Extinction, dissolution, and possible ocean acidification prior to the Cretaceous/Paleogene (K/Pg) boundary in the tropical Pacific

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 485; pp. 433 - 454
• Main Authors: Dameron, Serena N., Leckie, R. Mark, Clark, Kendra, MacLeod, Kenneth G., Thomas, Deborah J., Lees, Jackie A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2017
• Subjects: Deccan Traps volcanism; Foraminiferal dissolution; Inoceramid extinction; Mid-Maastrichtian Event; Paleoceanography; Mid-Maastrichtian Event; Foraminiferal dissolution; Deccan Traps volcanism; Paleoceanography; Inoceramid extinction
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2017.06.032

Biotic perturbations and changes in ocean circulation during the Maastrichtian stage of the latest Cretaceous raise questions about whether the biosphere was preconditioned for the end-Cretaceous mass extinction of calcareous plankton. A brief acme of inoceramid clams at ~71Ma on Shatsky Rise in the tropical North Pacific was followed by their extinction during the “mid-Maastrichtian event” at 70.1Ma associated with an abrupt warming of deep waters. This was later followed by an interval of intense dissolution beginning ~67.8Ma at ODP Site 1209 (2387m). The late Maastrichtian dissolution interval was initially gradual, and is characterized by a low planktic/benthic (P/B) ratio, highly fragmented planktic foraminifera, mostly an absence of larger taxa, low abundances of smaller taxa, extremely low planktic foraminiferal numbers, and low planktic foraminiferal and nannofossil species richness. A partial recovery in carbonate preservation and calcareous plankton simple diversity began ~250kyr prior to the K/Pg boundary associated with the incursion of a younger (more enriched δ13C) deep water mass, although total abundances of planktic foraminifera in the sediment remained a tiny fraction of their earlier Maastrichtian values. A second, brief dissolution event occurred ~200kyr before the boundary evidenced by renewed increase in planktic fragmentation, but without a decrease in P/B ratio. Our data show that changing deep water masses, coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the first ~1.6-Myr dissolution interval, while Deccan Traps volcanism (?) may have caused surface ocean acidification ~200kyr prior to the K/Pg mass extinction event.
•Extinction of inoceramid clams due to rapid incursion of warm deep water (~70.1Ma)•Late Maastrichtian dissolution initiated with cool water mass incursion (~68.5Ma).•Dissolution intensified as Shatsky Rise shifted away from upwelling zone (~67.8Ma).•Diversity of calcareous plankton began to recover ~250kyr before the K/Pg boundary.•Second ocean acidification (?) occurred ~200kyr before K/Pg boundary.