Investigation of Nazca Lithospheric Plate

This report covers work done under NSF Grant No. AG-329 during the period l January 1972 to 30 June 1974. The grant, in response to proposal number P2XOOll-OOO, originally provided support for the Pacific Oceanographic Laboratory (POL) from l January 1972 to 30 December 1975. In January 1973, however, the terms of the grant were modified with respect to the level and type of POL 1 s involvement as a consequence of realignment of priorities in oceanographic research activities within NOAA. As a result, POL participation in the Nazca Plate investigation was reduced to a single field effort in the spring of 1973 and the subsequent reduction and dissemination of the acquired data. During the period of this grant POL, now the Pacific Marine Environmental Laboratory (PMEL), participated in planning and review of program goals and accomplishments. Equipment was acquired to provide a seismic refraction system and to update and augment an existing seismic reflection profiling system. Sonobuoys for use in the seismic refraction measurements were obtained through the U. S. Navy. A 3.5 kHz system was assembled from existing and borrowed equipment and used for sounding and for sub-bottom profiling in regions with thin sediment cover away from the continental margin. The intent of the field effort was to survey, in detail, several regions of the rise crest, conduct a coring program in support of OSU's investigation of metal-rich sediments, participate with HIG in making seismic refraction measurements in the region of the rise crest, conduct geophysical traverses across the Nazca Plate enroute to and from the rise crest, and to make seismic reflection profiling measurements across the continental margin of South America . Grant no. AG-329