UNRAVELING CARIBBEAN GEOLOGY AND LINKING TROPICAL EVENTS TO REGIONAL AND GLOBAL CLIMATE AND BIODIVERSITY ISSUES
Mid-Cretaceous data from fossils and stratigraphic position indicate an Albian age for Barrancas, Rio Maton and Aguas Buenas Limestone Members. Shales yield C/S ratios and interpretation of fresh- and brackish water intervals. Fluvial deposits occur in lower sections, but sustained carbonates with decreasing volcaniclastic and siliciclastic input, and massive bedded packstones with gastropods and rudists, suggest a marine deepening trend upsection. Preliminary identification of transgressive system tracts allow for placement of sequence boundaries. Correlation into Gulf Coast sections will gain integration of tropical to temperate systems and ultimately greater understanding of the tropical contribution to Cretaceous ocean-climate system dynamics.
Late Cretaceous volcaniclastic sandstones occur in the El Rayo with limestone lenses of rudists, corals, sponges. C/S geochemistry from one site yielded low levels of organic carbon for limestones and high levels for shales. Sulfur levels were low suggesting no input from volcanics. El Rayo age, based on Eubaculites labyrinthicus (Cobban pers. com. 2001), is high in the Maastrichtian. Parastroma guitarti and Titanosarcolites giganteus are age-diagnostic fossils that allow for biostratigraphic links into the evolution and extinction record of circum-Caribbean systems.
Paleogene lithologic units and fossils transitional from San Sebastian to Lares Limestone were united with stratigraphic and lithologic data for interpretation of marginal marine to reef environments as part of a marine transgression. A strontium chemostratigraphic marker obtained from bivalves correlates to Oi2b via the 27my date obtained from tephra in ODP site 999, allowing for rare linkage of shallow reef episodes to deep water tropical events.
Ultimately, these mixed siliciclastic and carbonate systems will yield sufficient data to be synthesized into a circum-Caribbean database linked to Gulf Coast shallow- and Atlantic deep-water systems to analyze regional biodiversity patterns and contributions of the tropics to global climate events.