Tectonic maps of the northeast Pacific
The ideas of sea-floor spreading and plate tectonics were just exploding upon the oceanographic community when I (T.A.) was a young graduate student at the Scripps Institution of Oceanography in the late 1960s. This was an exciting time; it seemed that the whole world lay waiting for reinterpretation. Recognizing the power of the Vine-Matthews hypothesis, Bill Menard had asked his draftswoman, Isabel Taylor, to plot all of the magnetic anomaly profiles so far collected by ships traversing the Northeast Pacific. The resulting map and its updates occupied a central spot on Bill’s huge work table for many years. Although I was not officially working with Bill, I was almost irresistibly drawn to his laboratory and to this map whenever I had a spare moment. For some years before, Bill had been mapping and writing about the great North Pacific fracture zones. With the addition of the magnetic isochrons, the sea-floor spreading story of the region unfolded before our eyes. He was like a child in a candy store; I was in heaven.
It was on this chart that we identified and mapped out the isochron patterns for the region and, using their mapped geometry, we were able to explore many sea-floor spreading and plate- tectonic phenomena (e.g., Menard and Atwater, 1968, 1969; Atwater and Menard, 1970; Atwater, 1970; Menard, 1978). However, the compilation of the magnetic profiles, itself, was never published. Over the years since, many additional profiles have been measured, and various detailed surveys and partial compilations have been published. On Plates 3A and 3B we have collected and presented these, along with many of the original profiles, and superimposed them upon our updated interpretations. We present these tectonic maps in honor of H. W. Menard and in memory of his tremendous, contagious joy in science.
Figures & Tables
This new synthesis includes a section on plate kinematics, documenting the basis for a new interpretation of the magnetic anomaly patterns. It also includes: six chapters on various aspects of tectonics, petrologic characteristics, and hydrothermal processes of active ridges from the Galapagos Rift to the Juan de Fuca Ridge; a section on mid-plate volcanism, including the Hawaii-Emperor chain; five chapters on various aspects of northeastern Pacific sedimentary regimes; and nine chapters on the geology of the Pacific continental margin from the Aleutians to Guatemala, seen from the perspective of marine geology. Three separate oversize plates illustrate the bathymetry of the northeast Pacific; two more on the same base show distribution of sediment samples and types and magnetic anomaly data and tectonic interpretations; and others include a synthesis of the geology and bathymetry of the Hawaiian Islands, details of bathymetry along parts of the East Pacific Rise, and a major seismic profile across the Pacific margin of Guatemala.