Original Research ARTICLE
Remagnetization of Marcellus Formation in the Plateau Province of the Appalachian Basin
- 1Noble Energy Inc., United States
- 2University of Oklahoma, United States
- 3ConocoPhillips School of Geology and Geophysics, Mewbourne College of Earth and Energy, University of Oklahoma, United States
An integrated paleomagnetic, magnetic fabric, and petrographic study of two cores (EC: oriented; DB: unoriented) in the Devonian Marcellus Formation from the Plateau Province (PA) indicates the presence of chemical remanent magnetizations (CRMs) and extensive diagenetic alteration. Anisotropy of magnetic susceptibility results indicate a predominately oblate fabric. Some specimens contain a prolate fabric that is interpreted as diagenetically altered. A well-developed viscous magnetization, possibly contaminated by a drilling induced component, is not present in either core, and cannot be used for orientation. An intermediate temperature component with steep down inclinations (ITN) is removed in both cores below ~ 300°C. Specimens in DB also contain a component with steep up inclinations (ITR) that is removed between 300 and 440°C. The ITN is interpreted to reside in magnetite and/or possibly pyrrhotite, and the ITR resides in magnetite. The ITN could be a reversal of ITR, acquired in the Cretaceous to Cenozoic based on a comparison with the expected inclinations. Alternatively, the ITN could be a contaminated by a Brunhes viscous magnetization. Specimens from both cores contain a characteristic remanent magnetization (ChRM) with shallow inclinations that is removed by 500°C in DB and 460°C in EC, and is interpreted to reside in magnetite. The DB ChRM has an inclination of -9.0°, which corresponds to a range of ages between 310-225 Ma based on the expected inclinations. The ChRM in EC has streaked declinations, which may have been caused by core barrel rotation. Shallow inclinations (- 3.7°) in this core suggest a range of acquisition from 305-230 Ma. Rock magnetic data are consistent with the presence of magnetite but provide conflicting evidence for pyrrhotite. The ChRM in DB is interpreted as a CRM whereas the ChRM in EC could be thermoviscous in origin. Diagenetic studies indicate a complex paragenesis with authigenic minerals such as barite, sphalerite, baroque dolomite, and sylvite suggestive of alteration by external fluids. The presence of the CRM in highly altered zones suggests it is related to alteration by external fluids, although its presence in other facies suggests that burial diagenetic processes could also be a cause of remagnetization.
Keywords: Remagnetizations, paleomagnetism, rock-magnetism, Marcellus, Diagenesis
Received: 15 Feb 2019;
Accepted: 01 Jul 2019.
Edited by:Eric Font, University of Coimbra, Portugal
Reviewed by:Mike Jackson, University of Minnesota Twin Cities, United States
JUAN JOSE VILLALAIN, University of Burgos, Spain
Copyright: © 2019 Steullet, Elmore, Hamilton and Heij. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Dr. Richard D. Elmore, University of Oklahoma, Norman, United States, firstname.lastname@example.org