Light attenuation as a control for microbiogeomorphic features: Implications for coastal cave speleogenesis

摘要: San Salvador (Bahamas) is a carbonate island with dozens of flank margin caves formed in the phreatic zone by fresh seawater mixing within freshwater lens. These have no direct connection sea, and form at or close to tidally influenced fluctuating water table. After sea-level fall, their subaerial parts are enlarged mainly rock dissolution erosion level, condensation-corrosion breakdown processes. For understanding geomorphological features observed these how they related light attenuation, we investigated three sampling sites Lighthouse Cave, which has been re-invaded during Holocene highstand. A lens longer exists adjacent cave. Rock samples were collected above below internal lake shores entrance, twilight dark zones this Light electron microscopy examinations conducted for detecting microbial cells, as well bioconstruction bioweathering features. In addition, high precision laser scanner was used characterising sample microtopography. Our data showed that microtopography geomorphology shore (cave entrance) dominated bioweathering, whereas controlled combination both bioconstructive processes depending on availability. Bioconstructive structures, such semi-planar lamination, level Cave show due sea most important speleogenetic process. We propose evolution strongly degree diagenesis more than initial mechanism speleogenesis.