• Early Miocene to Middle Miocene deltas prograded rapidly eastwards, contributing to the infilling of the Kutai Basin (Hall & Nichols, 2002). Within this depositional regime, carbonate production took place in proximal delta-front settings contemporaneously with the rapid and near-constant siliciclastic input (Lokier et al., 2009). Miocene carbonates formed as low- and high-relief build-ups and coral carpets on delta-front mouth bars, and on the more distal shelf along the seaward margin of the Mahakam Delta where they are strongly influenced by siliciclastic input throughout their evolution (Wilson, 2005). These carbonates have been interpreted as transitional shelf sediments deposited between deltaic and deep-marine facies (Allen & Chambers, 1998).