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Abstract: Quaternary climate and sea-level research in coastal karst basins (caves, cenotes, sinkholes, blueholes, etc.) generally focuses on analyzing isotopes in speleothems, or associating cave elevations prior sea-level highstands. The sediments in coastal karst basins represent an overlooked source of climate and sea-level information in the coastal zone, but to accurately interpret these sediments first requires an understanding of the forcing mechanisms that emplace them. In this study, we hypothesize that coastal karst basins transition through vadose, littoral, anchialine, and finally into submarine environments during sea-level rise because groundwater and sea level oscillate in near synchrony in the coastal zone, causing each environment to deposit a unique sedimentary facies. To test this hypothesis, the stratigraphy in twelve sediment cores from a Bermudian underwater cave (Green Bay Cave) was investigated and temporally constrained with twenty radiocarbon dates. The results indicate that we recovered the first succession spanning the entire Holocene from an underwater cave (~13ka to present). The sediments were characterized with X-radiography, fossil remains, bulk organic matter, organic geochemistry (δ13Corg, C:N), and grain size analysis. Four distinct facies represent the four depositional environments: (i) vadose facies (>7.7ka, calcite rafts lithofacies), (ii) littoral facies (7.7 to 7.3ka: calcite rafts and mud lithofacies), (iii) anchialine facies (7.3 to 1.6ka: slackwater and diamict lithofacies), and (iv) submarine facies (<1.6ka: carbonate mud and shell hash lithofacies). The onset and duration of these sedimentary depositional environments are closely linked to Holocene sea-level rise in Bermuda, indicating that sea level controls environmental development in coastal karst basins. Finally, we present a conceptual model for interpreting the sediments and environments in coastal karst basins as a result of sea-level change. [Copyright &y& Elsevier]

Fossil testate amoebae and their non-marine finds are rare so their ecological importance through Earth history is poorly understood. The Lower Jurassic shallow water black-shales of Trento Platform (north-east Italy) are rich in micro-organisms and contain a thecamoebian and ostracod assemblage representing the first known record of Early Jurassic oligohaline forms from the European mainland. The thecamoebians are represented by the genera Difflugia, Pontigulasia and Centropyxis. The present discovery of Lower Jurassic thecamoebians in fine carbonate organic-rich deposits indicates, for the first time, that these sediments can preserve testate amoebae very well. The occurrence of difflugid testate amoebians confirm a transitional marine-terrestrial habitat, outside large bodies of water, and suggests occasional eutrophication in ephemeral restricted aquatic environment in the Sinemurian–Pliensbachian Trento Platform. [ABSTRACT FROM AUTHOR]