Shallow Water Multibeam Data Analysis of Complex Bedrock Geology in Penobscot Bay, Maine

TitleShallow Water Multibeam Data Analysis of Complex Bedrock Geology in Penobscot Bay, Maine
Publication TypeConference Abstract
AuthorsArmstrong, AA, Owen, H, Bothner, WA, Ward, LG, Moyles, D
Conference Name8th Annual International Conference on High Resolution Surveys in Shallow Water
Conference LocationSt. John's, NL, Canada
Conference DatesOctober 1-3
Keywordsbedrock geology, multibeam analysis, penobscot bay, shallow water

A 2016-2017 NOAA Office of Coast Survey-contracted shallow-water multibeam hydrographic survey completed by Fugro, Inc. in Penobscot Bay, Maine, revealed a complex oval-shaped semi-concentric structure exposed in the bedrock seafloor. The multibeam bathymetry and backscatter were cleaned and inspected with standard hydrographic data processing and visualization software.  Prompted by the striking nature of the seafloor feature, a literature search and review of geological maps was conducted at the Center for Coastal and Ocean Mapping/Joint Hydrographic Center and the Department of Earth Sciences at the University of New Hampshire and indicated that the survey area lies within the well-known middle Paleozoic coastal Maine magmatic province with multiple known plutonic and volcanic bodies.  These intrusive and related extrusive bodies, however, are best exposed on mainland and island areas where they have been accessible for land-based geologic observation and airborne lidar-based topographic mapping. One of these known features is located within about 10 km distance from the seafloor feature on Vinalhaven Island. This feature is part of a complex sequence of basaltic to rhyolitic volcanic and volcanoclastic rocks that comprise the Fox Island Syncline. Comparison of the Fox Island Syncline and the newly revealed seafloor feature indicates that the two have a similar size, shape, and configuration.  Existing Lidar topography of the region, provided by the State of Maine, was analyzed to develop a more-detailed characterization of the exposed topography of the land feature and the multibeam bathymetry from the hydrographic feature was analyzed to develop a similar characterization of the seafloor topography.  These characterizations suggest that the two features may have a similar geologic origin and composition.  A geological sampling campaign has been outlined and proposed to test this hypothesis.