Revisiting an old image for reprocessing. Pelham Bay has lots of Fordham gneiss. Here is a dense article on the Bedrock Geology of New York City: More than 600 m.y. of geologic history (sunysb.edu). I love geology. It was my manor at Hunter College.
Geology lesson: Boudinage is a structure which is sometimes present in metamorphic rocks apparently as a result of tension and in which a competent bed is thinned and thickened so that it resembles in cross section a string of sausages (Webster’s).