Paper No. 4
Presentation Time: 8:00 AM-12:05 PM
THE CLAREMONT, NEW HAMPSHIRE DIKE; AN EXTENSION OF A MESOZOIC FLOOD BASALT FEEDER DIKE IN SOUTH-CENTRAL NEW ENGLAND
The Claremont North 71/2' Quadrangle in west-central New Hampshire, USA, contains a wide, vertical and previously unmapped dike composed of porphyritc plagioclase and pyroxene basalt. The dike is exposed in a 19m wide trough striking N3°E at an elevation of 378 meters that crosses an electricity transmission path approximately 1066 meters east of Winter Street in Claremont, New Hampshire. South of the outcrop no exposures are present, however there is substantial float, presumably transported by glacial ice. Several ground survey traverses with a proton-precession magnetometer were conducted across areas where float was encountered along strike. The survey results illustrate consistent contrast between the Devonian Littleton Formation schist and mafic rock allowing us to map the dike for approximately 4500 meters south. Additionally, the dike appears to be offset several meters to the right twice along this length. Comparison with giant dikes mapped by other workers on strike to the south suggests that the Claremont dike is an extension of the Bridgeport dike, a 160-kilometer long, 50-meter wide dike responsible for feeding Mesozoic flood basalts in the Hartford Basin of central Connecticut and south-central Massachusetts. Petrographic and geochemical comparison and further mapping of the Claremont dike and might yield sufficient evidence to support a genetic relationship to the well-studied Bridgeport dike.