Summary for Field Activity Number 82016

Alternate Leg ID: NE-82-4

Area of Operations: Long Island Sound, New York, Connecticut, United States, North America, North Atlantic

Dates: June 13, 1982 to June 25, 1982

Chief scientist: Debbie Hutchinson
   

Objectives: Profile across the large positive gravity anomaly which crosses Long Island Sound in order to identify basement or subbasement structure; complete the survey begun in June 1981 to identify the southward termination of the Hartford graben in Long Island Sound; and compare profiles collected with the pre-amp 12-channel streamer and 15-inch watergun (June 1981) with those collected this cruise with the transformer 12-channel streamer and 15-inch watergun.

Type of Activity:

Information to be derived:

Summary: The near trace monitor record across the gravity high (Line 7A) using the 80 cu. in. watergun shows no convincing subbasement reflectors. However, the low frequencies and multiples make the record difficult to read. Several additional crossings of the large valley south of New Haven that we first profiled in June 1981 show that this potential continuation of the Hartford graben turns southward toward Stratford shoal. The valley loses its distinct cut-out shape and many widen and shallow toward the shoal, making it difficult to distinguish reflectors other than the coastal plain and basement surfaces. However, our present grid of profiles should be sufficient to locate the graben if it continues under the shoal using the processed data. Fathometer data: 185.2 km; Magnetometer data: 28.0 km; 80 cu. in. watergun data: 102.6 km (12-channel 10-m groups), 14.2 km (200-element streamer); 15 cu. in. watergun: 65.8 km (12-channel 10-m groups), 2.6 km (12-channel 20-m groups); Reflection data; Magnetic data.

USGS Project Number: 01830

Contact: Debbie Hutchinson (dhutchinson@usgs.gov)

InfoBank: uses the identifier N-4-82-LI. Visit this site for more information.