Albian integrated foraminiferal and calcareous nannofossil biostratigraphy in the southern high latitudes (IODP Site U1513, Indian Ocean) across OAE 1d, and correlation to low latitudes

The International Ocean Discovery Program (IODP) drilled Sites U1513, U1514, and U1516 during Expedition 369 that recovered “middle” to Upper Cretaceous sediments in the Mentelle Basin (offshore Australia, Indian Ocean) located at a paleolatitude of 57°S–62°S. While all three sites contain Albian strata, Hole U1513D provides the most extensive and well-preserved record. Calcareous nannofossils of Site U1513 are relatively diversified and show typical high-latitude assemblages allowing the construction of a biostratigraphic framework. The Albian strata span calcareous nannofossil subzones CC8a to CC9a-b as indicated by the sequential first occurrences of Tranolithus orionatus , Axopodorhabdus biramiculatus , Eiffellithus monechiae and Eiffellithus turriseiffelii . The planktonic foraminiferal biostratigraphy based on the occurrence of Clavihedbergella simplex , Ticinella primula and Laeviella bentonensis , identifies the upper Albian interval, although the lack of marker taxa hampered the application of the tropical-subtropical biozonation. The planktonic foraminiferal assemblage is dominated by the small-sized Microhedbergella praeplanispira . Benthic foraminiferal data document cosmopolitan agglutinated and calcareous taxa and contain the markers Gavelinella intermedia , Osangularia schloenbachi , as well as taxa typical in high latitudes, e.g., Eomarssonella crespinae and Scutuloris sp. The lower Albian is dominated by agglutinated foraminifera. Through the middle to lower upper Albian interval, calcareous benthic foraminifera increase in abundance followed by a decline with increasing abundance of agglutinated forms in the upper Albian. In the uppermost part of the studied section a previous publication identifies the Oceanic Anoxic Event 1d by changes in the δ13C signature. The biostratigraphic data documented in the study at hand support the placement of this event.