Diatom absolute abundance, Biogenic Silica, and preservation index at Site U1479 during the Mid-Pleistocene Transition

This dataset provides the Mid-Pleistocene Transition biogenic silica (BSi) concentrations from IODP Site U1479, drilled ~85 nautical miles southwest of Cape Town, South Africa in the southwestern Indian Ocean during IODP Expedition 361: South African Climate (30 January to 31 March 2016). BSi weight percent (wt. %) was measured for 74 samples using a modified Mortlock and Froelich (1989) method. Each sample, approximately 55 mg, was freeze-dried and processed to remove organic matter and carbonates with 30% hydrogen peroxide and 1-M hydrochloric acid. Following this preparation, the samples were treated with 10% sodium carbonate and heated at 80°C for 5 hours to break down the opal content. BSi concentration was then quantified using a molybdate-blue spectrophotometer, calibrated with standards ranging from 0 to 50 ppm. Absolute diatom abundance (ADA) was calculated using the methods outlined in Warnock and Scherer 2015. Relative abundance percentages came from diatom counts presented in Coenen et al. (2026). Additionally, Principal components analysis was used to separate diatoms into groupings based on environmental conditions and how these values were calculated is also discussed and outlined in Coenen et al. (2026).