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Tropical ecosystem shifts at the Eocene–Oligocene transition in the southwestern Caribbean region
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Resumo(s)
The Eocene-Oligocene transition (EOT; similar to 34 Ma) marks a pivotal climatic shift from a warm, ice-free world to a cooler, glaciated climate driven by a significant decline in atmospheric pCO2 levels. This global cooling event, characterized by the first major Antarctic glaciation and a similar to 50 m sea-level fall, triggered selective extinctions in marine ecosystems and restructured sedimentary processes, making it one of the most significant climatic events of the Cenozoic. While the global impacts of the EOT are well documented, its effects on the marine environment of NW South America remain poorly understood. This region's unique position as a connection between the Pacific and Atlantic oceans before the closure of the Central American Seaway provides a valuable window into tropical ecosystem responses during this period. This study integrates micropaleontological and geochemical data from the ANH-SJ-1 drill core in the Colombian Caribbean to evaluate the impacts of global climatic shifts on tropical marine ecosystems. Palynological indicators, including the terrestrial/marine (T/M) index, along with XRF-derived elemental ratios (Zr/Rb, Ti/Al, K/Al, and K/Rb), reflect enhanced continental input during the EOT. These patterns suggest intensified erosion and detrital transport to bathyal depths, likely driven by rapid sea-level fall and hypopycnal flows. Calcareous nannofossil trophic indices reveal elevated surface productivity, likely fueled by increased continental nutrient influx, supported by higher Ba/Ti ratios that indicate enhanced organic matter export to the seafloor. The resulting oxygen depletion favored infaunal over epifaunal benthic foraminifera, marking a shift in community structure. Improved carbonate preservation across the transition, evidenced by a shift from agglutinated to calcareous benthic foraminifera and higher Ca/Ti ratios, reflects a deepening of the carbonate compensation depth (CCD), likely due to enhanced alkalinity from continental weathering. A positive delta 13Corg excursion (similar to 0.84 parts per thousand) aligns with global records and supports contributions from organic carbon oxidation, volcanic inputs, and weathering. Although limited by the number of available samples and low fossil abundances in some intervals, our multiproxy approach enables a coherent reconstruction of environmental dynamics. The ANH-SJ-1 record highlights the sensitivity of tropical systems to global climatic shifts and reinforces the importance of tropical data for understanding Cenozoic climate evolution and anticipating future ecosystem responses.
Descrição
Palavras-chave
Sea-level changes Gulf-of-mexico Benthic foraminifera Kerguelen plateau Calcareous nannofossils Antarctic glaciation Dinoflagellate cysts Global climate South-america Oxygen index
Contexto Educativo
Citação
Editora
Copernicus Publications