Benthic foraminifera and paleoenvironmental turnover across the mid-Maastrichtian event in the Tropical Atlantic Ocean (ODP Site 1258)

In recent years, there has been an increasing number of studies describing significant disturbances of the global carbon cycle during the latest Cretaceous. One example of these disturbances is the Mid-Maastrichtian Event (MME), which was likely related to changes in deep ocean circulation, particularly in the Atlantic realm.

To track and characterize the influence of the MME in deep-water environments in the equatorial South American margin, we conducted micropaleontological (benthic foraminifers) and geochemical analyses of sediments from Ocean Drilling Program (ODP) Site 1258 (Demerara Rise, offshore Suriname). Both geochemical tracers and benthic foraminiferal assemblages suggest the occurrence of paleoenvironmental reorganizations during the entire Maastrichtian, related to changes of intermediate to deep-water oxygenation and surface productivity. Benthic foraminiferal assemblages, characterized by typical deep-sea taxa (Aragonia, Nuttallides truempyi, Coryphostoma, Strictocostella, among others), indicate suboxic bottom water conditions with some oxygenation pulses, which correlate with changes in elemental ratios of redox-sensitive trace metals (Ni/Al, Cu/Al). Sediment elemental ratios (log(Fe/Ca), Si/Ti, Fe/K) indicate fluctuations in the silica and carbonate export via surface productivity, and a probable hydroclimate disturbance since the early Maastrichtian. During the MME, three phases of environmental evolution occurred: (1) high surface productivity and reduced bottom water oxygenation during subinterval MME1, (2) moderate surface productivity and increased bottom water oxygenation in subinterval MME2, and (3) recovery in surface productivity, suboxic conditions in the deep-sea, and more humid conditions during subinterval MME3. These paleoenvironmental disturbances were probably caused by increased influence of high-latitude deep-waters (North Atlantic source instead of the Southern Ocean) on low latitudes, which likely influenced latitudinal migrations of the Paleo-Intertropical Convergence Zone.