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Using magnetic anisotropy to correct for paleomagnetic inclination shallowing in some magnetite-bearing deep-sea turbidites and limestones
Hodych J.P.a, Bijaksana S.a,b, Patzold R.a
a Department of Earth Sciences, Memorial University of Newfoundland, Canada
b Department of Physics, Bandung Institute of Technology, Indonesia
[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]In sediments, remanence inclination I may be shallower than the inclination I(H) of the Earth’s field in which they were deposited. Use of magnetic anisotropy to correct for this paleomagnetic inclination shallowing is tested for Quaternary turbidite muds from the Scotian Rise and for Cretaceous pelagic limestones from the Pacific Plate. Both are dominated by pseudo-single-domain magnetite carrying a stable remanence whose inclination I (determined by stepwise alternating field demagnetization) is shallower than I(H), by an average of 12°for the turbidites and 17°for the limestones. Anhysteretic remanence (ARM), applied identically to various axes, is weakest (ARM(min)) perpendicular to bedding and strongest (ARM(max)) parallel to bedding, with little anisotropy in the bedding plane and ARM(min)/ARM(max) averaging 0.84 for the turbidites and 0.87 for the limestones. Magnetite also dominates susceptibility with minimum (K(min)) and maximum (K(max)) susceptibility axes perpendicular and parallel to bedding, respectively, and with K(min)/K(max) averaging 0.91 for the turbidites and 0.95 for the limestones. In theory, we expect to find a correlation between tan I and ARM(min)/ARM(max) for a suite of specimens with the correlation line’s prediction of tan I when ARM(min)/ARM(max) = 1 yielding an I(H) estimate corrected for inclination shallowing. This correction method is also expected to succeed if ARM(min)/ARM(max) is replaced by K(min)/K(max), provided susceptibility is dominated by multidomain or pseudo-single-domain magnetite. In practice, both anisotropies do succeed in correcting for inclination shallowing in three of the four turbidite cores. Both anisotropies would also likely succeed for the limestones (if there were enough samples at any one site) since correlating tan I/tan I(H) in place of tan I for the five sites combined predicts tan I/tan I(H) ~ 1 when ARM(min)/ARM(max) = 1 or K(min)/K(max) = 1. Hence, we recommend routinely measuring anisotropy in paleomagnetic studies of magnetite-bearing sediments and looking for a correlation between tan I and ARM(min)/ARM(max) or K(min)/K(max). Remanence anisotropy is more laborious to measure but provides the more reliable estimate of inclination shallowing. In cases where no significant correlation is found, remanence anisotropy of the magnetite particles in the sediment may also have to be measured to correct for inclination shallowing.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Author keywords” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Indexed keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Compaction,Magnetic anisotropy,Magnetic inclination,Magnetite,Paleomagnetism[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Funding details” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”DOI” size=”size-sm” text_align=”text-left”][vc_column_text]https://doi.org/10.1016/S0040-1951(99)00125-0[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]