Palynomorph assemblages and geochemical indicators of Neogene ocean changes in the Eastern Equatorial Pacific: Insights from DSDP Site 568

Abstract

DSDP Site 568, off the west coast of Guatemala, was chosen to fill the palynological data gap in the Eastern Equatorial Pacific (EEP) region and improve tropical-to-subtropical regional paleoclimatic models of the Northern Hemisphere. This study analyses palynological assemblages and geochemical proxies, including Fe/Al, Ti/Al, and TOC, to evaluate precipitation and marine productivity. Statistical analysis of these variables indicates an oxic depositional environment with low marine primary productivity. The findings also show how dinoflagellate cyst assemblages (DCS) respond to global paleoceanographic and climatic events. These DCS are mainly composed of the phototrophic dinoflagellate taxa Polysphaeridium, Operculodinium , and Spiniferites , which are typical of subtropical and tropical settings. By combining DSDP data on diatoms, planktonic foraminifera, and calcareous nannofossils with dinoflagellate cyst data from this study, the depositional age is estimated from the Early Miocene (∼ 19 Ma) to the Early Pleistocene (> 0.62 Ma). A moderate rise in palynological assemblages is associated with the Middle Miocene Climatic Optimum. Lower TOC values and palynological concentrations were noted during the Middle-to-Late Miocene Carbonate Crash Event. Conversely, palynological concentrations increased somewhat during the Late Miocene-Early Pliocene Global Biogenic Bloom. Lastly, the Pliocene-Pleistocene Northern Hemisphere Glaciation is evident in the area through notable rises in TOC values and palynomorph concentrations.