Other
Scientific paper
Feb 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994jgr....99.2925i&link_type=abstract
Journal of Geophysical Research (ISSN 0148-0227), vol. 99, no. B2, p. 2925-2934
Other
20
Argon Isotopes, Geomagnetism, Mexico, Polar Wandering (Geology), Time Measurement, Calderas, Geochronology, Magnetic Fields, Plates (Tectonics), Rhyolite, Tektites
Scientific paper
Our mid-Pleistocene Ar-40/Ar-39 age recalibration of the geomagnetic polarity timescale is nearly in accord with the oxygen isotope, climate record calibration of the astronomical timescale proposed by Johnson (1982) and Shackleton et al. (1990). Ar-40/Ar-39 ages of a normally magnetized rhyolite dome in the Valles caldera, northern Mexico, yielded a weighted-mean age of 1.004 +/- 0.019 Ma. A K-Ar age of 0.909 +/- 0.019 Ma for this rock by Doell and Dalrymple (1966) was the linchpin for the recognition and calibration of the Jaramillo Normal Subchron (JNS). Other Ar-40/Ar-39 ages from the Valles caldera and Ar-40/Ar-39 ages of Ivory Coast tektites indicate that the JNS began at about 1.11 Ma and ended before 0.92 Ma, probably near 0.97 Ma. The Matuyama-Brunhes boundary occurred between 0.79 Ma and 0.76 Ma on the basis of Ar-40/Ar-39 sanidine ages from (1) three reversely magnetized rhyolite domes of the Valles caldera (0.793 +/- 0.018 Ma, 0.794 +/- 0.007 Ma, and 0.812 +/- 0.023 Ma) and pumice (0.789 +/- 0.006 Ma) from the reversely magnetized Oldest Toba Tuff of Sumatra and (2) pumice (0.764 +/- 0.005 Ma and 0.757 +/- 0.009 Ma) from the lower and upper units of the normally magnetized Bishop Tuff. The age of the boundary may be close to 0.77 Ma as deduced from rates of sedimentation in ancient Lake Bonneville, Utah.
Izett Glen A.
Obradovich John D.
No associations
LandOfFree
Ar-40/Ar-39 age constraints for the Jaramillo Normal Subchron and the Matuyama-Brunhes geomagnetic boundary 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 Ar-40/Ar-39 age constraints for the Jaramillo Normal Subchron and the Matuyama-Brunhes geomagnetic boundary, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ar-40/Ar-39 age constraints for the Jaramillo Normal Subchron and the Matuyama-Brunhes geomagnetic boundary will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1017401