Early Miocene marine palynology of the Colombian Caribbean Margin: biostratigraphic and paleoceanographic implications

摘要

Dinoflagellate cysts and acritarchs are excellent proxies for biostratigraphic and paleoceanographic studies in neritic sequences. However, Neogene marine palynological studies in tropical latitudes are scarce. Here, we analyzed the marine palynological contents (dinoflagellate cysts, acritarchs, foraminiferal test linings and prasinophytes) of 40 samples from a well drilled in northernmost Colombia, southern Caribbean Sea, spanning the late Chattian-late Burgidalian time interval (similar to 24.1-17.3 Ma). We propose a biostratigraphic scheme that includes an upper Chattian-lower Aquitanian Minisphaeridium latirictum Interval Zone (similar to 23.9-22.0 Ma), an upper Aquitanian Achomosphaera alcicornu Interval Zone (-22.0-20.3 Ma), and a Burdigalian Cribroperidinium tenuitabulatum Interval Zone (similar to 20.3-17.5 Ma). Our results reveal several biostratigraphic events that are heterochronous compared to high latitudes. Furthermore, the conspicuous shift from a peridinioid-dominated to a gonyaulacoid-dominated dinoflagellate cyst assemblage towards the Aquitanian-Burdigalian boundary (similar to 20.7 Ma) indicates a reduction in marine primary productivity. This paleoproductivity decline was probably driven by the initial constriction of the Central American Seaway.