Abstract

A 25-cm zone of anomalous paleomagnetic directions from lacustrine sediments near Summer Lake, Oregon, has the same age and the same paleomagnetic signature as the younger part of the proposed Mono Lake geomagnetic excursion. Both field observations and rock magnetic studies support the hypothesis that the anomalous directions represent actual geomagnetic field behavior, thereby confirming the existence of the Mono Lake excursion at the Oregon site. Although confirmation of its existence at this site does not make the Mono Lake excursion any more suitable as a chronostratigraphic horizon, this excursion may now be used as an additional constraint on models of geomagnetic field behavior including those that predict the morphology of transitional geomagnetic fields.

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