1. COASTAL PLAIN DRILLING AND THE NEW JERSEY SEA-LEVEL TRANSECT1Kenneth G. Miller2,3 |
A triad of processes controls the marine stratigraphic record: changes in sea level, tectonics, and sediment supply. Whereas the stratigraphic record may be objectively divided into sequences (unconformity-bounded units), the relative role of these three processes on development of passive continental margin sequences remains controversial. Three tasks must be accomplished before extracting process from the passive margin signal: the sequences must be identified, dated, and the facies changes within them mapped. The New Jersey Sea-level Transect (Ocean Drilling Program Leg 150X onshore drilling, Leg 150 slope drilling, and Leg 174A shelf drilling) has begun this task. The New Jersey Coastal Plain Drilling Project (Leg 150X) has completed boreholes at Island Beach (total depth 1223 ft [372.7 m]; April–May, 1993), Atlantic City (total depth 1452 ft [442.6 m]; June–August, 1993), and Cape May (total depth 1500 ft [457.2 m]; March–April, 1994). The papers contained in this volume present detailed lithostratigraphic, well-log, core-log, magnetostratigraphic, biostratigraphic, chemostratigraphic, paleoenvironmental, and hydrogeologic studies conducted on these boreholes. This introductory chapter outlines the general goals and strategies of onshore drilling in the context of the New Jersey Sea-level Transect, provides an overview of the material recovered onshore by Leg 150X in 1993–1994, and discusses the nature of post-drilling studies and the need for future work. Highlights of Leg 150X include the following: 1. Studies herein develop a chronology of late middle Eocene to middle Miocene onshore sequence boundaries, correlate them with major delta18O increases, and confirm that these unconformities were formed by global sea-level lowerings. 2. Comparison of New Jersey sequences with the Exxon syntheses shows that the Exxon Eocene to middle Miocene sequences are recorded on the New Jersey Margin where their ages are well constrained. 3. A sequence stratigraphic framework was obtained for the Paleocene to middle Miocene by integrating chronologic, lithostratigraphic, well-log, core-log, benthic foraminiferal biofacies, and isotopic studies. These studies include evaluation of unconformities and flooding surfaces, delineating systems tract variations within sequences, and estimating water depth variations within sequences. 4. Other studies address hydrostratigraphy, pore-water quality, pore-water isotopic composition, clay mineralogy, silica diagenesis, core-log/well-log integration, biostratigraphy, palynology, and climate. |
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