TY - JOUR
T1 - Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma)
AU - Li, Yong Xiang
AU - Bralower, Timothy J.
AU - Montañez, Isabel P.
AU - Osleger, David A.
AU - Arthur, Michael A.
AU - Bice, David M.
AU - Herbert, Timothy D.
AU - Erba, Elisabetta
AU - Premoli Silva, Isabella
N1 - Funding Information:
We thank B. Clement for providing paleomagnetic data of Chron M0 at the Santa Rosa section, S. Mulcahy for field assistance, T. Lin and B. Stotnick for laboratory assistance, the curatorial staff at IODP-ECR for their help with Site 398 sampling, and K.P. Kodama for discussion. This paper also benefited from thoughtful comments from M.L. Delaney, S. Voight, and two anonymous reviewers. This study is supported by NSF grant EAR0208212 to IPM and DAO, and EAR0318551 to TJB.
PY - 2008/7/15
Y1 - 2008/7/15
N2 - The early Aptian Oceanic Anoxic Event (OAE1a, 120 Ma) represents a geologically brief time interval in the mid-Cretaceous greenhouse world that is characterized by increased organic carbon accumulation in marine sediments, sudden biotic changes, and abrupt carbon-isotope excursions indicative of significant perturbations to global carbon cycling. The brevity of these drastic environmental changes (< 106 year) and the typically 106 year temporal resolution of the available chronologies, however, represent a critical gap in our knowledge of OAE1a. We have conducted a high-resolution investigation of three widely distributed sections, including the Cismon APTICORE in Italy, Santa Rosa Canyon in northeastern Mexico, and Deep Sea Drilling Project (DSDP) Site 398 off the Iberian margin in the North Atlantic Ocean, which represent a range of depositional environments where condensed and moderately expanded OAE1a intervals are recorded. The objectives of this study are to establish orbital chronologies for these sections and to construct a common, high-resolution timescale for OAE1a. Spectral analyses of the closely-spaced (corresponding to ~ 5 to 10 kyr) measurements of calcium carbonate content of the APTICORE, magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) of the Santa Rosa samples, and MS, ARM and ARM/IRM, where IRM is isothermal remanent magnetization, of Site 398 samples reveal statistically significant cycles. These cycles exhibit periodicity ratios and modulation patterns similar to those of the mid-Cretaceous orbital cycles, suggesting that orbital variations may have modulated depositional processes. Orbital control allows us to estimate the duration of unique, globally identifiable stages of OAE1a. Although OAE1a had a duration of ~ 1.0 to 1.3 Myr, the initial perturbation represented by the negative carbon-isotope excursion was rapid, lasting for ~ 27-44 kyr. This estimate could serve as a basis for constraining triggering mechanisms for OAE1a.
AB - The early Aptian Oceanic Anoxic Event (OAE1a, 120 Ma) represents a geologically brief time interval in the mid-Cretaceous greenhouse world that is characterized by increased organic carbon accumulation in marine sediments, sudden biotic changes, and abrupt carbon-isotope excursions indicative of significant perturbations to global carbon cycling. The brevity of these drastic environmental changes (< 106 year) and the typically 106 year temporal resolution of the available chronologies, however, represent a critical gap in our knowledge of OAE1a. We have conducted a high-resolution investigation of three widely distributed sections, including the Cismon APTICORE in Italy, Santa Rosa Canyon in northeastern Mexico, and Deep Sea Drilling Project (DSDP) Site 398 off the Iberian margin in the North Atlantic Ocean, which represent a range of depositional environments where condensed and moderately expanded OAE1a intervals are recorded. The objectives of this study are to establish orbital chronologies for these sections and to construct a common, high-resolution timescale for OAE1a. Spectral analyses of the closely-spaced (corresponding to ~ 5 to 10 kyr) measurements of calcium carbonate content of the APTICORE, magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) of the Santa Rosa samples, and MS, ARM and ARM/IRM, where IRM is isothermal remanent magnetization, of Site 398 samples reveal statistically significant cycles. These cycles exhibit periodicity ratios and modulation patterns similar to those of the mid-Cretaceous orbital cycles, suggesting that orbital variations may have modulated depositional processes. Orbital control allows us to estimate the duration of unique, globally identifiable stages of OAE1a. Although OAE1a had a duration of ~ 1.0 to 1.3 Myr, the initial perturbation represented by the negative carbon-isotope excursion was rapid, lasting for ~ 27-44 kyr. This estimate could serve as a basis for constraining triggering mechanisms for OAE1a.
UR - http://www.scopus.com/inward/record.url?scp=45449103244&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=45449103244&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2008.03.055
DO - 10.1016/j.epsl.2008.03.055
M3 - Article
AN - SCOPUS:45449103244
SN - 0012-821X
VL - 271
SP - 88
EP - 100
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 1-4
ER -