The basement rocks of the
Manhattan Formation located on the western side of Cameron's Line are metamorphosed sedimentary rocks and can be thought of as the remnants of the edge of the North American continent from 1 billion years ago. They were formed in roughly this location (
autochthonous) and have been tectonically stable over a long period. Through New England, generally, the rocks to the west of Cameron's Line are the remnants of an enormous mountain range (the
Grenville orogeny), sometimes called the "Crystalline Appalachians", which once stretched from Newfoundland to Mexico, the local remnants of which are exposed and create the Housatonic Highlands, the New Jersey Highlands (
Ramapo Mountains), and the thin
Manhattan Prong (including much of the Bronx). In general, to the east of the line are
allochthonous rocks formed elsewhere, which have experienced great tectonic movement in a westward direction on top of the underlying bedrock. In the geological past, around 450 million years ago, an ocean similar to the Atlantic began to shrink. As it did, the North American continent began to collide with island chains, which accreted at the edge of the continent and formed the land of what we now call New England. After the Taconic orogeny, a collision with Africa (the
Alleghanian orogeny) created the supercontinent Pangaea, which was later split by the rifting process that created the Atlantic Ocean,
Ramapo Fault,
Newark Basin, and the
Palisades. The material in Cameron's Line is described as "highly laminated, migmatized, complexly folded and annealed zones of commingled mylonitic rocks". ==References==