Introduction

Organic matter found dispersed in aqueous systems and in sedimentary rocks consists of organic compounds derived from both autochthonous and allochthonous sources. The form of this material ranges from wellpreserved particulate organic matter (POM or macerals) to dissolved organic matter (DOM). The total mass of this organic matter is very large, and Mclver (1967) notes that it is 500–1000 times the amount found in coal, and 10000 times the amount in all organisms living at the present time. Both Weeks (1958) and Hunt (1962) estimated the total mass to be 3.2 × 1015 metric tons.

The microscopic analysis of POM has gained widespread acceptance as a reliable means of assessing the petroleum source potential and thermal maturity of rocks in sedimentary basins. Numerous studies, using various classifications of organic matter, indicate that a relationship exists between POM and petroleum source potential (e.g., Burgess, 1974; Dow, 1977; Teichmüller & Wolf, 1977; Robert, 1981; Mukhopadhyay et al., 1985; Senftle et al., 1987). Thermal maturity measurements in the form of vitrinite reflectance and transmitted color are routine in petroleum source rock evaluation (Staplin, 1969; Bostick, 1971, 1974; Castaño & Sparks, 1974; Dow, 1977; Peters et al., 1911; Hunt, 1979; Dow & O'Connor, 1982; Saxby, 1982; Stach et al., 1982; Pearson, 1984; Tissot & Welte, 1984; Waples, 1985).

Contemporary depositional environments contain many clues to the origin of the sediments accumulating on the depositional surface. Unfortunately, rocks rarely preserve sufficient information to reconstruct accurately the original depositional environment. Information is lost principally at the sediment–water interface and during the diagenetic stage of lithogenesis.