Early Miocene lacustrine deposits from the Oued Tilatou Formation (Aurès Massif, Eastern Algeria): Sedimentology, micropalaeontology, and palaeoenvironmental implications

Abstract

Lacustrine depositional systems provide a valuable record of palaeoenvironmental conditions since they rely on a delicate balance between accommodation space and water-sediment supply controlled by tectonic activity and climatic conditions. This study presents new sedimentological and micropalaeontological information from the early Miocene lacustrine Oued Tilatou Formation, northeastern Algeria. Based on sedimentary facies and microfossil assemblages, the Oued Tilatou Formation (OTF) is divided into two discrete units, the Lower OTF and the Upper OTF. The Lower OTF is characterised by reddish clay-rich carbonate mudstone containing reworked foraminifera and ostracods interspersed by polymodal clast-supported conglomerates attributed to alluvial deposition. The Lower OTF was deposited under fluvial–palustrine conditions, marked by a notable terrigenous sediment influx. In contrast, the Upper OTF encompasses greenish charophyte-dominated (Sphaerochara sp.) carbonate mudstone interbedded with silty carbonate mudstone, and dolomitic wackestone containing charophyte thalli, several ostracod species, and stromatolites. The dominant ostracod taxa within this interval are Mediocypris sp. cf. M. candonaeformis, indicating freshwater–brackish water conditions. The transition in depositional facies from the Lower OTF to the Upper OTF is interpreted as reflecting changes in the environment from fluvial–palustrine to shallow water lacustrine with fluctuation in freshwater input during the Burdigalian (Early Miocene). This study provides new insights on the interplay between early Miocene climate conditions and the tectonic uplift of the Aurès Massif, and their implications for lacustrine palaeoenvironmental conditions.