Abstract: A Thermal Model for Evaluation of the Malay Basin

Douglas W. Waples, Leslie Warren, Ramly Mahadir

Detailed reconstruction of the present-day thermal structure of Malay Basin using downhole temperature, and paleoheat flow using an R_o database, leads to important conclusions and observations about the thermal history of the basin: (1) a major heating event occurred within the last 100,000 yr; (2) low R_o value throughout the basin indicates heat flow prior to the heating event, only slightly higher than that of stable cratons, (3) present-day heat flow is lowest in the eastern Malay Basin, where most of the erosion due to the late Miocene regional unconformity, and highest in the northwestern, where Pliocene-Pleistocene subsidence have been greatest.

Our data are consistent with the following general models for the basin evolution: (1) slight extension of the stable craton during late Eocene resulting from the collision of India with Asia, without the high heat flow, thermal doming, or rift development; (2) maintenance of slight extension and continued downwarping until the end of the middle Miocene, when local compression uplifted the basement in the eastern portion of the basin, leading to 15 km of erosion in some areas; and (3) establishment of a much stronger extensional regime throughout the basin during the Pliocene, causing submergence and greatest subsidence in the west, accompanied by an increase in heat flow to levels never seen before in the basin.

Although strong subsidence (and presumably the increase in basal heat flow) began about 5.5 Ma, the thermal effects were not noted in the upper sedimentary section until recently because of the time required for the increased basal heat flow to reach the surface.

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