Figure 5a. Striations and a groove (black marker) on phyllitic bedrock east of the Penobscot River (Interstate 395/Parkway South interchange in Brewer, see Figure 4 for location). During ice flow, rocks embedded in the base of the glacier were dragged across bedrock. The embedded rocks abraded the bedrock surface and produced striations and grooves parallel to the ice-flow direction. Striations and grooves provide non-unique directional data (i.e. ice flow could have been along the striation or groove in either direction, see arrows). Using the relative-size criterion, the deep striations and groove (red arrow) represent an older flow event (in this case the flow maximum, 172°/352° flow azimuth), and the more minor set (yellow arrow) represents younger overprinting (111°/291° flow azimuth).
Last updated on January 13, 2009