Deposition and sea level fluctuations during Miocene times, Grand Cayman, British West Indies
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Abstract
The Lower to Middle Miocene Cayman Formation on Grand Cayman, which is part of the Bluff Group, is at least 130 m thick. The mostly dolomitized Cayman Formation is herein divided into a ‘limestone member’ and ‘dolostone member’ as limestone is found in the formation in the central part of Grand Cayman. Sediments of the Cayman Formation were deposited in water 10-30 m deep on an isolated open bank with no evidence of reef development. Facies development was controlled primarily by water depth and energy levels. The Cayman Formation is divided into eight facies that range from Leptoseris-Amphistegina facies to Amphistegina-Bivalve facies. Depositional environments range from deep open bank to very shallow open bank. The succession reflects two shallowing-upward sequences that are separated by a transgressive event that saw sea level rise by 20-25 m. Sea level changes were probably related to eustatic changes rather than local tectonic changes.