Facies analyses and depositional environments of the Mio-Pliocene Alexandria Formation, Algoa Basin, South Africa

Abstract

The present study addresses the litho- and microfacies analyses and depositional environments of the Mio-Pliocene Alexandria Formation, Algoa Group, South Africa. The integration of petrographic and outcrop data aided in inferring a depositional model of the studied formation. Five facies types are recognized; bioclastic oyster floatstone to rudstone, sandy bioclastic ooidal packstone-grainstone, sandy bioclastic packstone-wackestone, sandy glauconitic bioclastic packstone, and wavy lenticular bedded limestone. These facies permitted the recognition of two major depositional environments: shoal and restricted marine environment. The presence of glauconite associated with bivalve faunal assembly and other skeletal fragments suggests a marine depositional environment of normal salinity that on the inner to middle shelf.