Abstract: Structural and Sedimentary Evolution of the Malay Basin

Mohd. Tahir Ismail, Shahrul Amar Abdullah, Kurt W. Rudolph

The Malay Basin is a back-arc basin that formed via Eocene(?) through Oligocene extension. This early extensional episode is characterized by large east-west and northwest-southeast-trending

normal fault systems with associated block rotation. Extensional subbasins are filled with a thick succession of alluvial and fluvial sediments that show increasing lacustrine influence toward the central basin dep.

In the early Miocene, the basin entered a passive sag phase in which depositional relief decreased, and there is the first evidence of widespread marine influence. Lower Miocene sediments consist of cyclic offshore marine, tidal-estuarine, and coastal plain fluvial sediments with very wide facies tracts.

The middle Miocene is dominated by increasing compressional inversion, in which preexisting extensional lows were folded into east-west anticlines. This compression continues well into the Pliocene-Pleistocene, especially in the northwest portion of the basin and is accompanied by an increase in basin-wide subsidence. There is significant thinning over the crest of the growing anticlines and an angular unconformity near the top of the middle Miocene in the southeast portion of the basin. Middle Miocene sedimentary facies are similar to those seen in the lower Miocene, but are influenced by the contemporaneous compressional folding and normal faulting.

Based on this study, there is no evidence of through-going wrench-fault deformation in the Malay Basin. Instead, localized strike-slip faulting is a subsidiary phenomenon associated with the extensional and compressional tectonic episodes.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994