Submarine Lithification of Jamaican Reefs: ABSTRACT

Abstract

Widespread lithification of recent reef framework is occurring just below the reef-water interface in all zones of the reef to depths of at least 70 m on the north coast of Jamaica. Several different framework-binding End_Page 727------------------------------ processes appear to be involved: (1) crusts of organic origin, commonly concentrically layered deposits of red algae, Foraminifera, and Bryozoa, and (2) thick, laminated, lithified, micrite crusts with a smooth to nodular surface, preferentially accreted upward and not clearly associated with any calcareous taxa. The organic crusts commonly occur just under the reef surface, whereas the hard concretionary crusts are common deeper within the reef, lining the numerous channels and cavities that permeate the framework. Many of the reef pores (both the primary inter- and intra-framework pores and also cavities produced secondarily by boring organisms such as Cliona) are filled with lithified sand, micrite, or acicular crystalline cement. Just beneath the reef surface is extensive lithification of poorly sorted micritic sediments between and within the framework. Sand trapped in interframework cavities is consolidated by drusy cements. In many places, the lithified material is bored by Cliona and the resulting cavities are refilled and relithified, indicating that these processes occur at a rapid rate. Similar features are recognized in Pleistocene reefs on the north coast of Jamaica. This observation suggests that the lithification processes are common in time as well as in space. End_of_Article - Last_Page 728------------