Is There Evidence of A “Strangelove Ocean” After The K/Pg Boundary? A New Unbiased Benthic Foraminiferal Record

The response of deep-sea ecosystems to the Cretaceous–Paleogene (K/Pg) mass extinction is crucial for understanding post-impact carbon-cycle disruptions and benthic ecological resilience. Our research presents a new unbiased quantitative record of deep-water agglutinated foraminifera (DWAF) with high resolution, coupled with calcareous nannoplankton and stable carbon and oxygen isotopes from Gubbio (Umbria-Marche Basin, Italy) ranging from 6.4 m below to 6.4 m above the K/Pg boundary clay. The dataset is based on highly standardized sampling intervals and weights, consistent sample preparation, in an attempt to minimize the Signor–Lipps bias, accurate taxonomic treatment and statistical analysis.

DWAF abundance and benthic foraminifera accumulation rates (BFAR) show an abrupt decline and reduction across the boundary, reaching a minimum point in the earliest Danian and followed by a slow recovery over a few hundred thousand years. The case of productivity collapse parallels with a negative excursion in δ¹³C and shifts in δ¹⁸O, suggesting marine carbon cycle disruption. Shannon H and Dominance D diversity indices, supported by diversity curves, display a sharp reduction in species richness and evenness below and above the boundary. The early Paleocene assemblages are described by low diversity, high dominance, and blooms of opportunistic taxa (Reophax, Spiroplectinella). Lazarus taxa were detected higher in the Danian, along with a gradual increase in BFAR and isotopic values.

Benthic foraminifera and isotopic signals point out a temporary reduction in food supply to the deep water, reflecting an unsteady and short-term Strangelove-like response rather than a true Strangelove Ocean as postulated by previous authors. Additionally, the evidence for the survival of benthic foraminifera, the absence of extensive-scale extinction, and the rapid recovery of BFAR and diversity values, does not fully support the Strangelove Ocean scenario. Instead, our unbiased record shows a short-lived decline in marine productivity, followed by a gradual recovery and ecological reorganization. Our results suggest that deep-sea ecological communities at the Cretaceous–Paleogene boundary were able to withstand the disturbance, and experienced a reduced food supply rather than a complete shutdown of biological productivity.