Deep-marine sedimentary facies in the Belaga Formation (Cretaceous-Eocene), Sarawak: Observations from new outcrops in the Sibu and Tatau areas

702001-100506-304-B
Author : Zainol Affendi Abu Bakar, Mazlan Madon and Abdul Jalil Muhamad
Publication : Bulletin of the Geological Society of Malaysia
Page : 35-45
Volume Number : 53
Year : 2007
DOI : https://doi.org/10.7186/bgsm53200707

Bulletin of the Geological Society of Malaysia, Volume 53, June 2007, pp. 35 - 45

 

Deep-marine sedimentary facies in the Belaga Formation (Cretaceous-Eocene), Sarawak: Observations from new outcrops in the Sibu and Tatau areas

Zainol Affendi Abu Bakar, Mazlan Madon and Abdul Jalil Muhamad

Group Research, Research and Technology Division, PETRONAS, Kawasan Institusi Bangi, 43000 Kajang, Malaysia


Abstract: Deep-marine rocks of the Belaga Formation (Cretaceous-Eocene) in the Sibu-Tatau area, Sarawak, show a variety of facies types, which are characterized by grain fabric, bed thickness, and sedimentary structures. The main facies types are (A) thick-bedded sandstone, (B) thinly-bedded heterolithic sandstone-mudstone interbeds, and (C) mudstone facies. These facies may be interpreted in relation to a submarine fan model, in which facies A represents a proximal position (near to source area) while facies B and C represent deposition in the middle to distal parts of the system, respectively. Within this general fan model, a detailed characterization of the facies can be made to understand the depositional processes operating in the deep-marine environment. Facies A, for instance, comprises massive and graded sand beds that appear to be linked genetically; the massive bed, often with floating mudclasts at the top, probably represent a debris flow deposit laid down over a pre-cursor turbidity flow deposit, which is commonly preserved as a thin graded bed at the base of the sandbody. Such linked debrite-turbidite facies association seems to be a common feature in the Belaga Formation, similar to many other deep-marine depositional systems, including the West Crocker in Sabah.

https://doi.org/10.7186/bgsm53200707