Miocene-Pliocene paleogeographic evolution of a tract of Sarawak offshore between Bintulu and Miri

A data base consisting of 5,200 km of seismic lines and data from six wells has been utilized to recontruct the evolution of the main environments of sedimentation in a tract of the Sarawak Offshore between Bintulu and Miri. A sequence of six maps shows the progressive shifting through time of the position of the paleo-coastline in the area as well as that of the major deltaic systems. The presence of a morphological paleoescarpment along the so-called West Baram line is evident since at least the Middle Miocene. The data suggest its presence also in older ages but it cannot definitely be demonstrated with our data set. The basin to the northeast of this paleoescarpment has been filled mainly during the Late Miocene-Pliocene by the deposits associated with the progradation of the paleo-Baram delta system. The spatial distribution of the different environments of sedimentation is at any time controlled by the position of the coastline (input of sediments) and by the presence of the paleoescarpment. This situation is still reflected by the present geography of the area