Biostratigraphy of ejected material from mud volcanoes in the Caribbean region of Colombia: Contribution to the stratigraphy of Sinu Basin

Mud volcanoes and mud diapirs are highly distinguishable geomorphological features in the Sinu Basin in the northwestern Caribbean coastal zone of Colombia. Material ascending through mud volcanoes carries with it fragments from the subsurface, allowing us to examine the stratigraphic record of the Sinu Basin. For instance, calcareous microfossils from the ejected material provide chronological information in which diapirs were formed. Previous studies have inferred the age of the Colombian Caribbean mud diapirism and volcanism from indirect proxies such as 2D seismic lines combined with regional studies, but very little evidence-based on micropaleontology. Our biostratigraphic analyses using calcareous nannofossils and planktonic foraminifera extracted from mud volcanoes and their host rocks in the Sinu Basin indicate ages ranging from Middle Eocene to Late Miocene. The well-constrained biostratigraphic ranges of microfossils indicate four chronostratigraphic intervals: 1) Middle to Late Eocene, 2) Late Oligocene 3) Early to Middle Miocene, and 4) Late Miocene. This analysis shows that the ages of muddy materials are younger in the south and older in the north of the study area. We observe that there is a good correlation between the ages of calcareous microfossils and oceanic geological formations of the Sinu Basin. Therefore, our micropaleontological analyses are the first direct evidence to date the sediment involved in the mud diapirism and vulcanism in the Colombian Caribbean region.