Latest Cretaceous climatic and environmental change in the South Atlantic region

Abstract

Latest Maastrichtian climate change caused by Deccan volcanism has been invoked as a cause of mass extinction at the Cretaceous‐Paleogene (K‐Pg) boundary (~66.0 Ma). Yet late Maastrichtian climate and ecological changes are poorly documented, in particular on the Southern Hemisphere. Here we present upper Maastrichtian‐lower Danian climate and biotic records from the Bajada del Jagüel (BJ) shelf site (Neuquén Basin, Argentina), employing the TEX86 paleothermometer, marine palynology (dinoflagellate cysts), and micropaleontology (foraminifera). These records are correlated to the astronomically tuned Ocean Drilling Program Site 1262 (Walvis Ridge). Collectively, we use these records to assess climatic and ecological effects of Deccan volcanism in the Southern Atlantic region. Both the TEX86‐based sea surface temperature (SST) record at BJ and the bulk carbonate δ18O‐based SST record of Site 1262 show a latest Maastrichtian warming of ~2.5–4°C, at 450 to 150 kyr before the K‐Pg boundary, coinciding with the a large Deccan outpouring phase. Benthic foraminiferal and dinocyst assemblage changes indicate that this warming resulted in enhanced runoff and stratification of the water column, likely resulting from more humid climate conditions in the Neuquén Basin. These climate conditions could have been caused by an expanding and strengthening thermal low over the South American continent. Biotic changes in response to late Maastrichtian environmental changes are rather limited, when compared to the major turnovers observed at many K‐Pg boundary sites worldwide. This suggests that environmental perturbations during the latest Maastrichtian warming event were less severe than those following the K‐Pg boundary impact.

Climate and sea‐level changes across a shallow marine Cretaceous–Palaeogene boundary succession in Patagonia, Argentina

“…; Woelders et al . ) this stratigraphic hiatus roughly covers planktic foraminiferal Zones P0 to P1a, with sedimentation starting again in Zone P1b of Olsson et al . (; see Keller et al .…”

“…; Woelders et al . ). The concurrence of this hiatus directly at the boundary in both sections suggests that it might have been caused by a regional or even global process.…”

“…; Woelders et al . ). Although tentative, in view of the concurrence with the stratigraphic hiatus at the Bajada del Jagüel section, it is plausible that the stratigraphic hiatus at the K–Pg boundary in the San Ramón section roughly covers the same biostratigraphic interval.…”

“…Woelders et al . ). Fortunately, organic‐walled dinoflagellate cysts (dinocysts) are often abundantly present in very shallow‐marine settings (e.g.…”

“…Correlation of our palynological and organic geochemical data from this very shallow, nearshore site with similar recently published data from the mid‐shelf deposits of the Bajada del Jagüel section in the Neuqúen Basin, Argentina (~500 km north‐north‐east of the San Ramón section; Woelders et al . ) may help to distinguish local from regional signals, and will allow an evaluation of the stratigraphical completeness of our record. Combining these records provides a way of assessing possibly synchronous climatic and sea level changes across the K–Pg boundary in Argentina.…”