Late Miocene to early Pliocene planktonic foraminiferal sea surface temperature estimates from DSDP Site 103 (northern Blake-Bahama Outer Ridge) based upon the Modern Analog Technique

The final closure of the Central American Seaway had significant and well-documented implications for global climate and oceanographic conditions, particularly in the northern hemisphere. In the North Atlantic, primarily at high latitudes, the most significant change was an overall increase in sea surface temperature (SST) via the intensification of the Gulf Stream leading to the onset of northern hemisphere glaciation. This study addresses the question of exactly how the closure of the Central American Seaway impacted the Gulf Stream prior to the complete isolation of the Caribbean from the Pacific and how this affected tropical and subtropical northwestern Atlantic SST. In order to answer these questions, planktonic foraminifers from the late Miocene through early Pliocene sediments of DSDP Site 103 (Blake-Bahama Outer Ridge) were analyzed using multivariate analyses and the Modern Analog Technique. These analyses, combined with qualitative faunal interpretation, suggest a trend of increasing SST between 9.7 and 3.5 Ma. Modern analog results provide mean annual SST estimates of 24.03°C at 9.7 Ma, 24.53°C at 8.2 Ma, 26.03°C at 5.2 Ma, and 27.98°C at 3.5 Ma. The increase in SST during the late Miocene and early Pliocene suggests considerable deflection of the Circumtropical Current and resulting intensification of the Gulf Stream in the period prior to complete closure of the Central American Seaway. These SST estimates indicate that significant oceanographic changes occurred in waters not only proximal to the Pacific- Caribbean gateway, but also in waters outside the Central American region, and provides evidence for the timing and magnitude of gradual oceanographic reorganization prior to complete closure of the Central American Seaway.