Preliminary gravity map of Seram, eastern Indonesia

Abstract

The island of Seram, in the outer Banda arc of eastern Indonesia, lies dose to the termination of the parallel arcuate belts of negative and positive gravity anomaly first mapped by F. A. Vening Meinesz. Gravity readings taken along the highly indented coastline of Seram and on some of the adjacent smaller islands have allowed a gravity map to be drawn that is unlikely to be changed in its broad features by future work. Steep gradients characterize the southern part of the area surveyed; these can be related to the transition from continental to oceanic crust and to die existence south of the islands of the root zone of an ultramafic thrust sheet. Small amplitude negative anomalies are associated with Pliocene-Pleistocene sedimentary basins. A positive anomaly of 80-mgal amplitude over a relatively small area of ultramafic outcrop on the mainland of Seram is the most surprising feature detected.