Geochemical evidence for global changes in climate, p sub CO2 , and organic carbon burial at Cenomanian/Turonian boundary

Conference · Tue May 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6702402

Dean, W E ^[1]; Arthur, M A ^[2]; Pratt, L M ^[3]

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1. Geological Survey, Denver, CO (USA)
2. Univ. of Rhode Island, Narragansett (USA)
3. Univ. of Indiana, Bloomington (USA)

One of the most significant events in the Cretaceous record of organic carbon (OC) burial is the short (< 1 m.y.) but intense period of global organic productivity and OC burial that accompanied a major global rise in sea level at the Cenomanian/Turonian (C/T) boundary (about 91 Ma). The C/T event was nearly synchronous throughout the Atlantic and Tethys basins as well as in higher latitude epicontinental seas. The increased rate of OC burial resulted in massive transfer of carbon from the oceans and atmosphere to marine sediments that contain as much as 50% OC in some areas. This massive removal of isotopically light ({sup 13}C-depleted) OC is recorded as a progressive increase in {delta}{sup 13}C of carbonate carbon by an average of about 2{per thousand} and as an increase in {delta}{sup 13}C of marine organic matter from values of about {minus}27 to {minus}28{per thousand} (typical of pre-C/T organic matter) to values as high as {minus}21{per thousand} at the C/T boundary. The authors calculate that the increased rate of OC burial at the C/T boundary was sufficient to strip the atmosphere of CO{sub 2} within several hundred thousand years. These calculations ignore feedback from oceanic and crustal carbon reservoirs but do suggest that there may have been a significant reduction in p{sub co2} at the C/T boundary. A reduction in p{sub CO2} has two major implications. First, lower p{sub CO2} may have caused global cooling, as suggested by the oxygen isotopic composition of inoceramids from northwest Europe. Second, decreased availability of dissolved p{sub CO2} have affected the isotopic fractionation of OC by phytoplankton, as suggested by experimental studies. The C/T event illustrates how changes in tectonism and sea level can induce significant, rapid paleoenvironmental changes and biotic turnover that affect the partitioning of carbon between sediment and oceanic reservoirs.

• OSTI ID: 6702402
• Report Number(s): CONF-900605--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:5
• Country of Publication: United States
• Language: English

Related Subjects

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54 ENVIRONMENTAL SCIENCES
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58 GEOSCIENCES
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CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CRETACEOUS PERIOD
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
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MESOZOIC ERA
MINERAL RESOURCES
ORGANIC MATTER
OXIDES
OXYGEN COMPOUNDS
PALEOCLIMATOLOGY
PALEONTOLOGY
PETROLEUM DEPOSITS
RESERVOIR ROCK
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SEA LEVEL
TECTONICS