Bio-sédimentaire de l’unité " sénonienne" (Crétacé-Eocène) de l’Oranie

Abstract

The study area is located in the north western part of Algeria, which is part of the Southern Tellian field. The studied land belong to the immigrant to Tellian affinities where the upper Eocene-Cretaceous deposits belong to the Senonian unit. Their study uses multiple approaches to order lithobiostratigraphique, paleoecological and paleobiogeographic. The lithobiostratigraphique study based on planktonic foraminifera has established a new division of well-individualized biozones. The study association’s ostracods highlight eleven Paleoecologicalecozones. Regional bathymetric evolution during the Late Cretaceous indicates a transgressive phase for épibathyale area. The transition to the lower Paleocene, the water column moving towards épibathyale area up to the mésobathyale area using Paleocene. From the Paleocene and Eocene until the environment sees a lowering of sea level to the continental shelf. The study area is characterized, during the interval analyzed by two major events: First, during the Cretaceous-Paleocene transition denotes a considerable impoverishment of wildlife ostracods; then, during the passage Paleocene-Eocène IETM is the area marked by a fall in ostracods and even the total absence. The Oran region see appear the movements of several species that indicate local palaeobiogeographic relationship then with the regions of South Tethyan province. Definitely, the appearance of the forms from the Atlantic coast until Mediterranean shows a phase of standardization as ecological conditions that palaeobiogeographic undoubtedly due to the opening of the Atlantic. The overall palaeobathymetry evokes similarities with the global eustatic scheme: transgression-regression but with the changing rate of the C13 isotope test carbonates.