Correlations of the Palisades Intrusive Conduit with the Orange Mountain Basalt, New Jersey

The Palisades Intrusive System is proposed to include the Jurassic sill and comagmatic sills and dikes in the Newark Basin of New Jersey and New York. Horizons within the Palisades have been linked to flows of the Newark Basin on the basis of closely similar chemical systematics and the relative stratigraphic succession observed for the Watchung flows. The proposed first magma of the lowermost 100 m of the Palisades at the George Washington Bridge section connects appropriately to the Orange Mountain basalt flows of New Jersey based on chemical correlations and systematic variations within the first Palisades magma. Point counting and morphological characterizations in this study are obtained using an automated EDAX imaging package, IMAGEPRO software and calibrated energy dispersive micro-analytic data. These for the first time create a discriminate facies map of magma one of the Palisades and the correlative Orange Mountain flows. Comparisons are created both along a north-south Palisades transect from the George Washington Bridge section to Upper Nyack, New York mapping the glomeroporphyritic to subophitic diabase relationships and the lowermost section of first Orange Mountain basalt. These show that the Cr- and Mg-enriched facies characteristic of the Palisades olivine hyalosiderite horizon (olivine zone; MgO > 9 %, Cr > 400 ppm) are present in modified form in the Orange Mountain basalt. Petrographic observations on hypersthene and olivine-derived serpentine support previous arguments for the ‘olivine zone’ as a remnant of the cumulus portion of a disarticulated magma chamber present at depth.