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41.
Whilst earth surface landforms evolve largely as a result of the activity of certain living organisms, the biologically driven geomorphic changes have evolutionary consequences on organisms and ecological communities. Recognition of complex biotic–abiotic feedbacks may lead to deep changes in our understanding of geomorphology. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
42.
The Cenozoic geodynamics of the north‐eastern Mediterranean Basin have been dominated by the subduction of the African Plate under Eurasia. A trench‐parallel crustal‐scale thrust system (Misis–Kyrenia Thrust System) dissects the southern margin of the overriding plate and forms the structural grain and surface expression of northern Cyprus. Late Eocene to Miocene flysch of the Kythrea (De?irmenlik) Group is exposed throughout northern Cyprus, both at the hanging‐wall and foot‐wall of the thrust system, permitting access to an extensive Cenozoic sedimentary record of the basin. We report the results of a combined examination of detrital zircon and rutile U–Pb geochronology (572 concordant ages), coupled with Th/U ratios, Hf isotopic data and quantitative assessment of grain morphology of detrital zircon from four formations (5 samples) from the Kythrea flysch. These data provide a line of independent evidence for the existence of two different sediment transportation systems that discharged detritus into the basin between the late Eocene and late Miocene. Unique characteristics of each transport system are defined and a sediment unmixing calculation is demonstrated and explained. The first system transported almost exclusively North Gondwana‐type, Precambrian‐aged detrital zircon sourced from siliciclastic rock units in southern Anatolia. A different drainage system is revealed by the middle to late Miocene flysch sequence that is dominated by Late Cretaceous–Cenozoic‐aged detrital zircon, whose age range is consistent with the magmatic episodicity of southeast Anatolia, along the Arabia–Eurasia suture zone. Deposition of these late Miocene strata took place thereupon closure of the Tethyan Seaway and African–Eurasian faunal exchange, and overlap in time with a pronounced uplift of eastern Anatolia. Our analytical data indicate the onset of prominent suture‐parallel sediment transport from the collision zone of south‐eastern Anatolia into the Kyrenia Range of northern Cyprus, marking the drainage response to the continental collision between Arabia and Eurasia. 相似文献
43.
New aspects of rhomb structures 总被引：1，自引：0，他引：1
Dov Bahat 《Journal of Structural Geology》1983,5(6):591-601
The acute angles of 48 rhombic, trapezoidal and triangular grabens, horsts and upthrusts throughout the world were determined. The results indicate an angular spread of 7—73°. In most structures the two acute angles differ considerably. Most rhomb structures are grabens which show affinities to seismic faults, and only a few are horsts and upthrusts. In this connection modes of static crustal fracture propagation are compared to dynamic propagation. Rhomb structures occur along strike-slip faults and in rifts. These results question the universality of the pull-apart model as a mechanism for rhomb structure development. The two mechanisms that can lead to the formation of rhomb structures are (1) interaction of en échelon or non-coplanar fractures by shear and extensional modes and (2) fracture bifurcation in an extensional mode. The two mechanisms may result in faults of different shapes characterized by curved and straight boundaries, respectively. The grabens and horsts in extensional regions are the consequence of early fracture and later vertical displacements. 相似文献