A 6000-year record of environmental change from Grand Cayman, British West Indies

Abstract

Three sediment cores from North Sound lagoon provide a continuous record of environmental changes (atmospheric moisture and temperature) that have affected Grand Cayman, British West Indies, over the last ~6000 years. Changes in the facies and carbonate components indicate a transition from fresh-brackish-water coastal ponds to a fully marine environment, which coincided with global sea level rise ~2000 years ago. Variations in ∑REE + Y (4 to 45 ppm), Ti (6 to 71 ppm), and Fe (284 to 11,783 ppm) concentrations in these sediments reflect past changes in atmospheric moisture. Sea surface temperatures inferred from δ18O values of the sediments provide a record of past temperature fluctuations relative to the present-day average of 28 °C for North Sound. This includes two cool-dry periods (CD1 and CD2) from ~3850 to 1280 BCE and ~480 to 800 CE, two mild-wet periods (MW1 and MW2) from ~1280 to 200 BCE and ~1850 to 1980 CE, one warm-dry period (WD1) from ~200 BCE to 480 CE, and one cool-wet (CW1) period from ~800 to 1850 CE. These patterns are consistent with records from elsewhere in the Caribbean region. Accordingly, during MW1, CW1A, and MW2 the Intertropical Convergence Zone (ITCZ) was in a northern position and/or the North Atlantic Oscillation (NAO) was in a negative phase, resulting in increased atmospheric moisture and elevated temperatures. In contrast, CD1, WD1, and CD2, resulted from a southern position of the ITCZ and/or a positive phase of the NAO, resulting in low temperatures and decreased atmospheric moisture.