The occurrence of pervasive chemical remanent magnetizations in sedimentary basins: implications for dating burial diagenetic events

Paleomagnetic results from Jurassic sediment on Skye, Scotland, are consist ent with the hypothesis that authigenic magnetite and an associated chemica l remanent magnetization (CRM) can form during the conversion of smectite t o illite. Sediment in north Skye, where smectite is abundant and the clays are unaltered, contain a weak and unstable magnetization. The same age sedi ment in south Skye, where the clays have been altered to illite by hydrothe rmal heating, contain a multi-component CRM residing in magnetite and/or py rrhotite. The CRM was acquired in the early Tertiary, which is consistent w ith the timing of the hydrothermal activity that caused the alteration. (C) 2000 Elsevier Science B.V. All rights reserved.