Thrust sequence and syntectonic sedimentation in a piggy-back basin: the Oligo-Aquitanian Mula–Pliego Basin (Internal Betic Zone, SE Spain)
The Oligo-Aquitanian deposits of the Mula–Pliego basin consist of a marine carbonate platform assemblage (bottom), transitioning into a turbidite wedge (top). This evolution was controlled by tectonics in a piggy-back basin by means of three main mechanisms: first, a flexural tectonic event created the basin; later on, blind-fault-propagation folds deformed it progressively from south to north; finally a tectonic event destroyed the basin. To cite this article: M. Martin-Martin, A. Martin-Algarra, C. R. Geoscience 334 (2002) 363–370.
Carbonate Ramps Drowning and Giant Slope Reef Mounds Growing in a
The hydrocarbon exploration require a detained understanding in foreland basins of the synchronous evolution between the foredeep and the forebulge: their lateral shifts may control either the size, the nature and the post depositional evolution of such good traps as carbonate buidups. This study describes the stepwise drowning of the Russian carbonate Platform located on the foreland margin of the prograding West Uralian foredeep during the Upper Paleozoic and the synchronous evolution of giant slope reef mounds. The Urals are a long, linear fold-thrust belt (2500 km long, 200 km wide and 1800 m high) at the boundary of Europe and Asia corresponding to the Upper Paleozoic suture of the Laurussian, Siberian and Kazakh cratons. The sedimentary cover of the Russian Platform that constitutes the Late Paleozoic foreland (Mid Carboniferous-Permian) of the Uralian fold belt is ca 3000 metresthick. A typical section in the foreland basin exhibits from base to top: (1) deepening upward, wave-dominated to turbiditic carbonate ramp deposits from late Visean to Late Artinskian-Kungurian times bordered by slope reefs mounds from the Kasimovian and huge ones in the lower Permian. (2) shaly condensed section with volcaniclastics, radiolarites, glauconite and phosphorites, (3) shallowing upward section of polymictic turbidites ending to coarse-grained fan deltas, evaporites and meandering rivers red beds by the late Permian. Westward, towards the Russian Platform, the terrigenous deposits thin out, the carbonate ramps become lacunar and evolve towards emersion. Weathering and karstification processes are the rule. From the Kasimovian to early Artinskian four reef mounds end-members are recognised: (1)KasimovianGhzelian biostroms and banks, 5 to 50 meters in thickness made up of Paleoaplysina, phylloid algae, corals and bryozoans; (2)Asselian-Sakmarian giant reef mounds, 150 to 350 meters thick, composed of bryozoans, Tubiphytes and Archaeolithoporella; (3)Artinskian bioherms and banks, 10 to 50 meters thick, with bryozoans, Tubiphytes, sponges and brachiopods; (4)Kungurian biostroms and patch reefs with stromatolites.
Sedimentation of the late geosynclinal stage
Abstract The sediments of the Upper Eocene to Middle Miocene Ranzano-Bismantova sequence of the Padan side of the Northern Apennines are considered late geosynclinal, because they were formed after the Middle Eocene folding stage in the Ligurian domain and were later involved in the main westward movement of the Allochthon. The sediments were essentially clastic. During the Oligocene they were deposited in adeep-water marine environment, in part by turbidity currents and slumping (e.g., Ranzano Sandstone); later, the environment tended to become shallower (e.g., Bismantova Formation) and deposition was by turbidity and normal currents. Other sediments in a clearly similar structural situation occur in eastern Tuscany and in the Romagna Apennines; they are of Middle to Late Miocene age and were formed in a shallow marine environment. This paper summarized published information on the lithology, stratigraphy and structural relations of the late geosynclinal rocks, and its includes a summary of paleogeographic evolution. It is also pointed out that in the Northern Apennines the late geosynclinal stage is defined essentially on the basis of structural relations. The term molasse, as understood in the Swiss Alps, applies only to parts of the sequences and, in general, it cannot be equalled with late geosynclinal sediments ( Aubouin , 1965).