IGNEOUS AND TECTONIC STRUCTURES IN NORTH MOUNTAIN BASALT, GRAND MANAN ISLAND, NB
Spectacular outcrops show features of this sequence. At Whale Cove, the contact between the Dark Harbour and Seven Days Work members is conformable but with layers that interfinger, showing co-liquid relationships. At Eel Brook Beach, the Ashburton Head member forms the hanging wall of a normal fault against Seven Days Work member in the foot wall. At Whistle Beach this same fault is also exposed, but in addition it shows an intrusion of basalt into the fault plane. At Indian Beach an even larger cliff exposes a fault between the Seven Days Work and overlying Ashburton Head member on the northeastern side, and the Dark Harbour member to the southwest. A large dike parallels the fault, containing basalt that crosscuts lower flows of Seven Days Work member, but in the cliff overhead it turns to become a flow about 5 m thick. Red siltstone intrudes this zone, apparently derived from sediment of the underlying Triassic Blomidon-type formation.
These exposures of igneous and tectonic contact features are unique in the region, and they illustrate the genetic sequence of this gigantic basalt formation, possibly the largest known single lava flow on earth.