Abstract
On the basis of single and multi-channel seismic reflection data, the stratigraphic framework and geologic history of the Lombok Forearc Basin is discussed. The Lombok Basin is built on the Southeast Sunda Shelf Continental Margin, and probably underlain by basement of thinned rifted continental crust. It represents a broad-ridged residual forearc basin which is still in an early stage of evolution.Five seismo-stratigraphic sequences reflecting the Cenozoic history and development of the forearc basin south of the islands of Bali and Lombok were identified. The lowermost sequence (1) probably is composed of synrift deposits of Paleogene age, which predate the initiation of the present convergent margin. Sequences (2) and (3) reflect two major phases of tectonic evolution of the accretionary prism, between the late Oligocene and mid-Miocene. Sequences (4) and (5), represent slope front fill deposits and reflect both volcanic activity as well as tectonic uplift of the magmatic arc from mid-Miocene times onwards.By the late Miocene, increased convergence between the subducting Indian and overlying Asian plates resulted in a stronger mechanical coupling between both plates. This was expressed in the southern forearc basin by folding of the oldest basin fill deposits.The present tectonic activity in the Lombok Basin is governed by the late Pliocene collision of the accretionary prism with the Scott marginal and Roo Rise oceanic plateaus. This resulted in uplift of both the outer-arc ridge and the southern part of the forearc basement.
Published Version
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