An actualistic investigation has been conducted on palynofacies recovered from a limited sample
set of water column and grab samples in freshwater fluvial, brackish water fluvial, and estuary
mouth (kuala) environments of the Rajang River and delta, Sarawak, East Malaysia.
Palynofacies are overwhelmingly dominated by Unstructured Organic Matter (OM), with varying
amounts of Structured OM, Palynological OM, and an insignificant amount of Indeterminate OM
(black opaques). Non-parametric statistical analyses (Chi-Square and Mann-Whitney rank sum)
were conducted to determine if different physical processes operating in the delta (tidal range,
time of sample collection, water chemistry, and depositional setting) affected assemblage
composition. Palynofacies assemblages were evaluated using UPGA clustering techniques to
determine if distributional patterns existed in the study area.
No statistical relationship was found between the OM particle category and sediment-grain size
within the delta. In general, assemblages from water-column samples recovered from freshwater
sites have significantly higher proportion of Unstructured OM than do assemblages from saltwater
influenced sites. A similar distribution is seen in grab samples, except that river channels active
during the dry season possess the same palynofacies assemblages at the sediment-water interface
and differ from abandoned, tidally flushed channels. The abandoned channels have higher
proportions of Structured OM both in the water column and at the sediment-water interface than
do OM assemblages from freshwater collection sites. There is no 1:1 relationship between the
OM assemblages found in the water column, at the sediment-water interface, and sediment
recovered from the subsurface (using vibracores) from the same generalized collection area.
Early diagenetic alteration in sites influenced by marine waters alters the character of the acid-resistant organic constituents with the production of Black Opaque Indeterminates, resulting in a
different acid-resistant organic assemblage.
Citation: PALYNOLOGY, v. 21, p. 145-171, 1997.