Collaborative Research:A Test of Macrofloral and MicrofloralBiofacies in a Peat-Accumulating Delta, Sarawak, Malaysia

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Coal exploration models have vacillated from one spectrum extreme to another during the past 30 years. When the Mississippi delta was believed to be the stereotypical depositional regime for thick peat accumulations (coal analogues), all attention was focused on the identification and delimitation of deltaic lithofacies. When it was demonstrated that conditions in the Mississippi delta were not precursors to thick peat accumulation, coastal models were generated in which thick peats were restricted to coastal plain sites adjacent to one or more deltas. No longer were deltas the exploration target. In modern peat accumulating regimes of southeast Asia both extremes do occur but intermediate conditions also prevail. Previously, the PI has identified five phytotaphonomic facies in the clastic-dominated, tide-influenced Mahakam River delta of eastern Kalimantan, Indonesia. In this system the only peat that has been encountered is detrital in origin, accumulating along the delta front. The present project is designed to test whether or not the same macrofloral biofacies are characteristic of a contemporaneous delta, the Rajang River delta, Sarawak (on the opposite side of the island of Borneo), in which ombrogenous peat swamps have formed. The project is designed to recover vibracores in the same clastic sedimentary environments as was previously sampled in the Mahakam River delta in order to determine if deltaic biofacies are applicable throughout the gradient of deltaic types occurring in the same climatic regime. In addition, the project offers the opportunity to assess palynofacies and determine whether or not proportions of palynodebris actually can be used to differentiate sedimentary environments, or if the systematic affinities of pollen and spores are necessary data to apply palynofacies characteristics as an aid in environmental interpretation. Additionally, macrofloral biofacies will be used to test whether the predisposition for autochthonous peat accumulation is based more on the vegetational community succession (as reflected in differences in prevailing edaphic conditions) than on other physical parameters.