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Abstract

Glacio-lacustrine varved clay of late Wisconsinan age in western New York has stable remanent magnetization and anisotropic magnetic susceptibility (AMS). Remanence is carried by interacting single-domain grains of magnetite, but coarse multidomain grains of magnetite are also present. 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 magnetic fabric and direction of remanence is demonstrated by comparison of remanence and AMS at closely spaced sites within individual clay laminae. Magnetic fabric resulted from alignment of multidomain grains by transient density currents at the time of deposition; alignment of single-domain grains by the geomagnetic field occurred later in a dilute slurry at rest on the surface of deposition to produce a post-depositional detrital remanent magnetization (pDRM). Rapid deposition and compaction resulted in anomalously low remanent inclination. Remanent declination and magnetic lineation were unaffected by compaction, but magnetic foliation may have been increased.

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