U.S. Geological Survey Woods Hole Field Center Woods Hole, MA 02543 March 24, 1987 Cruise Report: R/V FARNELLA East Coast EEZ GLORIA Survey, Leg 1-- Northern Blake Plateau, Continental Slope, and Rise Cruise name: Fl-87-EC Ship Name: R/V Farnella Project: East Coast GLORIA (Geologic long-range inclined asdic) EEZ Survey Area of Operation: Northern Blake Plateau, Continental Slope, and Upper Rise between the Blake outer Ridge and Cape Hatteras. Dates and Ports: Left Jacksonville, Florida at 1230 on Monday, February 2, 1987 Arrived Norfolk, Virginia at 0900 Friday, February 27, 1987 Scientific party: Peter Popenoe Chief Scientist USGS David Twichell Assoc. Chief Scientist USGS John B. Wilson Chief Scientist IOS Eric Darlington Senior GLORIA Engineer IOS Andy Harris GLORIA Engineer IOS Larry Kooker MASSCOMP Tech., B.Pac.Mar.G. USGS Colin Jacobs Photo Manager IOS Sarah Griscom Data Curator, watchstander USGS Simon Cargill Watchstander, B.Res.Anal. USGS Rob Wertz Watchstander, B.Pac.Mar.G. USGS Steve Whittle Mech. Tech. IOS Kay Potter Data Manager RVS Ships Crew: Richard Jowett Captain, J. Marr and Sons, Ltd. Albert Fuller First Officer Ian Newsome Second Officer Mike Baldwin Chief Engineer George McCarm Second Engineer Mark Burnett Third Engineer Richard Clarke Electrician Gary Macorison Chief Cook Emanulle Merin 2nd Cook Roberto Valiente Steward Peter Appleyard Radio Officer/Seaman Alan Thompson Bosun Coleman Kenny Seaman Jim Springall Seaman Cruise Objectives: This cruise was the first leg of the joint USGS/IOS GLORIA Survey of the East Coast Atlantic Margin Exclusive Economic Zone (EEZ). The cruise covered a portion of the EEZ that included the northern Blake Plateau and the Continental Slope and Rise off Georgia, South Carolina, and North Carolina, from the 400 isobath to the 200 mile EEZ boundary (fig. 1). The British Institute of Oceanographic Sciences, (IOS) long-range sidescan sonar system (GLORIA) was contracted by the U.S. Geological Survey to produce a reconnaissance type map of the seafloor within the U.S. EEZ of the conterminous United States, Hawaii, and Puerto Rico. The survey is being done to provide a basic understanding of the EEZ, including resource potential and geologic hazards. Instrumentation: GLORIA System The GLORIA sidescan sonar system is capable of ensonifying swaths of the seafloor up to 60 km wide (30 km to each side of the towed fish) at a survey speed of 8 knots. The sonar array on the fish consists of two rows of 30 transducers on either side of the fish that emit pulses of 1 second or 2 second duration in the 6.2-6.8 kHz range with a band width of 100 Hz. Usually pulses are emitted at 30 second intervals. The incoming reflected sound is fed to a data acquisition system, recorded on magnetic tape, and displayed on a strip recorders. Digital data are later fed to a disc where the data are slant-range corrected and geometrically stretched to compensate for changes in over the ground speed. The data are then converted to a raw monograph by a laser camera which produces an image similar to an aerial photograph. A mosaic at 1:375,000 scale is produced aboard ship from these images. The digital sidescan data are also read to magnetic tape, and final processing is done onshore from the digital tapes. Navigation: For the Leg I survey the navigation system consisted of the Farnella Racal-Decca MNS 2000 Loran-C, a Northstar Loran-C, and a Racal-Decca satellite navigation system. Data from all three instruments were fed to the ABC system where they were merged with incoming bathymetry and magnetic data. Because the USGS Megapulse Loran-C system was not operable for Leg 1, real time steering was done from the Northstar system. Seismic system: Three seismic systems were used: A 3.5 kHz system and Raytheon 10 kHz system were towed from davits mounted on the bow and recorded on a Raytheon 1807 LSR dry paper, and a Mufax wet- paper recorder, respectively. These systems are used for precision bathymetry and to compute slant-range corrections. Depth values from the 10 kHz profiles were entered into the ABC computer logging system and merged with the navigation. A 160 cu. in. airgun was fired at 10 second intervals, and the signal was collected by a 2 channel hydrophone streamer of French-Italian design. The resultant incoming signal was digitally recorded by a MassComp computer system for a 6 second sweep, delayed for water depth. The signal was displayed in real time data on a CRT monitor and Raytheon 1807 LSR recorder with a 4-second sweep, generally filtered for 15 to 80 Hz. Raw data were also recorded on 9-track magnetic tape. Magnetometer: A Geometrics proton precession magnetometer measuring total field was towed about 150 m behind the ship, and signal recorded on the ABC system. Chronological log of Leg 1 Leg 1 departed Jacksonville, FL at 1237 EST on Monday, Feb. 2, 1987. We arrived at the beginning of Line 1 of the survey off the Georgia coast at midnight. We deployed the GLORIA fish by 0045, however a test of the system showed a malfunction. The GLORIA signal was being transmitted and received, but temperature and depth gauges were malfunctioning and showed too much voltage draw. We began retrieving the GLORIA for repair at 0100 EST Tuesday, Feb. 3. The GLORIA was redeployed at 0300 after disconnecting the compass in the fish, which was flooded from a leak. The equipment was retested until 0630, but the problem persisted. There were also airgun problems and problems with the MASSCOMP system as well as the Megapulse. At 0700 the GLORIA fish was retrieved for further checking and was in by 0725. At 0845 a dissasembly of the fish showed that the compass was 1/2 full of seawater. The leak was substantial, since the fish had only been in the water for about three hours. After consultation with Wormley, the end portion of the GLORIA cable was wrapped with electrical tape in an attempt to waterproof it. The GLORIA fish was redeployed at 1430 without the compass and at 1640 we started recording data on the way back to line 1. The system seemed to be fixed. Because the GLORIA engineers had been up for 24 hours fixing the system, we decided not to deploy the airguns or to pull the fish to reinstall the compass until after they had slept. We deadheaded back to the start of line 1 arriving at 2330 Tuesday night. The system returned good records for the continuation of Line 1. At 0900 Wed., Feb. 4 (1400 GMT, day 35), we turned off all equipment, brought in the GLORIA fish and reinstalled the compass. We also worked on the airguns. By 1105 the compass was reinstalled and the fish back in the water returning good data. By 1200 (1700 GMT) the airguns were fixed, deployed, and we were back on line returning good records. By 1400 (1900 GMT) the magnetometer was deployed. At 2140 Wed., Feb. 4, I was informed that there was a leak in the cooling water system of the Farnella's diesel engine and that water was getting in the oil of that engine. At 2300 the leak was worse and the decision was made to pull all gear and hove-to to fix the engine. By 2330 all gear was in. Thursday, Feb. 5 (day 36). The engine water leak was in an elbow, and was repaired in about 1 and 1/2 hours. The gear was redeployed and back on line I by 0300 (0800 GMT). By 0900 the winds had increased to 20 to 30 knots and the seas were building to 4 to 8 feet (approx.). We were heading into the seas which caused the stern to pitch wildly, our speed to decrease, and the airgun to misfire on some shots. It was a rough day, but at 1500 we turned south onto line 2 and a following sea, which eased the motion somewhat. With the passing front the seas eased and gradually diminished. Friday, Feb. 6. was a beautiful day with warm temperatures and a 2-4 ft. sea. Pictures were developed and the mosaic was begun. Saturday, Feb. 7, began with another passing front. The ship rolled badly all night with 8 ft. or higher seas and high winds, and with lightning flashes every 2 to 4 seconds. Dishes were broken in the galley, gear was strewn all over the floors, and everything was knocked off tables. In spite of the weather, all equipment operated well. During the day it was pointed out by Eric Darlington that we were not ensonifying a strip of the seafloor directly under the ship because of our two second pulse length. Because we were in water of 400 to 600 m depth, the first returns from the bottom were coming back while the outgoing signal was still being broadcast. We calculated that in 400 m of water almost 3 km of the bottom was not ensonified. The GLORIA system had never been tried with a 1 second pulse, but the decision was made to try this setting, which was the lowest possible. At 1830 we tried 1 second pulse length data and did not seem to lose any range. We decided to keep the setting at 1 second until we got into deeper water. Sunday, Feb. 8, was again a beautiful day with sun and 3 to 5 ft. seas. Everyone had a good nights sleep, all equipment was operating well, and the mosaic was coming together nicely. our speed was not quite the 8 knot average we had hoped for, but not far behind. Sunday night and Monday morning, Feb. 9, was another night of high winds and high seas. We were bucking waves, some of which were over the bow, cutting our speed to zero. "Black ice" created by cold air (3 d C) over a warm sea steamed across the surface of the ocean, freezing to the ship. Because of high seas over the rear deck, all hatches were battened down. Because of both the rough seas and the Gulf Stream, our speed over the bottom decreased to less than 4 knots. During the day winds increased to 30 knots with gusts to 60 knots and breaking seas to over 10 ft. Fog filled all troughs and wisped across the tops of the waves. Mist towers are visible on the horizon. The scene was more dramatic because of the partially overcast sky, through which sun highlighted only certain areas of the ocean. On Tuesday, Feb. 10, the winds calmed to about 15 knots, and seas moderated. During the heavy weather a problem developed with the laser camera and the program that corrects for depths on the film. Also, because the film could not be developed in high seas, we were several days behind on the mosaic. Wednesday, Feb. 11 was the best day yet with 60 d F temperatures and 3-5 ft. seas. Everyone was on deck to take advantage of the sun (except those on watch). The slant-range correction for the camera was fixed, and three days worth of images were mosaicked. Warm weather and 3-5 ft seas continued into Thursday, Friday, and Saturday, Feb. 12, 13, and 14th. On Saturday, Feb. 14 we finished the Blake Plateau section of the survey and turned eastward onto the Rise at about 1000 EST. The day was overcast with 2-3' seas with slightly larger swells. This beautiful weather continued through Sunday, Feb. 15. All systems were operating well. Monday, February 16, was the worst day yet. High winds gusting to 60 knots very high seas, rain, and quite warm. Large waves were breaking over the rear deck of the Farnella and washing against the airgun and GLORIA maintenance labs. The airgun stopped firing but was soon fixed. Because beating into the waves was too hard for the equipment, we had to alter course on line 13, to parallel the slope, a course we maintained for the rest of the cruise. At 1000 a major electrical break occurred in the GLORIA maintenance shed, blowing the top off one of the large capacitors, and blowing the power amplifiers for the entire right bank of transducers. The decision was made to steam on the most gentle course for people and equipment until daylight, when repairs could be attempted. By 0730 on Tuesday, Feb. 17, winds had decreased to 45 knots, seas 10 to 15 ft, somewhat less than Monday. A second check of the GLORIA shack verified that 10 power transistors were blown, and that a electrical fire had fried most of the electronics in several amplifiers. Since the spare amplifiers had been activated in the original malfunction, almost all remaining amplifiers had blown and the whole power supply needed to be rebuilt. By 1400 enough power supplies had been rebuilt to test the equipment, and the cause of the trouble, a wire probably fatigued by the rough seas, had been found and fixed. On testing, the rebuilt power supplies malfunctioned and fried, so had to be returned again to the electrical shop. By 1900 testing had revealed that more than the power amplifiers had been fried by the power failure. Each circuit board was removed, checked and rebuilt, and by 2100, by tinkering with circuits, the system was minimally functioning. We returned to Line 13 although the magnetometer was also producing a noisy record and it was too dangerous on deck to pull it. On Feb. 18 the starboard side of the GLORIA system was producing only a faint signal, so the gain was adjusted to correct for this, something that had never needed to be done before. It later turned out that the cable had also been damaged by the storm, but not knowing this, we continued the survey without pulling the fish. Seas were moderating, so the magnetometer was brought in and checked for broken wires. One bottle of the gradiometer was removed which solved the noise problem. Other circuits were also worked on. February 19 was another good day with light seas. Eric Darlington, Andy Harris, and Larry Kooker took advantage of the weather to repair circuits and rebuild the spares. Since they were not able to test the spares before plugging them into the circuit, a number blew when turned on. Good weather continued Feb. 20, 21, and 22, with all equipment functioning and GLORIA still set with the increased gain and returning useable images. Seas started building again late on the 22nd and by morning on the 23rd had become quite rough, knocking everything off tables, trash cans over, books, dishes, and everything not secured on floors. On Monday morning, Feb. 23, seas had built to 10 to 20 ft. with the tops of the waves blown off by 20 to 45 knot winds. The bridge could not hold the course because of the seas, so the course was altered about 0700. On checking the GLORIA shack a loose circuit board was found on the floor, and much water was found in the shack. By 0720 all power was lost to the shack This time it was the A.C. power from the ship due to salt water in the waterproof connectors. Because of the power failure, the GLORIA system went down, but the ship could not hold a course anyway. The airgun also went down. I called the Woods Hole office to advise of our progress, and was told that the cruise had been extended 3 days to make up for our down time. By 1200, Farnella was quartering the high seas at 2 to 3 knot speeds, and we had recorded a number of rolls of greater than 45 degrees, the highest the instrument on the bridge could measure. As I passed the galley at 1100 we took a severe roll causing all of the pots of food cooking on the stove to be thrown over the stove rail onto the floor. Lunch was served as usual at 1130. I informed the IOS engineers of the decision to extend the cruise 3 days and received an extremely negative reaction. Simon Cargill who had experienced much seasickness during the cruise, was again reporting vomiting blood, possibly from a bleeding ulcer he had previously had trouble with, aggravated by seasickness. On advising Woods Hole of this additional problem, the decision was made not to extend the cruise and that we should rendezvous with the Coast Guard off Cape Lookout so that Simon could be removed from the ship. At 1800 we started pulling gear in somewhat diminished seas over decks that were extremely slick from oil, apparently pumped onto the decks from the compressor sump. In spite of this dangerous situation, by 1827 the airgun and streamer, magnetometer, and GLORIA fish were aboard. At 1840 the plan was changed to steam for Norfolk, rather than Cape Lookout, as the Coast Guard no longer considered Simon's situation "life threatening". Seas diminished on Tuesday, Feb. 24 at 0700 to 8 to 12 ft. Winds also diminished to 15 to 20 knots. During the transit to Norfolk we were able for the first time to thoroughly check out the GLORIA system with the fish on deck to determine why the gain had to be adjusted up to receive data from the starboard transducers. A check of the onboard system and the GLORIA fish showed no problems, however a check of the cable showed that it was bad and needed to be replaced. At 1350 seas were still diminishing allowing us to bring the 3.5 and 10 kHz systems on board. At 1500 we began the cable change. At 1930 we rendezvoused with a pilot boat off the Norfolk entrance buoy and Simon Cargill was transfered to the boat. Seas were down to 3-6 ft by this time. We turned east toward Norfolk Canyon to continue the survey and arrived at the planned start of the line at 0000 on Wednesday, Feb. 25. The engineers worked all night, and the cable change was finally completed and nose cone reinstalled by 0600. The airgun, streamer, 3.5 and 10 kHz fish were deployed, and we began the survey southward along the slope at 0721. After the cable change the GLORIA pictures were greatly improved, and the gains were adjusted down to their normal setting. Certainly the cable had been bad since February 17, when we had the major power failure. However the improvement in the data quality suggested that the cable may have been bad from the start of the survey on Feb. 2. If the fish had not been pulled for the transit to Norfolk, we would have operated with a defective cable for the duration of the cruise, and perhaps into or through Leg 2. The airgun had failed to seal on being redeployed, so it was pulled, repaired, and redeployed by 1000. All data looked great! Our mosaic was 8 days behind schedule at this point for two reasons: 1) we had experienced camera time-correction problems on about the 17th that had involved modifications in the computer program dictated from Wormley, and 2) the film could not be developed due to rough seas. Once the camera problem was solved and seas calmed, we were able to catch up on the mosaic on the 25th. Thursday, Feb 26, was a beautiful day with seas 1-3 feet and temperatures in the 60's. At 1200 we finished our southward steam on line 23, and turned northward toward Norfolk on line 24. Seas were still only 3-6' at this time, and winds 15-20 knots. We began to inventory data and package computer tapes in anticipation of the end of the cruise. The IOS engineers stated that in view of the weather and improved data quality, they would not have minded the three day extension of the cruise in retrospect. At 1800 we ran out of time for surveying, ended line 24, and started pulling gear. By 1920 all equipment was in, and we began the transit to Norfolk, arriving at the Waterside Pier in downtown Norfolk at 0900 on Friday, Feb. 27. During the transit all data were inventoried and packed, all recorders and instruments cleaned and reloaded with paper, and the laboratories cleaned. While at the dock on the 27th and 28th, in addition to onloading and offloading supplies, we were able to inspect damage from the month at sea. We had noted that sides of the van where two additional spare GLORIA cables were stored were bashed from inside. One of these cables was needed as a replacement of the damaged cable. On opening the van, not possible at sea because it is stored on top of the GLORIA electronics van, it was found that some equipment had broken free from storage racks and had slammed against the stored GLORIA cables, damaging both cables. Because these cables were damaged more than the bad cable we had changed on the trip to Norfolk, the latter cable was pulled onto the dock, to turn it around on its reel and re-fed to the hold so it could be repaired and used as the spare. Data collected during Fl-87-EC GLORIA 3440 naut. miles Airgun 3440 nm 3.5 kHz 4000 nm 10 kHz 3500 nm Magnetics 3000 nm Preliminary results of the GLORIA Survey of the northern Blake Plateau, continental slope and rise off Georgia, North Carolina, and South Carolina. The northern Blake Plateau in the area of the GLORIA Survey shallows across the elevated corner of the Carolina Platform known as the Charleston Bump. Water depths are on the order of 400-700 m shallowing from the southern plateau where they are 900-1000 m. On the south side of the Charleston Bump, because of shoaling bathymetry, the Gulf Stream interacts with the bottom, which deflects the Stream offshore and sends it into a series of meanders that persist to Cape Hatteras. Where the Gulf Stream is deflected, the bottom is scoured down to an older, indurated substrate of deep-water limestones that are armored by manganese- phosphorite pavements which supply an attachment surface for deep-water reefs. The GLORIA images clearly show the eroded nature of the bottom where the Gulf Stream has exposed strata of Miocene, Oligocene, Eocene, Paleocene, and Late Cretaceous (Maestrichtian) age. Many deep erosional pits and valleys are visible, as well as erosional mesas capped by phosphorite slabs. Because reflectance and erodability differences of strata of various ages, and our network of previously collected and analyzed high-resolution seismic reflection records in this area, we were able to create a geologic map of the outcrop areas of each unit. Because the manganese nodule fields are associated with the Oligocene and Miocene outcrop areas, the data will be useful in delineating the nodule resources. Also depicted on the images in this area are extensive areas of deep-water reef mounds, which show up as darker bands or circles on the GLORIA image. Older, high-reflectance strata end abruptly along a sharp line at the crest of the bump along a feature known as the Charleston Valley. Here, because of decreased Gulf Stream energy downstream, the North Carolina shelf is characterized by a low- reflectance Quaternary sand sheet that is essentially featureless except for scattered deep-water reef pinnacles, surrounded by scour moats. These reefs are virtually unknown and have never been studied except for a brief mention in the report we did for the BLM on hazards and constraints analysis of the North Carolina margin. The Continental Slope is characterized in the images by higher-reflectance outcropping older strata, including early Miocene, Oligocene, Eocene, and Late Cretaceous-age bands. These strata are cut by submarine canyons and massive slumps in the Cape Hatteras area where the slope has a high declivity, but southward toward the Blake outer Ridqe the slope decreases in declivity and becomes progressively covered by younger Quaternary sands and muds. The Blake outer Ridge, an area of post-Miocene deposition on the Upper Rise is characterized by relatively featureless, low-reflectivity sands, however higher-reflectivity older material outcrops along the north flank of the ridge. The salt domes at the base of the slope on the Upper Rise are visible on the images as high-reflectance circles. The GLORIA images show these features clearly, and we will be able to more accurately map them than with the old GLORIA II data. Two previously known massive slumps are also clearly visible in the data, the Albemarle Slump north of Cape Hatteras, and a slump off Cape Romain. Long rubble trains descend from these slumps and are traceable by a zone of higher reflectance to beyond the 250 mile EEZ limit. The submarine canyons have similar rubble trains that cross the rise.