SAN BUENAVENTURA FORMATION AND PROVIDENCE FORMATION: INSIGHTS INTO THE LATEST CAMPANIAN PALEOECOLOGY OF THE CARIBBEAN REGION

The Caribbean region of the Americas has an incredible geological complexity. This reveals a complicated tectonic history, with different blocks of continental and oceanic crust assembled. Sedimentary rocks with molluscan fossils can provide a useful and powerful tool for understanding this dynamic tectonic history. Here we provide insights into the sedimentology and paleontological of the San Buenaventura Formation of northwestern Costa Rica and the Providence Formation of Jamaica. Both formations show a similarity in their sedimentary environment (open shelf deposits), and they both overlie shallow-water rudist reef deposits. Ammonites are the most common fauna in both formations, sharing around 50% of the genera and 20% of the species. The ammonites found show a strong faunal affinity with the Mediterranean Tethys faunas (i.e. France, Belgium). However, the San Buenaventura Formation contains ammonites and bivalves which show affinity with Californian and northern Pacific faunas. Also, the presence of belemnites and scaphites in the San Buenaventura Fm. show affinity with faunas from the Western Interior Seaway and Gulf Coastal Plain. The Providence Shale contains a variety of bivalves and gastropods and solitary corals (Cyclolites); including more cosmopolitan forms (e.g., Neithea, Trigonia) and forms with links to California (e.g., Xenomytilus actus). Despite their differences in faunal affinities, tectonic models of the Latest Campanian of the Caribbean region propose a closer distance between Jamaica and northwestern Costa Rica during the Campanian. Also, the lack of a landbridge between North and South America allowed the dispersal of ammonite faunas from the Caribbean Tethys to the Pacific coast of North America. The relative sea-level rise recorded by both formations is an important correlation tool between different tectonic blocks that could also be present in Chiapas (the Jolpabuchil Formation?), which would further improve our understanding of the tectonic evolution of the Caribbean region and its molluscan paleoecological patterns just prior to the K-Pg mass extinction event, in which this region constitutes ground zero.