RECOVERY STRATEGIES OF THE PLANKTIC FORAMINIFERA IN THE AFTERMATH OF THE CRETACEOUS/PALEOGENE (K/PG) BOUNDARY EVENT

The Cretaceous-Paleogene (K/Pg) boundary event marks the near complete demise of the highly diversified planktic foraminiferal assemblage characteristic of the uppermost Maastrichtian, with only a few well-known surviving species.

The preserved record from a piston core drilled at a water-depth of 2,809 m, offshore Rio de Janeiro, SE Brazil, suggests that the starting point of recovery of the planktic foraminifera in the aftermath of the K/Pg boundary event, with the origination of the first Danian species, took place at a much faster pace than previously known (during an interval of ~3–6 kyr, and possibly even less).

Six main lineages of minute-sized planktic foraminifera are characteristic of the Danian and jointly gave rise to nearly all the subsequent Globigerinina families: 1) the microperforate, with blunt pustules and perforation cones, triserial to biserial, Guembelitria-Woodringina (Guembelitriidae) and Chiloguembelina (Chiloguembelinidae) lineage; 2) the microperforate, hispid, with blunt to sharp-pointed pustules, trochoid to trilobate, Globoconusa (Guembelitriidae) lineage; 3) the microperforate, pustulose to smooth, Parvularugoglobigerina (Guembelitriidae) lineage; 4) the cancellate, nonspinose, Praemurica (Truncorotaloididae) lineage; 5) the cancellate, spinose, Eoglobigerina-Subbotina (Globigerinidae) lineage; and 6) the cancellate, spinose, Parasubbotina (Globigerinidae) lineage.

Common patterns and processes underlie the speciation events, most probably induced by major changes in oceanic water masses as environmental conditions progressively improved in the Danian. The episodes of maximum radiation appear to be coeval with the progressive recovery of the surface water productivity and the oceanic carbon cycle, coupled with expanded surface-water oligotrophic settings and probable increasing reliance on symbiosis by the late Danian Zones P1c– P2, and the return to background oceanic conditions similar to those observed in the latest Cretaceous.