Transgressive-regressive cycles in the Ironshore Formation, Grand Cayman, British West Indie

Most studies of Caribbean carbonate deposits measure sea level in relation to established highstands. In this study, however, examination of the Ironshore Formation on Grand Cayman revealed a succession of 6 units (A, B, C, D, E, and F) whose deposition ages correlate to transgressive-regressive sea level cycles. The two youngest units, E and F, were discovered during the course of this study. Onshore and offshore fossil dates established that Unit D ranges in age from 123 to 147 ka (average133 ka), Unit E from 95 to 110 ka (average 101 ka), and Unit F from 80 to 87 ka (average 80 ka). Unit D was deposited during the transgression that led to the Sangamon highstand. Units E and F were deposited throughout the transgressive and regressive cycles of substages 5c and 5a, respectively.