Survey Report on Cooper River, S.C. (Shoaling in Charleston Harbor), Appendix A, Supplement 3. Special Geological Investigations Utilizing Diagnostic Minerals

摘要

X-ray diffraction and petrographic analysis of several hundred sediment samples from rivers, estuary, and tidal delta areas of the physiographic unit comprising Charleston Harbor has established mineral ratios and diagnostic minerals which may be used as natural tracers to delineate source areas. The minerals and their relations to source areas enable a process-response model capable of explaining the transport and deposition in shoal areas of Charleston Harbor. Suspeneded samples taken at regular intervals simultaneously at several stations in Charleston Harbor and approaches during a tidal cycle were analyzed for composition, salinity, and velocity parameters which confirm source areas delineated in bottom seidment as well as establishing tidal flow characteristics. The use of hornblende as a natural tracer in sand size sediment, as well as sedimentary parameter values, reveals that only fines are being contributed from the Piedomont-source santee watershed div erted to thge Cooper River, while kaolinite in t he clay-mineral suite from that source is abundant and in high proportions (70-80%) as contrasted to residual Coastal Plain clays (20-30%). Since montmorillonite is the most abundant Lower Coastal Plain clay mineral, the values of kaolinit e/mont morillonite enable an approximate statistical model which may be used as an index to source.