SUBSURFACE UPPER MANTLE-CRUST DYNAMICS IMPACTING OVERLYING CARBONATE WEDGES

Upper mantle and crust interact, extensively and complexly, with resultant interactions modifying overlying calcareous and other sediments. From top to bottom, sediments traverse from unconsolidated conditions akin to those of original deposition, to semi-consolidated with free waters partially expelled, and to consolidated and cemented to rocks and commencement of crust. Upper crust is brittle and given to brittle fracture, and lower crust, given estimated heat from 200 to 400 C, from a calculated thermal gradient of circa 25 C/km depth, is deemed semi-plastic with a transitional layer between. Upper mantle appears semi-plastic with potential for convective motion, lateral and vertical, from basin-spanning convection cells to small-scale cells, and multi-sized mantle plumes. Mantle/crust interaction can be driven by conduction, convection, and/or advection. Calcareous sediments are predominantly shallow water deposits, formed from coral reefs and shells, both able to be reduced to limey muds. Smaller grain sizes may be transported by oceanographic currents. Limestones are generally original deposits; with magnesium addition (pene-contemporaneously to later on by fluids) forms dolomite. Fluid temperatures, relative to ambient, can be hotter, same as, or cooler and the dolomitization mechanism can be hydrothermal, geothermal, or hydrofrigid, respectively with one or more mechanisms operating over a limestone/dolomite lifetime. Fluid origins range from upper crust to mantle, inputs include lateral flowage from adjacent sedimentary cover to surficial/shallow subsurface waters descending to calcareous beds, respectively. Groundwaters flowing hundreds if not a thousand km can be diverse.