A nonmarine record of eccentricity forcing through the Upper Triassic of southwest England and its correlation with the Newark Basin astronomically calibrated geomagnetic polarity time scale from North America: COMMENT and REPLY REPLY

Kemp, D. B. and Coe, A. L. (2009) A nonmarine record of eccentricity forcing through the Upper Triassic of southwest England and its correlation with the Newark Basin astronomically calibrated geomagnetic polarity time scale from North America: COMMENT and REPLY REPLY. Geology, 37 (1). e186-e187. DOI 10.1130/G24805C.1

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Abstract

Bailey and Smith (2008) question the veracity of the 116 cm cycle we observed in the spectral analysis and wavelet analysis of our Branscombe Mudstone time series, and, using a technique of their own design, suggest instead that this cyclicity could be an artifact of the spectral analysis. The spectral analysis methodology we employed to identify this cycle is the established technique for studies of this type (e.g., Hinnov, 2000; Weedon, 2003), and this method has been used to derive an astronomical time scale for much of the Cenozoic (Gradstein et al., 2005). Bailey and Smith appear to have a fundamental distrust of spectral analysis per se as a technique for constructing astronomical time series, rather than presenting any specific criticism of our particular study. To reiterate our findings, our interpretation that the 116 cm cyclicity is a real feature was based on the fact that spectral analysis showed that this cyclicity is present in two data sets, in both halves of these data sets, and was also unambiguously identified using wavelet analysis. Wavelet analysis was employed specifically to look at the time-frequency evolution of the data, and, as Bailey and Smith point out, time-localized peaks in wavelet power do indeed occur. However, spectral analysis demonstrates that these very short-lived peaks do not contribute a significant amount of power against the overall variance of the data; hence, they are not interpreted as cyclic components generated by Milankovitch forcing.

Item Type: Article
Additional Information: Attached pdf contains both comment and reply
Uncontrolled Keywords: 09AREP; IA59;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Geology
Volume: 37
Page Range: e186-e187
Identification Number: 10.1130/G24805C.1
Depositing User: Sarah Humbert
Date Deposited: 23 Jan 2010 00:32
Last Modified: 23 Jul 2013 09:56
URI: http://eprints.esc.cam.ac.uk/id/eprint/1303

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