Abstract of paper presented at American Geophysical Union 1991 Spring Meeting, Baltimore, Maryland.
Trans. American Geophysical Union (Eos), v. 72, p. 101.

Late Mesozoic, pyrrhotite CRM in Late Precambrian/Early Cambrian sedimentary rocks from the Inyo Mountains, Eastern California

D. R. Van Alstine, Applied Paleomagnetics, Inc.
R. E. Lewis, Shell Development Co.
S. L. Gillett, Dept. of Geology, Mackay School of Mines, Univ. of Nevada Reno

One of North America’s classic Cambrian/Precambrian boundary sections is exposed in the Inyo Mountains of eastern California. Sedimentary rocks of the Wyman Formation (late Precambrian) and Deep Spring Formation (latest Precambrian/Cambrian?) yield a moderately-steep northwesterly magnetization (D = 323°, I = +53°) that apparently reflects pervasive late Mesozoic remagnetization. Paleomagnetic results from both limbs of the Inyo anticline, a major NW-trending fold that may date from the mid Paleozoic Antler orogeny, indicate that the remagnetization is post-folding. The paleomagnetic results also seem to reflect minor post-remagnetization Basin and Range tilting.

In most samples, the magnetization probably resides chiefly in Fe₇S₈ pyrrhotite, as suggested by abrupt loss of intensity near 350°C coupled with high coercivity. The magnetization may partly reside in magnetite, based on persistence of the characteristic magnetization direction up to ~450°C in some samples. The paleomagnetic sample sites are within 9 km of the Papoose Flat pluton (K/Ar 78 Ma) and within 18 km of the main Sierra Nevada batholith. This study provides yet another example of pyrrhotite remagnetization associated with regional heating and plutonism.