Menotomy Rocks Park is located in Arlington, Massachusetts. It is a public park with woodland, walking paths, informal play fields, and a man-made pond.
As the rift valley opened in Avalon, it soon became filled with sediments which later formed the Cambridge Sandstone, and the Cambridge Argillite. These rock formations were created between 570 and 550 million years ago (late Precambrian and Cambrian), when Avalon was near the South Pole (Skehan). The argillite is a slightly metamorphosed, reasonably weak, layered sedimentary rock.
A jumble of rocks from a late Precambrian volcanic crater of the Avalon Terrane includes fine-grained pink granite crosscut by a brown-weathering dike of felsite--an extremely fine-grained, light-colored rock. Basalt dikes crosscut lumpy, fragmental felsic lavas (Skehan 175). |