Food supply to the seafloor; crisis after the Cretaceous/Paleogene boundary event

Author(s): Alegret, Laia; Thomas, Ellen
Author Affiliation(s): Primary:
University of Zaragoza, Zaragoza, Spain
Other:
Yale University, United States
Volume Title: 33rd international geological congress; abstracts
Source: International Geological Congress [International Geological Congress, Abstracts = Congrès Géologique International, Résumés, Vol.33; 33rd international geological congress, Oslo, Norway, Aug. 6-14, 2008. Publisher:], [location varies], International CODEN: IGABBY
Note: In English
Summary: In contrast to many other biota, benthic foraminifers living over a wide depth range did not suffer significant extinction at the Cretaceous/Paleogene (K/Pg) boundary. Their assemblages show temporal faunal restructuring (changes in relative abundance and diversity) that has been related to severe decrease in food deliver to the benthos on the ocean floor, either as the result of collapse of the pelagic food web or to the extinction of pellet-producing zooplankton and thus transport of organic matter to the seafloor rather than decreased productivity. We quantitatively analyzed benthic foraminiferal assemblages from the northwest Pacific (Shatsky Rise, Ocean Drilling Program Site 1210) in order to infer paleoenvironmental changes across the K/Pg boundary in the largest ocean on Earth, and to evaluate the different hypotheses regarding the nature of the biotic turnover. The sedimentary succession includes uppermost Maastrichtian white to pale orange nannofossil ooze overlain by lowermost Paleocene, grayish-orange foraminiferal ooze (10 cm) that grades upwards into a white foraminiferal nannofossil chalk (20 cm), and then into a grayish-orange nannofossil ooze. Abrupt changes in nannofossil and planktonic foraminiferal assemblages have been documented across the K/Pg boundary, although intense bioturbation disturbs the record. At Site 1210, calcareous nannoplankton shows a catastrophic mass extinction at the K/Pg boundary, followed by a recovery interval where survivors such as calcispheres (calcareous dinoflagellates) were abundant, followed by successive acmes (rapid colonization) of Danian nannofossil taxa (Bown, 2005). Benthic foraminiferal assemblages at Site 1210 contain abundant representatives of the cosmopolitan lower bathyal-abyssal Velasco-type fauna. Assemblages are diverse and the percentage of buliminid taxa increases towards the uppermost Cretaceous, then show a sudden decrease in diversity and heterogeneity across the boundary. In contrast to the oligotrophic seafloor environment due to extinction of primary producers ("Strangelove Ocean") or the biotic pump ("Living Ocean"), benthic foraminifers point to a high food supply during the earliest Danian, as indicated by the strong dominance of buliminids (45% of the assemblages; e.g., Bulimina kugleri, Aragonia aragonensis), as earlier observed at Pacific Site 465 (Alegret and Thomas, 2005). We suggest that high-food taxa such as buliminids may have bloomed at least at some locations when the vacant niches of calcareous nannoplankton producers were rapidly filled by other producers (e.g., dinoflagellates, prokaryotes), leading to reorganization of the planktic ecosystems, but not to a severe decrease in delivery of food to the seafloor.
Year of Publication: 2008
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Assemblages; Benthic environment; Benthic taxa; Bulimina; Buliminacea; Cenozoic; Clastic sediments; Cretaceous; Ecosystems; Food chains; Foraminifera; Invertebrata; K-T boundary; Leg 198; Lower Paleocene; Mass extinctions; Mesozoic; Microfossils; Nannofossils; North Pacific; Northwest Pacific; ODP Site 1210; Ocean Drilling Program; Ocean floors; Ooze; Pacific Ocean; Paleocene; Paleoecology; Paleoenvironment; Paleogene; Plantae; Productivity; Protista; Rotaliina; Sediments; Shatsky Rise; Stratigraphic boundary; Tertiary; Upper Cretaceous; West Pacific
Coordinates: N321300 N321300 E1581600 E1581600
Record ID: 2010071321
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data supplied by International Geological Congress Organizational Committee