Coring induced sediment fabrics at IODP Expedition 347 Sites M0061 and M0062 identified by anisotropy of magnetic susceptibility (AMS): criteria for accepting palaeomagnetic data

Type Article
Date 2019-05
Language English
Author(s) Snowball I1, Almqvist B1, Lougheed B C2, Wiers S1, Obrochta S3, Herrero-Bervera E4
Affiliation(s) 1 : Department of Earth Sciences, Uppsala University, Sweden
2 : Laboratoire des Sciences du Climat et de l'Environment, LSCE/IPSL, Laboratoire CNRS-CEA-UVSQ, France
3 : Graduate School of International Resource Science, Akita University, Japan
4 : School of Ocean Earth Science and Technology (SOEST) within the Hawaii Institute of Geophysics and Planetology (HIGP) of the University of Hawaii at Manoa
Source Geophysical Journal International (0956-540X) (Oxford University Press (OUP)), 2019-05 , Vol. 217 , N. 2 , P. 1089-1107
DOI 10.1093/gji/ggz075
WOS© Times Cited 6
Keyword(s) Magnetic fabrics and anisotropy, Palaeomagnetic secular variation, Palaeomagnetism
Abstract

Anisotropy of magnetic susceptibility data obtained from discrete sub-samples recovered from two Integrated Ocean Drilling Program sites (Expedition 347 sites M0061 and M0062 in the Baltic Sea) by an Advanced Piston Corer are compared to results obtained on sub-samples recovered by replicate 6 m long Kullenberg piston cores. Characteristic natural remanence directions were obtained from the total of 1097 sub-samples using principal component analyses. The three principal anisotropy axes of sub-samples taken from Advanced Piston Core liners align to the sub-sample axes, with the maximum axis (K1) parallel to the split core surfaces, possibly caused by outwards relaxation of the core-liners after splitting. A second anomalous anisotropy fabric is characterized by steep values of the angular difference between the inclination of the minimum anisotropy axes (K3) and that expected for horizontal bedding (90°). This fabric is confined to the upper 1–2 m of the Kullenberg cores and specific sections of the advanced piston cores, and we attribute it to conical deformation caused by either excessive penetration speeds and downwards dragging of sediment along the edge of the liner or stretching caused by undersampling. By using our data in an example, we present a protocol to accept palaeomagnetic secular variation data that uses (i) a threshold 90-K3 value of 15°, combined with a modelled, locally applicable minimum inclination of 65° and (ii) an A95 cone of confidence based on Fisher statistics applied to virtual geomagnetic pole distributions.

Full Text
File Pages Size Access
Publisher's official version 34 11 MB Open access
M0061 ChRM accepted GJI 6 57 KB Open access
M0062 ChRM accepted GJI 9 73 KB Open access
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How to cite 

Snowball I, Almqvist B, Lougheed B C, Wiers S, Obrochta S, Herrero-Bervera E (2019). Coring induced sediment fabrics at IODP Expedition 347 Sites M0061 and M0062 identified by anisotropy of magnetic susceptibility (AMS): criteria for accepting palaeomagnetic data. Geophysical Journal International, 217(2), 1089-1107. Publisher's official version : https://doi.org/10.1093/gji/ggz075 , Open Access version : https://archimer.ifremer.fr/doc/00481/59233/