Monterey Bay Aquarium Research Institute

Mendocino Fracture Zone Cruise - 2001
August 20 - 30, 2001
Over 300 km off the California-Oregon Coast
Cruise Description


Introduction

This cruise is a continuing collaborative effort, with NSF and NURP funded co-principal investigators from Oregon State University, to study the tectonic history and structure of the northernmost extent of the San Andreas System, as exposed along the Mendocino Fracture Zone. On August 20 the Western Flyer will return to the Mendocino Transform Zone for a series of dives to examine the tectonic history and methane seeps of the Mendocino Ridge and the Blanco Escarpment. Results from the first dive series revealed that slabs of intact Miocene oceanic crust have been uplifted due to compression between the Pacific and Gorda plates. The ages of rocks collected from the slabs (8-12 my) are too young to represent normal Pacific oceanic crust. The tectonic setting and youthful ages point to slabs of Gorda Plate transferred to the Pacific plate. However the geochemistry of the rocks collected in 2000 are very similar to seamounts studied in the California Borderland. Sediments collected during 2000 contain abundant microfossils that can be used to constrain the uplift history. We plan to complete our work this year by addressing the following questions? 1) What is the chemical variability of oceanic crust exposed in the transform? Could there be pieces from both the Pacific and Gorda Plates crushed together? Are volcaniclastic rocks and sediments broadly distributed? 2) Can the uplift of the discrete slabs be constrained to one time interval and correlated with the final steps of the formation of the San Andreas system? 3) Are the seep communities discovered in 2000 still present? Can we find additional communities? Click on the links above and on the picture below to find out more about this exciting cruise!

 

Click on the links to the left and the picture below to find out more about this exciting cruise!

 


All images created by K.A. Salamy MBARI, August 2000