Cruise report

Cruise Summary

The SE Caribbean Margin Continental Dynamics Project is a multi-disciplinary investigation to test hypotheses related to arc-continent collision and accretion, high-pressure/low-temperature rock exhumation, and the development of folded belts and sedimentary basins. The primary hypothesis to be tested by the project is that modern continental growth results from accretion of arcs that form on oceanic plateaus. As part of this program, an active-source seismic field program acquired multi-channel reflection and wide-angle data along the Caribbean-South American plate boundary zone in order to investigate the structure of the crust in the accretion zone of the Antilles Arc as it evolves along the plate boundary.

Figure 1. Location of OBSs and wide-angle profiles for the SE Caribbean seismic project.
 

Three teams were involved in the active-source seismic field program: 1) A science party aboard the R/V Maurice Ewing acquired approximately 6000 km of seismic reflection data. 2) A science party aboard the R/V Seward Johnson II deployed and recovered ocean bottom seismometers (OBSs) along 5 transects (Fig. 1); the Ewing provided the seismic source for these instruments. 3) A science party in Venezuela and the ABC islands deployed and recovered seismographs along 4 transects and the island arc; the Ewing and 8 land shots provided the seismic source for these instruments. Communications between the three teams were conducted via email and Iridium phones.

A total of 169 OBS deployments along 5 key transects were made from the R/V Seward Johnson II during the active-source field program. This was one of the largest field programs ever supported by the OBSIP group, and was the first major field program utilizing the WHOI D2 OBSs. Recovery rate was 96% for the WHOI D2 OBSs (122 deployed, 117 recovered) and 98% for the Scripps LC2000 OBSs (47 deployed, 46 recovered). 161 of the 163 recovered OBSs acquired full data. The OBSIP and shipboard personnel were outstanding, and allowed us to deploy and recover instruments much faster than expected. 3 students and 3 Venezuelan observers assisted in watchstanding duties. Shot files were e-mailed from the R/V Maurice Ewing letting us to create SEGY files for the majority of the OBSs at sea (2 OBSs required shore-based data download because of instrumentation problems; SEGY files from these instruments was delivered within 2 months of the cruise). Overall data quality for the project is excellent. Christeson was chief scientist aboard the R/V Seward Johnson II.