کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4690827 1636173 2007 15 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Formation, deformation and chertification of systematic clastic dykes in a differentially lithified carbonate multilayer. SW Iberia, Algarve Basin, Lower Jurassic
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
Formation, deformation and chertification of systematic clastic dykes in a differentially lithified carbonate multilayer. SW Iberia, Algarve Basin, Lower Jurassic
چکیده انگلیسی

This work presents original field evidence for tectonically controlled calciclastic dyke injection and subsequent chertification in shelf carbonates during rifting in the south-westernmost part of the Eurasian continent in the Early Pliensbachian. It is shown by the detailed description of tectonic structures (faults and joints), stratigraphic discontinuities and by the distribution, orientation and morphology of the injected dykes of calciclastic sands into fine-grained carbonates, that these soft-sediment deformation structures were tectonically controlled. Extensional tectonics developed vertical tensile joints in semi-lithified, fine-grained limestones permitting upward and downward injection of loose calciclastic sands, forming clastic dykes. The frequency of injection structures along strata was constrained by the thickness of the layer into which the injection was occurring, which implies an elastic behaviour; however the curvi-planar shapes of the dykes and drop-like nodules attests the ductile behaviour of the fractured limestones, indicating transition from elastic to ductile response to deformation with time. The multi-layered system consists of just two lithotypes. The two display different mechanical behaviours, which evolved in time to more brittle conditions as lithification progressed, as shown by the cataclastic faulting and jointing of the previously formed soft-sediment deformation structures and strata under an analogous stress regime. The injection dykes were disrupted by a short-lived episode of compression, after which tectonic extension resumed, still in the Lower Pliensbachian. Sometime before the deposition of the Upper Pliensbachian a pervasive selective event of chertification occurred: only the calciclastic sandy layers, dykes and nodules were substituted by silica, thus enhancing the mechanical contrast between the primary sedimentary structures and the soft-sediment deformation structures. All the described events occurred during a time interval of approximately 2 Myr as constrained by ammonoid stratigraphy.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Sedimentary Geology - Volume 196, Issues 1–4, 15 March 2007, Pages 201–215
نویسندگان
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