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1.
《Geodinamica Acta》2002,15(5-6):277-288
A close relationship between formation of approximately upright folds with axes normal to the extension direction and ramp/flat extensional geometries is established for well exposed Neogene syn-extensional rocks on the presently low-angle Gediz detachment fault, along the southern margin of the Gediz Graben region of western Anatolia, Turkey. Three unconformity-bounded sedimentary sequences and several metamorphic extensional allochthons were mapped in the upper-plate of the Gediz detachment. The oldest sedimentary sequence consists of deformed and folded strata of sandstones and conglomerates that are regarded as being deposited in a supra-detachment basin during the Miocene–Early Pliocene. This unit rests unconformably on the extensional allochthonous, but directly in fault contact with the lower-plate mylonitic rocks. The younger slightly tilted Late Pliocene–Pleistocene sedimentary sequences are post-detachment units that are controlled by EW-trending high-angle normal faults. The youngest alluvium comprises the undeformed present-day basin fill of the Gediz Graben. The supra-detachment sedimentary rocks contain a number of kilometric-scale longitudinal folds that are nearly parallel to the east-west-trending fault system of the Gediz Graben. The folds have a steeply inclined bisecting surface, an interlimb angle of 130–150°, and a plunge of <10°. These folds may be interpreted to form as a result of bending in the underlying Gediz detachment fault. The bending may have an alternation of ramp and flat geometries on which a hanging-wall syncline and rollover anticline formed, respectively. This study again shows the importance of local geology in understanding of some spectacular structures of the extensional basins. 相似文献
2.
《Geodinamica Acta》2013,26(3-4):283-297
Western Turkey is a place of active continental extension, characterized by the occurrence of several WNW-ESE-trending major grabens. The central part of the northern edge of the Edremit Graben is delineated by various geological units, namely the metamorphic Kazda? Massif, the Mid-Cretaceous Çetmi mélange, the sedimentary Küçükkuyu formation, and loose Plio-Quaternary deposits. Detailed structural and sedimentological study suggests a two-stage extensional evolution of the area, separated by a short break in the tectonic regime. The first stage, possibly related to back-arc extension and/or orogenic collapse, is marked by the activity of a newly described low-angle detachment fault, the ?elale detachment fault, from the latest Oligocene onward. The fault plane, separating the mylonitized rocks of the Kazda? Massif in the footwall from the unmetamorphosed Çetmi mélange and Küçükkuyu formation in the hanging wall, must have played a significant role in the initial exhumation processes of the Kazda? Massif at that time. The Lower Miocene syntectonic Küçükkuyu formation has recorded the initiation and filling up of a small basin, which has developed in a typical supra-detachment basin, above the detachment fault. After a short phase of possible compression and erosion, the second stage—which marks the onset of neotectonic activity—is marked by the development of Plio-Quaternary step-like normal faults, which cut through all the previous units. Coarse, loose sediments were deposited following the fault activity. These local results are extrapolated to apply to the entire Edremit Graben. In that case, its evolution is seen as the succession of two extensional stages, characterized by distinct structural and sedimentological patterns, and possibly separated by a short compressional phase. 相似文献
3.
南海北部珠江口盆地中段伸展构造模型及其动力学 总被引：1，自引：0，他引：1
位于南海北部大陆边缘上的珠江口盆地发育NNE向、NE向、NW向、近EW向等多组基底断裂,盆地结构复杂,并表现出明显的时空差异性。本文基于珠江口盆地中段地震资料解释的构造样式的变化推断地壳中存在一条向南缓倾斜、呈坡坪式形态的拆离断层,古近系构造属于这条拆离断层上盘的伸展构造系统。北部的西江凹陷属于拆离断层伸展构造系统的头部,凹陷边界正断层铲式断层面形态向深层延伸并收敛在拆离断层面上,凹陷表现为半地堑“断陷”样式;中部的番禺低隆起对应于拆离断层的低角度断坪部位,拆离断层上盘断块的伸展位移导致两侧的恩平组超覆在低隆起上;南部的白云凹陷位于拆离断层的深部断坡部位,充填的文昌组和恩平组表现为“断坳”或“坳断”样式;南部隆起位于拆离断层深部断坪部位,其上盘发育的分支断层控制着荔湾凹陷古近系、新近系的发育并使之表现为复杂的断陷断坳构造样式。该模型强调拆离断层上盘与下盘、不同地壳结构层均发生不同程度的伸展变形,且伸展变形方式、应变量等存在时空差异,而拆离断层正是不同构造单元、不同地壳构造层之间的调节性构造面。总体上,拆离断层上盘以脆性伸展构造变形为主,分支断层控制不同构造单元古近纪的构造演化,下盘则是以韧性伸展变形为主,并拖曳上盘发生不均一的伸展应变;西江凹陷的伸展应变量大于拆离断层下盘的伸展应变量,白云凹陷的伸展应变量则小于拆离断层下盘的伸展应变量。以西江凹陷北部边缘的NE向铲式正断层为头部的拆离断层控制了文昌组沉积,但在恩平组沉积期被近EW向高角度正断层切割破坏而被遗弃,拆离断层系统的头部由西江凹陷北部边缘迁移至番禺低隆起。盆地结构及断裂系统的时空差异性受盆地基底先存构造、地壳与岩石圈结构及伸展量等多方面因素的影响,但主要是对软流圈流动及岩石圈热结构变化的响应。用软流圈由北西向南东流动拖曳上覆岩石圈发生伸展变形的动力学模型能合理地解释珠江口盆地中段古近系构造的形成和演化。 相似文献
4.
This paper describes how a model of fixed-hinge, basement-involved, fault-propagation folds may be adapted to apply to thin-skinned thrust faults to generate footwall synclines. Fixed-hinge, fault-propagation folding assumes that the fold-axial surfaces diverge upwards, fold hinges are fixed in the rock, the fault propagated through the forelimb, thickness changes occur in the forelimb and the forelimb progressively rotates with increasing displacement on the underlying fault. The original model for fixed-hinge, fault-propagation folds was developed for the case of a planar fault in basement with a tip line that was at the interface between basement and the overlying sedimentary cover rocks. The two geometries applicable to thin-skinned thrusts are for the cases where a fixed-hinge fault-propagation fold develops above an initial bedding-parallel detachment, and an initial fault ramp of constant dip which flattens down-dip into a bedding-parallel detachment. 相似文献
5.
The inversion of the Middle Proterozoic Belt sedimentary basin during Late Cretaceous thrusting in Montana produced a large eastwardly-convex salient, the southern boundary of which is a 200 km-long oblique to lateral ramp subtended by a detachment between the Belt rocks and Archean basement. A 10 km-long lateral ramp segment exposes the upper levels of the detachment where hanging wall Belt rocks have moved out over the Paleozoic and Mesozoic section. The hanging wall structure consists of a train of high amplitude, faulted, asymmetrical detachment folds. Initial west-east shortening produced layer parallel shortening fabrics and dominantly strike slip faulting followed by symmetrical detachment folding. “Lock-up” of movement on the detachment surface produced regional simple shear and caused the detachment folds to become asymmetrical and faulted. Folding of the detachment surface after lock-up modified the easternmost detachment folds further into a southeast-verging, overturned fold pair with a ramp-related fault along the base of the stretched mutual limb. 相似文献
6.
《Geodinamica Acta》2013,26(3):145-167
Folds constitute a significant part within the dominantly extension-related deformation pattern of the Gediz Graben and their origin either extensional or contractional has been the subject of debate. Field and subsurface data presented in this paper suggest that folds of contractional and extensional origin coexist in the graben-fill sediments. Contractional folds are predominantly observed within the Alasehir formation. A north vergent, plunging, asymmetrical to overturned geometry characterizes these folds and they are commonly observed in association with south dipping both thrust and reverse faults; the presence of thrust/reverse faults in the Gediz Graben is documented for the first time here. Fault data suggest an approximately N–S direction of compression that has governed the contractional deformation. Yet the limited distribution of these structures prevents to relate them with confidence to a regional deformation phase. Extensional folds occur in association with normal faults either as structures longitudinal or transverse with respect to the general graben trend. Transverse folds are a very common within the buried graben block, owing to the lateral displacement gradients (lateral difference in offset) on the individual fault segments along the southern margin of the graben. Synclines and anticlines have formed at displacement maxima and minima, respectively. Thickness of strata increases at synclines and decreases at anticlines, thus indicating the syn-depositional origin of the folding. 相似文献
7.
《Geodinamica Acta》2013,26(5-6):239-257
Neogene volcanic rocks and granitoid plutons are among the most important geological components of western Turkey. Although they are voluminous north of the Gediz Graben, they are very scarce to the south, where volcanic rocks occur as isolated small exposures in a small number of localities. The Kiraz Basin of the Küçük Menderes Graben is a key locality, in which Tertiary volcanic rocks crop out at three locations. These rocks have been chemically analysed and dated (39Ar-40Ar whole rock and biotite analyses) in order to understand their tectonic setting of emplacement and its relation to the wider structure of western Anatolia. Whole rock and biotite 39Ar-40Ar ages vary between 13.9 ± 0.2 Ma and 14.6 ± 0.2 Ma. The Kiraz volcanic rocks are calc-alkaline, with a compositional range from basaltic andesite to dacite. They are strongly enriched in the light ion lithophile elements (LILE) and have chemistries typical of lavas erupted in subduction-related settings. Their close association with rift-bounding faults suggests eruptions via conduits flanking grabens in an extensional environment. The difference in chemical composition and age between the Kiraz volcanic rocks and the slightly older calc-alkaline volcanic rocks north of the Gediz Graben is attributed to their relatively younger ages and greater proximity to the Aegean Arc. Their calc-alkaline chemistry reflects magma generation influenced by the slab descending beneath this arc and eruption/emplacement in an extensional setting. 相似文献
8.
We use scaled physical analog (centrifuge) modeling to investigate along- and across-strike structural variations in the Salt Range and Potwar Plateau of the Himalayan foreland fold-thrust belt of Pakistan. The models, composed of interlayered plasticine and silicone putty laminae, comprise four mechanical units representing the Neoproterozoic Salt Range Formation (basal detachment), Cambrian–Eocene carapace sequence, and Rawalpindi and Siwalik Groups (Neogene molasse), on a rigid base representing the Indian craton. Pre-cut ramps simulate basement faults with various structural geometries.A pre-existing north-dipping basement normal fault under the model foreland induces a frontal ramp and a prominent fault-bend-fold culmination, simulating the Salt Range. The ramp localizes displacement on a frontal thrust that occurs out-of-sequence with respect to other foreland folds and thrusts. With a frontal basement fault terminating to the east against a right-stepping, east-dipping lateral ramp, deformation propagates further south in the east; strata to the east of the lateral ramp are telescoped in ENE-trending detachment folds, fault-propagation folds and pop-up structures above a thick basal detachment (Salt Range Formation), in contrast to translated but less-deformed strata with E–W-trending Salt-Range structures to the west. The models are consistent with Salt Range–Potwar Plateau structural style contrasts being due to basement fault geometry and variation in detachment thickness. 相似文献
9.
Mustafa Bozcu 《International Journal of Earth Sciences》2010,99(4):851-861
The Büyük Menderes and Gediz (Ala?ehir) grabens are two significant segments of the Western Anatolian extensional province. They merge around Buldan-Sar?caova in the east. Outcropping Neogene sedimentary units in this area display a rather complex structure. This paper summarizes the importance and meaning of the data obtained during a detailed investigation of the Neogene units and aims to improve our understanding of the neotectonic evolution of Western Anatolia. The Buldan-Sar?caova Neogene sequence is composed of three different sedimentary units: (1) the Lower Unit, (2) the Middle Unit, and (3) the Upper Unit. The Lower Unit crops out on the Buldan horst which is located between the Büyük Menderes and Ala?ehir grabens. The sequence starts as a coarse conglomerate and sandstone (?salar Formation) and continues as lagoonal-lacustrine mudstone, interbedded with coal seams and shales (Bostanyeri Formation) and also with lacustrine limestones. The age of this succession is Lower-Middle Miocene. The development of the basin is structurally controlled by NNW-trending normal faults. The Middle Unit begins with a conglomerate–mudstone sequence (K?z?lburun Formation), followed by a sandstone–mudstone–marl sequence (Sarayköy Formation). A lacustrine limestone–marl unit occurs at the top (Aktepe Formation). Some thin gypsum lenses and layers are observed in the Sarayköy Formation. The unit contains some brackish-water fossils. The rocks of the Middle Unit crop out mostly at the low altitudes of the Buldan horst, i.e. the southeast piedmont, around the junction of the Büyük Menderes and the Gediz grabens. The Middle Unit was deposited in fluvial and lacustrine environments during the Late Miocene–Pliocene period. These rocks were formed in response to the uplift of the Buldan horst. The Upper Unit, which is composed of conglomerates, was deposited within the Büyük Menderes Graben–Gediz Graben depressions as alluvial fill. 相似文献
10.
《Geodinamica Acta》2013,26(2):131-144
An extensional event affected the southwest Margin of Iberia during Late Triassic to Early Cretaceous times, giving place to the Algarve basin. This basin was subjected to tectonic instability and it became infilled with siliciclastic and carbonate sequences with abundant interspersed volcanic rocks. Normal and strike-slip faults accommodated the deformation in the Algarve basin. The presence of a single flat or listric detachment surface is inferred from the study of hanging-wall structures. The dynamic and kinematic analyses of fault systems in the Spanish exposure of the Algarve basin allow us to establish three extensional phases. 1) A Late Triassic to Hettangian NE-SW directed extension associated with the initial breaking of Pangea and the opening of the Tethys in the eastern Mediterranean. 2) NW-SE extension from the Sinemurian to the Callovian, interpreted as a result of the activity as a sinistral fault of the Azores-Gibraltar transform boundary. 3) Finally, E-W extension during the Late Jurassic and Cretaceous, related to the North Atlantic rifting process. 相似文献
11.
Although it is generally considered that near-surface earthquakes result from movements along faults that cut through the surface, several recent large earthquakes have been partly attributed to blind thrusts. Movements along blind thrusts lead to the formation of surface folds, which are highly dependent upon fault geometry at depth and often not considered in seismic hazard evaluation. Several authors have studied the relationship between surface folding and thrusting for geological situations in which fault geometries are quite simple. However, active fault geometries can be quite complex e.g., segmented thrust faults associated with strike-slip faults. The aim of this contribution is to reconstruct the fault kinematics at depth for a relatively complex geological structure located in the Eastern Betic Cordilleras (Orihuela-Guardamar-Torrevieja region) using the patterns of kilometre-scale folds observed in the field. In order to model surface deformation, the assumption is made that surface km-scale folds have been created by coseismic deformation associated with movement along blind thrusts. By means of a coseismic deformation model, movements at depth have been calculated for three possible hypotheses. Hypothesis 1 assumes that each superficial fold is created by an independent fault. Hypotheses 2 and 3 assume that a sequence of two superficial folds can be created by movement along a single fault displaying a flat and ramp geometry. In Hypothesis 2, the flat is a superficial décollement level between the sedimentary cover and the Betic basement; in Hypothesis 3, it is a deeper décollement level within the Betic basement.
Knowing the approximate age of surface deformation, rough estimates of fault slip-rates and recurrence periods for two possible earthquake magnitudes (7 Ms and 6.7 Ms) have been made, from calculated dislocations at depth. Slip-rates and recurrence periods for flat and ramp fault geometries are in the range of 0.75–1 mm/yr and 1000–2000 yr, respectively. These values are close to those calculated by direct methods in similar seismotectonic contexts. 相似文献
12.
Colby J. Vandenburg Susanne U. Janecke William C. McIntosh 《Journal of Structural Geology》1998,20(12):1747-1767
The Horse Prairie basin of southwestern Montana is a complex, east-dipping half-graben that contains three angular unconformity-bounded sequences of Tertiary sedimentary rocks overlying middle Eocene volcanic rocks. New mapping of the basin and its hanging wall indicate that five temporally and geometrically distinct phases of normal faulting and at least three generations of fault-related extensional folding affected the area during the late Mesozoic (?) to Cenozoic. All of these phases of extension are evident over regional or cordilleran-scale domains. The extension direction has rotated 90° four times in the Horse Prairie area resulting in a complex three-dimensional strain field with 60% east–west and >25% north–south bulk extension. Extensional folds with axes at high angles to the associated normal fault record most of the three-dimensional strain during individual phases of extension (phases 3a, 3b, and 4). Cross-cutting relationships between normal faults and Tertiary volcanic and sedimentary rocks constrain the ages of each distinct phase of deformation and show that extension continued episodically for more than 50 My. Gravitational collapse of the Sevier fold and thrust belt was the ultimate cause of most of the extension. 相似文献
13.
《Quaternary Science Reviews》1999,18(4-5):549-554
The Gediz and the Büyük Menderes Graben basins, two of the most important structural elements of western Anatolia, markedly differ in their palaeogeographic evolution during the Holocene. On the basis of the study of the facies and the geomorphological characteristics of the youngest sedimentary fills it is suggested that the evolution of the Büyük Menderes basin has a simple progradational history while the Gediz River basin has shown a complex evolution mainly controlled by intense tectonic periods. Comparison between the palaeogeographic evolution of these basins points to the fact that tectonism has been more effective in the Gediz basin during the Holocene. 相似文献
14.
《Geodinamica Acta》2013,26(6):417-430
The Longi-Taormina Unit forms the “Dorsale calcaire” of the Peloritani Alpine Belt (southern Calabria-Peloritani Arc). It is made by a thick sedimentary cover of Meso-Cenozoic age overlying a Variscan weakly metamorphosed Cambrian to Carboniferous succession. The Palaeozoic series consists of pelitic to arenaceous sediments containing layers of acidic and basic volcanics. The acidic volcanics are affected by the “Caledonian” compressional deformations and are referred to Early Ordovician. The basic rocks belong to two different volcanic cycles; the first, not dated, is ascribed to the Caledonian cycle according to its geochemical signature; whereas the second, middle-late Devonian in age, is interpreted to have formed in the framework of pre-Variscan extensional tectonics. During the Variscan Orogeny (330 Ma), the area recorded metamorphism up to subgreenschist-to-greenschist facies and two main deformation phases, marked by syn-schistose early folds (Dv1), overprinted by dominantly NW-SE trending late folds (Dv2). During the Aquitanian, deformation related to the Alpine Orogeny led to imbrication of the Palaeozoic and Meso-Cenozoic series. The sedimentary cover was affected by a series of N090° to N130° trending folds. Detailed stratigraphical and structural investigations on the tectonic contact between the Longi-Taormina Unit, and the overlying Fondachelli Unit indicate that this structure is part of a frontal thrust ramp which developed during the Aquitanian. Our geological and structural studies on the Cambrian to Aquitanian rocks of the Longi-Taormina Unit of the Calabria-Peloritani Arc enable to unravel the complex geodynamic history of the central-western Mediterranean area. 相似文献
15.
《International Geology Review》2012,54(11):967-982
We present an outcrop-scale example of a localized contractional fault geometry that developed as part of an imbricate normal fault system in response to regional extension. Although extensional regions are dominated by abundant normal faulting, local thrust duplication may occur during the same phase of deformation, and on a regional scale may concentrate important quantities of hydrocarbons. Characteristics of extension-related fold belts have mostly been derived from seismic sections; thus fault geometries, mechanisms of formation, and kinematics of these structures are not precisely understood. Abundant kinematic indicators and complete exposure of an extended sedimentary sequence within the Dead Sea Transform, however, provide the opportunity to examine these fault geometries and mechanisms in detail. The local contractional geometry developed within an imbricate normal fault system, as a result of an out-of-sequence normal fault that detached at a higher structural level. The out-of-sequence normal fault offset pre-existing faults, but was deflected into a contractional geometry upon encountering an earlier-formed rollover anticline, whose curved bedding surface served as a convenient ramp. Consequently, displacement across the out-of-sequence fault generated coeval extensional and contractional geometries along the same detachment surface. Geometries and kinematics derived from the outcrop structural analysis may serve as important analogs for larger structures identified as potential targets for hydrocarbon exploration. 相似文献
16.
《Geodinamica Acta》2013,26(3-4):239-253
The precise ages of the sedimentary successions within two prominent NE-SW-trending basins, the Gördes Basin and the Selendi Basin, are critical to an understanding of the Neogene evolutionary setting of western Turkey and associated calc-alkaline magmatism. Early radiometric dating was not always sufficiently precise to resolve alternative interpretations. During this study, high-precision Ar40-Ar39 radiometric ages were determined on single crystals of biotite and sanidine from silicic tuffs and associated intrusive rocks. Finegrained tuffaceous sediments near the top of the sedimentary succession in the Selendi Basin gave ages of 18.89 ± 0.58 Ma to 16.42 ± 0.09 Ma. Coarser-grained tuffaceous sediments near the top of the equivalent sedimentary succession in the Gördes Basin to the NW yielded ages of 18.78 ± 0.3 Ma to 17.04 ± 0.35 Ma. Associated intrusive rocks were dated at 20.86 ± 0.08 Ma to 17.62 ± 0.07 Ma. An andesitic body on the northern margin of the Gediz (Ala?ehir) Graben further south gave ages of 16.08 ± 10.91 to 14.65 ± 0.06 Ma. Combined with published radiometric age data, these new results confirm an Early Miocene age for the clastic sedimentary fills of the Gördes and Selendi basins. The results from the Gediz Graben are consistent with its formation in Early Miocene time, earlier than the Late Miocene or Plio-Quaternary ages suggested in some interpretations. 相似文献
17.
The Southern Rhodope Core Complex is a wide metamorphic dome exhumed in the northern Aegean as a result of large-scale extension
from mid-Eocene to mid-Miocene times. Its roughly triangular shape is bordered on the SW by the Jurassic and Cretaceous metamorphic
units of the Serbo-Macedonian in the Chalkidiki peninsula and on the N by the eclogite bearing gneisses of the Sideroneron
massif. The main foliation of metamorphic rocks is flat lying up to 100 km core complex width. Most rocks display a stretching
lineation trending NE–SW. The Kerdylion detachment zone located at the SW controlled the exhumation of the core complex from
middle Eocene to mid-Oligocene. From late Oligocene to mid-Miocene exhumation is located inside the dome and is accompanied
by the emplacement of the synkinematic plutons of Vrondou and Symvolon. Since late Miocene times, extensional basin sediments
are deposited on top of the exhumed metamorphic and plutonic rocks and controlled by steep normal faults and flat-ramp-type
structures. Evidence from Thassos Island is used to illustrate the sequence of deformation from stacking by thrusting of the
metamorphic pile to ductile extension and finally to development of extensional Plio-Pleistocene sedimentary basin. Paleomagnetic
data indicate that the core complex exhumation is controlled by a 30° dextral rotation of the Chalkidiki block. Extensional
displacements are restored using a pole of rotation deduced from the curvature of stretching lineation trends at core complex
scale. It is argued that the Rhodope Core Complex has recorded at least 120 km of extension in the North Aegean, since the
last 40 My. 相似文献
18.
断展褶皱要素对隐伏滑脱层深度及几何样式的约束:数学分析及其在重庆地区薄皮构造中的应用 总被引：1，自引：0，他引：1
根据平衡地质剖面原理,在前人建立的断展褶皱数学模型基础上,进一步推导出断展褶皱要素组合对隐伏滑脱层发育深度和几何样式的限定。需要给定的参数组合包括:断展褶皱后翼倾角2θ、翼间角γ、背斜的构造高度h、背斜的宽度LAB、断端点T以上地层厚度h0。这些参数均可由野外实测或地震剖面解释中给定。由这些参数可以推导出:断坡的倾角α、断坡的顶点T到断层滑距开始降低的点P的距离LTP、地层的压缩量f0、隐伏滑脱层的深度h’。将此推导过程用VC++编程软件ZB1.0加以实现。根据地震剖面的解释及地表资料整理结果,把上述演算结果应用于重庆方斗山地区的茨竹亚背斜的2个剖面中,计算出隐伏滑脱层的深度分别为8.10~8.63 km,证明茨竹亚背斜隐伏主滑脱层发育于寒武系底部。滑脱断层断坡倾角为29°~45,°属于中等倾角。这一研究成果既可在理论上定量计算隐伏滑脱层样式和深度,又能指导对潜伏构造的勘探实践。 相似文献
19.
Kadir Dirik 《Geodinamica Acta》2013,26(1-3):147-158
AbstractCentral Anatolia has undergone complex Neotectonic deformation since Late Miocene-Pliocene times. Many faults and intracontinental basins in this region were either formed, or have been reactivated, during this period. The eastern part of central Anatolia is dominated by a NE-SW-trending, left lateral transcurrent structure named the Central Anatolian fault zone located between Sivas in the northeast and west of Mersin in the southwest. Around the central part, it is characterized by transtensional depressions formed by left stepping and southward bending of the fault zone. Pre-Upper Miocene basement rocks of the region consist of the central Anatolian crystalline complex and a sedimentary cover of Tertiary age. These rock units were strongly deformed by N-S con- vergence. The entire area emerged to become the site of erosion and formed a vast plateau before the Late Miocene. A NE-SW- trending extensional basin developed on this plateau in Late Miocene-Early Pliocene times. Rock units of this basin are characterized by a thick succession of pyroclastic rocks intercalated with calcalkaline-alkaline volcanics. The volcanic sequence is uncon- formably overlain by Pliocene lacustrine-fluviatile deposits interrelated with ignimbrites and tuffs. Thick, coarse grained alluvial/colluvial fan deposits of marginal facies and fine grained elastics and carbonates of central facies display characteristic synsedimentary structures with volcanic intercalations. These are the main lines of evidence for development of a new transtensional H?rka— k?zd?rmak basin in Pliocene times. Reactivation of the main segment of the Central Anatolian fault zone has triggered development of depressions around the left stepping and southward bending of the central part of this sinistral fault zone in the ignimbritic plateau during Late Pliocene-Quaternary time. These transtensional basins are named the Tuzla Gölü and Sultansazl??? pull-apart basins. The Sultansazl??? basin has a lazy S to rhomboidal shape and displays characteristic morphologic features including a steep and stepped western margin, large alluvial and colluvial fans, and a huge composite volcano (the Erciyes Da??).The geometry of faulting and formation of pull-apart basins can be explained within the framework of tectonic escape of the wedgelike Anatolian block, bounded by sinistral East Anatolian fault zone and dextral North Anatolian transform fault zone. This escape may have been accomplished as lateral continental extrusion of the Anatolian Plate caused by final collision of the Arabian Plate with the Eurasian Plate. © 2001 Éditions scientifiques et médicales Elsevier SAS 相似文献
