HYDROGEOLOGIC FRAMEWORK BASED ON VAN HOUTEN CYCLIC STRATIGRAPHY AND GAMMA-RAY LOGGING, NAVAL AIR WARFARE CENTER, TRENTON, NEW JERSEY

The former Naval Air Warfare Center (NAWC), Trenton, New Jersey, serves as a research site for the U.S. Geological Survey Toxics Substances Hydrology Program to develop methods to investigate fractured sedimentary bedrock aquifers that are contaminated. A research goal is to describe the hydrogeologic framework so that geology and hydrogeology are an integral part of the remediation plans of the U.S. Navy.

The NAWC is underlain by northwest dipping mudstone and sandstone of the Stockton and Lockatong Formations in the Newark Rift Basin. Clay, silt, and organic matter were deposited as multiple Van Houten cycles. A full cycle is composed of a basal carbon-rich mudstone, a middle laminated dark mudstone, and an upper massive mudstone. Strata within each cycle respond differently to postdepositional compaction, lithification, folding, faulting, uplifting, and offloading.

About 105 observation wells have been drilled at the 56-acre trichloroethylene contamination site to define the framework, measure water levels, and collect water samples. Natural gamma-ray logs were used to develop a geophysical stratigraphic column; structure maps at land surface, at 100 ft, and at 200 ft below land surface; and 10 sections parallel to the dip. The maps and sections based on gamma-ray logs have been enhanced by adding lithostratigraphic information from four on-site rock cores and from gamma-ray and rock-core logs from the Newark Basin Drilling Program core site that is nearby at Nursery Road.

Interpretation of the hydrogeologic framework at NAWC is based on augmentation of the gamma-ray based framework with driller’s and geologist’s logs, aquifer and slug tests, static and stressed water levels, and contaminant concentrations and reflects an understanding of Van Houten-cycle stratigraphy and regional tectonic and off-loading history. Carbon-rich mudstones were most affected by the stresses of folding, faulting, and off-loading; therefore, they are the most extensively fractured strata and are pervasive water- and contaminant-bearing zones. Laminated dark-gray mudstones are less prone to fracturing than the carbon-rich mudstones. Bioturbidated and multiply desiccated lithified playa deposits are the most resistant and remain as massive, well-indurated strata that behave as semi-confining units.