Characterisation of Mesozoic-Cenozoic deformations and palaeostress fields in the Central Constantinois, northeast Algeria

Tectonic analysis in conjunction with the microtectonic study of Mesozoic-Cenozoic series of the Central Constantinois of Algeria are used to reconstruct the sequence of tectonic phases since Cretaceous times. The retrotectonic method used to marshal the microtectonic data makes it possible to distinguish deformations related to Mesozoic tectonic phases from those associated with Cenozoic pre- and post-thrust sheet phases. A N120 degrees E extensional and a N180 degrees E compressional phase are highlighted in Albian-Cenomanian and latest Maastrichtian times, respectively. The Cenozoic era is marked by a series of three compressional phases oriented N90 degrees-120 degrees E in the Late Eocene, and N20 degrees-30 degrees E and N170 degrees E in the Late Miocene. The first Late Miocene compressional phase related to the emplacement of Numidian flysch thrust sheets was followed by N-S compression affecting the overriding thrust sheets and their substratum. During latest Miocene-Pliocene and Quaternary times the tectonic pattern changed with NE-SW regional extension giving way in Quaternary and present-day times to a N130 degrees-150 degrees E compressional episode. The characteristics of the palaeostress fields and the regional structures are specified for the different phases defined. (C) 1998 Elsevier Science B.V. All rights reserved.