CALCITE RAFTS - RAPID DEPOSITION OF TRANSGRESSIVE INFILL CAVE SEQUENCES AS A NEW PALEO SEA LEVEL PROXY
Field experiments in cave sites near the Caribbean coast provide observations on the mineralogy and physical nature of calcite rafts, sedimentation processes, and formation and sedimentation rates. Under some conditions, rafts form over days to hours; they may reach visible size in 72 hours, and over three months cover 80% of 1 m2 experimental berms. While the greatest raft formation rate was observed in quiescent waters, floating rafts were transported intact particularly at higher water levels when flow at the water table was greatest. Sedimentation within each site was noted to be spatially heterogeneous within passages. Manual push cores from flat toped raft banks revealing intact stratigraphy, with variation in raft textures, size, and organic content. Raft sedimentation rates are on the order of 1 cm/100 years based on accumulation rates in traps, and dating down core.
These results support the potential of calcite rafts deposits as a valuable new expanded record for low latitude carbonate coastlines, particularly with the elevations of flat toped infill sequences sedimented near the modern and paleo water table level reflecting sea level transgressions.