Geochemical consequences of mass extinction; the K/Pg compensation depth excursion

Author(s): Norris, R. D.; Hull, Pincelli M.
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, La Jolla, CA, United States
Other:
Yale University, United States
Volume Title: AGU 2012 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2012; American Geophysical Union 2012 fall meeting, San Francisco, CA, Dec. 3-7, 2012. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Cretaceous-Paleogene mass extinction triggered a major depression of the lysocline in the global ocean. A global compilation of carbonate preservation indices--% carbonate and foraminifer preservation--shows that carbonate sediments are found in deeper waters and with better foraminifer preservation in the ∼300-400 kyr following the K/Pg mass extinction than in the late Cretaceous or during the rest of the early Danian. Indeed, foraminifer preservation commonly is very good to glassy in the earliest Danian, with translucent foraminifer shells even in very deep water deposits. For example, DSDP Site 356 in the South Atlantic has glassy preservation at 2.2 km paleodeth only during this time interval. Other very deep water sites, such as DSDP 398D offshore Portugal and IODP U1370 in the central South Pacific, are close to, or below, the carbonate compensation depth, but experience a brief taphonomic window of foraminifer preservation in the earliest Danian. We consider the three potential causes for this post-extinction transient depression of the lysocline: 1) increased carbonate ion availability due to >50% loss of calcareous nannofossil production (the major producers of late Cretaceous deep sea carbonate) and coastal reefs, 2) increased silica weathering associated with major disruption to terrestrial ecosystems at the K-Pg boundary, and 3) decreased organic matter flux to the deep sea following the extinction. An increase in planktic foraminifer production coincident with the lowest fluxes of calcareous nannoplankton and excellent preservation of calcareous microfossils suggests that the first mechanism is at least partly responsible for the preservation spike. The earliest Danian preservation spike of foraminifera, therefore in part reflects the transient alteration of plankton communities in the aftermath of the extinction--a phenomenon that ended with the reappearance of more biologically diverse pelagic communities several hundred thousand years after the mass extinction.
Year of Publication: 2012
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IPOD International Phase of Ocean Drilling
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Cenozoic; Chemical composition; Cretaceous; DSDP Site 356; DSDP Site 398; Deep Sea Drilling Project; East Pacific; Expedition 329; IODP Site U1370; IPOD; Integrated Ocean Drilling Program; Leg 39; Leg 47; Marine sediments; Mass extinctions; Mesozoic; North Atlantic; Pacific Ocean; Paleoecology; Paleogene; Sediments; South Atlantic; South Pacific; Southeast Pacific; Tertiary
Coordinates: S415107 S415107 W1530623 W1530623
S281713 S281713 W0410517 W0410517
N405736 N405736 W0104306 W0104306
Record ID: 2014061500
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