A record of the upper Cochiti polarity transition from the Southern Hemisphere (FIJI) |
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| Authors: | Bradford M Clement Luz Loresley Sierra Edward Smith Peter Rodda |
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| Institution: | (1) Department of Geology, Florida International University, 33199 Miami, FL, USA;(2) Mineral Resources Department, Suva, Fiji |
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| Abstract: | We sampled the upper Cochiti polarity transition recorded in the Suva Marl in Fiji (18° S, 178° E). The Suva Marl accumulated at an average rate of 83.2 m/m.y. and provides a unique opportunity to address the question of whether present-day overprints bias the transition records. Fiji has undergone a 30° counterclockwise rotation since the deposition of the Suva Marl and hence a present day overprint onto the transitions would bias the VGPs toward the east of the site. Replicate transition records yield VGPs over both Asia and the Americas. Progressive demagnetization reveals a normal polarity overprint which was acquired prior to the rotation of Fiji, and therefore does not produce an easterly bias to the transition data even after correction for the rotation. We collected an oriented block sample across a portion of the transitional interval in the upper Cochiti reversal. Subsampling of this block into 1.0 cm thick wafers cut parallel to bedding provides considerably greater detail during the transition. These detailed data suggest that the oscillatory movement of the VGPs in these sections may be a result of the averaging caused by standard, detailed minicoring and not by the sediments or the remanence acquisition process. |
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