OBJECTIVES

Coastal plain drilling conducted as part of Leg 174AX had several major objectives:

1. Evaluate the variability of Oligocene-Miocene sequences and the influences of tectonics and sediment supply on sequence distribution and architecture. This is a direct outgrowth of studies conducted during ODP Leg 150 slope and 150X coastal plain drilling, which dated Oligocene-Miocene sequences and correlated them with global ¹⁸O records.
2. Provide material suitable for one- and two-dimensional backstripping of mid-Cretaceous to Miocene sections, providing a eustatic estimate for the interval from 100 to 8 Ma that can be compared with backstripped records from other areas. Backstripping is a proven method for extracting amplitudes of global sea level from passive margin records (e.g., Watts and Steckler, 1979). One-dimensional backstripping progressively removes the effects of sediment loading (including the effects of compaction), eustasy, and paleowater depth from basin subsidence to obtain tectonic subsidence. By modeling thermal subsidence on a passive margin, the tectonic portion of subsidence can be assessed and a eustatic estimate obtained (Kominz et al., 1998). Two-dimensional backstripping assumes projection of onshore Oligocene sections onto a single composite dip section of prograding clinoforms, integrating various data sets into a single, internally consistent interpretation of sea-level change (Kominz and Pekar, 2001).
3. Determine the ages and distribution of Cretaceous sequences not previously sampled during Legs 150X, 150, or 174A and provide additional samples of Paleocene-middle Eocene sequences that were only sparsely sampled previously. These sequences provide a window into understanding sea-level changes during the greenhouse world, a time considered to be ice free.
4. Evaluate major global events in Earth history in continental margin successions. Earth history has been punctuated by rapid events that have profoundly affected life. These events include the Cretaceous/Tertiary (C/T) extinction and ocean anoxic event (Arthur et al., 1985), the Campanian/Maastrichtian cooling (Barrera and Savin, 1999), the latest Maastrichtian warming (Barrera and Savin, 1999), the Cretaceous/Tertiary (K/T) impact event (Alvarez et al., 1980), the PETM and carbon isotopic excursion (e.g., Kennett and Stott, 1990; Zachos et al., 1994), and the earliest Oligocene cooling and glaciation (Miller et al., 1987; Zachos et al., 2001). Whereas most reconstructions of global Late Cretaceous-Holocene events have focused on the deep-sea record because of its more continuous nature, passive continental margins potentially provide thick, continuous records of many of these events.
5. Evaluate stratigraphic continuity and hydrogeological potential of aquifers and confining units. The NJGS and DGS provided funds for drilling to address hydrogeological objectives that directly affect groundwater resources in the rapidly growing areas of southern NJ and DE. Sequence stratigraphy has the potential to increase our understanding of the stratigraphic architecture of aquifers in the same way it has improved our understanding of reservoir architecture in the oil industry.