ORIGIN OF THE REMANENCE RECORDING THE MONO LAKE EXCURSION IN THE MONO BASIN, CA
The paleomagnetic directions and relative field intensity during the MLE are negative inclination (about -30˚) and westerly declination (about 290˚) during reduced intensity that are followed by steep positive inclination (about 85˚) and easterly declination (about 100˚) during high intensity at eight of 11 localities around Mono Lake. The three exceptions are at wave-cut cliffs on the east side of the lake where the negative inclination and westerly declination are absent (Coe and Liddicoat, 1994). On Paoha Island, the entire excursion is recorded.
X-radiographs of the sediment and lineation measurements show patterns of normal bedding with layers aligned such that the minimum axes are within 5-10˚of normal bedding, with 10 percent foliation and 1 percent lineation (Coe and Liddicoat, 1994).
We explored reasons for the absence of part of the MLE at the wave-cut cliffs beyond the interpretation of Coe and Liddicoat (1994) that paleomagnetic field strength is a controlling factor. The reasons might be the sedimentation rate – it is about 60 percent greater at the wave-cut cliffs than at Wilson Creek and Mill Creek on the western margin of the lake – and the grain size and percentage of Total Inorganic Carbon (TIC) in the silt, acting separately or in combination. At Mill Creek, which is about 15 km from the wave-cut cliffs on the opposite side of the lake, the percentage of the finer-grained (less than 2 microns) non-magnetic sediment fraction is less than at the wave-cut cliffs by a factor of two (2.1 vs 4.2), whereas nearly the opposite occurs for the TIC percentage by weight (14.1 vs 6.0) for the two localities.