Late Cretaceous Paleoceanographic Evolution and the Onset of Cooling in the Santonian at Southern High Latitudes (IODP Site U1513, SE Indian Ocean)

Abstract

The latest Cenomanian to Santonian sedimentary record recovered at IODP Expedition 369 Site U1513 in the Mentelle Basin (SE Indian Ocean, paleolatitude 60°S at 85 Ma) is studied to interpret the paleoceanographic evolution in the Southern Hemisphere. The planktonic foraminiferal assemblage changes, the depth ecology preferences of different species, and the surface and seafloor temperature inferred from the stable isotopic values measured on foraminiferal tests provide meaningful information to the understanding of the Late Cretaceous climate. The hothouse climate during the Turonian‐Santonian, characterized by weak latitudinal temperature gradients and high atmospheric CO2 concentrations, is followed by a progressive cooling during the Campanian. At Site U1513 the beginning of this climatic transition is nicely recorded within the Santonian, as indicated by an ∼1‰ increase in δ18O values of planktonic foraminifera suggesting a decline in surface water paleotemperatures of 4°C. The onset of cooling is mirrored by changes in the planktonic foraminiferal assemblages including extinctions among surface and deep dwellers, appearances and diversification of newly evolving taxa, and changes from predominantly epifaunal oxic to infaunal dysoxic/suboxic taxa among co‐occurring benthic foraminifera. Overall, the data presented here document an interval in the Santonian during which the rate of southern high latitude cooling increased. Both surface and bottom waters were affected, although the cooling signal is more evident in the data for surface waters. This pattern of cooling ascribes the deterioration of the Late Cretaceous climate to decreased CO2 in the atmosphere and changes in the oceanic circulation correlated with enhanced meridional circulation.

Biotic and Paleoceanographic Changes Across the Late Cretaceous Oceanic Anoxic Event 2 in the Southern High Latitudes (IODP Sites U1513 and U1516, SE Indian Ocean)

“…The biostratigraphically diagnostic benthic foraminifera Gavelinella intermedia , Gavelinella schloenbachi , and Scheibnerova protoindica , which have been reported to occur across the Cenomanian‐Turonian boundary interval in southern high latitudes localities (Hornibrook et al., 1989; Scheibnerová, 1976) were also identified. Diversity throughout the studied interval averages 70 species and is quite low compared to the 100–200 taxa recorded in the Turonian to Santonian stratigraphic interval at Site U1513 (Petrizzo, MacLeod, et al., 2022; Wolfgring et al., 2022). Though no extinctions of benthic foraminifera are evident, a shift in dominant benthic foraminiferal taxa in the upper part of the OAE 2 interval is observed.…”

“…(2021) and Petrizzo, MacLeod et al. (2022). Specifically, rock samples were dried, weighed and soaked in a solution of water and H 2 O 2 , washed over 250, 125, and 38 μm sieves and dried to obtain washed residues.…”

Data report: Cenozoic and Upper Cretaceous bulk carbonate stable carbon and oxygen isotopes from IODP Expedition 369 Sites U1513, U1514, and U1516 in the southeast Indian Ocean

“…Here we present new and published (Petrizzo et al, 2021(Petrizzo et al, , 2022Vahlenkamp et al, 2020) Cretaceous and Cenozoic bulk carbonate carbon and oxygen stable isotope (δ 13 C and δ 18 O) records from Sites U1513, U1514, and U1516, which were cored during Expedition 369 (Figure F1). This chemostratigraphic data set provides an important empirical framework constraining the location of key intervals of environmental change, which should facilitate future sampling for high-resolution studies, including astrochronological work, that will ultimately help to better understand the relationship between tectonic and environmental changes in the high southern latitudes.…”

“…A total of 192 samples, including both 2 cm 3 samples collected for bulk isotopic studies as well as residues from samples for shipboard carbonate analyses from Core 369-U1513A-1H through Section 50X-1 and Sections 369-U1513D-6R-1 through 54R-4, were used to document trends in bulk carbonate isotopes at Site U1513 (Table T1). Of these bulk carbonate δ 13 C and δ 18 O analyses, 145 analyses are new in this study and 47 analyses were presented in Petrizzo et al (2022). Sampling density was typically one sample per core for most of the section with increased sampling density in the intervals predicted to span oceanic anoxic events (OAEs).…”

Planktonic foraminifera document palaeoceanographic changes across the middle Cenomanian carbon-isotope excursion MCE 1: new evidence from the UK chalk

“…Rotaliporids found in pelagic settings of the Tethyan Realm have been interpreted as oligotrophic, and thus required a relatively thick and stratified upper water column to complete their life cycle. Muricohedbergellids are adapted to relatively cold/deep layers of the water column in open ocean settings at low latitudes (Norris & Wilson, 1998; Wilson et al 2002; Petrizzo et al 2008; Ando et al 2010), but they may have inhabited shallower layers at the higher latitudes of the Southern Hemisphere, probably because sea-surface waters were cooler (Falzoni et al 2016; Petrizzo et al 2020, 2021, 2022a,b). Moreover, muricohedbergellids are commonly found in low-salinity coastal environments to normal-salinity open-ocean settings, indicating they had an opportunist meso-eutrophic life strategy (e.g.…”