Weiwei Feng

Master of Science

December 9, 1994

(B.S., Peking University, 1991)

Directed by Robert A. Gastaldo

Forty-five vibracores have been recovered from the alternating sand and silt facies recovered from deposits throughout the Rajang River Delta, Sarawak, East Malaysia. Eighty four samples taken from those vibracores have been processed and analyzed for palynofacies composition (acid-resistant organic matter). Palynofacies preparations were point counted (300 per preparation) following the Amsterdam Palynological Organic Matter Classification scheme.

The palynofacies of the Rajang River Delta's alternating sand & silt facies are mainly composed of land-derived organic matter with the rare occurrence of identifiable marine organism. The most abundant palynodebris categories derived from the Rajang River Delta are heterogeneous unstructured particles, homogeneous unstructured debris, finely dispersed organic material and other structured plant parts. The high amounts of heterogeneous unstructured particles, homogeneous unstructured debris and finely dispersed material indicate that the rate of organic matter degradation within the delta is high.

Palynofacies composition appears to be homogeneous within the delta. T-test and ANOVA analyses were conducted to determine if any distributional patterns could be developed in the seemingly homogeneous data set. When different depositional environments (fluvial, tidal, estuarine, or beach) or physical processes (mesotidal vs. macrotidal influence; saltwater vs. freshwater influence) were compared, statistically there is no significant difference for most palynodebris categories. Palynofacies components that do differ significantly include total structured debris, palynomorphs and indeterminate black material.

Multivariate statistical analyses were used to differentiate patterns of organic matter distribution within the delta. Results from Principal Component Analysis do not provide any satisfactory result. When comparing the organic matter categories, the first principal component accounts for more than 90% of the total variance. Results from the unweighted Average Linkage Cluster Analysis on a matrix generated by the Spearman rank-order correlation coefficient were found to be more suitable for this study. Three core assemblages and two palynodebris groups were linked in the cluster analysis. The distribution of linked core assemblages within the delta indicates some regular pattern. Group 1 is distributed within the interior of the delta, and originate from point or mid-channel bars or the channel margin. Group 2 was located to the exterior of the delta and derived from mid-channel and river mouth bars, estuarine, and beach environments. Group 3 shows up in a regular pattern related to channel bar development. It is most commonly found on the downstream side of the bar form.

By integrating the size, shape and texture of palynodebris with sedimentological characteristics, lithological characteristics, palynomorph assemblages, and micropaleontological data, depositional environments could be better evaluated.

See Nicolai Pedentchouk for related M.Sc. Thesis.