Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/7863
AuthorsPareschi, M. T. 
TitleStiffnites. Part II
Issue Date2011
Series/Report no.6/54(2011)
DOI10.4401/ag-4981
URIhttp://hdl.handle.net/2122/7863
KeywordsSubmarine sediment flows
Magnetic fabric and anisotropy
Magnetic confinement
Shear polymer media
Triboelectric fragmentation
Magnetic dipole Ambigua
Subject Classification04. Solid Earth::04.04. Geology::04.04.04. Marine geology 
04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport 
04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism 
AbstractThe dynamics of a stiffnite are here inferred. A stiffnite is a sheet-shaped, gravity-driven submarine sediment flow, with a fabric made up of marine ooze. To infer stiffnite dynamics, order of magnitude estimations are used. Field deposits and experiments on materials taken from the literature are also used. Stiffnites can be tens or hundreds of kilometers wide, and a few centimeters/ meters thick. They move on the sea slopes over hundreds of kilometers, reaching submarine velocities as high as 100 m/s. Hard grain friction favors grain fragmentation and formation of triboelectrically electrified particles and triboplasma (i.e., ions + electrons). Marine lipids favor isolation of electrical charges. At first, two basic assumptions are introduced, and checked a posteriori: (a) in a flowing stiffnite, magnetic dipole moments develop, with the magnetization proportional to the shear rate. I have named those dipoles as Ambigua. (b) Ambigua are ‘vertically frozen’ along stiffnite streamlines. From (a) and (b), it follows that: (i) Ambigua create a magnetic field (at peak, >1 T). (ii) Lorentz forces sort stiffnite particles into two superimposed sheets. The lower sheet, L+, has a sandy granulometry and a net positive electrical charge density. The upper sheet, L–, has a silty muddy granulometry and a net negative electrical charge density; the grains of sheet L– become finer upwards. (iii) Faraday forces push ferromagnetic grains towards the base of a stiffnite, so that a peak of magnetic susceptibility characterizes a stiffnite deposit. (iv) Stiffnites harden considerably during their motion, due to magnetic confinement. Stiffnite deposits and inferred stiffnite characteristics are compatible with a stable flow behavior against bending, pinch, or other macro instabilities. In the present report, a consistent hypothesis about the nature of Ambigua is provided.
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