SECONDARY MAGNETIZATIONS CAST DOUBT ON EXCEPTIONAL PALEOINTENSITY VALUES FROM THE LOUSETOWN CREEK LAVAS OF NEVADA, USA

Renewed palaeomagnetic investigation of Pliocene lavas of the Lousetown Creek Formation of Nevada, USA has given reason to question the conclusions of earlier palaeofield direction and palaeofield intensity studies of these lavas. Contrary to the suggestion of Heinrichs (1967), the lavas do not record a complete transition of the geomagnetic field from reversed to normal polarity. Rather, it is found that lavas recording an intermediate direction for the palaeomagnetic field overlie lavas recording a normal polarity direction. The presence of large secondary magnetizations of random direction is widespread. They might account for the unusually high transitional palaeointensity obtained for one of the lavas by Shaw (1977). Copyright © 1990, Wiley Blackwell. All rights reserved