CHAOTIC STRATA NEAR PERIPHERY OF THE RUMFORD DOMAIN, NEW VINEYARD, MAINE

During an effort to document paleocurrent features within the Day Mountain Formation, a zone of chaotic strata was discovered 2 miles SW of New Vineyard, Maine. The zone occurs within a large 100 m x 80 m exposure (19T 409563, UTM 4958563). The strata are dominantly medium to thickly bedded turbidites, with sharp bases, locally cross-laminated, and containing rare shale rip-up clasts. Bedding surfaces typically display flame and load structures. Beds in the chaotic zone are buckled, boudinaged, and show internal convolutions. Despite excellent exposure, beds can not be followed more than ten or so meters; they merge into chaotic shale-rich zones that contain discrete sandstone blocks. Locally, sub-angular sandstone olistoliths up to 25 cm in diameter are completely enclosed within a shale matrix. Three major relatively open synclines have highly variable orientations, facing north, northeast, and west. At least one of three large synclines is transected by the NNE-striking cleavage. The presence of a small syncline truncated by a sedimentary contact and the presence of non-cylindrical fold patterns point to a soft sediment slump origin. A 5 cm-thick rubbly-textured sandstone bed, which occurs between coherent graded beds, suggests this disruption was caused by either sliding or the passage of fluid through the permeable sand. The chaotic zone overlies black, sulfide-rich shale (Temple Stream Formation), which raises the possibility of a methane trigger for the slump. Elsewhere around the perimeter of the Rumford domain, an occurrence in Farmington of 10 to 20-cm sandstone blocks within shale as well as several large map-scale lenses of Madrid Formation suggest that this chaotic zone may be regionally extensive mélange.