Millville was the ninth site drilled as part of the Coastal Plain Drilling Project (CPDP) and the fifth site drilled as part of Leg 174AX. Drilling at the Bridgeton Pike Well Complex, Millville, New Jersey (39°24´16.67''N, 75°05´19.99''W; elevation = 89.7 ft [27.16 m]; Millville quadrangle, Cumberland County), targeted Upper Cretaceous sequences and aquifers with a 1500-ft (457.20 m) corehole drilled from 4 May to 24 June 2002. At Millville, we recovered 1254.85 ft (382.48 m); mean recovery was 83.7% for the 1500 ft (457.20 m) cored. Gamma ray, conductivity, spontaneous potential, and resistivity downhole geophysical logs were collected from the borehole. A team of scientists from the New Jersey Geological Survey (NJGS), Rutgers University, the Delaware Geological Survey (DGS), and the U.S. Geological Survey (USGS) collaborated in the drilling and stratigraphic studies of the borehole, which were funded by the NJGS (direct drilling costs) and the National Science Foundation (NSF; Earth Science Division, Continental Dynamics Program).
Surficial sand and gravel (0–37.4 ft; 0–11.40 m) assigned to the Bridgeton Formation are interpreted as fluvial deposits. The Cohansey Formation (37.4–157.8/160 ft; 11.40–48.10/48.77 m) consists of fine to coarse sands deposited in a variety of laterally contiguous nearshore and marginal marine environments including shoreface, lagoon, and back barrier. The overall facies association within the Cohansey Formation suggests regression followed by a stillstand. The sands assigned to the Bridgeton and Cohansey Formations are not dateable at the Millville site but probably represent middle–upper Miocene deposits.
The lower–middle Miocene Kirkwood Formation can be divided into at least three sequences at Millville:
No Oligocene sediments occur in the Millville corehole. The middle–upper Eocene is thick at Millville (321.9 ft; 97.47 m). Thick, glauconitic, shelly, slightly muddy quartz sands (410–605 ft; 124.97–184.4 m) are assigned to the upper Shark River Formation, Toms River Member. Biostratigraphy correlates these sands to upper Eocene Zones NP19–NP20 (P16–P17); thus, they are equivalent in age to downdip clays assigned to the Absecon Inlet Formation and are younger than previously dated sections of the Toms River Member. These sands are very porous and friable and comprise an aquifer. The sands can be divided into two sequences: one correlated with sequence E10 and the other comprising the highstand systems tract (HST) of sequence E9. They were deposited in inner neritic, predominantly lower shoreface (5–20 m) environments. The lower part of the upper Shark River Formation (605–640.35 ft; 184.4–223.74 m) consists of glauconitic sandy, shelly clays to clayey glauconite sands deposited in offshore, inner neritic environments; they span the middle/late Eocene boundary (Zones NP18–?NP17; P14–P16) and comprise the lower part of sequence E9 (Zone NP18) and sequence E8 (Zones NP18 to ?NP17). The lower Shark River Formation consists of silty clays to clays with varying glauconite, sporadic quartz sand, and shell content; the lower part is porcellanitic (= Horizon Ac cherts). This unit is primarily lower middle Eocene Zones NP14b–N15 and P8–P10 undifferentiated through P12, though the basal part is uppermost lower Eocene (Zone NP13; P8). It was deposited in middle neritic environments and comprises three sequences that correlate with sequences E7 (Zones NP15–NP16; P11–P12), E6 (Zones NP14b–NP14 undifferentiated), and E4 (Zone NP13).
The lower Eocene at Millville is comprised primarily of carbonate-rich clays of the Manasquan Formation (731.9–847 ft; 223.08–258.17 m). Sequence boundaries are subtle in these deeper-water (middle–outer neritic) environments and are recognized by gamma log kicks and biostratigraphy. Sequence E3 (Zone NP12; P7) is 24.5 ft (7.48 m) thick, sequence E2 (Zone NP11) is 80 ft (23.38 m) thick, and glauconite-rich sequence E1 (Subzone NP10d; P6a) is thin (11 ft; 3.35 m).
Basal Eocene (Subzone NP9b) clays (847–899.4 ft; 258.17–274.14 m) comprise an unusual lithologic unit previously identified at the Ancora, Bass River, and Clayton sites. At these latter sites, the clays contain the global Paleocene/Eocene carbon isotopic excursion, kaolinitic clays, and magnetic nanoparticles at their base (e.g., Kent et al., 2003). At these other sites, the carbon isotope excursion (CIE) is found a few meters above an unconformity. Preliminary nannofossil studies suggest that the CIE may not be complete at Millville, and the CIE is predicted at a disconformity. The clay unit at Millville (here, designated sequence Pa4) was deposited in middle–outer neritic environments; it is tentatively assigned to the Vincentown Formation, though a new name is probably warranted for these subsurface clays.
The Paleocene sequence at Millville consists of occasionally sandy and micaceous clays and slightly glauconitic clays of the Vincentown Formation (847–970.2 ft; 258.17–295.72 m) and clayey glauconite sands of the Hornerstown Formation (970.2–983.3 ft; 295.72–299.71 m). Sequence Pa3 comprises most of the Vincentown Formation, consisting of upper prodelta and lower middle neritic clays assigned to Zones NP8–NP9a (P4c). Sequence Pa2 spans the formational boundary and is assigned to Zones NP6–NP8 (P4a). The Hornerstown Formation also contains sequences Pa1 (Zoned NP3–NP4; P3b) and a very thin Zone P1a sequence at its base (982.0–982.95 ft; 299.39–299.69 m).
The Cretaceous/Paleogene (K/P) boundary at Millville does not appear to contain a complete record of the latest Cretaceous impact. The K/P boundary at Millville is placed between samples at 983.0 ft (299.62 m) and 983.05 ft (299.63 m). The presence of Parvularugoglobigerina eugubina in the sample at 983.0 ft (299.62 m) identifies lower Danian Zone P. The basal Danian Zone P0 may lie just below this. Samples at 983.05–983.5 ft (299.63–299.77 m) are placed in the uppermost Maastrichtian. Although biostratigraphically nearly complete, the Millville K/P boundary lacks the impact spherules and shocked minerals that were found in situ in the Bass River corehole (Olsson et al., 1997) and reworked in the Ancora corehole. This reflects the heterogeneity of preservation of this event on the New Jersey coastal plain.
The Maastrichtian section at Millville is relatively thick (53.7 ft; 16.37 m), and the lithologic units differ from coreholes and outcrops to the north. This may reflect a higher Maastrichtian sedimentation rate (13 m/m.y.) at Millville than previously encountered in New Jersey. Maastrichtian lithologic units at Millville consist of an upper carbonate-rich glauconitic clay (New Egypt equivalent) and a lower carbonate-rich glauconitic clay to clayey glauconite sand (Navesink equivalent). Two contacts in the Maastrichtian may be sequence boundaries, though the significance of these contacts requires further study:
The entire Maastrichtian section was deposited in relatively deep water (middle–outer neritic environments). In other New Jersey boreholes, the contact and sequence boundary at the base of the Maastrichtian Navesink sequence consists of glauconite sand above quartz sand containing phosphate and is associated with a large gamma ray peak. The contact at Millville has been obscured by extensive bioturbation and reworking. It is recognized at a rubbly contact at 1032.9 ft (314.83 m) just below a phosphate lag deposit and the largest gamma ray peak found in this borehole.
Campanian–Santonian sequences are marine and well represented at Millville, though age control is coarser than at Ancora or Bass River because of diagenetic effects on Sr isotopes. Nannofossil zones and limited Sr isotopic data provide age control that is consistent with the ages of Campanian–Santonian sequences found at Ancora and Bass River (Miller et al., 2004). Four definite and two possible Campanian–Santonian sequences are found at Millville:
The Magothy Formation (1254.4–1300.5 ft; 382.34–396.39 m) consists of variable sediments including fine to very fine sands with sphaerosiderite, lignitic pyritic silt, white clay, and mottled red and white clays and silty clays with red root zones. These sediments represent a complex of alluvial plain environments including levee, crevasse splay, fluvial overbank, soils, and subaqueous alluvial plain. The formation consists of one sequence at Millville dated as pollen Zone V (late Turonian to early Coniacian).
The Bass River Formation (1300.6–1422.1 ft; 396.42–433.46 m) at Millville consists primarily of silty, shelly, micaceous (including chlorite) clay deposited in lower shoreface to middle neritic environments. Sequence boundaries at 1342.55 and 1374.4 ft (409.21 and 418.92 m) divide the Bass River Formation into three sequences dated as late Cenomanian–early Turonian (limited Sr isotopic ages; pollen Zone IV), middle Cenomanian (Zone CC10 and pollen Zone IV), and early Cenomanian (Zone CC9 and pollen Zone III).
The Potomac Formation (1421.9–1495.5 ft; 433.4–455.83 m total depth [TD]) is dominated by paleosols consisting of mottled clays and silts, some with sphaerosiderite, and lignitic very fine sands all deposited in alluvial plain environments. Pollen dates this formation as late Albian to early Cenomanian (Zones III and ?IIc).
As an updip site, the Millville corehole provided little new information on Miocene sequences. Upper Eocene sequences (E8–E10) are well expressed at this site and should provide new insights into the distribution, facies, and aquifer potential of sequences of this age. Middle (E4, E6, and E7) and lower (E1–E4) Eocene sequences are consistent with results from other New Jersey coreholes. The Paleocene/Eocene Thermal Maximum sequence and the K/P boundary do not appear as complete as in other boreholes. Maastrichtian sequences at Millville appear to be thick and to provide evidence for two middle–late Maastrichtian sequences. Campanian–Santonian sequences (Marshalltown, Merchantville, and Cheesequake) are well represented, and the Millville borehole may provide new insights into late Santonian–early Campanian sequences contained within the Merchantville Formation. The Magothy and Potomac Formations at this site seem to provide little new sequence information, but the intervening Bass River Formation can be unequivocally divided into three sequences (late Cenomanian–early Turonian, middle Cenomanian, and early Cenomanian).
The Millville corehole has greater similarities to Cretaceous and Paleogene sections in Delaware than those to the north (e.g., generally thinner sequences, especially Magothy, with the exception of the upper Eocene, Maastrichtian, and Cenomanian sections). This reflects the South Jersey High as a tectonic feature that influenced the sedimentation patterns, separating north and southernmost New Jersey sedimentation patterns.