FROM SLAB WINDOW TO THE MTJ CRUSTAL CONVEYOR: BUILDING ON BILL DICKINSON’S FOUNDATIONAL INSIGHT TO UNDERSTAND THE DEVELOPMENT OF THE SAN ANDREAS PLATE BOUNDARY

The San Andreas plate boundary, although an iconic part of the development of plate tectonics, has always been problematic. Although a transform fault system, its growth and development with the formation and subsequent migration of the Mendocino Triple Junction (MTJ) makes it significantly different from oceanic transforms and complicates comparisons with other major 'continental transforms'. Key to those differences is that it forms at the expense of a long-established subduction system, and thus it develops as a new system of faults, but within pre-existing plate boundary structures. One could argue that Dickinson’s work on this plate boundary system from the mid-to-late 1970’s (Dickinson and Snyder, 1979a,b) to quite recently extended previous understandings and models of the kinematics of the development of the San Andreas system and began to explore the tectonic consequences and geologic signature of this profound plate boundary transformation. That early work has motivated a large suite of studies that have moved our understanding of the development of this system from one focused on plate kinematics to one rooted in the lithospheric scale processes that have made the San Andreas. At present we understand the substantial crustal deformation that North America undergoes in moving from subduction to translation, and an evolving series of geodynamic models, such as the MTJ Crustal Conveyor, have been developed to put these events into a process-oriented framework. We see evidence in spatially (and temporally) varying crustal structure, heat flow, crustal strain, upper mantle anisotropy, patterns and composition of volcanism, and uplift/subsidence along this evolving plate boundary that point to the profound effects that this plate boundary change has had on the western edge of North America. This deeper understanding of the evolution of the San Andreas plate boundary represents one area in which the insight of Bill Dickinson has profoundly motivated critical science advances.