CORALLINE ALGAE FROM THE MIOCENE MAHAKAM DELTA (EAST KALIMANTAN, SOUTHEAST ASIA)

Abstract

ABSTRACT Miocene crustose coralline algae (CCA) from Southeast Asia are poorly known, although the Miocene is the epoch of the onset of the biodiversity hotspot in the region and CCA are crucial to understanding the evolutionary history of reef building. To fill this knowledge gap, CCA from early and middle Miocene reefs and related carbonates in the Kutai Basin in East Kalimantan (Borneo, Indonesia) have been studied. The Kutai Basin was dominated by siliciclastic sediments of the proto-Mahakam Delta. Locally, carbonate buildups occur lateral to, or within, the deltaic succession. CCA in the Kutai Basin occur in carbonate beds that were deposited in a low-energy shallow-water platform setting and in association with coral reefs, encrusting the corals or bioclasts. Two main CCA assemblages are recognized herein: (1) a shallow-water assemblage (S-assemblage), dominated by Neogoniolithon spp., thick crusts of Spongites spp., and Hydrolithon spp.; and (2) the D-assemblage, which consists mainly of thin crust...