Hadley Point
Hadley Point is a popular spot for local clam and worm harvesters, as well as a great place to see the upper reaches of Frenchman Bay by foot or by watercraft. Hadley Point is characterized by outcrops of Ellsworth Schist (give a geologic map of the area) as well of glacial erratics with varying composition.
North
In this image we can see the fracture orientations of the Ellsworth Schist at Hadley Point
Map and legend modified after Gilman and Chapman, 1988
10 Km
Walking along the shore to the south of the point you will see an outcrop of Ellsworth Schist--a layered greenish grey stone--of about 60 feet by 30 feet in dimension dipping to the southeast. This outcrop is foliated, meaning that you can see repetitive layering. Foliation is an indication that the Ellsworth schist is a metasedimentary rock which underwent extensive deformation.
The northern faces of the outcrop are broken, and have an azimuthal direction of about 90 degrees. This fracture is seen elsewhere in the rock, indicating to us that it broke along planes of weakness.
Ellsworth Schist is around 600 million years old, formed in the late Precambrian era (Braun, 2012). Within the Ellsworth Schist, you can see beds of quartz up to 5 centimeters wide which were formed when this area was a shallow depositional environment characterized by sand and silt. The sand and silt were lithified, and when the sedimentary rock metamorphosed, the sand became quartz.
Looking around, you will see large boulders scattered along the eastern and western sides of the beach. Upon closer inspection, it is obvious that they are a different type of rock. Where did they come from? These boulders are glacial erratics that were brought here by the glaciers around 18000 years ago (Hall, 2017) From the outcrop of Ellsworth schist, continue along the south side of the beach, and you will see an example of a glacial erratic. The erratic is on the other side of a mudflat area, and may be difficult to access at high tides.
This rock is phaneritic (coarse grained), and has different mineral crystals. In this rock, you will see: quartz (the shiny gray mineral), potassium feldspar (pink), and biotite mica (black). This is an granite, an igneous rock which formed when magma cooled under the surface.The darker minerals that that you will see in these boulders is biotite mica, whereas the dark minerals that you will see in the Cadillac Granite that makes up much of the rest of MDI is hornblende.
Farther east along the beach, you will see more glacial erratics which contain the same minerals as the first erratic, but in different concentrations. Some of the erratics are fine grained, unlike the one mentioned above, while others were contained darker potassium feldspar. This implies that all of the erratics could be from different places where the glacier picked them up and then left on Hadley Point Beach.
Sources
Braun, D., and Braun , R., 2016, Guide to the Geology of Mount Desert Island and Acadia National Park: North Atlantic Books.
Gilman R.A. and Chapman C.A., 1988, Bedrock Geology of Mount Desert Island, Maine Geological Survey: https://www.coa.edu/shall/Geoscience/Maps_and_Links_files/GeologyMDI.pdf