Abstract:
We use Oligocene-Miocene sections to evaluate the benthic foraminiferal response to relative sea-level fluctuations, paleoceanographic changes, and sequence stratigraphic architecture in siliciclastic (ODP Legs 150 & 174A) and carbonate (Leg 166) passive margin slope settings. Our goal is to unravel the sea level, circulation, and climate changes that influence faunal, isotopic, and sedimentation changes within a sequence stratigraphic framework. delta (super 18) 0 results from NJ slope Site 904 and Bahamas Site 1006 provide direct evidence independent of age uncertainties for a causal connection between latest Oligocene to Miocene glacioeustatic falls (inferred from 8110 increases) and sequence boundaries (reflections and core disconformities). Comparison of faunal and isotopic records shows that peak Uvigerina spp. abundances correspond to sea level rises and possible maximum flooding surfaces at Sites 903, 904, and 1073. Transported shelf taxa B. gracilis and N. pizarrensis indicate that both lowstand and highstand shedding occur at these NJ slope sites. Similarly, benthic foraminiferal faunas at Site 1006 indicate that periods of increased downslope transport of shallow water material occurred during both sea level rises and falls. Benthic foraminiferal delta (super 13) C records from Site 1006, located within the modern thermocline, were compared with previously published records to reconstruct the middle-late Miocene circulation changes in the Straits of Florida. Ventilation was relatively low prior to 12.5 Ma and generally higher from 12.5-9 Ma, punctuated by several intervals of low ventilation. Increased thermocline ventilation is associated with increased Northern Component Water (NCW) flux. Associated faunal changes are minor, although P. wuellerstorfi decreases in abundance with increased thermocline ventilation. P. wuellerstorfi is generally associated with better ventilated water masses in other settings; however, the decreased abundances at Site 1006 may reflect minor water depth changes from middle to upper bathyal water depths.