Paleomagnetism of the Knight Island Ophiolite, Prince William Sound, Alaska

The Knight Island ophiolite, within the Chugach-Prince William Sound terrane, is inferred to have formed along a trench-ridge-trench boundary.  Although the ophiolite has not been directly dated, geochemical similarities to the 57 Ma Resurrection Peninsula ophiolite provides an indirect estimate of its age.   The previous paleomagnetic study of Knight Island yielded too many overprint magnetizations to estimate a paleolatitude of formation.  In this project we focused sampling to the sheeted dike complex, rather than pillow basalts, in the hopes this approach would increase the number of samples that retain a primary remnant magnetization.   The sampled sheeted dikes are within 2-8 degrees of vertical allowing for simple structural correction of paleomagnetic results, assuming they were intruded by vertical tabular bodies.  Analysis of core samples using alternating field demagnetization removes secondary magenetizations recognized in the previous study and hopefully will reveal the original paleomagnetic direction for the ophiolite.  Identifying the paleolatidude of Knight Island will assist in constraining plate motion of the Chugach-Prince William terrane from 57 Ma to the present.  The relationship of Knight Island to Resurrection Peninsula ophiolite may also be confirmed by the new paleomagnetic data.  Early analysis confirms the results of prior work: the scattering of characteristic magnetizations is too great to interpret an original magnetization.  However, further analysis of samples will hopefully provide clarification of the numerous overprints.