Deposition of the Tembungo deep-water sands

Author : Noor A’zim Ibrahim
Publication : Bulletin of the Geological Society of Malaysia
Page : 105-126
Volume Number : 47
Year : 2003

Bulletin of the Geological Society of Malaysia, Vol 47, Dec. 2003, pp. 105-126


Deposition of the Tembungo deep-water sands

*NOOR A’ZIM IBRAHIM (posthumous)

PETRONAS Research & Scientific Services Sdn. Bhd., Lot 3288 & 3289, Off Jalan Ayer ltam, Kawasan lnstitusi Bangi, 43000 Kajang, Selangor Darul Ehsan, Malaysia


Abstract: One of the main elements of the sequence stratigraphy model concerns the development of deep-marine systems (Posamentier and Vail, 1988). Deep-marine systems can be classified into basinfloor (lowstand) fans and slope fans where each, according to sequence stratigraphic concepts, is assumed to be primarily controlled by the rate of eustatic changes.

This seismic-based classification of deep-water systems is based on modifications of Mitchum‘s (1985) model. In contrast, many of the previous submarine fan models were based on smaller-scale observations from shallow seismic data integrated with shallow cores on modern submarine fans, and on detailed outcrop-based facies studies often with limited outcrop exposures (see review by Mutti and Normark, 1987). A notable exception is the submarine fan model proposed by Mutti (1985) which attempted to reconcile outcrop-based studies to variations in sediment influx and relative sea-level changes.

The different scales of observation of deep-marine systems have resulted in many, often conflicting, submarine fan models, each applicable to a particular setting. In addition, studies relating sedimentary facies to large-scale sequence stratigraphic models are lacking. The main aim of this paper is to use core and seismic reflection data to investigate the evolution of a Middle Miocene turbidite sequence offshore NW Borneo called the Tembungo deep-water sands. The origin of these turbidites is closely related to a prominent regional unconformity called the Shallow Regional Unconformity (SRU). The depositional model derived from this study is compared with the submarine fan models of Mutti (1985) and models arising from sequence stratigraphic concepts.

The approach is based on integrating information from high quality multichannel seismic data with wireline logs calibrated with sedimentary facies studies of cores. Seismic stratigraphy provides the large-scale framework useful for relating turbidite system deposition to temporal and spatial boundaries of depositional sequences. This, when combined with identification of the different seismic facies, and relating them to cores and wireline logs, can result in the recognition of the different phases of growth of the turbidite system.