SEDIMENTARY STRUCTURES IN THE LOCKATONG FORMATION ADJACENT TO THE BASE OF THE PALISADES SILL

A new outcrop of the contact between the base of the Palisades Sill and the Lockatong Formation of the Newark Basin sedimentary sequence has been exposed by recent construction at North Bergen, NJ. Preliminary field investigations have revealed some interesting structures within the sedimentary rocks at this site. While in some places the original sedimentary structures, such as channel deposits, are clearly visible right up to the contact, at other locations the sediments have clearly been remobilized as the sill was intruded.

Two logs were made at locations where the original sedimentary structures are still visible. These included cross-bedded channel deposits with conglomerate at the base and more fine grained lake deposits. All have been metamorphosed, with hornfels facies present close to the contact with the sill. A third location 80 m to the south presented more distorted sediments. At the base of one channel deposit the sands were remobilized as the sill was intruded. This resulted in the formation of a clastic dike that cuts across the more fine grained horizontal beds at an angle.

Future work will focus on the mineralogical and geochemical changes that have taken place within the metamorphic aureole, investigating whether they are the same in areas where the sediments were remobilized as in areas where the original sedimentary structures are preserved.