The Newark Basin in this region is actually a graben formed when Pangaea broke apart about 200 million years ago.  About 190 million years ago, the sediments that filled the basin were intruded by the Palisades sill which is exposed in the 1000 foot high cliffs along the river here.  The sill was injected between the sedimentary layers.  The exposure contains the Lockatong Formation consisting of sedimentary rocks at the base of the sill.  Along the boundary of the sill and the sedimentary rocks is a chill zone of fine-grained basalt formed when the magma was intruded.  In other areas where there are exposures (not here) the chill zone can be seen along the upper layers of sedimentary rock also.