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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.
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.
The marine reflection data were acquired with
the R/V Ewing’s 6 km, 480 channel digital streamer, firing a tuned 20 element
airgun array at 50m shot intervals.
Reflection data fold is nominally 60. The data were field processed through time
migration aboard the Ewing, using velocity analysis at 5 km or larger intervals.
Some data were lost due to marine mammal sitings, which normally required that
source intensity be reduced until the mammals left the survey area. The only
notable data gap lies between the 64W and 65W profiles, where we lost a second
crossing of the active El Pilar fault C-13 system due to cetacean activity. In
all
we acquired about 95% of our desired program. Paul Mann and Dale Sawyer were the
chief scientists aboard the Ewing. |
