SEDIMENTARY ORGANIC-MATTER IN DISTAL CLINOFORMS OF MIOCENE SLOPE SEDIMENTS - SITE-903 OF ODP-LEG-150, OFFSHORE NEW-JERSEY (USA)

A study of sedimentary organic matter (palynofacies) was carried out f or paleoenvironmental purposes in the siliciclastic, Miocene upper-slo pe sediments of Ocean Drilling Project (ODP) Site 903, Leg 150, Two gr oups of organic constituents were distinguished: a fraction derived fr om the continent, made of phytoclasts, pollen, and spores, and a marin e fraction consisting of amorphous organic matter (AOM), dinoflagellat e cysts, and foraminiferal linings, Palynofacies data reflect the over all trend of the Haq et al, (1987) eustatic curve. The rise in eustati c sea level during the early Miocene is associated with high levels of AOM and total organic carbon, indicative of low-energy, starved, deep er-water conditions. In contrast, during a fall in sea level from the early middle Miocene to the late Miocene. AOM became diluted by contin ental organic matter associated with prograding clinoforms. Site 903 p enetrated the distal part of progradational, well-developed clinoforms of Miocene age. Most of the seismic reflections bounding these clinof orms are the pelagic correlatives to sequence boundaries observed bene ath the adjacent shelf, and they correlate well with the sea-level rec ords of Haq et al, (1987), Within packages of clinoforms, palynofacies show important percentage variations. In most cases, seismic reflecto rs (i.e., sequence boundary correlatives) seem to be associated with a n increase in AOM indicative of a condensed section. Seismic stratigra phic interpretation landward of Site 903 indicates that these condense d sections may correspond to the downlap surface of prograding lowstan d or highstand wedges. Above the condensed section, AOM becomes progre ssively diluted by the renewed progradation of terrigenous sediments. The concentration of marine AOM near sequence boundaries, the ages of which correlate with the Haq et al, (1987) eustatic curve, tends to de monstrate that the distribution of AOM in the middle and upper Miocene slope sediments at Site 903 may be to a large extent related to relat ive sea-level variations.