PALEOENVIRONMENTAL INTERPRETATIONS OF PALEOGENE TO EARLY NEOGENE MARINE AND TERRESTRIAL PALYNOMORPHS IN THE DEEP GULF OF MEXICO

Dinoflagellates and acritarchs flourish in marine environments where their cysts are commonly preserved in sediments along with pollen, spores, and other terrestrial palynomorphs. Cored sediments from Deep Sea Drilling Project (DSDP) Sites 94 and 540 in the Yucatan Peninsula and south of the Western Florida Escarpment, respectively, provided the opportunity to study the palynomorphs preserved in the middle Eocene to middle Miocene interval. Since terrestrial palynomorphs can be used for stratigraphic correlation between non-marine and marine sequences, their records at these deep-water sites were evaluated against published data for Paleogene to early Neogene taxa from the Gulf coastal plain.

Dinoflagellate cysts were the dominant marine palynomorphs at both sites, which recorded largely biogenic sedimentation and significant hiatuses. Despite the paucity of palynomorphs in middle to upper Eocene core sections, the genera Impagidinium and Nematosphaeropsis, and occasionally Operculodinium, indicate more oceanic conditions. The lower Oligocene core sections at both sites were virtually barren of marine palynomorphs but dominated by terrestrial palynomorphs at Site 94. Deposition near the boundary of neritic and oceanic waters resulted in abundant Spiniferites and Operculodinium in the upper Oligocene sediments. The Oligocene/Miocene boundary records an abundance of Spiniferites in addition to Lingulodinium machaerophorum, which occurs in neritic waters with freshwater influence. Operculodinium increased in the lower Miocene sections as the deposition became more oceanic.

Terrestrial palynomorphs were mostly pollen, fluctuated in abundance and were not diverse. Carya simplex, Cupressacites hiatipites, Momipites spp. and bisaccate pollen were the common types found in both onshore and offshore records. These terrestrial palynomorphs are relatively small, light and have little or no ornamentation, allowing for greater traveling distance by water and/or wind.