Abstract

The Pendleside Formation, a sequence of bioclastic wackestones and grainstones, has been extensively dolomitized and silicified, especially towards the top and near the axis of the Clitheroe Anticline. Undolomitized limestones are characterized by the presence of magnetite and primary-style magnetic fabrics and an exclusively reversed NRM with mean direction of Dec: =204°; Inc: = —21°. The magnetization is considered to be a depositional/postdepositional remanent magnetization, acquired before any significant alteration of the limestones.

Dolomitized and silicified limestones are characterized by hematite; some silicified limestones show the intermediate state of co-existing hematite and magnetite. These rocks have non-primary style magnetic fabrics and a complex NRM with normal components. The best estimate of this component is Dec: = 22°; Inc; = +20° almost antiparallel to the primary remanence. The magnetization is considered to be a chemical remanent magnetization (CRM) generated during the dolomitization of the Pendleside Formation.

The origin of the dolomitization may be associated with mudrock-dewatering as the sequence was buried. The normal CRM indicates that the remagnetization spanned a post-Asbian normal event, possibly in the Westphalian, coincident with the maximum burial of the Pendleside Formation.

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