TY - JOUR
T1 - A climate-driven model and development of a floating point time scale for the entire Middle Devonian Givetian Stage
T2 - A test using magnetostratigraphy susceptibility as a climate proxy
AU - Ellwood, Brooks B.
AU - Tomkin, Jonathan H.
AU - El Hassani, Ahmed
AU - Bultynck, Pierre
AU - Brett, Carlton E.
AU - Schindler, Eberhard
AU - Feist, Raimund
AU - Bartholomew, Alexander J.
N1 - Funding Information:
This work was funded in part by grants to R.E. Crick and B. Ellwood from the National Science Foundation (NSF ; EAR-9628202 ) and the American Chemical Society PRF ( #30845-AC8 and #34259-AC8 ). We wish to thank Suzanne Ellwood for her important contribution to this work in designing the sampling method used in collecting our samples, for her participation in collecting all of the Moroccan samples and most of the French samples reported here, and for other significant contributions to the work. R. Feist acknowledges financial support from the French CNRS (contribution UMR 5554, ISEM 2008-000). We are grateful to Brad Sageman for permission to sample the AKZO core, acquired through funding from NSF ( EAR-9725441 ). We are also grateful to Michael Whalen and William MacDonald for their careful and constructive reviews of this paper.
PY - 2011/4/15
Y1 - 2011/4/15
N2 - Here we propose an approach to establish a preliminary age chronology for complete stages within the Phanerozoic by applying cyclostratigraphic methods that employ high-resolution data sets. This requires use of geochemical or geophysical data known to serve as a cyclic climate proxy. To demonstrate the method, we use the magnetostratigraphic susceptibility technique as the basis for fitting a climate model to the Givetian Stage of the Middle Devonian System. We show a Milankovitch eccentricity climate zonation for the Givetian that is pinned to time-series analyses from outcrop samples from its upper (Givetian/Frasnian, France) and lower (Eifelian/Givetian, Morocco) stage boundaries. Using these data sets we construct a uniform cyclicity model designed to conform to a ~. 405. kyr cyclicity, with a duration corresponding to the published duration for the Givetian of ~. 4.4. myr (Kaufmann, 2006). To this model we fit two well-established conodont zonation schemes, thus allowing time estimates for conodont ranges for the Givetian, indicating a range from ~. 1.8. myr to ~. 100. kyr before extinction of an individual conodont species. We then test and adjust the model using independent data sets from the eastern United States. Adjustments to the initial model yield a duration of ~. 28 climate half-cycles (zones) for the Givetian Stage and an increased age to ~. 5.6. myr. These zones allow high correlation among sections to better resolve timing of major bio-events, and provide a Floating Point Time Scale to which absolute ages can be applied.
AB - Here we propose an approach to establish a preliminary age chronology for complete stages within the Phanerozoic by applying cyclostratigraphic methods that employ high-resolution data sets. This requires use of geochemical or geophysical data known to serve as a cyclic climate proxy. To demonstrate the method, we use the magnetostratigraphic susceptibility technique as the basis for fitting a climate model to the Givetian Stage of the Middle Devonian System. We show a Milankovitch eccentricity climate zonation for the Givetian that is pinned to time-series analyses from outcrop samples from its upper (Givetian/Frasnian, France) and lower (Eifelian/Givetian, Morocco) stage boundaries. Using these data sets we construct a uniform cyclicity model designed to conform to a ~. 405. kyr cyclicity, with a duration corresponding to the published duration for the Givetian of ~. 4.4. myr (Kaufmann, 2006). To this model we fit two well-established conodont zonation schemes, thus allowing time estimates for conodont ranges for the Givetian, indicating a range from ~. 1.8. myr to ~. 100. kyr before extinction of an individual conodont species. We then test and adjust the model using independent data sets from the eastern United States. Adjustments to the initial model yield a duration of ~. 28 climate half-cycles (zones) for the Givetian Stage and an increased age to ~. 5.6. myr. These zones allow high correlation among sections to better resolve timing of major bio-events, and provide a Floating Point Time Scale to which absolute ages can be applied.
KW - Climate cyclicity
KW - Floating Point Time Scale
KW - Givetian
KW - Global bio-events
KW - Magnetic susceptibility
KW - Time-series analysis
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U2 - 10.1016/j.palaeo.2010.10.014
DO - 10.1016/j.palaeo.2010.10.014
M3 - Article
AN - SCOPUS:79954746842
VL - 304
SP - 85
EP - 95
JO - Palaeogeography, Palaeoclimatology, Palaeoecology
JF - Palaeogeography, Palaeoclimatology, Palaeoecology
SN - 0031-0182
IS - 1-2
ER -