EVIDENCE FOR A CALVING EMBAYMENT IN THE PENOBSCOT RIVER VALLEY, BANGOR, MAINE
We mapped the Bangor quadrangle as part of a STATEMAP project to find smooth bedrock surfaces preserving ice-flow indicators. We measured the orientations of 116 striations (showing non-unique flow direction) and crag-and-tail features (showing unique flow direction). The relative size criterion was used to evaluate ages of flow indicators. The data was analyzed using RockWorks99 to discern ice-flow patterns and calculate vector means. Only unique ice-flow direction data are reported here.
Ice flowed to the south (175° azimuth vector mean, n=18) during the oldest event (flow maximum) throughout the map area. West of the Penobscot River, a continuous range of younger flow indicators becomes more easterly (100° azimuth flow toward the river). East of the Penobscot River, a younger, robust westerly flow is indicated toward the river lowland (280° vector mean, n=14). Flow indicators between 174° and 280° are lacking, suggesting a rapid change in flow direction. These flow direction changes are in an area with gentle surface slopes, so changes were not caused by ice sliding down the bedrock surface. Westerly flow away from the coast has not been observed previously in this part of Maine and is evidence for a calving embayment.
An area within the embayment should only record flow indicators from the ice-flow maximum. Changes in flow direction can be seen as close as 1 km east and west of the river. Thus, a relatively narrow calving embayment (<2 km wide) must have existed in the Penobscot River valley near Bangor.