Date of Award

4-1978

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. W. David Kuenzi

Second Advisor

Dr. William B. Harrison III

Third Advisor

Dr. Lee C. Gerhard

Access Setting

Masters Thesis-Open Access

Abstract

Boiler Bay, on the northeast coast of St. Croix, is 200 m wide, 800 m long, and about 3-5 m. deep. The hay is separated from the open Caribbean by a barrier reef. Winds from the east drive currents westward across a narrow carbonate platform (where they entrain platform-derived carbonate mud) and into the east end of the bay. Longshore currents continue westward through the bay, and the entrained platform- derived suspended load is combined with bay-produced carbonate mud and swept northwestward off the platform after passing through a 6 km complex of bays along the northeastern shore. The suspended load leaving Boiler Bay consists of 60% carbonate mud, and includes: 54% high-magnesium calcite (HMC), produced mainly by coralline red algae and benthonic foram epibionts on Thalassia; 32% aragonite, derived largely from green algae and bored corals; and 14% low-magnesium calcite (LMC), contributed by pelagic forams and bored mollusks. The minimum quantity of carbonate mud produced in the bay, and contributed to the suspended load is 5.7X104kg CaCO3 per year.

Carbonate muds from two deep-sea cores, taken 6 and 12 km off platform and down drift from the bay dispersal system, contain: 21 and 36% HMC, 4 and 26% aragonite, and 75 and 38% LMC, respectively. The reduction in HMC and aragonite in the core reflects dilution by LMC coccoliths and pelagic forams; however, SEM observations and the Mg content of the HMC in the muds indicate addition of platform HMC and aragonite to the deep-sea muds. Differences between the carbonate mineralogy of the two cores apparently reflect their locations relative to off-platform dispersal patterns.

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