Paleointensity studies of a lava succession from Jilin Province, northeastern China: Evidence for the Blake event

Abstract

Paleomagnetic results are presented from a volcanic sequence in Tianchi, Jilin Province, northeastern China. Five basalt lava flows can be identified at the sampling site with ages from 210±4 to 88±15 kyr B.P. Rock magnetic analyses and reflected light microscopy indicate that magnetite with a significant fraction of pseudo-single-domain grains is dominant in these lava flows. A single stable characteristic remanence can be thermally isolated above 150-200°C. Intermediate direction is preserved in lava 3 at an age of ∼123 kyr corresponding to the Blake event, and its virtual geomagnetic pole is located in eastern Asia and Australia. From a total of 121 specimens used for paleointensity determinations by the Thellier method in an argon atmosphere, 34 specimens yielded reliable results with low within-flow scatter. The results indicate that a significant intensity low is coincident with the Blake event. Copyright 2000 by the American Geophysical Union.