Oligo-Miocene Alpine tectonic evolution and related igneous activity along the Central-Eastern Algerian margin

The Miocene calc-alkaline igneous activity in Northern Algeria is restricted to a narrow (50 km) coastal zone along the Mediterranean Sea. It occurs either in the external or in the internal units of the Alpine Tellian belt. The latter resulted from three episodes of nappe thrusting between Lower Burdigalian and Middle Tortonian. Comparatively, K-Ar ages of igneous rocks span between 17 and 9 Ma. The intensity of the various tectonic phases varies by sector through the Tellian belt. Between the three periods of thrusting, a significant detrital sedimentation took place and was accompanied by emplacement of calc-alkaline igneous materials as plutonic and/or volcanic bodies.

The main objective of this study is to outline the relationships between Miocene igneous eruptions and their associated sedimentary formations that make up a key portion of the Algerian Alpine belt. For this purpose, we gathered geochronological, geochemical and isotopic data from Miocene cal-alkaline igneous rocks emplaced over more than 800 km near the Algerian coast. In some sectors, the emplacement of igneous rocks within the sedimentary series allows a direct observation of their relationships. K-Ar ages carried on calc-alkaline igneous rocks collected between Tenes-Cherchel and Cap de Fer sectors range from 17.0 Ma to 9.10 Ma. Stratigraphic columns exhibit three successive tectonic cycles at 17 Ma, 15 Ma, and 9 Ma, which correspond to the three southward thrusting events (Burdigalian, Langhian and Tortonian) of Kabylian terranes responsible for the Alpine nappe stack. In various locations, these nappes include igneous rocks as volcanic levels or plutonic bodies. These new results, together with a critical review of previous studies, allow us to discuss the consistency between paleogeography, tectono-magmatic pulses and petro-geochemical evolution of northern Algeria after the closure of the Alpine Tethys.