PALEOMAGNETIC DATA APPLICABLE TO MODELS OF EARTH'S DEEP INTERIOR AND THEIR UTILITY FOR DATING LACUSTRINE AND PALEOCLIMATE RECORDS IN THE GREAT BASIN

The geomagnetic field is physical evidence of dynamic processes in Earth's outer core and at the core-mantle boundary and is used for models of the earth's deep interior. Past field behavior that is recorded in rocks also is used in the modeling, especially the behavior during changes in polarity (transitions) and brief departures (excursions) from expected long-term field behavior (secular variation). The Laschamp Excursion that is recorded in volcanic rocks in France (Bonhommet and Zahringer, 1969) and in marine sediments in the North Atlantic Ocean (Lund et al., 2005; Channell, 2006) and the Mono Lake Excursion that is recorded in lacustrine sediments in California (Denham and Cox, 1971), Nevada (Liddicoat, 1992), Oregon (Negrini et al., 1984) and in marine sediments in the Atlantic Ocean (Channell, 2006) are two excursions in the late Brunhes Normal Chron that have received recent attention because they are thought to be either a single excursion (Laschamp)( Kent et al., 2002) or two that are separated by about 8,000 years (Benson et al., 2003).

Because of its potential for dating Pleistocene lakes and paleoclimate in the Great Basin, we review the Mono Lake Excursion as it is recorded in the Mono (CA) and Lahontan (NV) basins and interpretations about the age of the excursion based on 14C (Benson et al., 2003) and 40Ar/39Ar dates (Kent et al., 2002) and relative paleointensity in the Mono (Zimmerman et al., 2006) and Lahontan basins. Comparisons are also made with relative paleointensity in marine sediment (Laj et al., 2000; Stoner et al., 2002; Lund et al., 2005; Channell, 2006) and the path of the Virtual Geomagnetic Poles for the Mono Lake and Laschamp excursions in the North Atlantic Ocean (Lund et al., 2005; Channell, 2006).