Upper Cretaceous and Cenozoic Sea-Level Change Estimates Through Backstripping Analysis of Borehole Data, Onshore New Jersey

W. A. Van Sickel¹, M. A. Kominz¹, and K. G. Miller^2
1Western Michigan University, Kalamazoo, MI
²Rutgers University, New Brunswick, NJ

Backstripping analysis of detailed stratigraphic data from the Bass River and Ancora boreholes on the New Jersey Coastal Plain (Ocean Drilling Project Leg 174AX) provides the first sea-level estimates from Upper Cretaceous borehole data and tests Cenozoic sea-level estimates from previously drilled boreholes. Results suggest a longterm (10⁸–10⁷ year) sea-level fall of approximately 100 m, mainly since the Paleocene. Superimposed 3rd order (0.5–3 m.y.) sea-level changes are less than 70 m. Amplitudes varied by as much as 50 m across sequence boundaries in the Cretaceous, suggesting a maximum amplitude of 3rd order sea-level change of more than 50 m. Sea-level amplitudes and durations were comparable when sequences were sampled at multiple borehole sites. This suggests that the resultant curves are an approximation of eustasy.

An important refinement included in this study was a reassessment of the compaction of New Jersey Coastal Plain sediments through electric log analyses of onshore wells. Porosity for the dominant lithologies (sand and mud) reveal considerably lower porosity than those seen at the Cost B-2 well. With the acquisition of new (older sequences) borehole data, along with improved porosity analysis, accurate sea-level estimates are produced from the backstripping method.

AAPG Search and Discovery Article #90900©2001 AAPG Eastern Section Meeting, Kalamazoo, Michigan