The Intensity of the Geomagnetic Field in the Cretaceous

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9725590 Johnson The time-dependent behavior of the geomagnetic field is a parameter related to the strength of fluid convection in the outer core, and understanding how this field intensity varies with polarity reversal rate is of fundamental importance. Compilations of previous paleointensity studies indicate that no reliable paleointensity data exists from the 30 My-long Cretaceous Normal Superchron (CNS). This project will sample a large lava field (Spences Bridge/Spius Formation; 104 My) in specifically to determine the field intensity during this CNS period. In Spring of 1998, the team will construct a new paleointensity oven at the University of Washington, using the design of French collaborators (Carlo Laj; Gif, France). They plan to test the new UW oven using samples from historical flows from Hawaii, where the field intensity is known. The field work to collect the CNS paleointensity samples at Spences Bridge will be completed in Fall of 1998. The remainder of the grant period will be spent with the experimental work in the UW laboratory, in interpretation of the data, and in publication of the results in the scientific literature. ***