Abstract:
The presence in most marine sediments of both terrestrial and marine palynomorphs can be used to reconstruct relative sea levels. Terrestrial palynomorphs (e.g. pollen and spores) record the transport of terrigenous particles to marine environments, so their concentration decreases exponentially with distance from the shoreline, as does the ratio of terrestrial vs. marine palynomorphs (e.g. dinoflagellate cysts). Dinoflagellate cyst distributions also reflect distance from the shoreline, with some dinoflagellate species being primarily estuarine, others inner, middle, or outer neritic. A small number of cyst taxa are relatively more common in oceanic environments. Although more precise paleoenvironmental reconstructions are possible in Quaternary sediments where the vast majority of species are extant, general trends can be applied throughout the record--for example, protoperidinioid cysts (produced by heterotrophic dinoflagellates) decline in abundance offshore relative to gonyaulacoid cysts (produced by photoautotrophic dinoflagellates). Variations in terrestrial vs. marine palynomorphs (P:D) and gonyaulacoid vs. protoperidinioid dinocysts (G:P) in hemipelagic continental margin sediments reflect sea level change. Because palynomorphs are easily transported and resistant to degradation in low oxygen environments, however, they can readily be redeposited. Palynomorphs are commonly eroded from neritic environments during sea-level lowstands and redeposited on continental rises and abyssal plains--deep-sea sediments rich in protoperidinioid dinoflagellate cysts, pollen and spores thus correlate with sequence-bounding unconformities on continental margins. We will demonstrate the application of palynology to sea-level and sequence stratigraphic studies in sediments of Miocene to Recent age.