Late Cretaceous Temperature Evolution of the Southern High Latitudes: A TEX₈₆ Perspective

Abstract

The Late Cretaceous was a greenhouse world, characterized by elevated temperatures and high atmospheric pCO2. Even in the context of an extreme greenhouse climate, existing planktic foraminiferal δ18O data from the Falkland Plateau (paleolatitude of ~55°S) suggest anomalous warmth, with sea‐surface temperatures (SSTs) >30 °C for much of the Late Cretaceous, followed by sudden cooling in the Campanian. Over the last two decades, there has been discussion as to whether these high δ18O‐based SSTs reflect a genuine temperature signal and, if so, whether there was a local temperature anomaly in the South Atlantic or whether the data are representative of zonal paleotemperatures at 55°S. To provide new insights into the degree of ocean warming in the southern high latitudes during the Late Cretaceous (Cenomanian to Campanian), new SST records from the Falkland and Kerguelen Plateaus are presented here using the organic geochemical paleothermometer TetraEther indeX of 86 carbon atoms (TEX86). Overall, the TEX86 data support the δ18O data, indicating extreme and widespread warmth in the middle to high southern latitudes in the Late Cretaceous, with SSTs from 27 to 37 °C. Crucially, the TEX86 data show slow, steady cooling from the Turonian to the Campanian and suggest that temperature gradients during the Campanian did not become as steep as suggested by some planktic foraminiferal data.

Maastrichtian-Rupelian paleoclimates in the southwest Pacific – a critical evaluation of biomarker paleothermometry and dinoflagellate cyst paleoecology at Ocean Drilling Program Site 1172

“…Reconstructions of deep-sea (Westerhold et al, 2020) and sea surface temperature (Bijl et al, 2009;2013a;Cramwinckel et al, 2018;Frieling et al, 2014;Hollis et al, 2014;Inglis et al, 2015;O'Brien et al, 2017;Evans et al, 2018;O'Connor et al, 2019;Sluijs et al, 2020) have revealed overall cool climate in the Maastrichtian and Paleocene, long-term warming towards the early Eocene Climatic Optimum (EECO; 53.4 -49.2 Ma), and subsequent cooling during the middle and late . The EECO stands out as particularly warm, with icefree polar regions (Bijl et al, 2013a;Hines et al, 2017;Pross et al, 2012;Frieling et al, 2014).…”

Late Cretaceous stratigraphy and paleoceanographic evolution in the Great Australian Bight Basin based on results from IODP Site U1512

“…The excellent recovery of Upper Cretaceous rocks achieved at IODP Site U1512 (>90%), and the deeper and more basinward position (relative to existing wells) of this site within the Great Australian Bight makes the new cores a novel, potentially important, archive of Late Cretaceous conditions in the region. The lower Turonian rocks from the base of the recovered sequence were deposited within the warmest portion of the Late Cretaceous greenhouse climate, and deposition continued through to the early Campanian by which time Earth had cooled significantly (e.g., Huber et al, 2018;O'Connor et al, 2019). The sediments also span the time of expected initiation of seafloor spreading within the western to central portions of the Southern Rift System and are partially coeval with thick marine shales in the Otway Basin to the east (Gallagher et al, 2005).…”

Supplemental Material: Geochronology of volcanically associated hydrocarbon charge in the pre-salt carbonates of the Namibe Basin, Angola

“…S11). Given that the cements formed during Upper Cretaceous greenhouse conditions (O'Brien et al, 2017;O'Connor et al, 2019) at a latitude of roughly 25°S (Torsvik et al, 2009), a conservative ambient surface temperature estimate of 25°C seems reasonable. Using typical meteoric water (δ 18 Owater) values of -2 to -20 (Standard Mean Ocean Water, SMOW; Moore and Wade, 2013), the C1 cements could have precipitated from meteoric waters at ambient temperatures to around 40°C.…”