About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 2. (February)

First Page: 316

Last Page: 316

Title: Diagenesis and Sea Level Change in a Pleistocene Coral Reef, San Salvador, Bahamas: ABSTRACT

Author(s): Brian White, Karen A. Kurkjy, H. Allen Curran

Article Type: Meeting abstract


Near the Cockburn Town reef (dated 125,000 yr B.P.), precisely surveyed bench marks are related to accurately measured mean sea level, and they provide a convenient datum plane. This coral reef developed during a sea level highstand of no more than 10,000 yr, which was insufficient time for significant subsidence; however, subsidence of approximately 3 m may have occurred since the formation of the reef. Sea level changes were caused by fluctuations in glacial-ice volume. The upper beach to dune transition, which is in the calcarenites overlying the reef, is at +4 m. A minimum highstand of +7 m is indicated when corrected for subsidence.

Below +2.5 m, marine aragonite cement occurs within the intragranular pore space of the following: Halimeda plates, benthic foraminifera, Favreina (Callianassid fecal pellets), gastropods, and corals. Marine aragonite cement also occurs as intergranular isopachous rims on matrix grains of coral rubblestone. Remaining pore space was partly to completely occluded by freshwater vadose calcite cements, which occur without marine cements in the overlying shallow subtidal, beach, and dune calcarenites. No unequivocal freshwater phreatic cements have been found, although syntaxial overgrowths and irregular calcite rims about grains do occur in finer grained sediments where local patches of freshwater saturation occurred within the vadose zone. Later calichification, which affected all facies is characterized by alveolar texture, whisker calcite, microsparite, rare bladed calcite spar, Microcodium, and rhizocretions.

End_of_Article - Last_Page 316------------

Copyright 1997 American Association of Petroleum Geologists