Magnetostratigraphy of Paleogene and upper Cretaceous sediments from Broken Ridge

The approximately 1400-m section of prerift sediments on Broken Ridge preserves a polarity sequence that spans the middle Eocene to Upper Cretaceous (Chrons C18/C20 to C34), including a 500-m continuous sequence from the lower Eocene (C23R) to the Maestrichtian/Campanian boundary (C32R).

The polarity record, together with biostratigraphic data, provides a well-constrained time framework for interpreting the history of Broken Ridge. Inclinations in the lower portion of the section are generally 5°-10° shallower than the expected geocentric axial dipole inclination. Comparison of inclination and porosity changes with stratigraphic depth suggests the importance of compaction in generating these shallow inclinations.