TY - JOUR
T1 - Oceanic anoxic cycles? Orbital prelude to the Bonarelli Level (OAE 2)
AU - Mitchell, Ross N.
AU - Bice, David M.
AU - Montanari, Alessandro
AU - Cleaveland, Laura C.
AU - Christianson, Keith T.
AU - Coccioni, Rodolfo
AU - Hinnov, Linda A.
N1 - Funding Information:
We would like to thank Luca Bice, Jen Macalady and Emily Banks for their patience during the original mapping out of the manuscript. Marina Ciummelli (University of Chieti) logged and sampled the R1 member of the Scaglia Rossa at Furlo. Nick Swanson-Hysell kindly provided detailed edits and posed intriguing questions. Ann Zawistoski very generously showed RNM the ropes of using a bibliographic program. LAH was supported by NSF Grant EAR-0718905. Insightful discussions with the following inspired the diligence of our study: Mike Arthur, Adam Maloof, Bruce Runnegar, and Bradley Sageman. Stephen Meyers, Mark Leckie, and several anonymous reviewers vastly improved the original manuscript and a subsequent version by providing generously detailed and constructive criticism. This is publication no. 19 of the Centro di Geobiologia of the Urbino University.
PY - 2008/3/1
Y1 - 2008/3/1
N2 - The prelude to the second global oceanic-anoxic event of the Cretaceous (OAE 2), as recorded in the classic sections of the Scaglia Bianca Formation in the Umbria-Marches region of Italy, is characterized by an oscillation between black to gray, organic-rich cherts and white pelagic limestones. Spectral analysis of these lithologic alternations reveals a robust set of cycles whose periods are remarkably similar to the orbital cycles calculated by Laskar et al. [Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., Levrard, B., 2004, A long term numerical solution for the insolation quantities of the Earth. Astronomy and Astrophysics, 428, 261-285.]. Bandpass filtering shows that the 140-80 kyr signal approximates the envelope of the 26-16 kyr signal, just as expected if these components represent responses to orbital eccentricity and precession. Matching the presumed eccentricity signal to the theoretical eccentricity of Laskar et al. yields an age for the base of the Bonarelli Level (onset of OAE 2 in Italy) of 94.21 Ma (93.72 Ma provides an alternative), consistent with radiometric constraints from a correlative section in the western United States. Given the strong orbital control on the cyclic deposition of the organic-rich precursors of OAE 2 within the Scaglia Bianca Formation, we hypothesize that the timing of OAE 2 itself is similarly controlled by astronomical variations. Indeed, the occurrence of OAE 2 coincides with a protracted period of unusually low insolation variation, owing to simultaneous nodes in all orbital parameters. We speculate that other OAEs similarly coincided with insolation nodes and dampened seasonality. From this perspective, some (but perhaps not all) of the OAEs may be periodic events reflecting cycles of oceanic anoxia that predictably punctuated a ~ 50 Myr period of Cretaceous climate.
AB - The prelude to the second global oceanic-anoxic event of the Cretaceous (OAE 2), as recorded in the classic sections of the Scaglia Bianca Formation in the Umbria-Marches region of Italy, is characterized by an oscillation between black to gray, organic-rich cherts and white pelagic limestones. Spectral analysis of these lithologic alternations reveals a robust set of cycles whose periods are remarkably similar to the orbital cycles calculated by Laskar et al. [Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., Levrard, B., 2004, A long term numerical solution for the insolation quantities of the Earth. Astronomy and Astrophysics, 428, 261-285.]. Bandpass filtering shows that the 140-80 kyr signal approximates the envelope of the 26-16 kyr signal, just as expected if these components represent responses to orbital eccentricity and precession. Matching the presumed eccentricity signal to the theoretical eccentricity of Laskar et al. yields an age for the base of the Bonarelli Level (onset of OAE 2 in Italy) of 94.21 Ma (93.72 Ma provides an alternative), consistent with radiometric constraints from a correlative section in the western United States. Given the strong orbital control on the cyclic deposition of the organic-rich precursors of OAE 2 within the Scaglia Bianca Formation, we hypothesize that the timing of OAE 2 itself is similarly controlled by astronomical variations. Indeed, the occurrence of OAE 2 coincides with a protracted period of unusually low insolation variation, owing to simultaneous nodes in all orbital parameters. We speculate that other OAEs similarly coincided with insolation nodes and dampened seasonality. From this perspective, some (but perhaps not all) of the OAEs may be periodic events reflecting cycles of oceanic anoxia that predictably punctuated a ~ 50 Myr period of Cretaceous climate.
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U2 - 10.1016/j.epsl.2007.11.026
DO - 10.1016/j.epsl.2007.11.026
M3 - Article
AN - SCOPUS:39649095388
SN - 0012-821X
VL - 267
SP - 1
EP - 16
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 1-2
ER -