Turbiditas asociadas a evaporitas(Mioceno, La Malá, Depresión de Granada)

Abstract

The Granada Basin is one of the most typical intramontane basins in the Betic Cordilleras. A turbidite-evaporitic sequence of upper Miocenic age is one of the deposita found in the Malá area (SW of Granada). Deposition occured in a sea which was closed in and where water circulation was restricted and only episodically comunicated with the open sea; thus it is a transition from a marine to a lacustrine environment. The sequences of primary internal sedimentary structures sole marks on sandstone beds and the mineralogical composition and texture of sandstones, indicate deposition by turbidity currents. The intercalated evaporite layers and the presence of hard grounds in the lutitic beds as well as the absence of autochtonous fossils are noteworthy inasmuch as they constitute the only features which dífferenciate these materials from the actually being deposited in deep marine basins. Tbe lack of autochtonous fossils and biogenic structures is explained by the hypersality of the waters, where life would be practically impossible. On the basis of the paleocurrents and the mineralogical composition of the sandstones, the turbidity currents were proved to originate in the Sierra Nevada area. The regional and paleogeographical data lead us to believe that fue shore line was located 20 Km. to the East. The turbidity currents flowed from the Sierra Nevada margins to the interior of an evaporitic basin and sediments supplied by there currents became interbedded in the evaporitic sequence. There currents carried sediments in succesive flows either from materials carried by Sierra Nevada rivers or from deposits previously accumulated at their mouths. Finally, a comparison is made of this facies with flysch, taking into account the definitions and concepts of different authors. Since we are dealing with materials displaying postorogenic character tue term turbidite is used instead of flysch.