HR: 1340h
AN: GP43C-1496    [Abstracts]
TI: Characterization of orogenic remagnetizations within various fold geometries in Carboniferous carbonates from thin skinned fold and thrust belts, SW Alberta and NW Montana
AU: * Zechmeister, M S
EM: zechmeim@ou.edu
AF: The University of Oklahoma, School of Geology and Geophysics, 100 E. Boyd St. Suite 810, Norman, OK 73019, United States
AU: Elmore, R D
EM: delmore@ou.edu
AF: The University of Oklahoma, School of Geology and Geophysics, 100 E. Boyd St. Suite 810, Norman, OK 73019, United States
AU: Ferre, E C
EM: eferre@geo.siu.edu
AF: Southern Illinois University Carbondale, Department of Geology, 102 Parkinson Lab Mailcode 4324, Carbondale, IL 62901, United States
AU: Pannalal, S J
EM: johari@ou.edu
AF: The University of Oklahoma, School of Geology and Geophysics, 100 E. Boyd St. Suite 810, Norman, OK 73019, United States
AU: Hamilton, E M
EM: Evan.M.Hamilton-1@ou.edu
AF: The University of Oklahoma, School of Geology and Geophysics, 100 E. Boyd St. Suite 810, Norman, OK 73019, United States
AB: Paleomagnetic and rock magnetic analysis was conducted on a complex fault propagation fold train in Kananaskis Country, Alberta to compliment an ongoing study of orogenic remagnetiztions in the thin-skinned, fold and thrust belt (NW Montana and SW Alberta). The complex structure is composed of an asymmetrical anticline to the west and chevron syncline to the east, with both folds plunging ~15° to the south. The fold train contains a magnetization with two stable ancient components. The characteristic remanent magnetization (ChRM) with northerly declinations and steep down inclinations is removed between ~350°C and the maximum unblocking temperature of 540°C. Tilt tests on the preliminary data reveal that the ChRM is early syntilting in the anticline and syntilting in the syncline. These results from this fold train are similar to a previous study in the Sawtooths (NW MT) which reported that fault propagation folds have a syntilting ChRM whereas fault bend folds contain a pretilting ChRM. An intermediate temperature reversed component is unblocked by 340°C and is late syntilting to post-tilting. Preliminary high-field rock magnetic data from folds in Montana and Alberta show that saturation is reached before 0.3T and the majority of the samples have wasp-waisted hysteresis loops. On a log plot of Mrs/Ms versus Hcr/Hc, the data has a power law distribution that is similar to trends reported by other authors. Interestingly though, samples from a fault bend fold have higher Mrs/Ms ratios than those measured in fault propagation folds, suggesting that strain induced by the various folding styles may influence the rock magnetic properties. Additional studies are underway to test these preliminary results and determine if the differences in the hysteresis ratios are significant. Petrographic analysis shows magnetite replacing pyrite in some samples suggesting an authigenic origin for the ChRM. The intensity of the ChRM as well as the strongest rock magnetic signal is most common in dark gray carbonates that are hydrocarbon reservoirs in the subsurface, suggesting the possibility that the origin of the ChRM may be related to hydrocarbon migration.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1533 Remagnetization
DE: 8005 Folds and folding
DE: 8045 Role of fluids
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting