Microfacies Analysis of the Reefal Limestone, Marah Formation, East Borneo, Indonesia

Abstract

Miau Baru, Kongbeng in East Borneo is a relatively narrow area with complex geological features. The abundance of larger benthic foraminifera shows diversity in the carbonate succession of the Marah Formation but previously has less attention from microfacies perspective. To achieve the objective in this microfacies analysis of the reefal limestone of Priabonian-Aquitanian. Marah Formation, limestone samples were collected and sectioned. A total of 35 samples were selected, 25 from the Goa Indah section and 10 from the Kongbeng section. The assemblage of larger benthic foraminifera was recorded to help determine the depositional age, and biota of the formation and to interpret the facies zone. Field observation, microfacies type, as well as the fossil content of larger benthic foraminifera and colonial scleractinian corals indicated that the deposition of the Marah Formation in the Miau Baru area probably ranged from open circulation shallow forereef to backreef shelf.