Remagnetization and orogenic fluids: testing the hypothesis in the central Appalachians

Summary Palaeomagnetic and geochemical studies on Devonian sedimentary rocks in the Valley and Ridge province in West Virginia indicate that the hypothesized relationship between orogenic fluids and remagnetization is not straightforward. The Helderberg Group, an aquitard, and the Oriskany Formation, a palaeoaquifer, both contain similar, synfolding late Palaeozoic chemical remanent magnetizations (CRMs) residing in magnetite. The results from the Oriskany Formation are consistent with remagnetization by orogenic fluids because the unit contains geochemical evidence for the migration of such fluids. In contrast, there is no geochemical evidence for the widespread migration of orogenic fluids into the Helderberg Group and thus the CRM cannot be related to such fluids. Another remagnetization mechanism, which remains elusive, must be responsible for the CRM in the Helderberg Group.