This data set presents the lithologic interpretation of rock cores from boreholes 83BR-89BR collected from the mudstone aquifer underlying the Naval Air Warfare Center (NAWC), West Trenton, NJ. Continuous core from these boreholes was collected and visually interpreted to identify characteristics of the depositional environment of the mudstone. Three types of mudstone were identified: a black-fissile mudstone (BLK-FIS); a gray-laminated mudstone (GRY-LAM); and a gray massive mudstone (GRY-MAS). The BLK-FIS mudstone is associated with a deep-water depositional environment. The GRY-MAS mudstone is associated with a shallow-water depositional environment. The GRY-LAM mudstone is associated with a transitional depositional environment between shallow and deep water conditions. The lithologic characteristic of the rock was assigned every 0.03 m along the length of the core. Sections of core that were not recovered are also noted.