Campanian‐Maastrichtian intermediate‐ to deep‐water changes in the high latitudes: Benthic foraminiferal evidence

Abstract

18 O transition reflects a change in intermediate-to deep-water circulation from low-latitude to high-latitude water masses, then this change would result in cooler temperatures, higher oxygen concentration, and possibly lower organic-matter flux at the seafloor, resulting in a major benthic foraminiferal assemblage change. If, however, the d 18 O transition was mainly triggered by ice formation, no considerable compositional difference in benthic foraminiferal assemblages would be expected. Our data show a separation of the studied succession into two parts with distinctly different benthic foraminiferal assemblages. Species dominating the older part (73.0-70.5 Ma) tolerate less bottom water oxygenation and are typical components of low-latitude assemblages. In contrast, the younger part (70.0-68.0 Ma) is characterized by species that indicate well-oxygenated bottom waters and species common in high-latitude assemblages. We interpret the observed change in benthic foraminiferal assemblages toward a well-oxygenated environment to reflect the onset of a shift from low-latitude toward high-latitude dominated intermediate-to deep-water sources. This implies that a change in oceanic circulation was at least a major component of the CMBE.

Late Cretaceous (late Campanian–Maastrichtian) sea-surface temperature record of the Boreal Chalk Sea

“…On the contrary, our results tend to show consistency with a glacio-eustatic scenario as previously supported by Barrera and Savin (1999) and Miller et al (1999). Despite the fact that Kominz et al (2008) used A Geologic Time Scale 2004 with the K-Pg and Campanian-Maastrichtian boundaries at 65.5 and 70.6 Ma, respectively, comparison of the timing of the two cooling episodes appears to match fairly well with that of the two major lowstands in the New Jersey margin sea-level curve (Kominz et al, 2008;Fig. 5).…”

“…Sealevel changes could trigger the onset and termination of the late Campanian-early Maastrichtian CIE by shifting calcium carbonate accumulation and organic-matter burial from shelf to open-ocean areas (Barrera and Savin, 1999;Friedrich et al, 2009). The occurrence of the CIE and the early Maastrichtian cooling have been recently explained mainly by a global change in the source of intermediate and deep-water masses and the onset of deep-water formation in the Southern Ocean, favoured by the opening of tectonic gateways (Robinson et al, 2010;Koch and Friedrich, 2012). However, a reorganisation in the global oceanic circulation is actually compatible with a glacio-eustatic scenario and could have been triggered both by tectonics and glaciation.…”

Episodes of intensified biological productivity in the subtropical Atlantic Ocean during the termination of the Middle Eocene Climatic Optimum (MECO)

“…Pullenia spp. are infaunal taxa [ Corliss , ; Frenzel , ] that are well adapted to eutrophic bottom water conditions [e.g., Kaiho , ; Mackensen et al ., ] but are typically found in cold water and used as an indicator for the influence of polar water masses [e.g., Koch and Friedrich , ; Mackensen et al ., ; Widmark , ]. Hence, we suggest that the abundance of Pullenia spp.…”

Campanian‐Maastrichtian ocean circulation in the tropical Pacific

“…The causal mechanisms of these changes in climate and the global carbon cycle are still a matter of debate, and controversial hypotheses exist. One hypothesis suggests a temporary reversal in ocean circulation manifested by the shift of intermediate to deep water sources toward high southern latitude sites [e.g., Barrera et al ., ; Li and Keller , ; D'Hondt and Arthur , ; Friedrich et al ., ; Koch and Friedrich , ]. Another model relates observed changes in benthic foraminiferal stable oxygen isotope signatures to eustatic sea level falls [e.g., Barrera , ; Barrera and Savin , ; Li et al ., ] and the buildup of small ephemeral ice sheets [e.g., Miller et al ., ; Miller et al ., ; Miller et al ., ].…”