Microfossils (ostracods and charophytes) from the non-marine Lower Cretaceous of Lebanon: Palaeoecology, biostratigraphy and palaeobiogeography

Abstract

A rich microfossil assemblage composed of six charophyte species and fifteen ostracod taxa has been recovered from eight stratigraphic sections raised in Lower Cretaceous rocks of the Abeih Formation/upper part of the Grès de base unit in Mount Lebanon (Central-South Lebanon). Four depositional environments have been distinguished within this unit based on sedimentological and microfacies analyses: fluvial, coastal freshwater lakes, estuary (intertidal and subtidal) and shallow marine. The charophyte assemblage is composed of Sphaerochara asema, aff. Mesochara harrisii, Atopochara trivolvis var. trivolvis, Ascidiella reticulata, Clavator ampullaceus, and Munieria martinclosasi extracted from costal freshwater lakes facies. The associated ostracod fauna is mainly represented by Cypridea libanensis, C. heliopolisensis, C. aaleyensis recovered along with accessory carapaces of C. baidarensis, C. quadrangulata, Cypridea sp. 1, Cypridea sp. 2, and Timiriasevia cardiformis. Part of this freshwater microfossil assemblage (A. trivolvis var. trivolvis, A. reticulata, C. ampullaceus, Cypridea libanensis, C. heliopolisensis, and C. aaleyensis) has been found in facies related to brackish water characterized by marine ostracods such as Fastigatocythere aff. naftaliensis, Fastigatocythere sp., Metacytheropteron parnesi, Majungaella (Progonocythere?) sp. Pontocyprella sp., Asciocythere sp., and Damonella sp. Shallow marine elements are also abundant including dasycladalean thalli, foraminifera and echinoid remains. This study indicates that the Abeih Formation/upper part of the Grès de base unit is late Barremian/early Aptian in age. The microfossil assemblage is dominated by endemic to subcosmopolitan taxa characteristic of the Levantine Island at the southeastern margin of the Tethys during the Early Cretaceous. © 2021 Elsevier Ltd