--> Abstract: Origin and Modification of Magnetic Fabric in Fine-Grained Detrital Sediment by Depositional and Postdepositional Processes, by W. J. Brennan; #91004 (1991)
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Origin and Modification of Previous HitMagneticNext Hit Fabric in Fine-Grained Detrital Sediment by Depositional and Postdepositional Processes

BRENNAN, WILLIAM J., State University of New York/Geneseo, Geneseo, NY

Glaciolacustrine varved clay of late Wisconsinan age in western New York has stable remanent magnetization and anisotropic Previous HitmagneticNext Hit susceptibility (AMS). The results of rock Previous HitmagneticNext Hit tests demonstrate that remanence is carried by interacting single domain grains of magnetite, but coarse multidomain grains of magnetite are also present. As in many fine-grained detrital sediments, remanent inclination is anomalously shallow, given the latitude of the area of deposition and the existence of a geocentric dipole field at the time of deposition.

The AMS consists of a foliation that is gently inclined to bedding and a weaker lineation in the plane of foliation. Independence of Previous HitmagneticNext Hit fabric and direction of remanence can be demonstrated by comparing remanence and AMS at closely spaced sites in the same beds and also between widely spaced sites of different age. The Previous HitmagneticNext Hit fabric suggests that deposition is accompanied by transient density currents which align large multidomain grains; Previous HitmagneticNext Hit alignment of single domain grains occurs later in a dilute slurry at rest on the surface of deposition, rather than during settling in still water. Compaction after deposition results in decrease of remanent inclination and increase in Previous HitmagneticNext Hit foliation. Remanent declination and Previous HitmagneticTop lineation are unaffected by compaction.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)