THE ENIGMATIC MARLBORO CLAY, PETM, AND PROPOSED CORING TRANSECTS ON THE U.S. MID-ATLANTIC MARGIN

The Marlboro Clay (lowermost Eocene) was a transient episode in depositional style on the U.S. Mid-Atlantic margin. Deposition on the New Jersey coastal plain (NJCP) generally follows a predictable pattern of basal glauconite shelf clays, medial silts, and upper sands with bounding unconformities and facies changes controlled by sea-level change. However, uppermost Paleocene glauconite sands and silts (Vincentown Formation, sequence Pa3a) are generally conformably overlain by ~10-15 m-thick sections of rapidly deposited kaolinitic silty clays termed the Marlboro Clay, with apparent deepening across the contact. The base of the Marlboro contains the global carbon isotopic excursion (CIE) onset and sedimentologically represents a major increase in the accumulation of fluid muds deposited on clinoform foresets in paleowater depths of 30-100 m. We evaluate the distribution of the Marlboro on the NJCP using a transect of cores across the paleoshelf (ODP Leg 174AX Medford, Wilson Lake, Ancora, Millville, and Bass River) to ground truth gamma log correlations among sites. We find that the Marlboro Clay is absent in the central NJCP (174AX Double Trouble and 150X Island Beach) and may have been deposited in two sub-basins. The Marlboro is thicker and more widespread in the south than in the north. In most sites, the Marlboro is capped by a sharp unconformity with the glauconitic marls of the Manasquan Formation above. However, at Medford, Millville, and Ancora the Marlboro is capped by sediments that are older than the Manasquan and remarkably similar to the Vincentown sediments below the Marlboro, indicating that the Marlboro was a brief interregnum with large input of muds. High sedimentation rates provide an opportunity to evaluate relationships among carbon injection, temperature, extraterrestrial impacts, volcanism, and this change in sedimentation. We have designed a drilling campaign of the Marlboro Clay in the NJCP and in Delaware-Maryland that should provide exceptional resolution of these cause/effect interrelationships.