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Anisotropy of magnetic susceptibility and sedimentary cycle data from Permo-Carboniferous rhythmites (Paraná Basin, Brazil): a multiple proxy record of astronomical and millennial scale palaeoclimate change in a glacial setting

By
Daniel R. Franco
Daniel R. Franco
Department of Geophysics, National Observatory, R. Gal. José Cristino, 77, 20921-400 Rio de Janeiro, RJ, Brazil
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Linda A. Hinnov
Linda A. Hinnov
Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 USA
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Published:
January 01, 2013

Abstract

In this study we examine glaciogenic rhythmites from the Late Palaeozoic Itararé Group, Paraná Basin, Brazil. We conduct spectral analysis on lithological cycle (‘couplet’) thickness series, and declination of maximum axis of anisotropy of magnetic susceptibility ellipsoidal tensor (K1) data. We tested the efficiency of K1 as a palaeoclimatic proxy. To constrain the timescale of harmonic features in the data, we analysed the couplet thickness spectra, converting the spectra to the time domain using an astronomical calibration based on Milankovitch frequency ratios. Comparison of the two rhythmites provides insights into their sedimentation rate evolution and cyclicity. Millennial-scale mechanisms of climatic origin influenced the deposition of both rhythmites, generating the lithological couplets, and are consistent with millennial-scale variations recognized as triggers for large-scale climatic changes during the Late Pleistocene. The common harmonic features in the couplet thickness and K1 spectra support the view that the azimuth of the K1 axis in sedimentary fabric is a useful palaeoclimatic proxy, reflecting sedimentation processes that were directly influenced by flow-induced, sediment transport, which is linked to external climate factors.

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Contents

Geological Society, London, Special Publications

Magnetic Methods and the Timing of Geological Processes

L. Jovane
L. Jovane
Universidade de Saão Paulo, Brazil
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E. Herrero-Bervera
E. Herrero-Bervera
University of Hawaii at Manoa, USA
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L.A. Hinnov
L.A. Hinnov
Johns Hopkins University, USA
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B. Housen
B. Housen
Western Washington University, USA
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Geological Society of London
Volume
373
ISBN electronic:
9781862396364
Publication date:
January 01, 2013

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