Evaluation of paleomagnetic and finite strain relationships due to the Alleghanian Orogeny in the Mississippian Mauch Chunk Formation, Pennsylvania

Abstract

[1] Three localities of the Mississippian Mauch Chunk Formation around the Pennsylvania Salient (Broad Top Synclinorium, Minersville Syncline, and a sublocality in the Minersville Syncline) were sampled for detailed paleomagnetic and strain analysis. Paleomagnetic analysis showed three magnetization components: an intermediate-and an SW component, unblocked over a wide range of temperatures and observed only on the northern segment of the salient. Normalized Fry strain and R f /f strain were measured in three dimensions and correlated to the paleomagnetic results. At one site (JTSF locality), a clear correlation between the amount of strain (e s ) and remanence direction indicates that axial planar cleavage formation has caused remanence rotation. The correlations at the Minersville Syncline and Broad Top Synclinorium are not definitive, but suggest that different mechanisms are operating. The observed heterogeneity in paleomagnetic response to strain indicates that the effects will be strongly dependent on the strain history at a particular site.

The impact of vertical-axis rotations on shortening estimates

“…(1) the Bolivian arc of the central Andes (e.g., Butler et al, 1995;Roperch et al, 2000;Arriagada et al, 2003Arriagada et al, , 2008; (2) the Pennsylvania salient in the central Appalachians (e.g., Schwartz and Van der Voo, 1984;Kent, 1988;Stamatakos and Hirt, 1994;Cioppa and Kodama, 2003); (3) the Southern Pyrenees (e.g., Dinarès et al, 1992;Pueyo, 2000;Sussman et al, 2003;Oliva-Urcia et al, 2008;Oliva et al, 2012;Mochales et al, 2012); (4) the Cantabrian-Asturian arc (e.g., Van der Voo et al, 1997;Weil et al, 2001;Weil, 2006); or (5) the Alps (Thöny et al, 2006;Pueyo et al, 2007).…”

Rock Magnetic Cyclostratigraphy of the Carboniferous Mauch Chunk Formation, Pottsville, PA, United States

“…There is the additional concern that a red bed, dominated by the antiferromagnetic mineral hematite, may not have a depositional remanence, although the Mauch Chunk has demonstrated a robust magnetostratigraphy (DiVenere and Opdyke, 1991) so it either carries a depositional remanence or a very early diagenetic (chemical) remanence. Additional paleomagnetic studies of the Mauch Chunk Formation (Kent and Opdyke, 1985;Stamatakos and Kodama, 1991;Cioppa and Kodama, 2003;Bilardello and Kodama, 2010) strongly suggest, in particular for the anisotropy/inclination shallowing detection and correction work, that the magnetization is a depositional remanence carried by the hematite grains.…”