Abstract: Sedimentology of Onshore Jurassic-Cretaceous Rocks and Probable Relevance to Offshore "Basement," Malay Peninsula
Mohamad Kamal Roslan, Jantan Ahmad, Abdullah Ibrahim
Onshore Malay Peninsula Jurassic-Cretaceous sediments are found mainly along the western and eastern flanks of the granitoid Eastern Highlands, i.e., the Tembeling and Gagau groups, the Koh, Bertangga, Ma' Okil, and Paloh formations along the former, and the Bt. Kluang, Redang, Kapas, and Murau formations along the latter. Preliminary studies of most of them indicate that they are similar in gross lithology and lithofacies and that they are terrestrial deposits in contrast to pre- Jurassic-Cretaceous, which are all marine. Their similarities include (1) thick, erosive-based, massive-bedded, poorly sorted, mainly matrix-supported, boulder to granule conglomerate, (2) thick, massive-bedded to medium scale cross-bedded, poorly sorted, very coarse-grained sandstone, and (3) thick, massive bedded reddish-colored mudstone. Detail studies of some of them limit their environments to alluvial fans, braided to low, sinuous fluvial to lacustrine mouth bar.
The Tembeling Group rocks appear to be fan braided to low, sinuous fluvial-lacustrine, the Paloh formation is lacustrine mouth bar, the Murau formation is fan to lacustrine, and the Bt. Kluang formation is fan to fluvial. Paleocurrent studies indicate that those of the western flank of the Eastern Highlands flowed west while those on the eastern flank flowed east.
Lithofacies and paleoenvironmental studies suggest that the Jurassic-Cretaceous sediments were deposited immediately after the formation of a series of half-graben basins. Paleocurrent studies suggest that the Eastern Highland could be the horst and the provenance of the Jurassic-Cretaceous sediments. The offshore Jurassic-Cretaceous "basement" could be studied in the light of onshore lithofacies and paleoenvironment.
AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994