My primary research specialty is the Earth's magnetic field and its variability through time. This includes the pattern of directional and intensity (secular) variation during intervals of stable magnetic field polarity such as today, the evidence for anomalous excursions, the sequence of magnetic field reversals, and the field geometry during transitions. All of these aspects of geomagnetic field variability provide insights into the magnetohydrodynamic processes active in the Earth's core which generate the geomagnetic field. One of my long-term goals is to define as best possible the space/time structure of the geomagnetic field, to then look for evidence in that structure of recurring, distinctive features of the field that may indicate coherent dynamical elements in the core dynamo, and finally to link the observed patterns of field variation to current theoretical studies of dynamo processes in order to better understand the fundamental dynamics of dynamo activity in the Earth's core.

This primary research focus has fostered the development of four other research specialties:

1) rock magnetism of sediments: Any paleomagnetic study of sedimentary rocks must evaluate the processes that produce (or subtract from) the natural magnetic remanence in sediments and estimate their relative times of remanence acquisition (or loss). These processes begin at the time of sediment deposition and may continue for an extended time thereafter as the sediment de-waters, compacts, and chemically alters. I am particularly interested in two aspects of these processes - early sediment diagenesis and biological factors in sediment magnetization.

2) quaternary paleoclimate/paleoceanography: The quantification and timing of continental and oceanographic environmental/climatic variability requires multidisciplinary efforts. I have strong interests in such problems and believe that paleomagnetism/rock magnetism can provide unique perspectives on them. The pattern of directional secular variation can be used regionally to date Quaternary sediment sequences. The pattern of intensity variation and ocurrances of excursions can provide additional isochrons on a global scale. These dating/correlation tools can often dramatically improve the time resolution of sediment sequences and permit more detailed studies of the paleoclimatic and paleoceanographic variability recorded within them. By understanding the rock magnetic variability in sediments, one can estimate the role of physical and chemical environmental factors in the sediment magnetizations and estimate their paleoclimatic/paleoceanographic causes.

3) microplate tectonics: I have maintained an interest in the application of paleomagnetic/rock magnetic tools to practical problems in structural geology and tectonics. I have focused on issues relating to the evolution of the North American Cordillera, especially evidence regarding possible large-scale strike-slip motions or rotations of crustal blocks (terranes) along the Cordilleran margin.

4) time-series analysis: Time series analysis and related linear or nonlinear data processing techniques are necessary for considering the broad range of paleomagnetic field variation and paleoclimatic/paleoenvironmental variability that has occurred in the geologic past. Specific techniques include 1-D and 2-D spectral analysis, scalar and vector statistical analyses, mathematical simulation modeling, vector waveform analysis, and both linear and nonlinear (dynamical) systems.