Abstract:
Palynomorphs are organic-walled microfossils that behave aero- and hydro-dynamically like silt particles. We employed terrestrial plant spores and pollen as tracers of terrigenous sediment transport onto and across the New Jersey margin, and marine palynomorphs, such as dinoflagellate cysts and foraminiferal linings, as proxies of marine productivity. The palynological content of Upper Miocene sediments differs markedly from that of Plio-Pleistocene sediments, recording very different sedimentological regimes. Upper Miocene sediments are highly organic, with total palynomorph concentrations almost an order of magnitude higher than in Plio-Pleistocene sediments. This records much lower siliciclastic sediment influx during the Late Miocene, consistent with palynological evidence of greater oxidation in these sediments. The ratio of terrestrial:marine palynomorphs is relatively high throughout the Upper Miocene sequence, is very high in glacial sediments of middle to late Pleistocene age, but low in sediments of late Pliocene to early Pleistocene age and in interglacial sediments deposited during the middle to late Pleistocene. Glacioeustatic sea-level fluctuations clearly controlled erosion and deposition on the New Jersey margin during the middle to late Pleistocene: palynomorphs record inner neritic conditions on the outer continental margin immediately above sequence-bounding unconformities, followed by evidence of rising sea-level to a highstand, marked by very low terrestrial:marine palynomorph ratios. In contrast, palynomorphs record a trend toward greater terrestrial influence up-sequence in Upper Miocene sediments, possibly recording shoaling, but not consistent with sediment accumulation during rising sea-level.