Origin and Modification of Magnetic Fabric in Fine-Grained Detrital Sediment by Depositional and Post-Depositional Processes
Published:January 01, 1993
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William J. Brennan, 1993. "Origin and Modification of Magnetic Fabric in Fine-Grained Detrital Sediment by Depositional and Post-Depositional Processes", Applications of Paleomagnetism to Sedimentary Geology, Djafar M. Aïssaoui, Donald F. McNeill, Neil F. Hurley
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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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Applications of Paleomagnetism to Sedimentary Geology
Applications of Paleomagnetism to Sedimentary Geology - Based on the 1991 SEPM Research Symposium, the results are directed towards bringing the disciplines of Paleomagnetism and sedimentary geology closer together. Advances in the field of sedimentary geology will likely result from continued development of new ideas, questioning of old dogma, and, most importantly, providing means for testing these new hypotheses. It is hoped that the union of these two disciplines will help address many fundamental geological questions, such as the perennial problems of precise age-dating, stratigraphic correlation and geometries, understanding the timing and nature of post-depositional diagenetic fabrics, and the intriguing relationship between hydrocarbons and magnetization. The reader will find an unusual diversity of research topics presented in this volume. This diversity serves as a testimony to the potential applications awaiting the sedimentary geologist willing to explore these new paleomagnetic tools.