Non-skeletal carbonate production and stromatolite growth within a pleistocene deep ocean (Last glacial maximum, Red Sea)

Abstract

Quasi modern non-skeletal carbonates and stromatolites occur from the Red Sea shelf, proximal to the reef systems and continuous into the axial basin (512 to 2704 metres below present sea level). The lithified carbonates are intermixed with carbonate ooze forming a hard layer of 50 to 90 cm thickness. Decimetric platey fragments of lithified carbonate exhibit planar to columnar stromatolitic growth forms, lumpy microbial fabrics and internal brecciation features. The ultrastructures of lithified carbonates are formed by cryptocrystalline carbonate, mainly as aragonite spherulites, Mg-calcite peloids, anhedral mosaics of Mg-calcite and aragonite. Biogenic overgrowth, intercalations of calciturbidites and the type of interlocking relationships in the crystalline fabrics all indicate precipitation at the sea floor or close by. Morphological and mineralogical similarity with previously published microfabrics indicate microbial mediation of carbonate precipitation.