreas: An International Journal of Quaternary Research》2001,30(1):31-41
Approximately 35 parallel, discontinuous glacial ridges occur in an area of about 100 km2 in north‐central Wisconsin. The ridges are located between about 6 and 15 km north (formerly up‐ice) of the maximum extent of the Wisconsin Valley Lobe of the Laurentide Ice Sheet. The ridges are between 1 and 4 m high, up to 1 km long, and spaced between 30 and 80 m apart. They are typically asymmetrical with a steep proximal (ice‐contact) slope and gentle distal slope. The ridges are composed primarily of subglacial till on their proximal sides and glacial debris‐flow sediment on the distal sides. In some ridges the till and debris‐flow sediment are underlain by sorted sediment that was deformed in the former direction of ice flow. We interpret the ridges to be recessional moraines that formed as the Wisconsin Valley Lobe wasted back from its maximum extent, with each ridge having formed by a sequence of (1) pushing of sorted ice‐marginal sediment, (2) partial overriding by the glacier and deposition of subglacial till on the proximal side of the ridge, and (3) deposition of debris‐flow sediment on the distal side of the ridge after the frozen till at the crest of the ridge melted. The moraines are similar to annual recessional moraines described at several modern glaciers, especially the northern margin of Myrdalsjokull, Iceland. Thus, we believe the ridges probably formed as a result of minor winter advances of the ice margin during deglaciation. Based on this assumption, we calculate the net rate of ice‐surface lowering of the Wisconsin Valley Lobe during the period when the moraines formed. Various estimates of ice‐surface slope and rates of ice‐margin retreat yield a wide range of values for ice‐surface lowering (1.7–14.5 m/yr). Given that ablation rates must exceed those of ice‐surface lowering, this range of values suggests relatively high summer temperatures along the margin of the Wisconsin Valley Lobe when it began retreating from its maximum extent. In addition, the formation of annual moraines indicates that the glacier toe was thin, the ice surface was clean, and the ice margin experienced relatively cold winters. 相似文献
6.
Structural analysis in the well-exposed and well-preserved Neyriz ophiolite suggests that it is a relatively undisturbed piece of oceanic lithosphere. Detailed structural mapping of high-T deformation mantle flow revealed the presence of three elliptical shaped diapirs trending NW–SE. These diapirs are characterized by vertical mantle foliations associated with vertical plunging stretching lineations, which progressively incline toward parallelism with the gently NE-dipping Moho. The NW–SE direction of asthenospheric upwelling of diapirs is parallel with the orientations of the vertical sheeted dike complex. This suggests that the Neyriz ophiolite was created by two NW–SE palaeo-ridge axes. These palaeo-ridges are classified as fast-spreading ridges. These ridges are segmented by a dextral palaeo-transform fracture zone. This is consistent with fast-spreading ridges. Comparison between the Neyriz and Oman ophiolites reveals that they show similar characteristics. Most of the Oman palaeo-ridge systems are oriented NW–SE and NNW–SE. They also display similar sheeted dike complex orientations and crustal thickness variations. These two ophiolites originally were part of the Neo-Tethyan oceanic lithosphere and afterwards were separated by the Oman line during continental collision of the Iranian micro-continent and Afro-Arabian continent. 相似文献
7.
Depositional and diagenetic history of Pleistocene and Holocene oolitic sediments and sabkhas in Kuwait, Persian Gulf 总被引：1，自引：0，他引：1
FRANTISEK PICHA 《Sedimentology》1978,25(3):427-450
The Pleistocene and Holocene oolitic sediments of southern Kuwait appear as parallel ridges—ancient and recent barrier beaches and coastal dunes. They are underlain by Tertiary clastic deposits and interfingered with sabkhas. Considering the superposition, primary composition and diagenetic alterations five lithostratigraphic units were distinguished within the oolitic complex. Their formation and preservation were related principally to eustatic oscillations of sea level during Quaternary times, although post-Pliocene tectonics also played an important role both in physiographic and sedimentary developments of the region. The large accumulation of oolites in southern Kuwait might be related, at least partly, to the existence of two tidal channels, khors, discharging waters over-saturated with respect to calcium carbonate over broad tidal flats. The formation of oolites culminated in late Pleistocene probably due to an extreme aridity of the climate. The subaerial diagenesis of the oolitic ridges led to gradual cementation and recrystallization of oolites. The four stages of progressive diagenesis distinguished in the area are compared with schemes suggested by Land, Mackenzie & Gould (1967) for Quaternary sediments in Bermuda and by Gavish & Friedman (1969) for aeolianite ridges in Israel. On the sea floor the cementation has produced widespread beach rocks and hard layers. Aragonite encrustations and dripstones occur within the intertidal zone of channels and lagoons. The shallow, occasionally flooded depresssions in sabkhas are occupied by algal mats. The amount of dolomite in sabkha sediments is rather low in comparison with similar environments of the southern Persian Gulf. This might be at least partly explained by the absence of dolomitic rocks in the Tertiary substratum in Kuwait. The complex of Quaternary sediments in southern Kuwait represents a petroleum setting in which the organic rich source sediments of lagoons and sabkhas are closely associated with highly porous reservoir rocks of the oolitic coastal ridges. 相似文献
8.
Palaeokarst, tidal erosion surfaces and stromatolites in the Silurian Eke Formation of Gotland, Sweden 总被引：1，自引：0，他引：1
LESLEY CHERNS 《Sedimentology》1982,29(6):819-833
Irregular, scalloped erosion surfaces in the shelf carbonate sequences of the lower Eke Formation (Ludlow Series, upper Silurian) in the east of Gotland, Sweden, comprise series of shallow hollows separated by sharp-crested ridges, and cavities with sculptured, undercut walls, cut into lithified sediment. These represent analogues of the solution basins formed in modern coastal and subaerial karst terrains. Discrete erosional cavities merge on enlargement by breaching of the intervening walls to leave remnant, tapering ridges. Sets of the ridges and basins seen in surface view show an average width of basins of 1–2 m, with relief of 40–50 cm and pronounced N-S axes for the ridges; this alignment may reflect the local drainage direction. The lowermost erosion surface passes laterally into a planar, mineralized horizon at the top of the underlying Hemse Group that was resistant to and forms the base level of erosion. Because of restricted exposure of higher Eke Formation sediments the upper limit of erosion remains unknown. There is no evidence of caliche or subaerial diagenetic textures, but solution vugs are common in the eroded limestones. Marine hard-bottom biota attached to some surfaces, and transition from scalloped to planar surfaces indicate erosion in tidal zones, but subaerial karstic erosion is also inferred. The resubmerged karst-eroded topography is overlain by shallow marine carbonates, including small organic buildups. Finely-layered stromatolitic mats developed over the initial infill, in subtidal environments, and grew to form domed mounds within the erosional cavities. They abut sharply against bounding side walls and overhangs. Some emergence is evident from desiccation features in the upper parts of mounds. Biostratigraphical evidence dating the events from initial uplift and karstic erosion to covering of the drowned relief topography places the whole sequence within upper Ludlow times. 相似文献
9.
Products of marine processes occupy a considerable vertical range, which varies along the shore. Extreme waves can both cause erosion and form depositional structures up to several metres above the high tide mark. Temporary supra-elevation of water level by surge or wave set-up shifts effects upward. The preservation potential of products of extreme storms is relatively high, when compared to those associated with more frequent events. The level to which coastal landforms develop depends upon the conditions under which they form; thus sand beach ridges which are related to fairweathcr periods have a restricted height range when compared to gravel beach ridges building up under extreme storms. The varied coastal scenery of eastern Ireland provides many examples of storm-related products (barriers. cliffs, platforms, etc.). They have been related to a latc-Holocene eustatic sea level or even a partly isostatically controlled raised late-Holoccne sea level, but both elevations and apparent tilts can be explained by longshore variations in waves, tides and surges. Such an explanation is more consistent with other studies of latc-Holocene coastal evolution around the Irish Sea basin. 相似文献
10.
西湖凹陷平湖组受潮汐影响作用明显,但前人研究鲜有提及潮汐砂脊这种典型的潮汐作用下的沉积体。综合运用地震、测井、岩芯及分析化验资料,在西湖凹陷平湖组发现潮汐砂脊沉积体系。潮汐砂脊在地震振幅属性图上,呈条带状特殊地貌特征;岩芯上为典型的反旋回,旋回上部发育板状交错层理、冲刷面等反映强水动力的沉积构造,旋回下部细粒沉积中则发育潮汐层理、生物扰动等沉积构造;测井曲线上,砂脊底部表现为突变界面,并且砂脊发育区重矿物相对富集。潮汐砂脊砂质纯、物性好,并多发育于泥质背景中,与周围泥岩储盖配置好,可构成良好的岩性油气藏勘探目标。另外,砂脊的发育情况可以反映不同时期西湖凹陷与南部广海的沟通情况,因此对于研究西湖凹陷的古地理具有一定的参考意义。 相似文献
11.
月岭形成机制及其与潮汐力的相关性分析 总被引：1，自引：0，他引：1
月岭作为月表常见的线性构造类型之一,具有一定的分布规律。利用LRO(Lunar Reconnaissance Orbiter)的DEM数据提取月岭剖面并进行了构造分析,认为月岭主体为逆冲断层叠加牵引褶皱的挤压构造形成机制。前人多用月海盆地沉降叠加月球热能收缩解释月岭的成因,但它无法解释盆地中央月岭呈近南北向的优选方位,这种现象可能是受到近东西向区域性挤压应力的影响,与潮汐力对月球中低纬度区域的应力作用状态相符,推测潮汐力可能是盆地中央月岭形成的主因。综合利用嫦娥一号CCD影像数据、Lunar Orbiter和LRO全色波段影像数据,解译识别出月球正面中低纬度1 464条月岭。对其进行方向统计,结果表明,月岭整体走向也与Melosh预测的在潮汐力作用下形成的构造样式相似。由此推测,月岭的展布与潮汐力具有很强的相关性,进一步论证了月岭的形成与潮汐力有关。 相似文献
12.
The origin and geological significance of lunar ridges 总被引：3，自引：1，他引：3
YUE Zongyu OUYANG Ziyuan LI Haobin LIU Jianzhong WU Ganguo 《中国地球化学学报》2007,26(4):418-424
Lunar ridges are a kind of familiar linear structures developed on the lunar surface. The distribution pattern, formation mechanism and research significance of lunar ridges are discussed in this paper. Single lunar ridges are usually distributed in the form of broken lineation, and, as whole, lunar ridges are trapezoidal or annular in shape around the maria. As to the formation mechanism, only volcanism or tectonism was emphasized in the past, but the two processes are seldom taken into combined consideration. On the basis of detailed analyses, the authors thought that tectonism is a prerequisite for the formation of lunar ridges, while volcanism is the key factor controlling their particular shapes. Finally, the authors pointed out that it is very significant in the study of lunar ridges to link the course of lunar structure evolution with the stress state in the lunar crust. 相似文献
13.
Volcanic gaps due to oblique consumption of aseismic ridges 总被引：1，自引：0，他引：1
The present-day consumption of oceanic ridges and other buoyant rises and fragments at circum-Pacific subduction zones, and presumably elsewhere, are closely related to existing gaps in volcanism. Examples are the gaps associated with the Nazca, Juan Fernandez, Cocos, Marcus-Necker and Louisville ridges. The buoyancy of these ridges breaks the continuity of the subducted plate, which may lead to reduced water supply required for melting of magma, and therefore create temporary volcanic gaps. The oblique consumption of these ridges causes the gap to migrate with time. This mechanism may be useful in interpreting time-space patterns of past volcanic chains associated with subduction in terms of the consumption of the disruptive oceanic plateaus and ridges. 相似文献
14.
月岭是月球表面上最常见的线性构造之一,大多分布于被玄武岩充填的月海之中。虽对于月岭成因的观点不一,但多数月岭具有明显的挤压变形特征,其展布形式有单列、组或群(常见)、网状或雁列状等。月岭的形成和展布既受到月海盆地构造的控制,又受到区域应力状态的影响。文中以雨海为研究区域,利用美国环月球巡逻者(LRO)的宽视角影像(WAC)数据和激光高度计(LOLA)数据对雨海地区的月岭构造进行解译和提取,对月岭进行分类和统计分析,结合雨海盆地构造特征以及月岭构造的样式解析,并运用沙箱构造物理模拟方法对月岭的形成和分布进行模拟实验,讨论了雨海地区影响月岭形成和分布的主控因素。结果表明,月岭是挤压体制下形成的;盆地构造是控制月岭类型Ⅰ分布的主要因素;月岭类型Ⅱ的分布主要受区域构造应力控制,其走向主要反映区域构造的最大主应力方向。综上推断,雨海地区月岭形成于近东西向最大主应力并受到雨海盆地构造的控制,表现为月岭类型Ⅰ和月岭类型Ⅱ的综合样式。 相似文献
15.
Yu. M. Pushcharovsky 《Geotectonics》2011,45(2):101-112
The first-order Line, Hawaiian, Emperor, Pukapuka, Louisville, Ninetyeast, and Chagos-Lackadive tectonovolcanic ridges in
the Pacific and Indian oceans are considered. These ridges are combined into the category of demarcation tectonic units separating
the largest morphostructural sectors of the oceans. The ridges extend for thousands kilometers and are a few hundred kilometers
in width. Their crest zones are crowned by numerous volcanoes. The volcanic rocks are largely basalts with elevated alkalinity.
All of the ridges were formed in the Late Cretaceous-Cenozoic; the ages of particular ridges are variable. The dimensions
of the demarcation tectonic units allow us to refer them to the processes proceeding in the mantle, including tectonic flow,
faulting, and significant strike-slip displacements. 相似文献
16.
应用光学显微镜及扫描电镜对Ｍｕｅｎｚｈｉｇｒａｐｔｕｓ一属的一些构造进行研究发现，在其原胎管和线管壁上均发育有纵脊，线管纵脊是原胎管纵脊向线管的延伸，纵脊的形成晚于原胎管壁及线管壁的形成。Ｍｕｅｎｚｈｉｇｒａｐｔｕｓ的副胞管呈简单管状，随着正胞管在笔石体始部呈末端孤立至笔石体末部变为直管状无孤立部分，相应地，副胞管在笔石体始部至末部绕过正胞管背缘弯曲生长逐渐转为直管状 相似文献
17.
E. V. Verzhbitskii L. I. Lobkovskii A. F. Byakov M. V. Kononov 《Doklady Earth Sciences》2012,444(2):666-670
In order to specify the origin and evolution of the Alpha-Mendeleev and Lomonosov ridges, profiles of the bottom relief and crustal basement were made. Additionally, the coefficients characterizing the rate of subsidence of the crustal basement in different parts of the ridges for the last 25 Ma were calculated and the depth of the crustal basement prior to the beginning of subsidence in the Early Miocene was estimated. The calculation results were compared with the model of thermal subsidence of the Greenland-Iceland and Iceland-Faroe thresholds, which were also formed by plume-tectonic processes. A large dome rise of the basement was found in the central parts of the Alpha-Mendeleev and Lomonosov ridges. It was also found that the coefficients of thermal subsidence of the crustal basement in the central parts of the Alpha-Mendeleev and Lomonosov ridges are close to those for the Greenland-Iceland and Iceland-Faroe thresholds. It was shown that the depth of the crustal basement prior to the beginning of subsidence in the Early Miocene grew going outwards from the central parts of the ridges, analogous to the present-day pattern. All the information given above indicates the thermal origin of subsidence for the Alpha-Mendeleev and Lomonosov ridges starting from the Early Miocene and the substantial influence of the Arctic Plume on the genesis and evolution of these ridges. 相似文献
18.
多波束测深技术在国际上是海洋科学研究、海底资源开发和海洋工程建设中的重要技术手段。基于对国内外多波束
地形数据的广泛调研,对洋中脊附近洋底构造地貌形态进行分析研究。文中利用不同扩张速率洋中脊附近的50 m分辨率的多
波束地形数据,基于数字地形空间分析方法,利用不同滑动窗口和阈值自动识别来提取洋中脊附近地形面的最大、最小曲率
以及坡度,并以此对洋中脊进行构造解译。对中大西洋洋中脊和东太平洋洋隆两个实验结果的定量分析表明,基于地形曲面
曲率和坡度的洋中脊构造解译方法是有效且可行的,其结果为洋中脊构造样式解译提供重要参考。但是相比之下, 相似文献
19.
ROLF NYBERG 《Boreas: An International Journal of Quaternary Research》1988,17(3):333-345
Moraine-like ridges in the Skäralid canyon at the Söderåsen horst, Southern Sweden, are interpreted not as features formed during the deglaciation of the Weichsel ice sheet, but as forms related to lateglacial tundra conditions. This is suggested by their location and morphology and is supported by TL-dates of the sandy matrix in two of the ridges, yielding ages between 10,400 and 10,800 B.P. The environmental significance of the ridges is further discussed on the basis of their sedimentology. As severe wind action in lateglacial time in this part of Sweden is implied by numerous wind-polished rocks, the ridges may have formed as protalus ramparts or end moraines in front of snowfields or small glaciers, nourished by strong snowdrifting. Alternatively, small openwork ridges may be incipient fossil rock glaciers. 相似文献
20.
Late Quaternary glaciation in the south-western Barents Sea 总被引：1，自引：0，他引：1
TORE O. VORREN YNGVE KRISTOFFERSEN 《Boreas: An International Journal of Quaternary Research》1986,15(1):51-59
Moraine ridges have been morphologically and seismically identified in the south-western Barents Sea. Some of these ridges were deposited in front of ice lobes from the northern part of the Fennoscandian Ice Sheet, others in front of glaciers located on the southern Barents Sea shelf. The moraine ridges were probably deposited during the Weichselian, possibly the Late Weichselian. 相似文献