Summary for Field Activity Number 1984-019-FA

Alternate Leg ID: LANG1

Area of Operations: southern Chesapeake Bay, United States, North America, North Atlantic

Dates: October 15, 1984 to October 26, 1984

Objectives: Collection of high-resolution seismic reflection and sidescan sonar data in order to define the geology and shallow structure of the Chesapeake Bay.

Type of Activity: Seismic profiling

Information to be derived: Seismic reflection and sidescan sonar data

Summary: The cruise was very successful, due in part to excellent weather and to little equipment-related down-time. More than 700 km (380 nm) of seismic profile lines were obtained in 11 days at sea. Local problems with penetration were encountered, apparently due to gas in the sediments or to hard substrates (packed sand or oyster reefs). However, penetration depths were typically about 75 m (0.1 seconds two-way travel time), allowing excellent resolution for the entire Quaternary section and for the upper part of the Tertiary section. On-board observation of the records suggests that cyclic incision and deposition related to sea level changes is recorded in the Quaternary sediments, and that filled paleochannels are commonly unrelated to present bathymetry. The sidescan sonar records showed most of the bay bottom to be smooth and featureless, but local areas of distinct bedforms were encountered, especially near the present channels.

USGS Project Number: CHESAPKE

Contact: Steve Colman (scolman@usgs.gov)

InfoBank: uses the identifier L-1-84-CH. Visit this site for more information.