Sedimentary facies and ammonites relations between Arequipa and Tacna during Lower to Middle Jurassic

Abstract

Arequipa basin has been studied by different authors, such as Jenks (1848), Wells (1953), Benavides (1962), Vargas (1970), Leon (1981) and Vicente (1981). These authors refer to the layers of the Chocolate Formation (Lower Jurassic) in Arequipa, as a succession of andesitic and sedimentary rocks, containing Sinemurian ammonites. There are geological investigations in localities of Tacna made by Wilson & Garcia (1962), Jaen & Ortiz (1963), Salinas (1987), among others; whose produce the first geological maps of the zone. Currently, data showed in this report (stratigraphic columns, ammonites paleontology) (Fi. 2), corresponds to a set of information not yet publicated, obtained from INGEMMET field jobs. Data sets were taken from outcrops along coastal strip of southern Peru, in localities of Yura (Department of Arequipa) and ceros Palquilla and Pelado (Department of Tacna) (Fig. 1), within the Arequipa Mesozoic basin, southern Peru. Lower and Middle Jurassic sediments have been analizad in Arequipa (Yura) and Tacna (cerros Palquilla and Pelado) in terms of stratigraphy, sedimentology and paleontology. A taphonomic study of ammonites and its paleoenvironmental and chronological implicances and has been related one to another.