Paleoenvironmental Synthesis of the Meridional part of Tafna basin

Abstract

The paleontological study at the meridional part of Tafna Basin that consists of thre sections (Ain Youcef, Route Amieur and Oued Bir Moka section) with the aim of clarifying the paleoecological conditions that prevailed during the upper Miocene period. this study aims at establishing the vertical evolution of benthic foraminifera. In general 22 and 19 taxa have been determined in AinYoucef and Route Amieur respectively. The species got generally hyaline and porcelaneous tests. The barren levels may indicat to high influx of detrital sediments, this latter is materialised by the lithological natures of that levels (sandy marls). The epiphytic taxa are omnipresent from the basal tote summit parts of the whole sections. This presence is the sign of a weak transport of the microfauna as an autochthony of foraminifera assemblages. The mixture of deep forms and coastal forms is thus very limited. The microfaunistic analysis allowed us to define Paleoecological Unit I; dominated by Ammonia and the Paleoecological Unit II; shows no dominance. Thus; the comparison of quantitative results (biocoenotic indices) and qualitative results (analysis of the taxonomic set) leads to consistent results. While the low values of pelagic index corresponds always to low number benthics species, as well as, the high values corresponds to an important number (diversity) of species. As a whole, benthic foraminifera in the three section erefer to shallow marine environment (costal to upper bathyal).