Selected Aspects of Plant Taphonomic Processes in Coastal Deltaic Regimes

Abstract

Ancient coastal physiographic provinces have been sites of detrital plant accumulations since the advent of terrestrial vegetation in the Silurian. These lowlands contain remnants of vegetation from a diversity of ecological habitats in a variety of preservational modes and depositional environments. Deltaic regimes within these coastal systems have acted as principal locales for the preservation of in situ (autochthonous) and transported (hypoautochthonous/allochthonous) community elements. A vast majority of our understanding concerning plant diversity and community structure has been centered in the refugia of lowland deltas because of the propensity of these terrigenous sites to become part of the stratigraphic record either by autocyclic or allocyclic mechanisms. Deltaic systems have played a major role in the accumulation of hydrocarbons either as subaqueous (topogenous) and subaerial/aerial (ombrogenous) peats, to be subsequently metamorphosed to coal (McCabe, 1985), or precurssors to natural gas and petroleum (Durand et al., 1986). In certain instances, these peats have been subjected to permineralization and provide the scientific community with an insight into the original standing community biomass (Phillips et al. 1985). Where peats have been coalified, palynomorphs recovered from coal macerations provide information on trends in regional vegetation. Additionally, depending on the relative rates of clastic vs. organic sedimentation in these environments, deltas have acted as repositories for coalified compression and authigenically cemented megafloral and microfloral assemblages (taphocoenoses).