Echinoderms and Oligo‐Miocene Carbonate Systems: Potential Applications in Sedimentology and Environmental Reconstruction

摘要: Echinoderms represent a major ecological component and contribute considerably to Oligocene–Miocene carbonate sediments, both as macrofossils skeletal grains. The morphology of all five extant echinoderm classes (echinoids, asteroids, ophiuroids, crinoids, holothuroids) is reviewed. Disarticulated elements are muchmorecommoninsedimentsthanarticulatedspecimensforallechinodermclasses except for echinoids; studies relying on complete specimens alone may be severely biased. reproduction growth echinoderms, the composition skeleton, crystallography diagenesis ossicles skeleton consists high-Mg calcite with 3–18.5 wt% Mg. exhibits strong interlacing microcrystalline organic material nonrandom orientation crystals, achieving considerable hardness durability. Echinoderm biostratinomy identification disarticulated considered. origin sediment particles can usually recognised by their characteristic microstructure. Due high degree specialisation, remains often identified family or genus level, leading more accurate picture spatial temporal distributions. geochemistry reviewed respect Mg-content palaeotemperature proxy, Mg/Ca ratio monitor ancient seawater composition; Sr/Ca ratios carbon oxygen stable-isotopes altered during transformed low-Mg calcite. microstructure largely unaffected this process, but changes in isotopic signature minor/trace-element contents occur. These factors, together physiological effects isotope intake, hamper geochemical applications. However, echinoderms have been used successfully Phanerozoic chemistry:theMgandSrcontentsofechinodermskeletonsapparentlystronglycorrelate temperature. Asteroids ophiuroids probably best suited reconstructions because lack known fractionation within andbecausegeneticeffectsarelesspronouncedthaninechinoids.Controlledlaboratory experiments needed establish calibrations. account 5–30% specific Oligocene Miocene facies. They seem abundant temperate shelf carbonates than tropical settings. Diagenetic associated strongly affect embedding promote lithification. Bioerosion grazing echinoids important budgets coralreefs influencesthe modal size-distribution sediments production mud. Burrowing cause intensive bioturbation reworking sediments. provide valuable evidence palaeoenvironmental reconstructions. Ecological information gained actualistic comparisons modern functional morphological approach, allowing detailed assessment general life habits, substrate conditions, nutrient availability hydrodynamic regimes.