Further Chemostratigraphic Characterization into the Valanginian Weissert Oceanic Anoxic Event in the Proto-Caribbean Basin

Intermittent organic-rich Cretaceous strata of Western Cuba indicative of deep oceanic oxygen depletion in the Proto-Caribbean Basin correspond with the Late Valanginian nannofossil subzone NK3B and calpionellids support the correlation up to earliest Hauterivian [1;2]. These limestones archived the local response of the Proto-Caribbean Basin to the Valanginian global carbon perturbation correlative with the Weissert OAE [3;4]. Here we present a high-resolution chemostratigraphic data of a 4-meter interval in a 30-meter quarry outcrop where thin grayish black chert-bearing carbonaceous marlstones (TIC: 44.7–77.3%; TOC: 3.5–10.8%) interbed with medium dark gray limestones (TIC >90%; TOC: average 2.3%). Thin section and electron microscopy (SEM-EDS), Computed Tomography (CT) X-ray imaging show isotropic fabric, scattered single framboids and bioturbation indices BI<2 in the carbonaceous layers. The carbon isotopic (δ13Corg) profile averages ~27.3‰, with a peak at ~25.6‰ (~1.7‰ excursion). Enrichment of major trace elements (Al, Si, Ti, Li), biolimiting elements (P, Fe), and TOC, along with microscopic traces of plant remains, suggest periodic increased of terrestrial fluxes enhancing productivity. Enhanced redox sensitive trace elements (S, Cr, Ni, Mo, Ti, Tl, V, U) in these intervals suggests prolonged dysoxic conditions favoring organic matter preservation. This study marks the initial step in elucidating the widespread oxygen-deficient conditions associated with this event in the Proto-Caribbean Basin.

[1]Orihuela et al (2023) 14th RSP. Abs, 90 - 91 [2] Pszczółkowski (1978) Acta Geologica Polonica 28 (1), 1-96. [3]. Weissert et al (1979) Ocean. Geol.7, 147-151. [4] Orihuela et al (2023) Goldschmidt, Poster 503.