A Late Pleistocene to Mid-Holocene Stable Oxygen Isotope Record from a Belize Stalagmite

Abstract

A ~7,000 year stable isotope record from a Central American stalagmite is presented as a record of rainfall and consequently Intertropical Convergence Zone (ITCZ) tropical rain belt strength over the late Pleistocene to mid-Holocene. The "amount effect" explains the well-documented inverse relationship between rainfall amount and stable oxygen isotope values observed in tropical monsoon regions and consequently in stalagmite calcite from those regions. ITCZ rainfall influences much of the Central American tropical region and here a ~7,000 year stable isotope record from stalagmite ATM1 harvested from Actún Tunichil Muknal Cave in Belize is presented as a record of ITCZ influenced rainfall during the late Pleistocene to mid-Holocene (5,561 ± 2,488 BP - 12,605 ± 284 BP). Three major oxygen isotope excursions occur within the record. These excursions correspond to the global cold Younger Dryas and 8.2 ka events and a relatively undocumented wet period around 6,300 bp. The Younger Dryas manifests as a relatively moist period in central Belize while the 8.2 ka event manifests as a relatively dry period. The reason for the opposite responses to cooling elsewhere in the globe is posited to be due to orbital forcings. The 6,300 bp relatively wet period appears to be synoptic in scale and two possible triggers for the isotope excursion are presented: eustatic sea level rise causing lagoonal constriction, warming of water off the coast of Belize, and thus increased evaporation and precipitation over the study region; and hurricane clusters, evidenced in the region in the succeeding 1,000 years, in which the location of the Azores High funnels hurricanes to make landfall near the central Belize region. ATM1 provides evidence for tropical leads and/or lags to global climate events and bolsters the idea that high and low latitude climate relationships are complexly interlinked.