Other ID: BRKN88-2
Organization(s): USGS, Woods Hole Coastal and Marine Science Center
Location: Boqueron Bay, southwestern Puerto Rico, Caribbean Sea, United States, North America, North Atlantic;
Principal Investigator(s): Juan Luis Trias
Data Type(s): Location-Elevation: Navigation, Sampling: Biology, Sampling: Geology, Seismics: Boomer
Scientific Purpose/Goals: General seismic and sediment survey of Boqueron Bay.
Start Date: 1988-06-01
Start Port/Location: Boqueron, Puerto Rico
End Date: 1988-06-06
End Port/Location: Boqueron, Puerto Rico
Equipment Used: Boomer, Grab sampler, Grab sampler - Shipek, Alpine Vibracorer, Motorola Mini-Ranger III, Single channel hydrophone
Information to be Derived: Grain size analysis; Sea floor map;
Summary of Activity and Data Gathered: Boqueron Bay's surficial sediment cover is a not-too-exciting light gray carbonate mud with some shelly gravel in places. The cohesiveness of the mud made core extraction from the sea bottom extremely difficult and time consuming. The exciting findings came in the seismic. Boqueron Bay is the western extension of the Lajas Valley graven. It appears on seismic that the northern boundary of the basin is a hinge, not a fault, in that dipping strata and a classic angular unconformity can be clearly seen. This would make the valley a half-graben. Unfortunately, we never could track down the southern boundary fault. With more time, we could have extended the seismic survey farther to the south, outside of the bay and probably located the fault. Unfortunately, it would have been too large an area to cover in the allotted time. In addition, the same southeasterly swells and winds that knocked us out in Vieques would have done the same on the shelf outside of Boqueron Bay. Preliminary findings make the Mayaguez Quadrangle for marine geologic mapping a potentially exciting study area, one that certainly could be used to help update some of the details of the land geology, at least as far as precise fault locations. Perhaps even a deep-penetration seismic array should be considered for at least a few north-south lines. Compressed air for the divers was a severe limitation in that bottles had to be ferried to shore on the Zodiac to be refilled at a dive shop. The JEAN A's on-board compressor would have been handy in this situation. In addition, the same logistical problems mentioned under Cruise 1 apply to Cruise 2. Uniboom lines: 14; Jack-hammer vibracores: 7; Beach samples: 8; Shipek samples: 13.
Staff: David Nichols
Notes: This cruise was to collect data to be used by N. Torres for her master's thesis. Original Center People field contained: Dave Nichols - Electronic Technician, Thorton Tyson - ET Assistant.