Tectonic evolution of the North Pacific during the Cretaceous quiet period

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Abstract
The Cretaceous Quiet Period ended with a significant reorganization of the plate tectonics of the North Pacific. The Farallon plate broke into three primary pieces: (1) the Kula plate, (2) a large fragment transferred to the Pacific plate, and (3) the continued Farallon plate. The time of the rearrangement is constrained to just before magnetic anomaly 34 by its presence, contrasts in tectonic spreading fabric (TSF), the Emperor Trough, and the Chinook Trough. Our model is based on (1) a complete reevaluation of primary bathymetric and magnetic data, (2) the distribution of major troughs (Emperor, Chinook, Hokkaido, and Krusenstern), (3) mapping and analysis of TSF orientation and amplitude on Quiet Zone crust, and (4) available Deep Sea Drilling Project drill hole data. East‐west trending magnetic reversal lineations and TSF south of the Aleutian Trench are bounded on the west by the Buldir Fracture Zone at 175°E. The major troughs mark the abandonment and initiation of spreading in the reorganization; their absence elsewhere precludes other long‐distance boundary relocations. Emperor Trough is the abandoned Pacific‐Farallon spreading center. Rift initiation and early slow spreading have created the high amplitude topography of the Chinook Trough. We believe that the Hokkaido Trough is the initiation site of a failed oceanic rift. The incorporation of large amounts of Farallon plate into the Pacific plate obviates the need for the very rapid Pacific‐Farallon spreading rates of previous models and significantly alters the interpretation of mid‐Pacific geology.