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Paleomagnetism of a Keweenawan age intrusive near Clam Lake, Wisconsin
Author(s) -
Kean William F.,
Swingen Regina A.
Publication year - 1981
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl008i006p00579
Subject(s) - geology , apparent polar wander , paleomagnetism , precambrian , dike , polar wander , intrusion , declination , gabbro , igneous rock , paleontology , geomorphology , geochemistry , physics , astronomy
Two long cores from a magnetite‐rich gabbroic intrusion near Clam Lake, Wisconsin were studied to obtain paleopole positions to aid in determining the time of intrusion and learn more about the tectonics of the area. This intrusion was suspected to be late Precambrian in age. A.F. demagnetization above 150 oe. produced reliable remanent directions. The cores were not azimuthally oriented, therefore small circle plots were made for each sample using 12 different horizontal orientations. The best pole position was considered to be where the small circle paths crossed the Precambrian polar wander curve. This gave a normal pole at N 30° E 176° which is middle Keweenawan in age. The average inclination and declination for 14 of the 18 core sections was 35° and 288° respectively, which is consistent with aeromagnetic maps of the area. The 35° inclination is consistent with most middle Keweenawan rocks of the area, after they have been corrected for a 10° ‐ 30° tilt. This suggests that the Clam Lake area was not tilted after intrusion. Basalt dikes in the gabbro gave consistently lower inclinations, which suggest a late Keweenawan time for their formation.