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1.
The Gulf of Corinth in central Greece is an active normal fault zone with particularly clear evidence of isostatic footwall uplift, constrained by Quaternary marine terraces, and hanging-wall subsidence and sedimentation. It is bounded to the south by a Pliocene to Early Pleistocene sedimentary basin, which is now eroding into the Gulf. Previous work has suggested that the relief across this region has increased dramatically since the Early Pleistocene, due to the isostatic response to increased rates of footwall erosion and hanging-wall sedimentation. It is indeed assumed here that incision accompanying the draw-down of global sea-level at 0.9 Ma, during the first major Pleistocene glaciation, initiated the erosion of the basin south of the Gulf of Corinth and so abruptly increased the sedimentation rate in the Gulf. The resulting transient thermal and isostatic response to these changes is modelled, with the subsiding depocentre and eroding sediment source coupled by flow in the lower continental crust. The subsequent enhancement of relief, involving an increase in bathymetry from near zero to 900 m and 500 m of uplift of the eroding land surface in the sediment source, is shown to be a direct consequence of this change. The model is sensitive to the effective viscosity of the lower crust, and can thus resolve this parameter by matching observations. A value of 6×1019 Pa s is indicated, suggesting a viscosity at the Moho no greater than 1018 Pa s. Similar transient topographic effects caused by increased rates of sedimentation and erosion are likely to be widespread within the geological record, suggesting that this coupling process involving flow in the weak lower crust may be of major geological and geomorphological importance.  相似文献   

2.
太行山中段左权羊角镇发育新生代玄武岩, 记录了太行山新生代以来的构造隆升事件。在详细的野外调查和研究的基础上, 通过与玄武岩发育相关的地貌面及其上的地层特征分析, 初步确定该玄武岩是上新世末期到早更新世初期的喷发产物, 初步揭示了太行山中段区域上晚上新世以来地貌发育历史, 主要存在6次构造隆升与剥蚀期: 在唐县期宽谷面形成的基础上, 于上新世晚期存在一次隆升和一次稳定侵蚀期, 并侵蚀形成“U”形谷; 早更新世初, 玄武岩开始间歇性喷发, 同时发生以西武家坪为中心的地区上拱, “U”形谷为玄武岩充填, 之后经剥蚀堆积形成第四级阶地面; 早更新世末, 该区再次发生隆升, 并形成第四级阶地; 中更新世末, 该区发生隆升, 形成第三级阶地; 晚更新世以来, 太行山中段又连续发生两次抬升, 从而在玄武岩体上形成了4级阶地, 形成太行山现今地貌。研究同时表明, 太行山中段上新世晚期以来的隆升主要发生于上新世末到早更新世时期。这一认识为探讨太行山中段晚上新世以来的构造隆升提供了具体证据。  相似文献   

3.
《Geodinamica Acta》2013,26(3-4):209-238
The chronology of extension of the continental crust in western Turkey has been the subject of major controversies. We suggest that these difficulties have arisen in part because of past misuse of dating evidence; and in part because the assumption often made, that deposition of major terrestrial sedimentary sequences implies crustal extension to create the necessary accommodation space, is incorrect. We report evidence that the present phase of extension began in the Denizli region at ~ 7 Ma, around the start of the Messinian stage of the Late Miocene. This timing matches the estimated start of right-lateral slip on the North Anatolian Fault Zone, and corresponds to a substantial increase in the dimensions of the Aegean extensional province to roughly its present size: beforehand, between ~ 12 Ma and ~ 7 Ma, extension seems to have only occurred in the central part of this modern province. In some localities, terrestrial sedimentation that began before this start of extension continued into this extensional phase, both within and outside normal fault zones. However, in other localities within the hanging-walls of normal faults, the start of extension marked the end of sedimentation. Relationships between sedimentation and crustal extension in this region are thus not straightforward, and a simple correlation should therefore not be assumed in structural interpretations. During the time-scale of this phase of extension, the Denizli region has also experienced major vertical crustal motions that are unrelated to this extension. The northern part of this region, in the relatively arid interior of western Turkey, has uplifted by ~ 400 m since the Middle Pliocene, whereas its southern part, closer to the Mediterranean Sea and with a much wetter climate, has uplifted by ~ 1,200 m since the Early Miocene, by up to ~ 900 m since the Middle Pliocene, and by an estimated ~ 300 m since the Early Pleistocene. This regional uplift, superimposed on the local effects of active normal faulting, is interpreted as a consequence of lateral variations in rates of erosion. A reliable chronology for this phase of extension in western Turkey, in relation to changes in the geometry of motions of adjoining plates and Late Cenozoic environmental change, is now in place.  相似文献   

4.
《Quaternary Science Reviews》2007,26(22-24):2783-2800
The Strouma and Mesta are two of the largest rivers that drain across SW Bulgaria and northern Greece into the northern Aegean Sea. Their modern valleys, flanked by Quaternary river terraces, are incised into a diverse landscape, which records the region's complex tectonic history. A network of lacustrine basins existed in the region in the Late Oligocene to earliest Miocene, but was disrupted by thrusting and folding related to Early Miocene transpression. This deformation was followed by a period of erosion, covering most of the Early and Middle Miocene, which probably marked the initiation of the Strouma and Mesta fluviolacustrine system, with geometries unrelated to the older systems. The first clear evidence of these river systems dates from the Middle Miocene (late Badenian to Sarmatian). The systems evolved in the Late Miocene (Maeotian to early Pontian), when lakes existed, characterized by diatomaceous algae and by occasional burial of abundant plant fragments and coal formation. Areas in the south, south of the Kerkini fault, were intermittently submerged beneath the Aegean Sea at this time. Intense localized uplift of horst blocks in late Pontian and Pliocene, associated with crustal extension, resulted in deposition of thick alluvial fans, with tilting of sedimentary successions in adjacent grabens evident by the end of the Pliocene. The highest horsts (Osogovo, Rila, Pirin, and Belasitsa) experienced additional uplift in the Pleistocene, in part as a result of regional uplift and in part through continued normal faulting. Pleistocene climate change also resulted in influxes of glacial and fluvioglacial systems. The present form of the Strouma and Mesta fluviolacustrine systems is thus the result of interplay between crustal extension, regional uplift, and global climate change.  相似文献   

5.
《Quaternary Science Reviews》2007,26(22-24):2844-2863
We present the first overall synthesis of the terrace deposits of the River Euphrates in SE Turkey, northern Syria, and western Iraq, combining new observations with summaries of data sets from different reaches that had previously been independently studied on a piecemeal basis. The largest number of terraces observed in any reach of the Euphrates is 11, in western Iraq, where this river leaves the uplands of the Arabian Platform. In many other localities not more than 5 or 6 terraces have previously been identified, although we infer that some of these are resolvable into multiple terraces. These terraces are typically formed of gravel, principally consisting of Neotethyan ophiolite and metamorphic lithologies transported from Anatolia. Although older gravels are also evident, most of the Euphrates terrace deposits appear, given the chronologies that have been established for different parts of the study region, to date from the late Early Pleistocene onwards, the cold stages most often represented being interpreted as marine Oxygen Isotope Stages 22, 16, 12, 8, 6 and/or 4, and 2. The formation of this terrace staircase reflects regional uplift of the Arabian Platform. Estimated amounts of uplift since the Middle Pliocene decrease southeastward from almost 300 m in SE Turkey to ∼150 m in western Iraq. Uplift rates increased in the late Early Pleistocene, the uplift estimated since then decreasing from ∼110 m in SE Turkey to a minimum of ∼50 m in the Syria–Iraq border region, then increasing further downstream across western Iraq to ∼70 m. Numerical modelling of this uplift indicates a relatively thin mobile lower-crustal layer, consistent with the low surface heat flow in the Arabian Platform.  相似文献   

6.
Summary The Tertiary and post-Tertiary chronology of faulting in the Gregory Rift Valley is discussed with particular reference to areas where Middle Pleistocene deposits have been mapped. It is concluded that while strong faulting occurred at the end of the Middle Pleistocene period, the main faulting was earlier. At least three pre-Middle Pleistocene phases of faulting are recognised; the maximum movements probably occurred in late Pliocene or earliest Pleistocene times.  相似文献   

7.
The eastern Ecuadorian Andes appear as a fold-and-thrust belt adjacent to a continental foredeep represented by one of the world's largest tropical alluvial megafans, the Pastaza megafan, debouching into the Amazonian lowland. The apex of the Pliocene–Pleistocene megafan situated in the present-day wedge top (Subandean Zone) has been cut by an erosion surface, the western part of which has been uplifted of 500 m along the frontal thrust, forming a poorly dissected plateau, the Mera plateau. This erosion surface erased most of the previous fluvial landscape but preserved a large thrust-related anticlinal hinge deforming less erodible underlying strata, the Mirador fold and smaller-sized anticlines. This surface has been then incised by two antecedent major rivers, the Pastaza and the Napo, and few tributaries. The plateau edge is marked by a series of large scale gently sloping landslides clustered along a 70 km long concave eastward line associated with the frontal thrust fault. The newly formed immature rivers issued from the landslides or sourced within east-dipping remnants of the erosion surface downstream of the landslide line constitute the greatest part of the streams feeding the Ecuadorian Amazonian basin. At 70 to 100 km from the landslide line, the drainage abruptly changes from highly immature to mature with a well-defined hinge line representing the outer limit of landslide and tectonic control. The diversions of the Pastaza River indicate ongoing fold growth since at least the late Pleistocene in the Eastern Cordillera, and the early Holocene in the Mera plateau. The preserved terraces of the Pastaza valley are all degradational and are ascribed to periods of tectonic (seismic) activity alternating with periods of tectonic quiescence or decreased seismic activity rather than to climatic events. 14C dating of the plateau erosion surface and of the upper Pastaza terraces indicates that the minimum average incision rate since 18,000 years BP varies locally in the upper Pastaza valley from 0.5 to 0.67 cm year−1 , increasing from 18,000 years BP to now. A comparison of these incision rates with fold-and-thrust fault uplift rates indicates that incision in the upper Pastaza valley was a result of rapid uplift (up to 1 cm year−1) along the Mirador fold-and-thrust which caused a restoration of the local equilibrium profile of the upper reach, combined with smaller local fault uplift along the westernmost thrust faults. The uplift of the whole Mera plateau with respect to the upper Amazonian basin gives a minimum average uplift rate of 2.8 cm year−1 since 18,000 years BP. The overall uplift of the Mera plateau and the Eastern Cordillera is likely to have been caused by a regional-scale low angle thrust ramp emerging as the frontal thrust fault.  相似文献   

8.
玉龙雪山位于青藏高原东南缘,它以其独特的地貌特征而引人关注。其顶部为一古残留面,在30×20km2范围内海拔>5000m的山峰达18座,高出其周围地区平均海拔近1000m。在分析该区地质地貌特征基础上,我们根据岩石圈弹性挠曲地壳均衡理论,以较保守的残留面海拔4250m为当时金沙江下切玉龙雪山的基准面,结果表明:由于虎跳峡中大规模物质剥蚀而引起玉龙雪山地壳均衡反弹,导致山体隆升了468m,这完全是侵蚀作用对于玉龙雪山隆升的贡献。而玉龙雪山与周围地区的剩余地势高差,主要由正断层等构造作用造成。因此,玉龙雪山的隆升是侵蚀与构造作用共同控制的结果。该区最大量地壳均衡反弹的触发机制是5.02.5M a期间玉龙雪山东西两侧正断层的发生。另一方面,作为玉龙雪山的南东延伸部分——点苍山(4122m)在5.02.5M a同样也发生了构造伸展,但是没有遭受大规模的河流侵蚀作用,因此其海拔相对要低很多。这进一步说明地壳均衡反弹导致了玉龙雪山隆升,并加大了玉龙雪山与点苍山在原有基础上的地势高差。  相似文献   

9.
《Tectonophysics》2001,330(1-2):25-43
A detailed gravimetric study has been integrated with the most recent stratigraphic data in the area comprised between the Arno river and the foothills of the Northern Apennines, in northern Tuscany (central Italy). A Plio–Pleistocene basin lies in this area; its sedimentary succession can be subdivided from the bottom, in five allostratigraphic units: (1) Lower–Middle Pliocene shallow marine deposits; (2) Late Pliocene (?)–Early Pleistocene fluvio-lacustrine deposits; (3) late–Early Pleistocene–Middle Pleistocene alluvial to fluvial red conglomerates (Montecarlo Formation); (4) Middle Pleistocene alluvial to fluvial red conglomerates (Cerbaie and Casa Poggio ai Lecci Formations); (5) alluvial to fluvial deposits of Late Pleistocene age. The Bouguer anomaly map displays a strong minimum in the northeastern sector of the basin, and a gentle gradient from west to east. The map of the horizontal gradients permits to recognise three major fault zones, two of which along the southwestern and northeastern margins of the basin, and one along the southeastern edge of the Pisani Mountains. A 2.5D gravimetric modelling along a SW–NE section across the basin displays a thick wedge of sediments of density 2.25 g/cm3 (about 1700 m in the depocenter) overlying a layer of density 2.55 g/cm3, 1000 m thick, which rests on a basement of 2.72 g/cm3. The most of the sediment wedge is here referred to Upper Pliocene (?)–Lower Pleistocene, because borehole data show Pliocene marine deposits thinning northward close to the southern margin of the area. The layer below is referred to Ligurids and upper Tuscan Nappe units; the densest layer is interpreted as composed of Triassic evaporites, quartzites and Palaeozoic basement. According to Carmignani low-angle extensional tectonics began between Serravallian and early Messinian, thinning the Apennine nappe stack. At the end of Middle Pliocene, syn-rift deposition ceased in the Viareggio Basin (west of the investigated area) as demonstrated by Argnani and co-workers, and high-angle extensional tectonics migrated eastward up to the Monte Albano Ridge. A syn-rift continental sedimentary wedge developed in Late Pliocene–Early Pleistocene, until its hanging wall block was dismembered, during late Early Pleistocene, by NE-dipping faults, causing the uplift of its western portion (the Pisani Mountains). This breakup caused exhumation and erosion of Triassic units whose clastics where shed into the surrounding palaeo-Arno Valley in alluvial–fluvial deposits unconformably overlying the Lower Pleistocene syn-rift deposits. In the late Pleistocene SW–NE-trending fault systems created the steep southeastern edge of the Pisani Mountains and the resulting throw is recorded in Middle Pleistocene deposits across the present Arno Valley. This tectonic phase probably continues at present, offshore Livorno, as evidenced by the epicentres of earthquakes.  相似文献   

10.
《Quaternary Science Reviews》2007,26(22-24):2823-2843
Fluvial and karstic data sets indicating Late Cenozoic surface uplift in the eastern United States are modelled for the first time using a technique, incorporating coupling between surface processes and flow in the lower continental crust, which has been extensively used for modelling similar data sets elsewhere in the world, notably in Europe. Distinct phases of lower-crustal flow forcing, starting in the early Middle Miocene, Late Pliocene, and late Early Pleistocene, are evident, as observed elsewhere, and relate to combinations of cyclic surface loading (by sea-level variations and ice loads) and to variations in regional erosion rates, as elsewhere. However, the detailed uplift histories inferred are rather different from those indicated in many other regions, notably Europe, primarily because of different properties of the crust. In particular, in the Late Proterozoic/Phanerozoic crust of the Appalachians, the mobile lower-crustal layer seems to be relatively thick, causing a prolonged uplift response for each phase of lower-crustal flow forcing, whereas in the Early Proterozoic crust of the Yavapai crustal province farther west, underlain by a thick basal mafic layer, this mobile layer is much thinner, leading to a very different response consisting of abrupt alternations of uplift and subsidence, as is also observed in other regions of Early Proterozoic crust. Another important difference relative to western and central Europe is the much smaller number of terraces in the eastern US rivers that have been studied. The general applicability of this type of physics-based modelling technique is thus confirmed.  相似文献   

11.
基于TM遥感图像解译和野外调研,分析了攀西地区大渡河、安宁河深切河谷地貌特征和断裂带构造变形特征,建立了安宁河断裂带晚新生代5阶段变形历史。研究表明,中新世晚期—上新世早期,安宁河断裂以挤压走滑活动为主;上新世晚期至早更新世时期,断裂以斜张走滑活动为主,活动强度较弱;早中更新世之间发生的元谋运动使昔格达组湖相地层褶皱变形;中晚更新世时期发生断陷作用,形成安宁河两堑夹—垒的构造格局;晚更新世—全新世时期又以左旋走滑活动为主。综合安宁河、大渡河河谷地貌和晚新生代地层记录和变形特征,提出了攀西高原晚新生代4阶段隆升模式:中新世早中期(12Ma之前)以缓慢隆升与区域夷平化作用为主,中新世晚期—上新世早期(12~3.4Ma)是高原快速隆升与河流强烈下切的时期,上新世晚期—早更新世(3.4~1.1Ma)为昔格达湖盆发育时期,中晚更新世—全新世(1.1Ma以来)是高原快速隆升与河谷阶地发育时期。最后指出,至上新世晚期(3.4Ma以前),攀西高原海拔高度可能超过了3000m。  相似文献   

12.
第四纪洞庭盆地赤山隆起与安乡凹陷升降运动的沉积记录   总被引:12,自引:0,他引:12  
通过地表地质调查和钻井资料,对第四纪洞庭盆地南部赤山隆起及其西侧安乡凹陷的沉积和地貌特征进行研究,进而探讨二者的升降过程。赤山隆起为居于洞庭盆地南部的小型抬升断块,主要受东、西边界正断裂所控制,长约18 km,宽4~5 km。隆起内早更新世汨罗组和中更新世新开铺组、白沙井组组成多级阶地。安乡凹陷内充填200~300 m厚的河流和湖泊相沉积,自下而上依次为早更新世华田组、汨罗组,中更新世洞庭湖组,晚更新世坡头组,全新世湖积、冲积等。地貌与沉积特征表明,早更新世—中更新世中期赤山隆起总体表现出抬升期与稳定期交替的脉动式抬升,而安乡凹陷则表现出缓慢与快速沉降交替的幕式沉降特征;前者构造较稳定期和构造抬升期分别对应于后者缓慢沉降期和快速沉降期。中更新世晚期二者因区域构造反转而整体抬升并遭受剥蚀。晚更新世—全新世安乡凹陷在拗陷背景下接受沉积。上述第四纪早期赤山隆起脉动式抬升与安乡凹陷幕式沉降的对应关系,为洞庭盆地与周边隆起的盆—山耦合过程提供了约束,同时暗示盆地断陷活动可能与地幔上隆导致中地壳物质自凹陷向周边迁移有关。  相似文献   

13.
14.
This study aims to reconstruct the Cenozoic and Pleistocene morphodynamic evolution of the Orb, a Mediterranean river which crosses all the structural units of the south Massif Central border. A geomorphological and sedimentological analysis of detrital deposits was carried out as a basis for correlating the different formations and reconstructing the palaeodrainage. Heavy minerals were used to reconstruct the main sedimentary palaeochannels since the Messinian. The successive Orb longitudinal profiles show anomalies which can be caused by structure and by interactions between fluvial dynamics and tectonics. Evidence of volcanic heavy minerals on the Faugères Mountains and in the Upper Pliocene deposits of the Languedocian piedmont demonstrates that a north–south flow took place during the Upper Pliocene. Nevertheless, a palaeo‐Orb existed at the place of the present course when the basaltic lava flows were spreading, but headward erosion did not reach them until the Upper Pleistocene, because the Orb middle and high terraces do not contain volcanic minerals sourced from the Escandorgue. The successive Orb longitudinal profiles show that headward erosion due to Pleistocene low sea levels does not reach beyond Béziers and that a tectonic hinge has functioned near the shoreline. The non‐lithologic knickpoints are explained by the Montagne Noire and Avant‐Monts uplift up until the Pleistocene. A progressive continental uplift is necessary to explain the Orb terraces staircase in the Béziers district, and the fluctuations of incision from upstream to downstream are due to laterally differential movements, which are isostatic effects of thick regressive deposits on the Gulf of Lion shelf during the cold periods. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

15.
The Fichtelgebirge and Steinwald areas are situated at the western end of the Cenozoic Eger graben. Repeated Neogene fault activity and polyphase morphogenesis created a complex morphotectonic structure. Based on morphotectonic criteria three stages of tectonic activity can be determined: (a) late Oligocene to early Miocene; (b) middle-late Miocene; and (c) late Pliocene to early Pleistocene. Due to the Neogene tectonic movements, the pre-basaltic (preOligocene to Miocene) landscape has been differentially uplifted/downthrown and intensely modified by post-basaltic surface planation (HF). Broad paleovalleys (AT) of late Miocene to early Pliocene age and a system of Pliocene and Quaternary fluvial terraces and pediments (BT and ET) have been incised into the widespread HF relief elements. Due to repeated faulting and erosion, the stratigraphic record of Neogene sediments within the studied area is fragmentary.  相似文献   

16.
CENOZOIC FAULTING ALONG THE SOUTHEASTERN EDGE OF THE TIBETAN PLATEAU IN THE YANYUAN AREA AND ITS TECTONIC IMPLICATIONS  相似文献   

17.
The Atlas Mountains have been uplifted by two mechanisms: Cenozoic thickening of the crust and thinning of the mantle lithosphere due to a buoyant thermal anomaly, previously inferred by indirect criteria to have started some 15 Ma. Because crustal shortening‐related uplift and mantle‐related uplift affect the topography at different spatial scales, we use scattered direct surface evidence to clarify the palaeoelevation dynamics. Uplifted Messinian shallow marine sediments in the southern margin of the Saïss Basin and in the northern Middle Atlas, tilted Pliocene lacustrine deposits in the Saïss Basin and in the piedmont of the southern High Atlas and drainage‐network reorganization in the Saïss Basin underscore the long‐wavelength rock uplift of the Atlas domain of mantle origin. The low erosion of the aforementioned deposits indicates that such uplift is a true surface uplift that occurred in post‐Miocene times at a minimum rate ranging from 0.17 to 0.22 mm yr?1.  相似文献   

18.
新疆库木库里盆地发育有巨厚的渐新统一更新统陆相沉积序列,记录了青藏高原西部自渐新世以来的隆起过程和幅度,盆地主夷平面形成于中中新世以后,上新世以前,该盆地中新世山旺生物群及上新世Cyprideis介形类动物群的发现显示了青藏高原中新世夷平作用这后的再次隆升并对中国自然环境变化产生了重大影响,导致中国西部生物组合由中新世晚期类似于现代江南山地的种类转变成为上新世以适应咸水环境为优势的组合,形成了西部内陆强蒸发的干旱环境,生物分异度大幅度降低,特别是库木里盆地晚更新世晚期乳动物化石的发现和含化石层的研究及区域对比,表明20-30ka以来高原存在一次幅度超逾百米的快速隆升。  相似文献   

19.
1. IntroductionThe Qinghai-Tibetan Plateau is an importantregion for the study of the global change andstructural evolution history). The in-depth knowledgeon its uplift process is the ke}' to understand theformation and development of temporary ph}'sicalenvironment of China or even East Asia. Therefore.a large quantity of researchers have given muchmore attention on this field (Burbank et al.. l982;Fang Xiaornin et al.. 1995f Ruddoman. ]997f AnZhisheng et al.. 1998). The macroscopic e\'o…  相似文献   

20.
Neotectonic observations allow a new interpretation of the recent tectonic behaviour of the outer fore arc in the Caldera area, northern Chile (27°S). Two periods of deformation are distinguished, based on large-scale Neogene to Quaternary features of the westernmost part of the Coastal Cordillera: Late Miocene to Early Pliocene deformations, characterized by a weak NE–SW to E–W extension is followed by uppermost Pliocene NW–SE to E–W compression. The Middle Pleistocene to Recent time is characterized by vertical uplift and NW–SE extension. These deformations provide clear indications of the occurrence of moderate to large earthquakes. Microseismic observations, however, indicate a lack of shallow crustal seismicity in coastal zone. We propose that both long-term brittle deformation and uplift are linked to the subduction seismic cycle.  相似文献   

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