Paper No. 52-7
Presentation Time: 10:30 AM
FORAMINIFERA AND XRF ELEMENTAL ANALYSIS OF TWO CUBAN LAGOONS DOCUMENT INCREASED ARIDITY IN CUBA DURING THE LATE HOLOCENE
Coastal lagoons are not often used as paleoclimate archives because of their complex geomorphic history which can be affected by climate and sea-level change. This study from Punta de Cartas and Playa Bailen, Cuba shows that combined foraminiferal and XRF elemental analysis can isolate the effects of climate change (wet vs dry) on lagoon environments. Foraminiferal assemblages from both Punta de Cartas and Playa Bailen show increasing diversity over the past 4000 yrs BP with a prominent increase at ~1100-1400 yrs BP. Assemblages were initially dominated by Ammonia spp. (eg. Ammonia tepida) and Elphidium spp. (eg. Elphidium excavatum) indicating brackish salinity but increasing minor species, such as miliolids (eg. Triloculina spp. Quinqueloculina spp.), indicate a shift to more marine conditions up-core. Correspondingly, terrigenous input into the lagoon (Fe, Ti and K) generally declined over the past 4000 yrs BP but showed a flexion point at ~1100-1200 yrs BP likely due to decreasing precipitation. Fe, Ti and K have been used as proxies for weathering rates in tropical and sub-tropical basins with greater input during wet vs dry periods but have never been applied to shallower lagoon systems with their complex geomorphic histories. The shared timing between the XRF and foraminiferal data inferring decreased freshwater input into the lagoon provides confidence for the onset of drier climate conditions. The correspondence between the two lagoons situated ~ 10 kms apart suggests a regional effect with increasingly arid conditions developing since the mid-Holocene (4 kyr BP) but with a pronounced trend over the last ~ 1200 yrs BP which matches other climate records from the Caribbean.