Convergent margin processes
Lead Scientist: Gary Greene
Project Manager: Norman Maher

This project addresses problems associated with convergent margins, primarily the oblique convergent transform margin offshore central California. More specifically, this project addresses the relationship of allochthonous block transport along a transform boundary, fluid flow, submarine canyon and slope mass wasting and turbidity current processes.

Through the ROV dives we have discovered a potentially significant outcrop of ponded sediments in the Goosenect meander area of Monterey Canyon where we suspect that the canyon axis was dammed by a landslide, filled in, and subsequent exhumation has exposed a nearly vertical 100 m high cliff-like outcrop that exhibits thin to laminated horizontal beds. We propose to sample these beds to develop a detailed stratigraphy through these canyon fill deposits. The stratigraphy will provide a record of oceanographic changes and insight into the rates of canyon development.

We also propose to focus on the materials that are passing through submarine canyons. Initially we will concentrate on what they are, where they come from, and how and when they are transported. Comparison among various potential sediment sources within Monterey Bay (e.g. fluvial sediments, materials eroded from the canyon wall, pelagic sediments) and the sediments that are currently within the canyon floor and found on the fan below will be made. Off Mexico, the existence of rhodoliths, a shallow water red algae that forms balls, provide a datable tracer for sediment transport in canyons. Recovery and dating of these organisms will reveal significant information on canyon sediment transport processes that can be compared with canyons in higher latitudes. In addition, we want to investigate the Sur Slide and Shepard Meander region to determine and date turbidity current activity. Ultimately we intend to design instruments to monitor down canyon sediment transport mechanisms. Some engineering time will be necessary to design prototype instruments for measuring physical and chemical parameters in submarine canyons.

Fluid induced mass wasting and fluid sapping are inferred mechanisms for the formation of submarine canyons and thus may be an important process in the shaping of continental margins. We are interested in determining the origin of potential fluid induced features including pipes, pits, and scallops imaged in the EM 300 data, both in Monterey Bay and elsewhere. We propose to use Tiburon in diverse areas such as Ascension, Ano Nuevo, Aquello, Eel, Cascadia, San Pedro and La Paz canyons to conduct coupled fluid and geomorphic studies. In addition, we propose to investigate cold and warm seeps associated with transtensional faults in the Gulf of California to determine the similarities and differences of fluid flow and fluid induced morphologies associated with divergent, convergent and transform boundaries.