Reconstructions of the Mediterranean Outflow Water during the quaternary based on the study of changes in buried mounded drift stacking pattern in the Gulf of Cadiz     

Estefania Llave  Francisco J. Hernández-Molina  Dorrik A. V. Stow  Mari Carmen Fernández-Puga  Margarita García  Juan T. Vázquez  Adolfo Maestro  Luis Somoza  Victor Díaz del Río 《Marine Geophysical Researches》2007,28(4):379-394

Contourite deposits in the central sector of the middle slope of the Gulf of Cadiz have been studied using a comprehensive acoustic, seismic and core database. Buried, mounded, elongated and separated drifts developed under the influence of the lower core of the Mediterranean Outflow Water are preserved in the sedimentary record. These are characterised by depositional features in an area where strong tectonic and erosive processes are now dominant. The general stacking pattern of the depositional system is mainly influenced by climatic changes through the Quaternary, whereas changes in the depositional style observed in two, buried, mounded drifts, the Guadalquivir and Huelva Drifts, are evidence of a tectonic control. In the western Guadalquivir Drift, the onset of the sheeted drift construction (aggrading QII unit) above a mounded drift (prograding QI unit) resulted from a new Lower Mediterranean Core Water hydrodynamic regime. This change is correlated with a tectonic event coeval with the Mid Pleistocene Revolution (MPR) discontinuity that produced new irregularities of the seafloor during the Mid- to Late-Pleistocene. Changes in the Huelva Drift from a mounded to a sheeted drift geometry during the Late-Pleistocene, and from a prograding drift (QI and most part of QII) to an aggrading one (upper seismic unit of QII), highlight a new change in oceanographic conditions. This depositional and then oceanographic change is associated with a tectonic event, coeval with the Marine Isotope Stage (MIS) 6 discontinuity, in which a redistribution of the diapiric ridges led to the development of new local gateways, three principal branches of the Mediterranean Lower Core Water, and associated contourite channels. As a result, these buried contourite drifts hold a key palaeoceanographic record of the evolution of Mediterranean Lower Core Water, influenced by both neotectonic activity and climatic changes during the Quaternary. This study is an example of how contourite deposits and erosive elements in the marine environment can provide evidence for the reconstruction of palaeoceanographic and recent tectonic changes.  相似文献   

Structural development of the Tso Morari ultra-high pressure nappe of the Ladakh Himalaya   总被引：2，自引：0，他引：2  

Jean-Luc Epard  Albrecht Steck   《Tectonophysics》2008,451(1-4):242-264

A continental subduction-related and multistage exhumation process for the Tso Morari ultra-high pressure nappe is proposed. The model is constrained by published thermo-barometry and age data, combined with new geological and tectonic maps. Additionally, observations on the structural and metamorphic evolution of the Tso Morari area and the North Himalayan nappes are presented. The northern margin of the Indian continental crust was subducted to a depth of > 90 km below Asia after continental collision some 55 Ma ago. The underthrusting was accompanied by the detachment and accretion of Late Proterozoic to Early Eocene sediments, creating the North Himalayan accretionary wedge, in front of the active Asian margin and the 103–50 Ma Ladakh arc batholith. The basic dikes in the Ordovician Tso Morari granite were transformed to eclogites with crystallization of coesite, some 53 Ma ago at a depth of > 90 km (> 27 kbar) and temperatures of 500 to 600 °C. The detachment and extrusion of the low density Tso Morari nappe, composed of 70% of the Tso Morari granite and 30% of graywackes with some eclogitic dikes, occurred by ductile pure and simple shear deformation. It was pushed by buoyancy forces and by squeezing between the underthrusted Indian lithosphere and the Asian mantle wedge. The extruding Tso Morari nappe reached a depth of 35 km at the base of the North Himalayan accretionary wedge some 48 Ma ago. There the whole nappe stack recrystallized under amphibolite facies conditions of a Barrovian regional metamorphism with a metamorphic field gradient of 20 °C/km. An intense schistosity with a W–E oriented stretching lineation L₁ and top-to-the E shear criteria and crystallization of oriented sillimanite needles after kyanite, testify to the Tso Morari nappe extrusion and pressure drop. The whole nappe stack, comprising from the base to top the Tso Morari, Tetraogal, Karzok and Mata–Nyimaling-Tsarap nappes, was overprinted by new schistosities with a first N-directed and a second NE-directed stretching lineation L₂ and L₃ reaching the base of the North Himalayan accretionary wedge. They are characterized by top-to-the S and SW shear criteria. This structural overprint was related to an early N- and a younger NE-directed underthrusting of the Indian plate below Asia that was accompanied by anticlockwise rotation of India. The warping of the Tso Morari dome started already some 48 Ma ago with the formation of an extruding nappe at depth. The Tso Morari dome reached a depth of 15 km about 40 Ma ago in the eastern Kiagar La region and 30 Ma ago in the western Nuruchan region. The extrusion rate was of about 3 cm/yr between 53 and 48 Ma, followed by an uplift rate of 1.2 mm/yr between 48 and 30 Ma and of only 0.5 mm/yr after 30 Ma. Geomorphology observations show that the Tso Morari dome is still affected by faults, open regional dome, and basin and pull-apart structures, in a zone of active dextral transpression parallel to the Indus Suture zone.  相似文献   

华南海岸带第四纪碳酸盐岩及其地质地理意义   总被引：2，自引：0，他引：2  

陈伟光 《华南地震》1990,10(3):25-33

分布在华南沿海各种第四纪碳酸盐岩与海岸带的海陆变迁,新构造运动有明显的相关关系。研究表明,华南全新世以来海陆变动受新构造运动制约而不同于华北,华中地区,其各岸段之间的变化也有先后之分。应当从地貌学、岩石学、沉积学等多学科综合地研究第四纪碳酸盐岩的成岩机制,以便取得比较客观的科学解释。  相似文献   

北天山强震活动特征及对未来强震三要素的分析     

李凡德 《内陆地震》1992,6(4):370-376

北天山带具有强烈新构造活动的背景,分析地震历史资料还可看出,强震活动具有明显的韵律特征。本文对北天山强震活动特征作了分析,并探对了未来强震活动三要素问题。  相似文献   

吉林舒兰断裂带的基本特征          下载免费PDF全文

刘祥 《地震地质》1988,10(3):28

舒兰断裂带是东北地区著名的依兰—伊通断裂带的中段。本文从构造分析和历史发展的角度出发,阐述了舒兰断裂带的基本特征及其晚近时期新活动  相似文献   

Neotectonics of the Marikina Valley fault system (MVFS) and tectonic framework of structures in northern and central Luzon, Philippines     

Rolly E. Rimando  Peter L.K. Knuepfer   《Tectonophysics》2006,415(1-4):17-38

Recognition of neotectonic features along the Marikina Valley fault system (MVFS) in central Luzon, Philippines indicates a dominantly dextral strike-slip motion during its most recent activity believed to be Late Pleistocene to Holocene in age. Variations in the ratios of vertical to horizontal displacements for the segments imply a dominantly dextral motion of the West Marikina Valley fault (WMVF) and oblique dextral motion for the East Marikina Valley fault (EMVF). The displacement data further suggest that rupturing along the EMVF involved multiple segments and occurred separately from the events along the WMVF segments. Estimated earthquake magnitudes for the WMVF and EMVF based on single-event offsets fall within the range M 7.3–7.7. The vertical slip component in the northern part of the Marikina Valley is associated with the development of a basin between the EMVF and WMVF while the large vertical component in the southernmost segment of the EMVF (Talim) is attributed to volcanism-related extension. Lateral advection of the block bounded by the MVFS and the Philippine fault zone (PFZ), rather than pure shear resulting from an assumed east–west compression, best explains the observed kinematics of the MVFS. This is the result of compression during the westward drift of the Philippine Sea Plate and northern Luzon and occurs through slip along the WMVF and EMVF at rates of 5–7 mm/yr.  相似文献   

对庐山东麓第四纪沉积物物源及新构造运动的新认识   总被引：19，自引：1，他引：19  

朱诚 《地理学报》1995,50(1):41-50,T002

根据在庐山山上和庐山东麓采集的基岩和沉积物砾石标本薄片鉴定，发现山上基岩和山麓沉积物在岩性之间没有必然的联系。山麓大多数沉积物在岩性和沉积相上类似于白砂井组，作者认为该沉积物主要是古赣江上游搬运来的物质。论证了网纹红土主要是中更新世初湿热低平地形下形成，而庐山现今１０００－１２００ｍ高度存在着变位网纹红土，由此推论，庐山在网纹红土形成后（中更新世中期以来）的新构造运动中，山体抬升了约６００－８００  相似文献   

Morphological,sedimentological and tectonic features of diamante-m. Carpinoso Marine terrace flight (tyrrhenian coast of northern Calabria,Italy)     

Luigi Carobene  Gianluca Ferrini 《地球表面变化过程与地形》1993,18(3):225-239

Marine terrace flights resulting from the interaction of Quaternary glacio-eustatic fluctuations and tectonic uplift are a typical feature of the Tyrrhenian coast of Calabria in Southern Italy; in particular a térrace flight with four orders of terraces is evident in the Diamante area. The lowest terrace levels (fourth order: Diamante-Cirella terrace) are typified by a calcarenitic deposit with Cladocora caespitosa which give a Th/U age > 300,000 years. The third order terrace has a sedimentary cover formed of a basal discontinuous level of well rounded pebbles which underlies a deeply weathered coarse-grained sand horizon. The deposit ends with a paleosol locally cut by erosional scours filled by yellowish tuff deposits. The formation of this terrace dates from the Middle Pleistocene. The second order terrace presents a sedimentary cover composed of two generations of soils and is attributed to Middle Pleistocene age. The first order terrace (M. Carpinoso terrace) presents a wave-cut platform covered by a clastic deposit of marine and continental origin; this deposit consists of superimposed depositional events separated by unconformities, bounded by two diachronous surfaces. The formation of the wave-cut platform could be related to several sea-level stands during a long-lasting slow subsidence phase of the coastal area during the Lower Pleistocene. The uplift following terrace formation displaced the first order terrace most markedly; tectonic lineations controlled the hydrographic pattern and erosion of the surfaces.  相似文献   

Quantifying the slip rates, spatial distribution and evolution of active normal faults from geomorphic analysis: Field examples from an oblique-extensional graben, southern Turkey   总被引：1，自引：0，他引：1  

Sarah J. Boulton  Alexander C. Whittaker 《Geomorphology》2009,104(3-4):299-316

Quantifying the extent to which geomorphic features can be used to extract tectonic signals is a key challenge in the Earth Sciences. Here we analyse the drainage patterns, geomorphic impact, and long profiles of bedrock rivers that drain across and around normal faults in a regionally significant oblique-extensional graben (Hatay Graben) in southern Turkey that has been mapped geologically, but for which there are poor constraints on the activity, slip rates and Plio–Pleistocene evolution of basin-bounding faults. We show that drainage in the Hatay Graben is strongly asymmetric, and by mapping the distribution of wind gaps, we are able to evaluate how the drainage network has evolved through time. By comparing the presence, size, and distribution of long profile convexities, we demonstrate that the northern margin of the graben is tectonically quiescent, whereas the southern margin is bounded by active faults. Our analysis suggests that rivers crossing these latter faults are undergoing a transient response to ongoing tectonic uplift, and this interpretation is supported by classic signals of transience such as gorge formation and hill slope rejuvenation within the convex reach. Additionally, we show that the height of long profile convexities varies systematically along the strike of the southern margin faults, and we argue that this effect is best explained if fault linkage has led to an increase in slip rate on the faults through time from  0.1 to 0.45 mm/yr. By measuring the average length of the original fault segments, we estimate the slip rate enhancement along the faults, and thus calculate the range of times for which fault acceleration could have occurred, given geological estimates of fault throw. These values are compared with the times and slip rates required to grow the documented long-profile convexities enabling us to quantify both the present-day slip rate on the fault (0.45 ± 0.05 mm/yr) and the timing of fault acceleration (1.4 ± 0.2 Ma). Our results have substantial implications for predicting earthquake hazard in this densely populated area (calculated potential M_w = 6.0–6.6), enable us to constrain the tectonic evolution of the graben through time, and more widely, demonstrate that geomorphic analysis can be used as an effective tool for estimating fault slip rates over time periods > 10⁶ years, even in the absence of direct geodetic constraints.  相似文献   

Pie de Palo, Argentina: A cataclastic diapir     

Claudio Vita-Finzi   《Geomorphology》2009,104(3-4):317-322

The term cataclastic diapirism is proposed for the low-temperature extrusion of highly fractured rocks through more competent strata to produce domed topographies at the surface. The process is illustrated by reference to the geomorphology, neotectonics and microseismicity of the Pie de Palo, an elongated ridge in the western Sierras Pampeanas of Argentina composed of shattered and sheared Lower Palaeozoic rocks and subject to coseismic uplift. The Pie de Palo is conventionally interpreted as a fault-driven basement fold linked to low-angle eastward subduction of the Nazca plate beneath South America; the diapiric model implies instead that deformation is powered by regional compression from west-verging, near-surface, crustal shortening which results ultimately from Atlantic spreading.  相似文献