Les séries silicoclastiques miocènes du Nord-Est au Sud-Ouest de la Tunisie : une mise au point

Abstract

During the Miocene time, the Atlas-pelagian block, which is limited northward by the atlasic-alpin chain of North Africa-Sicily, southward by the Gafsa–Jeffara–Azizia fault and eastward by the Malta escarpment, resulted from the extension-compression regime, mainly controlled by the subduction–collision processes. This regime induced the opening of many Miocene microbasins, which have been infilled by silicoclastic materials showing lateral and vertical facies variations and several hiatus associated to tectonic and stratigraphic unconformities. Excepting the very local transgressive regimes, such as those of Langhian and Messinian periods, most of the Miocene deposits took place on internal platforms, especially at the NE part of the country. The fluviodeltaic and alluvial sediments are, in fact, lateral equivalents which infilled the valley and depression enclosed systems towards the SW. In this context (rapid facies variations in time and space, superposition of tectonic and eustatic unconformities, climatic variations, rare or absent stratigraphic markers…), some controversies remain as regards the correlation and dating of these series. This work consists of a study of the lateral and vertical facies and thickness variations, coupled to the identification of the main unconformities. It is also a study of significance of the main sedimentological mechanisms and an inventory of the different palynological and paleontological content of the sediments. The aim of this work is to propose a new vision on the Miocene deposits in Tunisia along a NE–SW axis. Then, using these data, we have correlated the different lithological formations, discuss their age and, finally, proposed paleogeographical drafts for them.