U.S. GEOLOGICAL SURVEY
Coastal and Marine Geology Program
Woods Hole, MA 02543

CRUISE REPORT _ _ CRUISE REPORT

  1. Ship Name/Owner Operator: R/V H.J.W. FAY/Tracor Marine
  2. Cruise Identifier: FAY 018
  3. Cruise Dates: 2 - 15 July 1976
  4. Cruise Objective: geophysical reconnaisance of the S.E. Georgia Embayment for regional environmental analyses.
  5. Chief Scientist: L.D. McGinnis, USGS
  6. Survey Area: S.E. Georgia Embayment
  7. Approximate Survey Area Limits:
  8. Data Acquired:
  9. Survey Track Map: click HERE for a detailed cruise map.
  10. Scientific Party: L.D. McGinnis, USGS
  11. Navigation Techniques: Western Geophysical integrated navigational system with:
  12. Scientific Equipment:
  13. Days at Sea: 13 days, 4 hrs, 25 min (12 days, 12 hrs, 25 min working days)
  14. Ship's Captain: J.P. Olander
  15. Ship's Crew: unknown
  16. Cruise Narrative: FAY cruise 018 departed Charleston, S.C. at 0700 GMT on 2 July 1976 with 14 science staff, 15 ships crew and the captain's wife and 2 children. All equipment was over the side and operations began on line 18 at 1000 GMT. All systems were operational except the sparker which was on loan from Teledyne and received on 1 July 1976. A malfunctioning sparker triggering condensor was diagnosed by Frank Jennings and it was decided to complete the first two lines (18 and 19) without the sparker before returning to Charleston for spares. D. Moller requested 1 to 2 hours delay at the end of line 18 to determine satellite fixes. We returned to Charleston at 1900 GMT on 3 July for spares. After receiving them from Kevin King put to sea at 1920 GMT. On July 3 at 2030, all systems were again in the water and operations were continued. On the final day of the cruise, line 19 was repeated with the sparker, since the line crossed two sites of the proposed USGS drilling program

    17. Profiling proceeded uneventfully, with watchstanders becoming familiarized with equipment by 5 July. All sea sickness among the troops was gone by the 5th and cruise schedules started to fall into routines. Seas were calm and weather generally fair. The captain's wife and son began to stand watches in the lab regularly. Cooperation between ship's crew and science personnel was excellent.

    Marked differences in geological provinces are evident from the sparker and airgun records. Relief on the shelf, west of the Florida-Hatteras slope, is negligible. A mound or erosional remnant generally marks the shelf break. The Blake Plateau displays considerable diversity, with hills and valleys having relief up to 70 to 80 meters. Stratification in the hills and truncation of strata along the slope strongly suggests the entire Blake Plateau is a product of erosion. Sparker records on the shelf we're generally excellent with Penetration of 0.4 to 0.5 seconds (two-way time) not unusual. Penetration on the Blake Plateau was another matter. Reflection times greater than 0.2 (two-way) were rare. I suspect this is due to the acoustical properties of the near bottom lithologies. A flat-lying, good reflector could often be followed from the continental shelf under the slope to the Blake Plateau where it lies near the surface of the Plateau. This unit was probably critical in preventing deeper erosion on the Plateau.

    An area of complex faulting was observed on the sparker records-on the dogleg between lines 24 and 25. Although bottom sediments ate the water sediment interface were smooth and underformed, horst-graben structures, having throws 15 to 30 meters, were evident at two-way times about 0.1 to 0.2 sec below the interface. Strike of the faults is not known, although they did not show up on the lines radiating away from the shoreline and thus they may parallel these lines. Efforts were made to repeat these observations on the tie line paralleling the dogleg, but rough seas and high noise levels prevented the recording of not only subsurface reflectors but even a reliable bottom reflector. The failure of achieving good sparker records along the tie line was the most serious disappointment of the cruise. Consideration was given to resurveying the tie lines (31 and 32), but lack of time prevented any make-up work. No time lee-way was available for weather delays, thus it was necessary to continue along the planned tracks without deviation. Because of the nature of the faults described above and the fact that they lie about 100 km due east of a prime lease area in the S.E. Georgia Embayment serious consideration should be given to planning a cruise to survey in detail, this fault system. Time loss during the cruise included that (about 4 hours) involving the sparker triggering device, 10 hours to evacuate an ailing crewman (Bob Crews, wiper) suspected of having a heart attack but which turned out to be a ruptured esophagus and a 15 hour delay at the beginning of the cruise while waiting for an engineer replacement.

    A final malfunction of one of the surveying systems occurred about midnight GMT on July 8 when the gravity meter was discovered by Don Moller to be behaving erratically. After some three hour ship-to-shore communications with Perry Parks, the meter again became operational late on 12 July, barely on time to do the tie lines 31 and 32.

    Personnel on the cruise were a pleasure to work with. Ships moral was far above that experienced last year. Capt Olander went out of his way to assist our programs and made every effort to complete the cruise outline, evento the point where he encouraged completing lines on the south end of the survey area knowing this would eat into his scheduled shore time. Dick Gardner from the USGS-WRD in Montgomery, Alabama, was an excellent addition to the cruise for his knowledge of onshore geology and hydrology and also for his broad experience in geological and geophysical reconnaisance techniques. Bill Patterson from the USGS seismic data reduction center in Denver, was able to assume watch standing responsibilities in a relatively short time as he became proficient in the mid-watch period. Since participating in FAY cruise 018 we feel that the acquisition of cruise personnel from various branches of the survey is certainly an excellent idea. The practice should be continued and perhaps expanded to include technical specialists in instrumentation and navigation as well.

    Description of geophysical lines:
    13 lines were run normal to the coastline beween 33dN and 29d30'N. Two lines comprised 1 long tie line parallel to the shelf break. In addition 4 short lines were run in the area between latitude 30d40'N to 31d10'N and longitudes 80d30' to 80dW. The lines and numbering system was continued from Fay cruise 017 to the north at 18. Lines on 018 were numbered from 18 to 32 and the "dogleg" following each line was considered part of the preceeding line.

    12 sonobuoy refraction profiles were completed along lines 31 and 32, all on the Blake Plateau. Sonobuoy stations were numbered from 2 to 13 with #2 on the north and #13 on the south.

  17. Attached Figures/Illustrations:
    1. Total data collected by day
    2. Base track map
    3. Track map detailing 3.5 kHZ data
    4. Track map detailing minisparker data
    5. Track map detailing airgun data
    6. Track map detailing magnetometer data
    7. Track map detailing gravity data
    8. Track map detailing sonobuoy data

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