TIMING AND ORIGIN OF DOLOMITIZATION IN THE ARBUCKLE GROUP, OKLAHOMA

An integrated paleomagnetic and petrographic study of Arbuckle Group dolomites from the Amoco SHADS 4 core (NE OK) and from in and around dolomite pipes near Bally Mountain (SW OK) indicates at least two dolomitization events: one in the Ordovician and one in the late Paleozoic. The SHADS 4 core is not oriented, and the samples from the core contain a chemical remanent magnetization (CRM) with shallow inclinations that resides in magnetite. Based on inclination only data and comparison with the expected inclination for the core location, the CRM could be Ordovician or late Paleozoic. Orienting the CRM using the viscous magnetization method indicates a southerly CRM consistent with a Permian pole positon; some samples also contained an easterly CRM corresponding to an Ordovician pole position. The rocks contain evidence for alteration by hydrothermal fluids (e.g., baroque dolomite) which agrees with the results of diagenetic studies on the core by other workers. The dolomite and limestone in and around the pipes at Bally Mountain are dominated by a southerly and shallow Permian CRM in magnetite although at least one site contains an easterly and shallow ‘Ordovician’ CRM. Previous studies from the Arbuckle Mountains (south-central OK) have indicated that dolomite with ~ coeval ⁸⁷Sr/⁸⁶Sr values and dull luminscence contain an Ordovician CRM, whereas samples with elevated ⁸⁷Sr/⁸⁶Sr values, bright red luminscence, and abundant authigenic K-feldspar contain a late Paleozoic CRM. The late Paleozoic CRMs can be related to widespread alteration by external fluids. The Ordovician CRM may be related to burial diagenetic mechanisms. We are testing for a connection between the petrographic/geochemical characteristics and CRM ages of the SHADS 4 and Bally Mountain dolomites. Results will be compared with those of previous studies to determine if the same events occurred over a larger area.