MEASURING THE SEDIMENTATION RATES ALONG THE K-T BOUNDARY IN THE GLAUCONITE-BEARING HORNERSTOWN AND NAVESINK/NEW EGYPT FORMATIONS

We investigated the K-T boundary section in the glauconite-bearing Hornerstown and Navesink/New Egypt Formations, including the Main Fossiliferous Layer [MFL], at two locations near Inversand and New Egypt in Southern New Jersey. The study locations were systematically sampled to determine glauconite morphology, chemical composition, and lattice parameters.

Changes in K2O concentrations and micromorphology of glauconite grains indicate slow sedimentation rates which progressively decrease up section. According to the model of Odin and Matter (1981), glauconite morphology changes from Stage 3 in the Navesink/New Egypt Formations to Stage 4 in the Hornerstown Formation. The general sedimentation rate at the second location is faster than at Inversand and the site is interpreted to be near the edge of the basin. Periods of glauconitization may approach 106 years [Stage 4 Morphology]. This is consistent with rapid deepening that starves the shelf environment of sediments during transgression. There is no obvious evidence of a long hiatus at the MFL. The presence of framboids in the Navesink Formation and trace amounts in the Hornerstown Formation implies paleo-environmental changes from reduced to more oxidizing conditions up-section.