ABSTRACT

Field reconnaissance and petrographic and mineralogic studies of rocks from Cozumel Island indicate at least two periods of submergence with associated shallow-water deposition, and two intervening periods of emergence with associated subaerial vadose diagenesis during the late Pleistocene.

Two older Pleistocene, ten late Pleistocene and one Holocene shallow-water carbonate facies are differentiated by their geometries and positions, megafauna, sedimentary structures, textures, carbonate grain-types, mineralogies and cements. The two older Pleistocene facies represent patch reef and sandy bank interior environments of deposition. The younger late Pleistocene facies were deposited in windward and leeward coral reef, reef pass, seagrass-stabilized backreef, oolite shoal, storm channel, beach and dune environments. Holocene beachrock is also found on the island.

Previously described 122,000 ± 2,000 years B.P. reef, backreef and beach-nearshore facies on the eastern Yucatan coast are similar in character and position to the 121,000 ± 6,000 years B.P. late Pleistocene facies found on Cozumel Island. In reconstructing the depositional history of Cozumel Island, it was determined that no movement of the island relative to the mainland has occurred in the last 125,000 years.