Paleointensity values for the Cretaceous Normal Polarity Superchron from Thellier analyses of feldspars separated from xenoliths

Alteration of basalt, on geological and experimental time scales, has motivated a search for alternative recorders of geomagnetic paleointensity. Here we report results from xenoliths from the Mount Carmel area (Kerem Maharal) Israel. These rocks, which are of mid-Cretaceous age (Cenomanian, approximately 96-97 Ma), contain small (0.5-1.0 mm) feldspar grains that were separated for rock magnetic and paleointensity analyses. Magnetic hysteresis properties indicate that the feldspars contain magnetic inclusions with single to pseudo-single domain properties. Warming of a low temperature (20 K) saturation remanent magnetization (2.5 T field) shows a blurred Verwey transition, consistent with the presence of a low-Ti magnetic carrier. The feldspars show little anisotropy (as would be expected if elongated grains with a preferential orientation were present) and do not alter significantly during standard thermal demagnetization experiments. Preliminary Thellier analyses have yielded relatively high VDM's (greater than 10 x 10²² Am²). Although it is likely that the samples measured to date represent a very short period of time (and hence do not average secular variation), the data are in agreement with the high time-averaged field value obtained from the approximately coeval lavas of the high Arctic (Tarduno et al., 2002).