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31.
32.
Christine Authemayou Olivier Bellier Dominique Chardon Zaman Malekzade Mohammad Abassi 《Comptes Rendus Geoscience》2005,337(5):539-545
Field structural and SPOT image analyses document the kinematic framework enhancing transfer of strike-slip partitioned motion from along the backstop to the interior of the Zagros fold-and-thrust belt in a context of plate convergence slight obliquity. Transfer occurs by slip on the north-trending right-lateral Kazerun Fault System (KFS) that connects to the Main Recent Fault, a major northwest-trending dextral fault partitioning oblique convergence at the rear of the belt. The KFS formed by three fault zones ended by bent orogen-parallel thrusts allows slip from along the Main Recent Fault to become distributed by transfer to longitudinal thrusts and folds. To cite this article: C. Authemayou et al., C. R. Geoscience 337 (2005). 相似文献
33.
中国古代海相钾盐找矿是一个"久攻不破"的难题,古代海相及海陆交互相盆地能否成钾也是长期争议的问题,也就是中国小陆块能否成钾、成大钾矿的关键问题。为此,本文以板块构造运动为主线,对中国主要小陆块漂移历史、成盆构造、古气候、古地理及海相/海陆交互相蒸发岩沉积特征进行了系统梳理和总结;在此基础上,基于盆地"构造-物源-气候"三要素耦合成钾理论,分析中国小陆块海相盆地成钾条件、成矿机理;同时,总结和借鉴全球海相钾盐成矿标志,建立钾盐成矿评价指标体系。基于这些研究基础,借助对主要陆块的区域构造和古地理特征、物质来源、古气候面貌等恢复及分析,对主要陆块的海相成钾潜力进行评价,同时预测找钾战略靶区。钾盐成矿模式研究表明:兰坪—思茅盆地白垩系、上扬子陆块四川盆地中—下三叠统、华北陆块陕北盆地中奥陶统及塔里木陆块库车盆地古近系等盆地及其层位具有较大的成钾潜力。结合成钾指标对比分析,优选圈定了思茅盆地南部、四川盆地中东部及塔里木的库车盆地等战略靶区内较为明确的重点靶区,可以进一步开展钻探验证。这些研究成果为在中国继续开展海相钾盐成矿研究和找钾提供科学依据。 相似文献
34.
Tim Pharaoh 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):278-328
The surface geology of central England and Belgium obscures a large ‘basement’ massif with a complex history and stronger crust and lithosphere than surrounding regions. The nucleus was forged by subduction-related magmatism at the Gondwana margin in Ediacaran time. Partitioning into a platform, in the English Midlands, and a basin stretching to Belgium, in the east, was already evident in Cambrian/earliest Ordovician time. The accretion of the Monian Composite Terrane during the Penobscotian deformation phase preceded late Tremadocian rifting, and Floian separation, of the Avalonia Terrane from the Gondwana margin. Late Ordovician magmatism in a belt from the Lake District to Belgium records subduction beneath Avalonia of part of the Tornquist Sea. This ‘Western Pacific-style’ oceanic basin closed in latest Ordovician time, uniting Avalonia and Baltica. Closure of the Iapetus Ocean in early Silurian time was soon followed by closure of the Rheic Ocean, recorded by subduction along the southern margin of the massif. The causes of late Caledonian deformation are poorly understood and controversial. Partitioned behaviour of the massif persisted into late Palaeozoic time. Late Devonian and Carboniferous sequences show strong onlap onto the massif, which was little affected by crustal extension. Compressional deformation during the Variscan Orogeny also appears slight, and was focussed in the west where a wedge-shaped mountain foreland uplift was driven by orogenic indentation, splitting the massif from the Welsh Massif along the reactivated Malvern Line. Permian to Mesozoic sequences exhibit persistent but variable degrees of onlap onto the massif. 相似文献
35.
Jonathan R. Lee Ian Candy Richard Haslam 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):452-481
During the Neogene and Quaternary, tectonic and climatic processes have had a profound impact upon landscape evolution in England and, perhaps as far back as 0.9 Ma, patterns of early human occupation. Until the Late Miocene, large-scale plate tectonic processes were the principal drivers of landscape evolution causing localised basin inversion and widespread exhumation. This drove, in places, the erosion of several kilometres of Mesozoic cover rocks and the development of a regional unconformity across England and the North Sea Basin. By the Pliocene, the relative influence of tectonics on landscape evolution waned as the background tectonic stress regime evolved and climatic influences became more prominent. Global-scale climate-forcing increased step-wise during the Plio-Pleistocene amplifying erosional and depositional processes that operated within the landscape. These processes caused differential unloading (uplift) and loading (subsidence) of the crust (‘denudational isostasy’) in areas undergoing net erosion (upland areas and slopes) and deposition (basins). Denudational isostasy amplified during the Mid-Pleistocene Transition (c.0.9 Ma) as landscapes become progressively synchronised to large-scale 100 ka ‘eccentricity’ climate forcing. Over the past 0.5 Ma, this has led to the establishment of a robust climate record of individual glacial/interglacial cycles enabling comparison to other regional and global records. During the Last Glacial-Interglacial Transition and early Holocene (c.16–7 ka), evidence for more abrupt (millennial/centennial) scale climatic events has been discovered. This indicates that superimposed upon the longer-term pattern of landscape evolution is a more dynamic response of the landscape to local and regional drivers. 相似文献
36.
Renas I. Koshnaw Brian K. Horton Daniel F. Stockli Douglas E. Barber Mazin Y. Tamar-Agha 《Basin Research》2020,32(4):688-715
In the northwestern sector of the Zagros foreland basin, axial fluvial systems initially delivered fine-grained sediments from northwestern source regions into a contiguous basin, and later transverse fluvial systems delivered coarse-grained sediments from northeastern sources into a structurally partitioned basin by fold-thrust deformation. Here we integrate sedimentologic, stratigraphic, palaeomagnetic and geochronologic data from the northwestern Zagros foreland basin to define the Neogene history of deposition and sediment routing in response to progressive advance of the Zagros fold-thrust belt. This study constrains the depositional environments, timing of deposition and provenance of nonmarine clastic deposits of the Injana (Upper Fars), Mukdadiya (Lower Bakhtiari) and Bai-Hasan (Upper Bakhtiari) Formations in the Kurdistan region of Iraq. Sediments of the Injana Formation (~12.4–7.75 Ma) were transported axially (orogen-parallel) from northwest to southeast by meandering and low-sinuosity channel belt system. In contrast, during deposition of the Mukdadiya Formation (~7.75–5 Ma), sediments were delivered transversely (orogen-perpendicular) from northeast to southwest by braided and low-sinuosity channel belt system in distributive fluvial megafans. By ~5 Ma, the northwestern Zagros foreland basin became partitioned by growth of the Mountain Front Flexure and considerable gravel was introduced in localized alluvial fans derived from growing topographic highs. Foredeep accumulation rates during deposition of the Injana, Mukdadiya and Bai-Hasan Formations averaged 350, 400 and 600 m/Myr respectively, suggesting accelerated accommodation generation in a rapidly subsiding basin governed by flexural subsidence. Detrital zircon U-Pb age spectra show that in addition to sources of Mesozoic-Cenozoic cover strata, the Injana Formation was derived chiefly from Palaeozoic-Precambrian (including Carboniferous and latest Neoproterozoic) strata in an axial position to the northwest, likely from the Bitlis-Puturge Massif and broader Eastern Anatolia. In contrast, the Mukdadiya and Bai-Hasan Formations yield distinctive Palaeogene U-Pb age peaks, particularly in the southeastern sector of the study region, consistent with transverse delivery from the arc-related terranes of the Walash and Naopurdan volcano-sedimentary groups (Gaveh-Rud domain?) and Urumieh-Dokhtar magmatic arc to the northeast. These temporal and spatial variations in stratigraphic framework, depositional environments, sediment routing and compositional provenance reveal a major drainage reorganization during Neogene shortening in the Zagros fold-thrust belt. Whereas axial fluvial systems initially dominated the foreland basin during early orogenesis in the Kurdistan region of Iraq, transverse fluvial systems were subsequently established and delivered major sediment volumes to the foreland as a consequence of the abrupt deformation advance and associated topographic growth in the Zagros. 相似文献
37.
The Upper Quaternary seismic stratigraphy and active faults of the Gulf of İzmit were investigated by means of high-resolution
shallow seismic profiling data in the source region of 1999 İzmit earthquake. High-resolution seismic reflection data correlated
with borehole data indicate that the stratigraphy of İzmit Bay consists of three distinct depositional sequences formed in
response to middle Pleistocene-Holocene sea-level changes. Reflector R, separating the pre-Holocene sequences (1 and 2) from
the Holocene sequence (3), represents an erosional unconformity produced by the subaerial fluvial erosion of the continental
shelves at the time of the last glacial maximum. Occasional, anomalous reflections (acoustic turbidity) observed within the
Holocene sequence are interpreted as gas accumulations. The maximum thickness of the Holocene sediments is found to be about
25 m. The isopach map of Holocene sediment implies that the thickness of the Holocene decreases from the east towards the
central and western basins of İzmit Bay. Two distinct fault systems are interpreted in İzmit Bay. The main fault system extending
roughly in an E-W direction along the Gulf of İzmit is an active right lateral strike slip fault with a normal component.
The secondary faults are normal faults striking in different directions and these are identified as being both active and
inactive. In addition, prominent compressive features are identified in the seismic cross-sections of some profiles acquired
to the east of Hersek Peninsula where the focal mechanisms of the aftershocks of the 1999 İzmit earthquake also reveal predominantly
reverse faulting mechanisms, as identified by a local dense seismic network. 相似文献
38.
L. Cocchi F. Caratori Tontini C. Carmisciano M. Marani 《Marine Geophysical Researches》2008,29(4):251-266
We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northwestern edge of the southern Tyrrhenian
Basin. The tectonic evolution of the Tyrrhenian Basin is dominated by a Tortonian-Quaternary extension through the eastward
movement of the Apennine subduction system. This migration has generated a diffuse stretching of the continental crust with
the emplacement of new oceanic material. This latter occurred in several localized zones where the eastward retreating of
the Ionian subduction system produced a strong depletion of the crust with formation of basins and correlated spreading. Nowadays
the presence of oceanic crust is confirmed through direct drilling investigation but a complete mapping of the oceanic crustal
distribution is still lacking. The Selli-Vavilov region shows a differentiated crustal setting where seamount structures,
the oceanic basement portions and continental crust blocks are superimposed. To this aim, a 2D inversion of the magnetic data
of this region was conducted to define buried structures. The magnetic susceptibility pattern was computed by solving the
least squares problem of the misfit between the predicted and real data for separated wavebands. This method produced two
2D models of the high and low frequency fields of the Selli-Vavilov region. The two apparent susceptibility maps provide different
information for distinct ranges of depth. The results of the inversions were also combined with seismic data of the Selli
region highlighting the position of the highly magnetized buried bodies. The results confirm a role for the Selli Line as
a deep crustal boundary dividing the Sardinian passive domain from the easternmost active region where different oceanic structures
are located. The Selli Line has worked as a detachment fault system which has moved eastward. Finally, the Selli-Vavilov region
may be interpreted as a tectonic result due to a passive asymmetrical rift occurred between the Tortonian and Pliocene. 相似文献
39.
40.
Jan Pleuger Sybille Roller Jens M. Walter Ekkehard Jansen Nikolaus Froitzheim 《International Journal of Earth Sciences》2007,96(2):229-252
The boundary zone between two Penninic nappes, the eclogite-facies to ultrahigh-pressure Zermatt-Saas zone in the footwall
and the blueschist-facies Combin zone in the hanging wall, has been interpreted previously as a major normal fault reflecting
synorogenic crustal extension. Quartz textures of mylonites from this fault were measured using neutron diffraction. Together
with structural field observations, the data allow a refined reconstruction of the kinematic evolution of the Pennine nappes.
The main results are: (1) the contact is not a normal fault but a major thrust towards northwest which was only later overprinted
by southeast-directed normal faulting; (2) exhumation of the footwall rocks did not occur during crustal extension but during
crustal shortening; (3) the Sesia-Dent Blanche nappe system originated from a continental fragment (Cervinia) in the Alpine
Tethys ocean, and the Combin zone ophiolites from the ocean basin southeast of Cervinia; (4) out-of-sequence thrusting played
a major role in the tectonic evolution of the Penninic nappes.
An erratum to this article can be found at 相似文献