SUMMARY AND FUTURE WORK

Drilling at Millville was successful in providing the first continuous corehole data from southernmost central New Jersey coastal plain (Cumberland County) (1) to evaluate local and regional aquifers and (2) to document the regional and global significance of Upper Cretaceous sequences (<100 Ma). Groundwater availability is limited mainly to Tertiary aquifers. Our examination of the hydrostratigraphy at Millville yields the following observations:

  1. The top 150 ft (45.72 m) of the Cohansey and Bridgeton Formations forms a very productive unconfined aquifer. It is the best aquifer sampled at this site. However, because of its shallow nature, it is highly vulnerable to surface pollutants.
  2. A leaky confining bed separates the Cohansey aquifer from the Atlantic City 800-foot sand. The confining bed is correlative with the Wildwood member of the Kirkwood Formation and the Kw2a sequence. This updip equivalent of the Wildwood-Belleplain confining bed is coarser grained than typical sections along the coast. The confined Kirkwood aquifer at this site (Atlantic City 800-foot sand) is predominantly composed of the upper sand from the Brigantine Member, or Kw1a sequence, and some sand from the Shiloh Member (Kw1b sequence). The thin "confining bed" that separates the upper and lower 800-foot sand is <10 ft (3.05 m) thick at Millville and probably doesn't function as a confining bed.
  3. The "Piney Point aquifer" is in the upper part of the Shark River Formation. It is thick (~180 ft; 54.86 m), although thin clay beds and clay-silt in the matrix limit its productivity. Its assignment to Zones NP19–NP20 (upper Eocene) differs from other locations in New Jersey where the aquifer has been dated as middle Eocene and late Oligocene. Further study of this interval will be required to better resolve the relationship of these upper Eocene sands to other aquifers.
  4. The Englishtown aquifer system (lower and upper Englishtown Formations) is a potential aquifer and 80 ft (24.38 m) thick, although it is predominantly silty fine sands and finer grained in the lower part. The quality of water in this aquifer is unknown.
  5. The Magothy Formation is thin and a poor aquifer at this location vs. a major aquifer in sections to the north (e.g., Ancora, Bass River, and Sea Girt).

We previously evaluated the timing of Upper Cretaceous sequence boundaries at Bass River and Ancora with global records and noted the similarity of these records, suggesting that glacio-eustasy was responsible for sea level changes in the Late Cretaceous greenhouse world. Drilling at Millville and Sea Girt provides additional sites to evaluate Upper Cretaceous sequences and sea level history. Subsequent studies of the Millville Maastrichtian and upper Santonian–lower Campanian sequences may provide clues about the number and ages of sequences in these enigmatic intervals. The Millville Cretaceous and Paleogene sections are similar to those to the south in Delaware and differ from sections to the north; in particular, the Magothy is thin, the K/P and P/E boundaries may be truncated (although further studies of these sections are needed), and the Santonian to Maastrichtian sections have much less of a deltaic influence, with much of the section truncated. We suggest that the South Jersey High acted as feature that influenced sedimentation patterns, separating north and southernmost New Jersey/Delaware provinces.

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