Reconnaissance reassessment of the late Eocene Oceanic unit, Barbados: Microtektite geochemistry, zircon U-Pb geochronology, micropaleontology, and provenance
John Weber, Brent Wilson, Christian Koeberl, Paul O’Sullivan, Ray Donelick, Esther S. Posner, "Reconnaissance reassessment of the late Eocene Oceanic unit, Barbados: Microtektite geochemistry, zircon U-Pb geochronology, micropaleontology, and provenance", 250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco, Christian Koeberl, David M. Bice
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We measured stratigraphic sections and collected samples from Oceanic suite outcrops at Gay’s Cove and Bath Cliffs, Barbados, in order to restudy the late Eocene microtektite layer(s) and provide new geological context. We disaggregated and processed samples into separates of microfossils, microtektites, and heavy minerals, and we present up-to-date glass geochemistry, biostratigraphic analysis, and detrital zircon U-Pb analysis. Results from the new Barbadian microtektite glass chemistry analysis (Gay’s Cove) compare well with those from other published microtektite analyses, as well as those from the correlative North American strewn field. Micropaleontology confirms a late Eocene age for the Oceanic microtektite horizon at Gay’s Cove. Using U-Pb, we dated 24 Tertiary zircon grains, probably from volcanic ash-fall events, which at Gay’s Cove yielded a preliminary, poorly defined, and incorrect depositional age for the microtektite layer (≤31.84 ± 0.85 Ma; weighted mean of only three grains). Three additional new U-Pb depositional ages (≤38.52 ± 1.0 Ma, ≤39.23 ± 0.3 Ma, ≤35.25 ± 0.82 Ma) were obtained from bottom to top in the 24 m section at Bath Cliffs. We also dated 46 Paleozoic–Proterozoic zircon grains using U-Pb and discuss whether these “old” grains represent recycled (subducted and extruded) volcanic grains or windblown silt/sand from Africa.
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250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco
Central Italy has been a cradle of geology for centuries. For more than 100 years, studies at the Umbria and Marche Apennines have led to new ideas and a better understanding of the past, such as the Cretaceous–Paleogene (K-Pg) boundary event, or the events across the Eocene–Oligocene transition from a greenhouse to an icehouse world. The Umbria-Marche Apennines are entirely made of marine sedimentary rocks, representing a continuous record of the geotectonic evolution of an epeiric sea from the Early Triassic to the Pleistocene. The book includes reviews and original research works accomplished with the support of the Geological Observatory of Coldigioco, an independent research and educational center, which was founded in an abandoned medieval hamlet near Apiro in 1992.