GLACIOMARINE SEDIMENTS BENEATH EASTERN CASCO BAY, MIDCOAST MAINE

Previous studies in eastern Casco Bay have focused on distal sedimentation processes to interpret the role of sea level in the deposition of the Presumpscot Formation. In this study, high-resolution chirp sonar profiles and vibracore samples were obtained to observe glacial marine sediments beneath eastern Casco Bay. Analysis of data shows the influence of varying sea level on sedimentation and sedimentary processes of the region proximal to the Brunswick braid plain delta during the time period after the exposure of Maine’s southern coastline approximately 14000 KBP. A seismically well-stratified unit imaged by chirp sonar in the intertidal zone adjacent to the Bunganuc Bluffs of Maquoit Bay is found in vibracore samples to be a sedimentary unit of alternating fine sand and muddy layers. A relatively coarser sediment texture indicates a proximal environment under the direct influence of the braid plain delta that forms the Brunswick Sand Plain. Conformable seismic laminations suggest hemipelagic sedimentation. Slump-like features beneath modern mud flat sediments directly east of Bunganuc Bluffs show that slumping played a role in shaping the morphology of Maquoit Bay before the present eustatic marine transgression. Tentative interpretations of a single seismic profile from northern Maquoit Bay located immediately seaward of the southern toe of the Brunswick sand plain indicate evidence of turbidity currents and possible debris flows.