Alternate Leg ID: ATL2 89-4; 89, Leg 4
Area of Operations: Baltimore Canyon Trough area, outer continental shelf, United States, North America, North Atlantic
Dates: June 01, 1975 to June 12, 1975
Objectives: This 4th leg of the ATLANTIS II cruise had 3 primary objectives. The first objective was to obtain long vibracores to deduce characteristics and ages of sub-bottom sediments. These cores were in support of the acoustic survey completed in Baltimore Canyon Trough in May 1974. Second, short cores of sub-bottom sediments were to be collected. By measuring relative amounts of Pb-210 in these short cores, ages and accumulation rates of sediments for the past 100 years could be determined. Finally, stability of sediments at shelf edge was to be studied. Near-surface (apparently recent) fault displacement had been observed in high-resolution seismic records, suggesting that a mechanism existed for generation of slumps at the shelf break and on the upper continental slope. In addition, several special studies were pursued: sampling surface sediments to determine trace metal and hydrocarbon contents; sampling suspended sediments at water surface; emplacement of pipes into the sea floor by vibracore rig to use as reference points during submersible dives; outlining the areal extent of a sand-wave field near Wilmington Submarine Canyon; dropping sea-bed drifters at selected sites; and outlining the path of the ancestral Delaware valley across the continental shelf.
Type of Activity: Sampling
Information to be derived: Samples and chemical analysis
Grain size analysis
Summary: Cruise concentrated on vibracoring and bottom sampling off New Jersey. 3.5 kHz records: 1774 km; Minisparker records: 659 km; Sample stations: 42; Bottom sediment samples: 78 (Vibracores: 19; Hydrostatically damped gravity cores: 37; Smith-McIntyre grab samples: 15; Gravity cores: 7); Suspended sediment samples: 50; Sea-bed drifters released: 57; Reference pipes emplaced in sea floor: 3.
USGS Project Number: EA
Contact: Harley Knebel (firstname.lastname@example.org)