We present a detailed taxonomic assessment of Late Cretaceous (Turonian–Santonian) agglutinated and calcareous benthic, and planktonic foraminifera from IODP Site U1512 in the Great Australian Bight, also known as the “Australo-Antarctic Gulf” (AAG). This study expands upon the dataset of Wolfgring et al. (2021, 2023) with 25 additional samples and a systematic revision of key taxa. Agglutinated foraminifera (Kalamopsis grzybowskii, Haplophragmoides) dominate the assemblages, reflecting the persistent low-carbonate setting. Dysoxic conditions in the semi-restricted AAG were influenced by high terrestrial input from the Ceduna River system. The marginal marine seaway documents limited oceanic exchange. Calcareous benthic (e.g., Notoplanulina, Gyroidinoides) and planktonic foraminifera (e.g., Whiteinella baltica) occur only sporadically, marking short-lived phases of improved marine connectivity, possibly tied to tectonic subsidence and eustatic highs during the Turonian–Coniacian. The Coniacian–Santonian strata record an increase in calcareous taxa and the appearance of Uvigerinammina jankoi, together with the consistent presence of Bulbobaculites problematicus, offering a link to the Tethyan agglutinated foraminiferal biozonation of Geroch and Nowak (1984). By integrating new taxonomic data with existing geochemical and biostratigraphic records, this work refines paleoenvironmental reconstructions of the AAG, highlighting the interplay of tectonics, freshwater runoff, and ocean circulation patterns during the stages of the opening of the AAG and the breakup of eastern Gondwana.