Oxygen and carbon isotope data for benthic foraminifera from DSDP Site 94-608 and ODP Site 208-1264, supplement to: Smart, Christopher W; Thomas, Ellen (2006): The enigma of early Miocene biserial planktic foraminifera. Geology, 34(12), 1041-1044

• Main Authors: Smart, Christopher W, Thomas, Ellen
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2006
• Subjects: Drilling/drill rig; Leg94; Leg208; Glomar Challenger; Joides Resolution; Deep Sea Drilling Project DSDP; Ocean Drilling Program ODP; Antarctic; Indian; Pacific; Weddell; Weddell Sea; Antarc*
• Online Access: https://dx.doi.org/10.1594/pangaea.713696; https://doi.pangaea.de/10.1594/PANGAEA.713696

Small biserial foraminifera were abundant in the early Miocene (ca. 18.9-17.2 Ma) in the eastern Atlantic and western Indian Oceans, but absent in the western equatorial Atlantic Ocean, Weddell Sea, eastern Indian Ocean, and equatorial Pacific Ocean. They have been assigned to the benthic genus Bolivina, but their high abundances in sediments without evidence for dysoxia could not be explained. Apertural morphology, accumulation rates, and isotopic composition show that they were planktic (genus Streptochilus). Living Streptochilus are common in productive waters with intermittent upwelling. The widespread early Miocene high Streptochilus abundances may reflect vigorous but intermittent upwelling, inducing high phytoplankton growth rates. However, export production (estimated from benthic foraminiferal accumulation rates) was low, possibly due to high regeneration rates in a deep thermocline. The upwelled waters may have been an analog to Subantarctic Mode Waters, carrying nutrients into the eastern Atlantic and western Indian Oceans as the result of the initiation of a deep-reaching Antarctic Circumpolar Current, active Agulhas Leakage, and vigorous vertical mixing in the Southern Oceans.