Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander

Details Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander

Apr 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994jgr....99.6695b&link_type=abstract

Journal of Geophysical Research (ISSN 0148-0227), vol. 99, no. B4, p. 6695-6710

Other

11

Colorado, Geochronology, Paleomagnetism, Polar Wandering (Geology), Utah, Demagnetization, Magnetic Poles, North America, Remanence, Stratigraphy

Scientific paper

The paleomagnetism of the approximately 147 Ma (Tithonian) Brushy Basin Member of the Morrison Formation was analyzed to obtain a Late Jurassic paleomagnetic pole for North America. A total of 200 samples were collected from 25 sedimentary horizons (sites) at Norwood Hill in southwest Colorado. At Montezuma Creek in southeast Utah, 184 samples were collected from 26 sites. Detailed thermal demagnetization (up to nine temperature steps between 600 C and 680 C) and principal component analysis were required to confidently isolate characteristic remanent magnetization (ChRM) directions carried by hematite. Demagnetization behavior for many horizons is erratic and does not allow isolation of a high unblocking-temperature ChRM. Data selection criteria required sample ChRM directions to be defined by three or more thermal demagnetization steps and maximum angular deviations of sample ChRM directions to be less than or equal to 20 deg. Eight sites from the Norwood Hill location and 10 sites from the Montezuma Creek location passed these criteria. The 18 site-mean virtual geomagnetic poles yield a paleomagnetic pole position from the Brushy Basin Member of 68.3 deg N, 156.2 deg E (A(sub 95) = 4.8 deg, K = 53). This pole position is within 2 deg of the paleomagnetic pole which Steiner and Helsley (1975a) reported for the 'upper' Morrison Formation at Norwood Hill, Colorado. A second paleomagnetic pole was calculated after excluding sites with site-mean alpha(sub 95) is greater than 20 deg and sites with fewer than three samples that passed the above selection criteria. This additional editing did not significantly change the paleomagnetic pole position at the 95% confidence level. Along with other paleomagnetic poles from the continental interior the paleomagnetic data from the Brushy Basin Member of the Morrison Formation are interpreted to indicate that the Late Jurassic part of the North American apparent polar wander path progresses from a late Middle Jurassic (approximately 160 Ma) position at approximately 60 deg N, 135 deg E toward the mid-Cretaceous pole position at 72 deg N, 191 deg E.

Affiliated with

Also associated with

No associations

Rating

Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1259104