The on-site scientific team provided preliminary descriptions of sedimentary textures, structures, colors, fossil content, identification of lithostratigraphic units (NJGS Information Circular 1, 1990), and lithologic contacts (Table T1; Figs. F2, F3, F4, F5, F6, F7). Subsequent studies integrated preliminary descriptions with additional descriptions, biostratigraphy, biofacies studies, isotopic stratigraphy, and geophysical well logs. Unconformities were identified on the basis of physical stratigraphy, including irregular contacts, reworking, bioturbation, major facies changes, gamma ray peaks, and paraconformities inferred from biostratigraphic breaks (Fig. F9). For the nonmarine and nearshore sections (primarily the Miocene and younger section and the Magothy and Potomac Formations), lithofacies interpretations provide the primary means of recognizing unconformities and interpreting paleoenvironments. For the neritic sections (primarily the Paleogene, Santonian–Maastrichtian, and mid-Cenomanian to Turonian sections), biostratigraphic and biofacies studies provide an additional means of recognizing unconformities and the primary means of interpreting paleoenvironments. Recognition of these surfaces allows identification of sequences at the Millville borehole. Benthic foraminiferal biofacies were used to recognize inner (0–30 m), middle (30–100 m), and outer (100–200 m) neritic and upper bathyal (200–600 m) paleodepths.
Cumulative percent plots of the sediments in the cores were computed from samples washed for paleontological analysis (Table T2). Each sample was dried and weighed before washing, and the dry weight was used to compute the percentage of sand. This differs from the method used in previous New Jersey coastal plain cores (Bass River, Island Beach, Atlantic City, and Cape May) in which the samples were not dried before washing.
The hole spudded into the top of a plateau that is mapped as a fluvial channel bar in the Bridgeton Formation by Newell et al. (2000), which is assumed to be upper Miocene (Fig. F2). The top 7.4 ft (2.26 m) contained reddish yellow and yellowish brown coarse to very coarse sand with gravel layers. From 7.4 to 15.5 ft (2.26 to 4.72 m), the lithology is a coarse to very coarse sand with occasional granules. The interval from 15.5 to 15.9 ft (4.72 to 4.85 m) is a poorly sorted granuliferous sand, with no recovery from 15.9 to 20 ft (4.85 to 6.10 m). From 20 to 26.8 ft (6.10 to 8.17 m) is thinly interbedded sand and granuliferous sand with feldspar grains that weather to kaolinite; beds are 15–45 mm thick, with alternating yellow silty fine to medium sand and pale brown medium to coarse sand. The section fines slightly downsection. There is a gravel bed from 26.8 to 27.2 ft (8.18 to 8.29 m), and washed residues (Fig. F2) show an increase upsection in coarse sand from this level to the top of the borehole. The interbedded sands and granuliferous sands continue down to 36.7 ft (11.19 m), though the color changes to light gray at 30 ft (9.14 m); the beds are ~1 ft thick. A sandy clay (36.7–37.1 ft; 11.19–11.31 m) overlies a gravelly, clayey sand with weathered feldspar that marks the contact of the Bridgeton Formation with the underlying Cohansey Formation. The environment of deposition of the Bridgeton Formation at Millville is fluvial.
The upper part of the Cohansey Formation (Fig. F2) consists of an interlaminated silty clay and clayey sand (37.4–37.65 ft; 11.40–11.48 m), a poorly recovered medium to very coarse sand (40–40.4 ft; 12.19–12.31 m), and a limonitic yellow-brown, thinly interlaminated (1–3 mm) silty fine sand and silty clay (43–55.15 ft; 13.11–16.81 m) with dominant flaser and subordinate lenticular structures. Coring gaps at 37.65–40 and 40.4–43 ft (11.48–12.19 and 12.31–13.11 m) separate these lithologies. The succession from 37.4 to 55.15 ft (11.40 to 16.81 m) was deposited in lagoonal environments. A facies shift at 55.15 ft (16.81 m) to primarily "beachy" sands deposited in back barrier environments is associated with a gamma log kick. From 55.15 to ~80 ft (16.81 to ~24.40 m), the section consists primarily of silty fine to medium sand with scattered mica throughout, scattered reddish (hematitic) clay laminae, silty clay interbeds (66.8–69.0 ft; 20.36–21.03 m), iron staining (75–76.7 and 77.7–78.95 ft; 22.86–23.38 and 23.68–24.06 m), and a gray, slightly more micaceous sand (76.6–77.7 ft; 23.35–23.68 m). The section from 55.15 to ~80 ft (16.81 to ~24.40 m) was deposited in back barrier environments as evidenced by common clay drapes within otherwise clean fine–medium sands, the lack of obvious placers of opaque heavy minerals that are typically found on the shoreface (though opaque heavy minerals are scattered throughout), and poorly preserved root traces.
Below 80 ft (24.4 m), the clay-silt fraction increases slightly as exemplified by higher gamma log values and more poorly sorted and "soupy" sands (Fig. F2). Medium sands increase below 90 ft (27.43 m), with a trace of coarse sand; the facies appear as clayey silty fine–coarse sand that probably reflects disrupted thinly interlaminated sand and clay beds. These more poorly sorted facies are probably also back barrier environments, though they could be lagoonal.
Interbedded clay-sand (100–101.75 ft; 30.48–31.01 m) probably represent tidal channel sands with clay drapes. From 101.75 to 108 ft (31.01 to 32.92 m), the fine–medium sand with scattered clay drapes again represent a back barrier beach. Clay rip-up clasts of the laminae, possible burrows, and circular brown root casts occur from 107 to 108.5 ft (32.61 to 33.07 m). From 108.5 to 110 ft (33.07 to 33.53 m) is a coring gap.
Laminated yellow-brown clays with thin (1–3 mm) silty sand laminae appear at 110 ft (33.53 m); the clays become browner downsection to a sharp contact at 111.35 ft (33.94 m) with very dark gray-black, slightly sandy, organic-rich clay below; the dark clays have fine dispersed plant debris and are interpreted at a marsh deposit.
Yellow-brown clays (114.5–115.3 ft; 34.87–35.14 m) reappear immediately above an indurated zone (Fig. F2). Pebbly granuliferous very coarse sand interpreted as tidal channel deposit grades down by 121 ft (36.88 m) to medium–coarse sand with opaque heavy mineral laminae. Though associated with a distinct gamma log kick and interpreted in the field as a sequence boundary, we interpret the 115.3-ft (35.14 m) surface as a facies change from tidal channel sands below to marsh above. From 121 to 150.7 ft (36.88 to 45.93 m), the section consists of medium-grained, slightly micaceous, distinctly cross bedded sands (with opaque heavy mineral laminae and cross beds up to 20°), with occasional clay rip-up clasts and scattered granules; these sands clearly fit the upper shoreface model of Miller, McLaughlin, Browning, et al. (Chap. 3, this volume). Facies variations within the upper shoreface setting are reflected by the following: 130–130.2 ft (39.62–39.68 m) is slightly clayey sand, 130.2–130.7 ft (39.68–39.84 m) is granule-rich sand with an ironstone cemented base, 136.9 ft (41.73 m) is a granule layer, and 150.7 ft (45.93 m) is a zone of iron-cemented concretions. This surface at 150.7 ft (45.93 m) could be a sequence boundary, although it most likely reflects a facies shift in nearshore environments. Silty, clayey, heavily bioturbated, homogeneous, fine–medium sand with carbonaceous debris from 150.7 to 157.8 ft (45.93 to 48.10 m) represents deposition in lower shoreface environments (deposited below wave base, as evidenced by common fines); the lack of shells is attributed to postdepositional dissolution. These sands develop an oxidized brownish yellow stain reflecting Fe-rich groundwater. A lithology shift across a coring gap (157.8–160 ft; 48.1–48.77 m) to grayer interbedded sand, silt, and clay is associated with a sharp upsection increase in gamma log radiation beginning at 157 ft (47.85 m). We tentatively place a sequence boundary at 157.8 ft (48.10 m) at the contact of the Cohansey Formation above with the interbedded sands and clays of the Kirkwood Formation (Fig. F2). Sediments from 157.6 to 157.8 ft (48.04 to 48.10 m) contain clay blebs and darker organic material that may reflect ripping up of the underlying clays. In summary, the Cohansey Formation at Millville appears to comprise one sequence (37.4–157.8 ft; 11.40–48.10 m) with a regressive lower section (111.35–157.8 ft; 33.94–48.10 m) and a general stillstand upper section (37.4–111.35 ft; 11.40–33.94 m).
The Cohansey Formation forms the upper part of the Kirkwood-Cohansey aquifer system (Zapecza, 1989) (Fig. F2). The lower part of the Cohansey Formation is an excellent aquifer, with medium to very coarse sand concentrated in tidal channels and the upper shoreface from ~100 to 150 ft (30.48 to 45.72 m). Wells screened in this interval have reported yields of up to 1000 gpm (Rooney, 1971).
Interbedded sand and clay (160–185.7 ft; 48.77–56.60 m) at the top of the Kirkwood Formation (Fig. F3) consists of
Subsequent to drilling, the cores developed a thin yellow (sulfur-rich?) and orange (?limonitic) coating, suggesting Fe- and S-rich groundwater (Fig. F3). The section appears to fine downsection to ~170 ft (51.82 m) and then coarsen to 185.7 ft (56.60 m). The environment of deposition is possibly lagoonal, though it could be estuarine.
From 185.7 to 190 ft (56.60 to 57.91 m) is very dark grayish brown, heavily bioturbated, slightly micaceous clayey silty sand to clayey sandy silt with scattered granules and lignite; the environment was probably lagoonal, although mica and carbonaceous material suggest a probable deltaic/riverine influence (in a lower delta plain).
Clayey, sandy, heavily bioturbated silts with thin, lenticular cross-sand laminae (190–200 ft; 57.91–60.96 m) represent a finer-grained lagoonal facies (Fig. F3). A silica-cemented sandstone lens (204–204.1 ft; 62.18–62.21 m) overlies a coarser grained, burrowed, silty clayey sand with scattered granules (204.1–217 ft; 62.21–66.14 m). Gypsum crystals and a brownish coating develop on the core surfaces, indicating the presence of Fe- and Ca-rich (dissolved shells?) groundwater. The section fines down from 217 to 219.6 ft (66.14 to 66.93 m) and returns to silty very fine sand with scattered granules and dispersed plant debris from 220 to 221.4 ft (67.06 to 67.48 m). Possible environments of deposition include lower shoreface or lagoonal; we favor the latter interpretation in view of facies successions. Blue-gray silty clays (221.4–223.6 ft; 67.48–68.15 m) are slightly micaceous and weather with a thick brown rind; these are interpreted as lagoonal, although the low organic content is not consistent with this interpretation. The top of the clay (221.4 ft; 67.48 m) is interpreted as a maximum flooding surface (MFS), and we place a sequence boundary at the base of the clay (223.6 ft; 68.15 m) in association with a distinct gamma ray kick and a facies shift from the clay to delta-front sands below. Below the clay is a varied, 0.5-ft (0.15 m) lithologic interval containing a thin-bedded succession of silty sands, lignite, and clay rip ups similar to the clay above. The sequence from 157.8/160.0 to 223.6 ft (48.10/48.77 to 68.15 m) probably correlates with the Kw2a sequence of Miller et al. (1997). The Kw2a sequence at Millville appears to have been deposited on a delta plain in contrast to the prodelta clays that dominate the Kw2a sequence to the north.
If our correlation of this sequence with the Kw2a is correct, then the Wildwood Member at Millville is a very leaky confining unit separating coarse sands in the overlying Cohansey Formation from coarse sands in the underlying Shiloh Member (the "Atlantic City 800-foot sand" aquifer of Zapecza, 1989) (Fig. F3). This contrasts with the Ocean View corehole (Chap. 2, this volume), where the Wildwood Member is thick clay–silt that comprises an effective confining bed (Wildwood-Belleplain confining unit of Sugarman, 2001). The Rio Grande water-bearing zone is not found at Millville.
The interval from 223.6 to 224.0 ft (68.15 to 68.28 m) is a thin-bedded to cross-bedded clayey silty coarse to very coarse sand. From 224.0 to 230 ft (68.28 to 70.10 m) the section is slightly finer, with medium–coarse sand with lignite beds (225.2–225.3, 228.1–228.2 ft; 68.64–68.71, 69.52–69.56 m) and scattered granules (Fig. F3). The section becomes slightly coarser again from 230 to 248 ft (70.10 to 75.59 m), consisting of homogeneous coarse to very coarse sands. There are some thin (3–30 mm) laminae of peaty silty clay between 243 and 247.9 ft (74.07 and 75.56 m). These organic-rich homogeneous sands develop a yellow-brown limonitic rind indicative of Fe-rich groundwater. The sands from 223.6 to 247.9 ft (68.15 to 75.56 m) were deposited in delta-front environments. A burrowed surface at 247.9 ft (75.56 m) separates medium–coarse sand above from laminated, slightly micaceous, slightly lignitic silty clay below. These silty clays develop gypsum and sulfur overgrowths. This surface (247.9 ft; 75.56 m) is a facies change from delta-front sands above (upper highstand systems track [HST]) to prodelta silts and clays (lower HST) below. The laminated prodelta silty clays continue to 250.2 ft (76.26 m). From 250.2 to 250.6 ft (76.26 to 76.38 m), a clay with sandy laminae and sand blebs that appear to be burrows is present; this clay was also deposited in a prodelta environment. There is a facies shift at 250.6 ft (76.38 m) to heavily burrowed silty, clayey fine sands below, deposited in a shelf environment. The sands continue to 255.3 ft (77.82 m) where there is a gamma log increase and a subtle burrowed contact overlying muddy delta-front sands. This contact is a sequence boundary. Identification of Actinoptychus heliopelta (East Coast Diatom Zone 1; R. Benson, pers. comm., 2003) at 249.4 ft (76.17 m) suggests correlation of the 223–255.3 ft (67.97–77.82 m) sequence with the Kw1a/b sequence and probably the Kw1b sequence (Fig. F3). These sediments represent a generally shallowing upward succession within a deltaic setting. The sands at the base of the sequence (250.6–255.3 ft; 76.38–77.82 m) are interpreted to be the transgressive systems track (TST) of the sequence. The facies shift at 250.6 ft (76.38 m) represents the MFS, and the prodelta clays and delta-front sands are the HST.
The coarse nature of the sands from 224 to 248 ft (68.28 to 75.59 m) in the Shiloh Member (Kw1b sequence) form a confined aquifer equivalent to the upper sand of the Atlantic City 800-foot sand aquifer (Zapecza, 1989) (Fig. F8). At this site, the leaky confining unit that typically separates the upper and lower sands in the Atlantic City 800-foot sand is ~8 ft (2.44 m) thick (247–255 ft; 75.29–77.724 m) and consists of silty clay, clayey silt, and silty very fine sand.
Sands from 255.3 to 286.6 ft (77.82 to 87.36 m) can be divided into several distinct delta-front facies:
From 285.7 to 286.6 ft (87.08 to 87.36 m), there are muddy coarse-grained sand beds separated from clean coarse-grained sands. There appears to be a flooding surface at 284.4 ft (86.69 m), with some burrowing and a trace of phosphatic granules present around this surface (Fig. F3).
Below a coring gap (286.6–290 ft; 87.36–88.39 m) the facies change to an interbedded muddy, slightly micaceous medium to fine sand, with silty clay to clayey silt laminae to beds (290–302.4 ft; 88.39–92.17 m). The sand becomes slightly coarser with less mud downsection. We interpret these sediments as lower shoreface deposits, based on heavy bioturbation and the paucity of lignite.
The sand (255.3–290.0 ft; 77.82–88.39 m) at the top of the Brigantine Member (Kw1a sequence) at Millville is equivalent to the lower Atlantic City 800-foot sand aquifer (Zapecza, 1989) (Fig. F8). The sand within this aquifer is coarser (medium sands) both in the upper part (255–270 ft; 77.72–82.30 m) and near its base (281.6–290 ft; 85.83–88.39 m). The two upward-fining successions defined by these coarser beds may reflect subaqueous channel deposition.
A granule laminae (2 mm thick) caps a prodelta silty clay succession (302.4–340 ft; 92.17–103.63 m). The top of this succession (302.4–303.3 ft; 92.17–92.45 m) consists of organic-rich interlaminated silty clay to clayey silt with sandy silt and interspersed 0.1–0.5 ft (3–15 cm) thick granule laminae. Sand decreases downsection to 310 ft (94.49 m) as shown by increasing gamma log values; sands are very fine grained and found in lenticular beds with wispy cross-laminations that decrease downsection. Although deposited in prodelta environments, these coarser-grained sediments at the top reflect interfingering with prodelta/nearshore environments. Interlaminated, dark, "chocolate" brown organic-rich silty clays to clayey silts continue down to 340.6 ft (103.81 m). Laminations are generally well preserved, though a moderate number of small burrows are present, especially small vertical burrows (?Planolites) from 324.5 to 325.0 ft (98.91 to 99.06 m). Crystals of gypsum are noted on the core, suggesting that carbonate was present but has dissolved. The gamma log suggests several cycles containing coarser-grained sediments at 313, 317, 324, and 335 ft (95.40, 96.62, 98.76, and 102.11 m); these intervals are generally slightly lighter gray and appear to be siltier. Very fine sand to silt laminae occur throughout the section (Fig. F3).
A lithologic change occurs at 340.6 ft (103.81 m) from silty clay above to lighter-colored, less distinctly laminated (fewer partings), slightly clayey silt that continues to ~350.4 ft (106.80 m; position uncertain). Burrowed clayey shelly silt appears at 355 ft (108.20 m) below a coring gap and continues down to a contact at 372.1 ft (113.42 m). Below this contact is a facies change to a slightly silty clay with sand laminae. Sr isotopic age estimates between 355 and 410 ft (108.20 and 124.97 m) ranging from 19.2 to 21.0 Ma indicate correlation to the Kw1a sequence of Miller et al. (1997). The top of the shelly zone (372.1 ft; 113.42 m) may mark an MFS or a sequence boundary. We interpret it as an MFS based on the lack of a Sr isotopic break and ages that correlate to the Kw1a sequence above and below (Fig. F3). The facies above and below the contact were deposited in a prodelta environment; the sediments below the contact are clayier with more common shells and more bioturbation, suggesting slower sedimentation rates.
Uniform slightly silty to silty, micaceous, laminated dark clay with sparse shells continues below the contact at 372.1 ft (113.42 m) to a sequence boundary at 410 ft (124.97 m), with shells increasing below 400 ft (121.92 m). From 372.1 to 374 ft (113.42 to 114.00 m), the silty clay contains burrows filled with the lighter shelly clayey silt from above. The section is fairly uniform down to 406 ft (123.75 m), where coarse to very coarse quartz sand with reworked, scattered glauconite that increases downsection in these silty clays to a contact at 410 ft (124.97 m) (10% at the top grading down to ~50%) with common granules. Variations in sand content from 408 to 410 ft (124.36 to 124.97 m) yield clear laminae, some of which appear to be inclined (408–410 ft; 124.36–124.97 m). Shell concentrations occur in this section (407.9, 408.15, 408.9, and 409.2 ft; 124.33, 124.40, 124.63, and 124.72 m). The environment from 406 to 410 ft (123.75 to 124.97 m) appears to be distal lower shoreface on a storm-dominated shelf. The section from 372.1 to 410 ft (113.42 to 124.97 m) is interpreted as the TST of the Kw1a sequence (Figs. F3, F10).
A distinct sequence boundary at 410 ft (124.97 m) associated with a large gamma log kick separates granuliferous, silty clayey sand above from a shelly, slightly muddy, glauconitic sand below (Fig. F4). This is the contact between the Miocene Kirkwood Formation clays and sands (particularly glauconitic sands) of the upper Shark River Formation. Onsite studies considered that the glauconitic sands might be assigned to the Oligocene Atlantic City or Sewell Point Formations. However, our studies show that these sands are upper Eocene:
At Millville, upper Eocene glauconitic quartz sands are lithologically similar to the sandy upper Shark River Formation (= Toms River Member of Enright, 1969), which is correlated to Zones NP18 and NP19–NP20 at Millville (Fig. F4). In other New Jersey coreholes, the Shark River Formation is restricted to Zone NP18 and older (i.e., this formation just breaks into the upper Eocene; Browning et al., 1997b). Zone NP19/NP20 sediments at Atlantic City and ACGS#4 (Mays Landing) are clays that stratotypify the upper Eocene Absecon Inlet Formation and comprise sequences E10 and E11 (Browning et al., 1997a). At Millville, however, the NP19–NP20 sands (= sequence E10) are assigned to the upper Shark River Formation (= Toms River Member of Enright, 1969) (Fig. F4). Thus, this formation must be time transgressive.
Below the 410-ft (124.97 m) contact, shells increase in the heavily bioturbated glauconitic shelly silty sands from 410 to 412 ft (124.97 to 125.58 m), with alternating concentrations of shellier and less shelly zones. Shells (mostly fragments <3 mm) compose a significant portion (typically 20%) of the sediments down to 620 ft (188.98 m); there are a few concentrated shell zones (e.g., 447.8 ft; 136.49 m). Glauconite increases downsection from ~10% at ~410 ft (124.97 m) to ~30% below 414 ft (126.19 m); alternations of glauconite-rich and less glauconitic beds continue to 620 ft (188.98 m), varying by ~10%–25%. The sand fraction is dominated by fine- to medium-grained quartz, with scattered coarse and very coarse grains and fine- to very fine grained glauconite varying by ~20%. Rare pyrite is present, and scattered, thin, rusty brown clayey sand laminae are present through the interval. The sediments appear similar to the reworked glauconite sands that comprise the Oligocene in New Jersey, although biostratigraphy clearly indicates that they are older (Fig. F4). Zones with less mud (cleaner sands) and concentrations of shell material (447.8–447.9, 448.6–448.7, 450.7–450.9, 451.7–452.8, 453.3–453.7, and 454.6–454.8 ft; 136.49–136.52, 136.73–136.76, 137.37–137.43, 137.68–138.01, 138.17–138.29, and 138.56–138.62 m) become increasingly common down to 457.5 ft (139.45 m). The sands from 407.95 to 457.5 ft (124.34 to 139.45 m) are very porous and friable and comprise the upper part of an aquifer (the term "Piney Point" has been applied to this aquifer by Nemickas and Carswell [1976], although it is best termed the Shark River aquifer). The sands were deposited in an inner neritic environment and probably represent lower shoreface deposits.
Shelly, clayey to slightly clayey, heavily burrowed glauconitic (15%–30%) quartz sands with clayier interbeds are present from 457.5 to 543.9 ft (139.45 to 165.78 m). This section has slightly less shell material, slightly more clay, and slightly more glauconite (typically 25%–30%) than the section above. The lower amounts of shell and higher amounts of clay are expressed by higher gamma log values below 457.5 ft (139.45 m). The section becomes generally clayier downsection, and there are alternations between sandier and clayier zones. Contacts in which the clays overlie the sands are sharp and may be minor flooding surfaces (e.g., 475.1, ~482.7, 484.75 [heavily burrowed], and 490.35 ft [burrowed]; 144.81, ~147.13, 147.75, and 149.46 m) (Fig. F4), whereas the shifts back to sands are gradual. Sandier intervals are present from 500 to 505.3 ft (152.4 to 154.02 m), as shown by slightly lower gamma logging values. The section from 510 to 540 ft (155.45 to 164.59 m) is slightly sandier, with clay burrows decreasing, shell increasing, and sand increasing downsection. Below ~540 ft (164.59 m), the section shifts to muddier sand that fines down to a sequence boundary at 552.5 ft (168.40 m; see below). This change from fining to coarsening upsection is interpreted as an MFS at ~540 ft (164.59 m), although there is no distinct kick on the gamma log or obvious surface in the core (Fig. F4).
The environment of deposition for the muddy sands from 457.5 to 547.0 ft (139.45 to 166.73 m) is middle neritic (suggested by the heavy bioturbation, predominance of clay, and benthic foraminifers). Benthic foraminifers from 440 to 541 ft (134.11 to 164.90 m) are a moderately diverse assemblage of guttulinids, dentilinids, Cibicides, and Cibicidoides; the paleodepths are middle neritic (Table T4).
A very clayey medium glauconitic quartz sand (547.0–547.15 ft; 166.73–166.77 m) fines downsection to interlaminated, bioturbated slightly clayey to very clayey sand (547.15–548.3 ft; 166.77–167.12 m). Medium-grained, very glauconitic (25%–30%), shelly (with abundant weathered fragments), slightly muddy sand with scattered coarse sand to granules (550–552.5 ft; 167.64–168.40 m) overlies a granuliferous unit, and we place a sequence boundary at this facies change (552.3–552.5 ft; 168.34–168.40). The sequence boundary is obscured by extensive bioturbation, though it is apparent on the gamma log (Fig. F4). We correlate the sequence from 410 to 552.5 ft (124.97 to 168.40 m) with sequence E10 of Browning et al. (1997a) based on assignment to biozones P16–P17 (see "Biostratigraphy").
Coarser-grained, poorly sorted, slightly muddy glauconitic shelly granuliferous medium–very coarse sand (552.5–555.1 ft; 168.40–169.19 m) appears below the sequence boundary. This granuliferous unit was deposited in proximal lower shoreface environments. It fines downsection to muddy, tighter, medium-grained glauconitic quartz sand with scattered chalky shelly fragments and coarse grains (555.1–608 ft; 169.19–185.32 m). This unit contains a few less muddy granuliferous sand beds in the upper part (555.7–556.2, 556.8–557.1, 557.4–557.9, and 558.0–558.1 ft; 169.38–169.53, 169.71–169.80, 169.90–170.05, and 170.08–170.11 m). Shell material increases downsection from ~12% at 570–605 ft (173.74–184.40 m) to >20% at 605 ft (184.40 m). This sandy unit was deposited in distal lower shoreface environments. Clay content increases downsection from 596 to 611 ft (181.66 to 186.23 m). Predominantly sandy clay occurs below ~608 ft (185.32 m), with homogeneous sandy glauconitic shelly silty clay (608–616 ft; 185.32–187.76 m) to very clayey sand (616–620 ft; 187.76–188.98 m) with abundant shell fragments and shells. The section is slightly less silty, more glauconitic, and has slightly larger shell fragments below 619.45 ft (188.81 m). These sandy clays and clayey sands were deposited in offshore environments (middle neritic based on foraminifers, dentilinids, and Cibicides). A hard (but not cemented) zone of muddy, glauconitic, shelly fine–medium quartz sand was encountered between 620 and 620.5 ft (188.98 and 189.13 m). A sequence boundary is placed at 619.5 ft (188.82 m) in a minor coring gap (619.45–620 ft; 188.81–188.98 m) above the hard zone with sequence E9 (Zone NP18/NP19–NP20) above and E8 (Zone ?NP17/NP18) below (Fig. F4). The sequence boundary is interpreted from the gamma log, which shows an increase from 619.5 to 615 ft (188.82 to 187.45 m).
Below a coring gap (620.5–625 ft; 189.13–190.50 m), a facies change occurs with darker, more glauconitic sandy clays with whole shells below (Fig. F4). From 625 to 640.35 ft (190.50 to 195.18 m), the section is a heavily bioturbated clayey sand that becomes increasingly glauconitic downward, from more quartz than glauconite above ~623 ft (189.89 m) to more glauconite than quartz below 623 ft (189.89 m). The increase in quartz suggests shallowing in the HST. The section below 623 ft (189.89 m) has more prominent burrows. The burrows have a thick lining of silty clay and become more common downsection and larger below 635.3 ft (193.70 m). A contact at 640.35 (195.18 m) marks the base of the sequence.
Aquifer sands within the 230-ft-thick (70.10 m) upper Shark River Formation are present from 410 to 590 ft (124.97 to 179.83 m). The upper part of the aquifer sands (407.95–457.5 ft; 124.34–139.45 m) contain the coarser, cleaner sands and should have the highest permeability (Fig. F8). Higher percentages of clay and glauconite and thin clay interbeds probably decrease permeability lower in the aquifer.
A significant contact was encountered at 640.35 ft (195.18 m) with burrowed glauconitic sand resting on a heavily burrowed, dark greenish silty clay with abundant glauconite sand stringers modified by burrows (Fig. F4). A pyritic silt-filled burrow lies just under the contact (640.45 ft; 195.21 m). The amount of glauconite ranges from 15% to 75% (average = ~20%) and decreases downsection to 643.75 ft (196.22 m). We place the clays in the lower part of the Shark River Formation vs. the coarser, more glauconitic upper Shark River Formation. The lower part of the Shark River Formation at Millville is greenish gray, bioturbated, and laminated to thin-bedded silty clay and clay with some very fine sand and 1%–2% very fine grained glauconite (Fig. F4).
A coring gap from 643.75 to 651 ft (196.22 to 198.42 m) separates more glauconitic clays from slightly glauconitic clays (651–652.2 ft; 198.42–198.79 m). A subtle surface at 652.2 ft (198.79 m) separates dark greenish gray, slightly glauconitic silty clays from grayish green clays ("ash colored marls") below (Fig. F4). This surface is most likely an MFS. There is a gamma log kick at 649 ft (197.82 m) that implies a ~4 ft (1.22 m) offset in the cores vs. logs.
Uniform grayish green foraminiferal-rich clays with scattered shell and lignite debris continue to 670 ft (204.22 m). Burrows are present but are mostly small scale (few millimeter). Subtle color bands are preserved (1 cm scale), reflecting lighter, more microfossil rich zones and darker, more clay rich zones (Fig. F4). The clay becomes slightly silty (670 ft; 204.22 m) with very minor amounts of very fine sand and very fine glauconite sand (1%–2%). From 675 to 682 ft (205.74 to 207.87 m), the lithology is similar to above, although it is harder and contains more foraminifers and a thin porcellanite zone (677.3–678.3 ft; 206.44–206.75 m). From 682 to 684.6 ft (207.87 to 208.67 m), the section is clayier, consisting of slightly silty clay with distinct color banding and wormy bioturbation (1- to 2-mm burrows filled with lighter material). Silty clay returns from 684.6 to 685.6 ft (207.87 to 208.97 m) and returns to slightly silty clay similar to that above from 685.6 to 690.7 ft (208.97 to 210.53 m). The gamma log suggests a cyclicity with hotter zones at 643–649, 651–653, 657.5–659.5, 663.5–665, 669–672, 674–676, 681–684, and 686–698 ft (195.99–197.82, 198.42–199.03, 200.41–201.02, 202.23–202.69, 203.91–204.83, 205.44–206.04, 207.57–208.48, and 209.09–212.75 m); these zones may reflect a higher clay content (Fig. F4).
A lithologic change to glauconitic sandy silty clay with common mud-lined burrows is present at 690.7 ft (210.53 m). Glauconite increases downsection from ~10% to 15%–20% in the interval 694–699 ft (211.53–213.06 m). A porcellanite nodule occurs at 694.9–695.05 ft (211.81– 211.85 m). Glauconite is high (20%–50%) in the interval from 695 to 698.85 ft (211.84 to 213.01 m), marking the lower part of the sequence (TST?). A sequence boundary at 698.85 ft (213.01 m) consists of a heavily burrowed contact zone (698.5–699 ft; 212.90–213.06), with glauconitic sandy clay above and brownish clay below. Glauconite filled, mud-lined burrows extend down to 699 ft (213.06 m). This sequence is assigned to Zones NP15 and NP15–NP16 (P11 and P12) (see "Biostratigraphy") (Fig. F4) and correlates with sequence E7 of Browning et al. (1997b).
Brown, burrowed, slightly glauconitic, slightly silty clay with scattered fine to very fine glauconite sand extends to 712.9 ft (217.29 m). Wormy burrows (similar to those between 682 and 684.6 ft; 207.87 and 208.67 m) are common. Porcellanite zones are found at 704–704.9, 706.8–707.2, 708.8–709.2, and 709.8–709.9 ft (214.58–214.85, 215.43–215.55, 216.04–216.16, and 216.35–216.38 m) (Fig. F4). These porcellanites are lower middle to upper lower Eocene and thus correlate with the "Horizon A cherts."
Between 712.9 and 720.6 ft (217.29 and 219.64 m) the section becomes more glauconitic (15%–20%), harder, and siltier clay with abundant Planolites-type burrows. There is a porcellanite bed from 713 to 713.1 ft (217.32 to 217.35 m). From 720.6 to 721.55 ft (219.64 to 219.93 m), a porcellanitic carbonate claystone with 3%–5% glauconite sand and abundant small burrows is present. From 721.55 to 722.5 ft (219.93 to 220.22 m), a slightly glauconitic silty clay is present. There is a faint surface at 722.5 ft (220.22 m) that may be a sequence boundary separating sequence E4 from E6. Although the lithologic evidence for this as a sequence boundary is weak, calcareous nannoplankton Subzone NP14a is cut out and indicates a hiatus. There is a gamma log kick at 719.5 ft (219.30 m), again suggesting a 3-ft (0.91 m) core-log offset (Fig. F4).
From 722.5 to 723.5 ft (220.22 to 220.52 m), a more glauconitic silty clay with glauconite increasing downsection to 10% (Fig. F4) is present. An extensively burrowed (with clay lined burrows from 1-cm to millimeter) very glauconite-rich (20%–25%) silty clay (730–731.9 ft; 222.50–223.08 m) appears below a coring gap (723.5–730 ft; 220.52–222.50 m). A distinct sequence boundary occurs at 731.8–731.9 ft (223.05–223.08 m) with an irregular surface that includes a nodule that may be an ash bed; the sequence boundary separates very glauconitic silty clay from a slightly glauconitic silty clay below (Fig. F4). This sequence is assigned to Zone NP13 (P8) and thus correlates with lower Eocene sequence E4 of Browning et al. (1997b).
The Manasquan Formation at Millville (731.9–847 ft; 223.08–258.17 m) is a dark greenish gray carbonate-rich clay with sparse glauconite ("Ash Marl" of Cook, 1868). The section from 731.9 to 732.75 ft (223.08 to 223.34 m) is more glauconitic than below because of bioturbation from above (Fig. F5). Below this, much less glauconitic (generally <5%) soft dark greenish gray clay with abundant foraminifers is found from 732.75 to 746 ft (223.34 to 227.38 m). Glauconite decreases from 3%–5% to <1% and becomes finer grained at 746 ft (227.38 m); there is a gamma log kick here that may indicate the MFS (Fig. F5). Glauconite decreases from 746 ft (227.38 m) to trace amounts at 756 ft (230.43 m) and increases slightly at 767–768 ft (233.78–234.09 m) from trace to 1%–2%. The clays are slightly stiffer from 756 to 770 ft (230.43 to 234.70 m), and there are porcellanite zones: 758–759.4, 763.6–764.0, and 764.8–765.0 ft (231.04–231.47, 232.75–232.87, and 233.11–233.17 m). No obvious surface was noted in the section. The sequence from 731.9 to 768 ft (223.08 to 234.09 m) is assigned to Zones NP12 and P7 (see "Biostratigraphy"). This section correlates with sequence E3 of Browning et al. (1997b). We tentatively place a sequence boundary at ~768 ft (234.09 m) at an upsection gamma radiation and glauconite increase.
Sequence E2 is thick at Millville (~69 ft; 21.03 m) and comprises a uniform dark greenish gray carbonate-rich clay with sparse glauconite (Fig. F5). The clays continue below the inferred sequence boundary, with glauconite dropping again to trace amounts at 772 ft (235.31 m), and varying between trace and 1% down to 799 ft (243.54 m). Heavy bioturbation typifies the section from 760 to 791 ft (231.65 to 241.10 m) with silty, very fine to fine sand occasionally infilling the burrows. Below a coring gap (778.2–780 ft; 237.20–237.74 m), the section from 780 to 786 ft (237.74 to 239.57 m) is sandiest, with sand concentrated in the burrows and decreasing downsection. Laminations of clay and slightly silty clay occur from 791 to 798 ft (241.10 to 243.23 m). From 798 to 804 ft (243.23 to 245.06 m), slightly darker green foraminiferal clay with small shell fragments is present; laminations are not obvious, with only small (2–5 mm) burrows. The interval 791–804 ft (241.10–245.06 m) appears to be of deeper water than above or below based on greater amounts of clay and foraminifers. These clays were deposited in offshore environments (middle–outer neritic).
Surfaces and lithologic variations are faint in the Manasquan Formation, particularly sequence E2, making sequence stratigraphic subdivisions vague. There is a faint, slightly irregular contact at 804.0 ft (246.06 m) with a dark gray clay above burrowed down into a foraminifer-rich silty clay. This surface may mark a flooding sequence (FS) (Fig. F5). There is a coring gap from 804.25 to 806.0 ft (245.14 to 245.67 m). More common to pervasive burrowing with scattered sand-filled wispy burrows returns from 806 to 811.3 ft (245.67 to 247.28 m). Foraminifers decrease in abundance slightly downsection from 807 to 811.3 ft (245.97 to 247.28 m). A contact at 811.3 ft (247.28 m) separates the burrowed clays above from slightly bioturbated, slightly glauconitic (<1%) laminated slightly silty clay to slightly sandy clay that continues downsection to 814.9 ft (248.38 m). This contact is a facies change with no evidence for erosion and probably marks the MFS. The sandier clays above the surface are interpreted as the HST. The clay below 814.9 ft (248.38 m) is less sandy, has fewer foraminifers, and is less laminated than the clays above; these clays continue down to 832 ft (253.59 m). There is a gradual downsection transition to a slightly glauconitic, foraminiferal-bearing clay (832–844.6 ft; 253.59–257.43 m); foraminifers increase downsection at 831 ft (253.29 m), whereas glauconite increases downsection at 832 ft (253.59 m). Based on biostratigraphy, we tentatively place a sequence boundary in a coring gap (834.5–840 ft; 254.36–256.03 m) at a gamma ray kick at 836 ft (254.81 m), with sequences E2 (Zone NP11 (P6b) above and E1 (Zone NP10) below (Fig. F5).
Sequence E1 is thin (<10 ft; 3.05 m) at Millville (Fig. F5), as it is at most New Jersey sites where it comprises a glauconite clay to clayey glauconite sand (Farmingdale Member). Below 840 ft (256.03 m), there is a gradual downsection increase in glauconite from trace amounts to as much as 50% between 846 and 847 ft (257.86 and 258.17 m). A contact separating glauconitic sandy clay above from laminated clay with glauconite-filled burrows below at 847 ft (258.17 m) is a sequence boundary separating the lower Eocene (sequence E1) from an unnamed basal Eocene clay found at Bass River and Ancora (Fig. F5).
Age: late Paleocene to basal Eocene
Interval: 847–970.2 ft (258.17–295.72 m)
The upper part of the Vincentown Formation is a slightly micaceous, glauconitic, generally laminated silty clay (Fig. F5). From 847 to 850 ft (258.17 to 259.08 m), the section is a slightly glauconitic laminated clay with the glauconite concentrated in burrows. The coarser glauconite is burrowed down from the sequence boundary; the fine, disseminated glauconite appears in situ. Sandy silty clay from 850 to 852.7 ft (259.08 to 259.90 m) is more glauconitic (>5%) and contains very fine quartz sand (as much as 10%). Between 852.7 and 855.5 ft (259.90 and 260.76 m) a clay with shell and common foraminifers is present. The section gradually fines downsection to a clay at 860.1 ft (262.16 m), where glauconite disappears and a planktonic foraminiferal excursion fauna (e.g., Acarinina africana) (Table T3) is found. The clays below 860.1 ft (262.16 m) are presumed to be the equivalent of clays at Ancora, New Jersey, that contain the carbon isotopic excursion fauna (figure F4 in
Chap. 1, this volume) (Fig. F5). From 860.1 to 890 ft (262.16 to 271.27 m), the laminated to thinly bedded clay appears to be rhythmically bedded, with alternating darker, thin (5 mm thick) layers and lighter (15 mm thick) very slightly silty layers. Burrows (some with nodules), shells, and replaced shells are scattered through the section. Foraminiferal clays with a trace of mica and traces of scattered glauconite (890–896.0 ft; 271.27–273.10 m) show increasing burrowed glauconite from 896 to 898.3 ft (273.10 to 273.80 m). There is a transition zone of clay and burrowed glauconite clays from below (898.3–898.8 ft; 273.80–273.95 m) and a contact at 898.8–899.4 ft (273.95–274.14 m) with slightly silty glauconitic clay below (glauconite increasing to 10%). At Bass River and Ancora, a similar change in lithology accompanies a ~5
decrease in carbon isotopic values that marks the onset of the CIE and Paleocene/Eocene Thermal Maximum (Cramer et al., 1999; Cramer, 2002; Kent et al., 2003); the interval from 897 to 898.8 ft (273.41 to 273.95 m) is therefore predicted to mark the Paleocene/Eocene boundary (Fig. F5). This is consistent with nannofossil biostratigraphy that assigns the section from 855 to 895 ft (260.60 to 272.80 m) to Subzone NP9b (the section below 895 ft is barren/indeterminate; see
"Biostratigraphy").
The interval from 898.9 to 899.4 ft (273.98 to 274.14 m) is a transition from the clay to micaceous, glauconitic sandy silty clays below. The contact at 899.4 ft (274.14 m) could either be a classic sequence boundary or the reflection of a bolide impact followed by rapid deposition of impact ejecta. We believe the surface at 898.4 ft (273.83 m) is a sequence boundary separating a previously unnamed sequence (Pa4) (Fig. F5) from sequence Pa3. The CIE is probably truncated at this site based on nannofossil studies (see "Biostratigraphy").
We assigned the slightly micaceous, glauconitic, generally laminated silty clay from 847 to 899.4 ft (258.17 to 274.14 m) to the Vincentown Formation (Fig. F5), although this unit is distinctly finer grained than typical outcrops or other subsurface sections of the Vincentown Formation. A similar fine-grained subsurface unit has been noted at Clayton, Bass River, and Ancora (Kent et al., 2003). We apply the term upper Vincentown Formation to these fine-grained facies, although we recognize that a distinct member or formation name should be sought for this unit (e.g., Ancora Member/Formation) (Fig. F8). We interpret that this clay was deposited in middle–outer neritic environments.
Micaceous glauconitic quartzose sandy silty clays below the contact are assigned to the Vincentown Formation (Fig. F5). Laminations of sandy silty clay and less sandy silty clay begin at 902 ft (274.93 m), with scatted concretions around burrows. Glauconite, mica, and quartz sand content decrease downsection, as does burrowing (899.4–920 ft; 274.14–280.42 m) (Fig. F5). Burrowed, micaceous, slightly sandy silty clay with traces of glauconite and quartz sand restricted to burrows becomes clayier and less sandy down to 930 ft (283.46 m). Fairly uniform burrowed micaceous silty clay continues to 950 ft (289.56 m), with slightly fewer burrows downsection; glauconite occurs in trace quantities. A very fine sand bed is present from 938.7 to 938.9 ft (286.12 to 286.18 m). The lithofacies variations from 899.4 to 950 ft (274.14 to 289.56 m) reflect a shallowing upward HST deposited in prodelta environments.
Glauconite and foraminifers increase downsection in slightly micaceous clays beginning at 950 ft (289.56 m), becoming a increasingly coarser, progressively more burrowed sandy clay from 955.8 to 959.4 ft (291.33 to 292.43 m), with glauconite up to 5% (Fig. F5). This represents a shift to deposition in middle neritic environments with minimal deltaic influence. A shelly bed with Gryphaea dissimilis (959.1–959.3 ft; 292.33–292.39 m) overlies an irregular burrowed erosional surface (959.4 ft; 292.43 m), marking a sequence boundary. An MFS is either at the shell bed or the top of the glauconitic interval (955.8 ft; 291.33 m); in either case, the MFS is only slightly above the sequence boundary (Fig. F5). This correlates the shell bed at 959.1 ft (292.33 m) to an apparently coeval bed at 1230 ft (374.90 m) at Bass River (Miller et al., 1998b). The sequence from 899.4 to 959.9 ft (274.14 to 292.33 m) is assigned to Zones NP8–NP9 and thus correlates with sequence Pa3 of Liu et al. (1997).
The underlying sequence (959.4 ft–974.9 ft; 292.43–297.15 m) is thin, with a truncated TST (i.e., the clays that represent the TST in this setting are very thin). Clays with common pyrite (959.4–960.0 ft; 292.52–292.61 m) underlie the 959.4 ft (292.52 m) sequence boundary (Fig. F5). From 960.0 to 963 ft (292.52 to 293.52 m), the section is lighter-colored glauconitic sandy clayey silt with common foraminifers. Lighter laminations represent more foraminiferal rich intervals. Gryphaea shells occur at 961.9 ft (293.19 m), with scattered shells from 961.9 to 964 ft (293.19 to 293.83 m). Foraminifers increase in abundance downsection from 962.5 ft (293.37 m) (Tables T5, T6, T7, T8). Glauconite increases and becomes coarser downsection from 963 to 967.6 ft (293.52 to 294.92 m), reaching 20%. The core progresses from siltier to clayier at 966.9 ft (294.71 m). From 967.6 to 970.2 ft (294.92 to 295.72 m), the core is foraminiferal-rich micaceous sandy clayey silt.
We placed the top of the Hornerstown Formation at a change to glauconite-rich clay at 970.2 ft (295.72 m) (Fig. F5). This places the Vincentown/Hornerstown Formation contact in Zone P4a at Millville, Ancora, and Bass River. From 970.2 to 974 ft (295.72 to 296.88 m), the section is heavily burrowed, very glauconite rich (40%) silty clay with scattered thin shell fragments; glauconite increases downsection to a clayey glauconite sand (977–980.1 ft; 297.79–298.73 m). Shells occur from 974.7 to 974.9 ft (297.09 to 297.15 m; Oleneothyris harleni). We place a sequence boundary at this level (Fig. F5). Above the contact is a dark greenish gray very clayey glauconite sand; below the boundary is a micaceous quartzose glauconite sand with weathered glauconite. The sample at 976 ft (297.48 m) is assigned to Subzone P3b, correlating the sequence from 959.4 to 974.9 ft (292.43 to 297.15 m) to sequence Pa2 of Liu et al. (1997).
Quartzose glauconite sand with weathered glauconite continues below the 974.9-ft (297.15 m) sequence boundary. From 980 to 981 ft (298.70 to 299.01 m), the sands contain small clay blebs and hard cemented nodules that are either concretions or rip-up clasts. From 981 to 982.5 ft (299.01 to 299.47 m), the section contains clayier zones. The K/P boundary occurs in a zone from 982.5 to 983.4 ft (299.47 to 299.74 m). At 982.5–983.3 ft (299.47–299.71 m), there is a shift to sandy clay with decreasing sand downsection. We place the base of the Hornerstown Formation at 983.3 ft (299.71 m), although a very similar glauconite sand (987.1–988.1 ft; 300.87–301.17) recurs below an intervening clay (Fig. F5).
Samples from 981.0 to 983.5 ft (299.08 to 299.85 m) in a glauconitic clay interval were processed for planktonic foraminifers to identify the K/P boundary (Fig. F6; Table T5). Planktonic foraminifers from the lower Danian were sparse and moderately preserved, whereas those from the Cretaceous were more numerous and well preserved. The K/P boundary is placed between the samples at 983.0 ft (299.70 m) and 983.05 ft (299.71 m). The presence of P. eugubina in a sample at 983.0 ft (299.70 m) identifies the lower Danian Zone P
(Fig. F6). The basal Danian Zone P0 may lie just below this. Our experience shows this zone to be a centimeter or so thick in the New Jersey Coastal Plain boreholes. Danian Zone P1a is identified from samples at 982.95–982.0 ft (299.68–299.39 m) and on the occurrence of Eoglobigerina edita, E, eobulloides, Guembelitria cretacea, and Praemurica taurica. The identification of Subbotina triloculinoides in the sample at 981.0 ft (299.08 m) indicates Danian Zone P1b. There is a probable unconformity between 981.0 ft (Zone NP3 [P1b]; younger than ~63.8 Ma) and 983.0 ft (299.62 m) (Zone P1a; older than 64.6 Ma); this is a regional unconformity, with the underlying sequence spanning the K/P boundary (Miller et al., 2004).
The Cretaceous samples 983.05–983.5 ft (299.85–299.85 m) are placed in the uppermost Maastrichtian based on the occurrences of Hedbergella monmouthensis, Pseudoguembelina hariaensis, Rugoglobigerina macrocephala, R. reicheli, and G. cretacea. The environment of deposition was too shallow to allow a full complement of deeper-dwelling planktonic foraminiferal species to occur. For instance, the genus Globotruncana is very rare. The range of P. hariaensis falls within the uppermost Maastrichtian Abathomphalus mayeroensis Zone.
Sandy silty clay with burrowed glauconite sand occurs from 983.3 to 987.5 ft (299.71 to 300.99 m), with glauconite and burrowing increasing downsection to a clayey glauconite sand from 987.5 to 988.1 ft (300.99 to 301.17 m) (Fig. F6). At the base of the glauconite sand (988.1 ft; 301.17 m), there is a phosphate nodule and a probable sequence boundary. This is a previously poorly recognized uppermost Maastrichtian sequence (983.3–988.1 ft; 299.62–301.17 m) that elsewhere spans the K/P boundary (i.e., it extends into Danian Zone P1a) (Miller et al., 2004); here it assigned to uppermost Maastrichtian Zone CC26 (see "Biostratigraphy") (Fig. F11).
Below the sequence boundary, the lithology is a glauconitic (15%–20%) slightly silty clay with finely disseminated mica from 988.1 to 994.7 ft (301.17 to 303.18 m). There are common foraminifers (Table T6) and glauconite-filled burrows. Slight bedding contrasts occur between clay-rich and glauconite-rich beds. At 994.7 ft (303.18 m), there is a shift to a very slightly silty, heavily bioturbated clay with lower (<5%) glauconite and silt content (Fig. F6). The clay is uniform and heavily bioturbated with a few glauconite-filled burrows. There is a gradational downsection change beginning at 997–997.9 ft (303.89–304.16 m) to more glauconitic, more carbonate/gypsum-rich clays. The increase in carbonate results in a change from dark gray to black to lighter greenish gray clays downsection. From 997.9 to 1010 ft (304.16 to 307.85 m), an intensely bioturbated silty clay with glauconite sand (~5%–10%) is present; burrows are often clay filled, with a few glauconite filled. Lighter gray clay-filled burrows, carbonate, and glauconite increase from 1003 to 1010 ft (305.71 to 307.85 m).
Formational assignment of these glauconitic clays and subordinate clayey glauconite sands is difficult because of facies changes from type sections in Monmouth County, New Jersey, to Millville (Fig. F8). Olsson (1960, 1963) defined clayey glauconite sands and glauconitic clays in Monmouth County as the New Egypt Formation. At Bass River, Miller et al. (1998b, 2004) assigned glauconitic clays with subordinate clayey glauconite sands at the top of the Maastrichtian to the New Egypt Formation. At Millville, the facies from the K/P boundary to ~1010 ft (307.85 m) consist of a clayey glauconite sand at the top to a carbonate-rich glauconitic clay below, with carbonate increasing downsection; although similar to the facies in the Bass River corehole, Millville differs from the sections of the New Egypt Formation by its high carbonate content, and we apply the term New Egypt equivalent to these facies at Millville.
The transitional contact to the Navesink equivalent is at ~1010 ft (307.85 m) based on the appearance of coarse glauconite, an increase in glauconite to 20%, an increase in carbonate content, and a decrease in clay content to ~50% (Fig. F6). In the downdip Bass River corehole, Miller et al. (1998b, 2004) assigned glauconitic carbonate-rich clays to the Navesink Formation, which is generally a clayey glauconite sand in outcrop and updip boreholes (e.g., Olsson, 1960, 1963). At Millville, the Navesink Formation is very carbonate rich (Fig. F6). The lithology is a hard, foraminifer-rich clay with glauconitic sand and intense bioturbation from 1010 to 1012.4 ft (307.85 to 308.58 m), passing into a heavily burrowed, very dark clayey glauconite (~50%) sand from 1012.5 to 1014.5 ft (308.58 to 309.22 m). A contact at 1014.5–1015.1 ft (309.22–309.40 m) has glauconite sand overlying heavily bioturbated, light gray, microfossil-rich, slightly glauconitic (5%) carbonate-rich clay that continues down to a coring gap at 1016.4 ft (309.80 m). Burrows in the carbonate-rich clay are filled with darker gray silty clay from above. The contact at 1014.5 ft (309.22 m) may be an MFS or a sequence boundary. This contact is present in the lower part of Subzone CC25c (~66–66.5 Ma) (see "Biostratigraphy;" Fig. F11) and appears to correlate with the poorly documented mid-Maastrichtian Navesink I/Navesink II sequence boundary of Miller et al. (2004). If so, then the Millville borehole has the best characterization and dating of Maastrichtian sequence(s) of any New Jersey CPDP corehole to date.
The section from 1020 to 1033 ft (310.90 to 314.86 m) is an extensively burrowed light gray carbonate-rich glauconitic clay, with glauconite generally increasing downsection. The section from 1020 to 1030 ft (310.90 to 313.94 m) contains fairly abundant small (1–2 mm) carbonate concretions. Glauconite increases downsection from 1020 to 1024.5 ft (310.90 to 312.27 m) from 10% to 50% (Fig. F6). Glauconite decreases at 1024.5 ft (312.27 m) 10%–20% and increases downsection to 1027 ft (313.03 m). At 1027 ft (313.03 m), there is a slight decrease in glauconite (20%–30%), with glauconite increasing again downsection. There is a coring gap from 1029.1 to 1030 ft (313.67 to 313.94 m). There is an extensively burrowed, shelly (including corals), glauconite sand-rich chalky light gray clay (1030–1033 ft; 313.94–314.86 m), with glauconite increasing downsection to a rubbly contact at 1032.9 ft (314.83 m). The base of the Navesink and top of the Mount Laurel are difficult to pick lithostratigraphically and biostratigraphically at Millville because of extensive reworking (e.g., Subzone CC23a material extends into the Navesink, whereas elsewhere in the coastal plain this zone is restricted to the underlying Mount Laurel Formation) (Miller et al., 2004) (Fig. F11). Just above the contact at 1032.9 ft (314.83 m), there are thick (2 cm) cemented burrows. A dramatic gamma log peak occurs at Millville at 1032 ft (314.55 m); this peak is regionally associated with a phosphorite lag deposit in the top 1–4 ft (0.30–1.22 m) of the Mount Laurel Formation, just below the base of the Navesink Formation (i.e., the sequence boundary actually separates Mount Laurel sands from phosphatic reworked Mount Laurel sands) (Fig. F6). We thus place the sequence boundary and the base of the Navesink Formation at 1032.9 ft (314.83 m). These glauconite sands and sandy clays were deposited in middle–outer neritic paleoenvironments.
The clayey glauconite sand of the Navesink Formation rests on a softer, mottled, extensively burrowed, lighter greenish gray glauconitic (20%–30%) chalky clay admixed (~50%) with darker gray clay burrow fill (1032.9–1034 ft; 314.83–315.16 m). Burrow fill decreases downsection (Fig. F6). Small dark grains (phosphate) are found in this section, along with small (<10 mm) dark concretions (burrows?); the phosphate yields a high gamma log signature. From 1034 to 1038 ft (315.16 to 316.38 m), a hard, light gray, heavily bioturbated glauconitic (10%–20% with zone up to 40% in burrows) marl (calcareous clay) with scattered dark grains (?phosphate) is present. The section becomes increasingly clayier downsection from 1038 to 1040 ft (316.38 to 316.99 m), with some hard marly burrows extending down from the overlying unit. Shells become increasingly common below 1039 ft (316.69 m). Glauconite sand increases downsection from 20% to 50% in a gray, extensively burrowed silty clay (1040–1047.1 ft; 316.99–319.16 m). Clayey glauconite sand (1047.1–1049.7; 319.16–319.95 m) becomes clayier and more glauconitic downsection. Shell concentrations (1040.6–1040.7, 1041.7–1041.8, 1042.3–1043.0, 1044.5, 1046.7–1046.8, and 1047.6–1048.0 ft; 317.17–317.21, 317.51–317.54, 317.69–317.91, 318.36, 319.03–319.06, and 319.31–319.43 m) may mark flooding surfaces; a gamma log kick at 1049 ft (319.74 m) probably marks the MFS (Fig. F6). This clayey lithologic unit underlying the Navesink Formation at Millville differs from outcrop and other borehole sections that have quartz sand (Mount Laurel Formation) and/or sandy silt (Wenonah Formation) beneath the distinctive Navesink greensand. The finer-grained facies expressed at Millville reflect less of a deltaic influence along strike to the south. These shelly glauconite sands and sandy clays are interpreted to have been deposited in middle neritic paleoenvironments.
From 1049.7 to 1058 ft (319.95 to 322.48 m), a very clayey, silty, fine to very fine glauconite sand with thin shell fragments is present; glauconite sand equals or slightly exceeds the amount of clay at 1049.7 ft (319.95 m), marking the top of the Marshalltown Formation (Fig. F6). Glauconite is highest and quartz sand is lowest at ~1055 ft (321.56 m). From 1058 to 1059.5 ft (322.48 to 322.94 m), there is an increasing amount of quartz sand and a color change from darker green above to yellow green below, in part reflecting the higher amounts of quartz sand, reworked glauconite, and weathering by groundwater from the underlying Englishtown Formation. The Marshalltown Formation is interpreted to have been deposited in middle–outer neritic paleoenvironments.
A clear change in lithology occurs at 1059.5 ft (322.94 m) in association with a gamma ray decrease and a sequence boundary separating the Marshalltown Formation above from the upper Englishtown Formation below (Fig. F6). The top of the Englishtown Formation (1059.5–1077.5 ft; 322.94–328.42 m) is a heavily burrowed, very fine to fine-grained quartz sand with scattered shells. Large thick oyster shells are present at 1065.6, 1071.4, 1073.05, and 1076.3 ft (324.79, 326.56, 327.07, and 328.06 m); thinner shells are present from 1080 to 1086 ft (329.18 to 331.01 m). There is an indurated zone from 1065.6 to 1065.7 ft (324.79 to 324.83 m). Clay-lined, sand-filled burrows as thick as 1 cm are most abundant in the upper part of the formation. The sands have a mottled appearance due to bioturbation and patchy distribution of yellow- and orange-stained quartz grains. The sands were deposited in a lower shoreface environment, although common organic material suggests a deltaic influence. The sand becomes silty and slightly micaceous below 1077.5 ft (328.42 m), with abundant silt from 1080 to 1086.5 ft (329.18 to 331.17 m); medium sand decreases at this level. These slightly micaceous silty sands were deposited in distal lower shoreface and/or prodelta environments. Glauconite is largely absent in the upper sands, appears in trace amounts at 1070 ft (326.14 m), and increases to a few percent below 1080 ft (329.18 m). The finer-grained sediments below 1077.5 ft (328.42 m) comprise the lower HST of the upper Englishtown sequence. Glauconite increases at 1086 ft (331.01 m) to 30% in very silty fine sand immediately above a spectacular contact at 1086.85 ft (331.27 m) (Fig. F10); the glauconite-rich sand comprises the TST of the upper Englishtown sequence deposited in distal lower shoreface to offshore environments. The sequence boundary is associated with a minor gamma ray peak (Fig. F6). The contact has rip-up clasts of material from below and material from above burrowed down into the underlying fine to medium sand.
Heavily burrowed, silty, slightly micaceous fine to medium quartz sand with a trace to 1%–2% glauconite and scattered shells appears below the sequence boundary (1086.85 ft; 331.27 m) and continues to 1092.4 ft (332.96 m). The section becomes siltier and more micaceous below an indurated, slightly more glauconitic sand (1092.4–1092.6 ft; 332.96–333.02 m); very silty micaceous sand with thin-walled shells occurs from 1092.6 to 1096.5 ft (333.02 to 334.21 m). We interpret facies from 1086.85 to 1092.6 ft (331.27 to 333.02 m) as the HST of the Englishtown-Woodbury-Merchantville sequence; this section was deposited in a distal lower shoreface environment with a deltaic influence. The section becomes progressively indurated from 1096.5 to 1096.8 ft (334.21 to 334.30 m), becoming an indurated, burrowed, slightly glauconitic, slightly shelly "dirty" sand from 1096.8 to 1097.6 ft (334.30 to 334.55 m). Brown glauconite appears below this indurated zone. A thin, silty, fine sand (1097.6–1100 ft; 334.55–335.28 m) with clayey burrows and scattered shells becomes progressively siltier downsection in a gradual transition to the micaceous silty clays that mark the Woodbury Formation beginning at 1100 ft (335.28 m).
The Englishtown sand is rarely used as a water supply in Cumberland and Salem Counties and is considered a minor aquifer (Fig. F8). The limited supply potential of the Englishtown sands in this area is due to high percentages of clay and the dominance of fine sand. At Millville, the sands are relatively thick (90 ft; 27.43 m) and might have potential for limited water supply and aquifer recharge, although the sands are dominantly fine grained with a silty matrix.
Micaceous, heavily burrowed sandy silty clays appear at 1100 ft (335.28 m). This lithology also appears at 2.5 ft (0.76 m) in Core 149B (1090–1100 ft; 332.23–335.28 m); however, the top 9.8 ft (2.99 m) recovered in Core 146A (1090–1100 ft; 332.23–335.28 m) consists entirely of sands, suggesting that Core 149B is from the lower part of the drilled interval and the lithologic change is at ~1100 ft (335.28 m). A log increase at 1101 ft (335.58 m) also suggests that the transition to the Woodbury Formation is close to 1100 ft (335.28 m) (Fig. F6). The downsection change from the sands of the Englishtown to the clays of the Woodbury Formation is gradational: the section from 1100 to 1126 ft (335.28 to 343.20 m) consists of 60%–70% silty clay that we place in the Woodbury Formation, although consistently high (80%–98%) clay is not attained until 1130 ft (344.42 m).
The Woodbury Formation at Millville consists of dark greenish gray to greenish black burrowed, very micaceous, very sandy silty clay at the top that becomes progressively finer downsection (Fig. F6). The Woodbury Formation represents a classic prodelta deposit. The sand is very fine grained. Dark organic matter, scattered pyrite/marcasite nodules, small (<1 cm), very thin shell fragments, wood fragments, and clay laminae are scattered throughout. Sand decreases from 1110 to 1120 ft (338.33 to 341.38 m) to <20% and further decreases below 1140 ft (347.47 m) to <10%. Clay laminations are progressively preserved from 1128 to 1136 ft (343.81 to 346.25 m) as the unit fines downsection. The section at ~1140 ft (347.47 m) is the finest grained (slightly sandy, slightly silty clay), with silt increasing below this to a slightly sandy silty clay. Scattered very thin laminae of very fine sand appear below 1140 ft (347.47 m). The section from 1154.5 to 1164.7 ft (351.89 to 355.00 m) is finer grained very slightly silty clay. At 1170 ft (356.62 m), the section shifts back to silty clay and becomes clayier from 1180 to 1190 ft (359.66 to 362.71 m). From 1190 to 1192 ft (362.71 to 363.32 m) the core is coated with a dusting of gypsum crystals; foraminifers and shell fragments become common in the washed residues (up to 3.5%) from 1190 to 1221 ft (362.71 to 372.16 m). Slightly silty clays continue to 1210 ft (368.81 m). There is a very subtle change at 1196.9 ft (364.82 m) from very slightly glauconitic carbonate-rich silty clay above to carbonate-bearing, more micaceous silty clay below. At 1210 ft (368.81 m) there is a change from silty clay above to clay below; glauconite sand starts to increase at this level. Between 1210 and 1220 ft (368.81 and 371.86 m), the amount of glauconite in the core increases from 2%–3% at the top to nearly 50% at the bottom. This section is heavily burrowed (5 mm–1 cm diameter), with clay-lined burrows and high amounts of glauconite in sand-filled burrows (e.g., 1216.8 and 1217.7 ft; 370.88 and 371.15 m). Mica occurs in trace quantities throughout. The shift from fine-grained sediments above to glauconite sandy clay/clayey sand below is the contact with the Merchantville Formation, and the formational boundary is placed at 1219.9 ft (371.83 m).
The contact between the Woodbury and Merchantville Formations is a gradational one. In this borehole, the contact is identified at the place where the amount of glauconite in the core is ~50% (Fig. F6). The Merchantville Formation is a heavily bioturbated clayey to very clayey (~30%–50% clay) glauconite sand with traces of mica and quartz sand, scattered pyrite nodules, common clay-filled burrows, and rare to scattered shell debris. There are large shells at 1225.9 and 1231.1 ft (373.65 and 375.24 m).
There are subtle facies changes in the Merchantville Formation. Silvery gray glauconitic clay (1220 ft; 371.86 m) grades down to clayey glauconite sand (1222 ft; 372.47 m) to a surface at 1225.7 ft (373.59 m). From this level down to ~1228.4 ft (374.42 m) there is an overall increase in the amount of glauconite; there is a surface at 1228.4 ft (374.42 m) where glauconite decreases and the color changes from silvery gray to blue-gray. Glauconite increases downsection from 1228.4 to 1232 ft (374.42 to 375.51 m); the interval below this (1232.7–1234.3 ft; 375.73–376.21 m) has more clay, but this appears to be a drilling artifact. Glauconite sand (~60%) increases (Fig. F6) from 1234.3 to 1238.2 ft (376.21 to 377.40 m), where it shifts back to a clayey glauconite sand. The section is heavily burrowed. Shells are found at 1236.3, 1237, and 1238.1 ft (376.82, 377.04, and 377.37 m). A glauconite silty clay is present from 1238.2 to 1239.2 ft (377.40 to 377.71 m); there is a possible sequence boundary and facies shift at 1239.2 ft (377.71 m). Below this, the section is a mottled mixture of very muddy glauconite sand with reddish clay-filled burrows; the reddish clay reflects reworked soils. Muddy glauconite sand with reddish clay-lined burrows continues to 1246.25 ft (379.86 m); medium–coarse quartz sand with shell fragments and pyrite nodules is mixed in below 1240 ft (377.95 m). We interpret this lower 6 ft (1.83 m) as a TST; the surface at 1239.2 ft (377.71 m) may be an MFS or the Merchantville I/II sequence boundary of Miller et al. (2004).
The contact between the Merchantville and Cheesequake Formations occurs at 1246.25 ft (379.86 m), with fine to very fine silty glauconite sand above to slightly silty, slightly glauconitic (~3%) fine-grained quartz sand below (Fig. F6). The contact zone is burrowed with quartz granules and dark angular cemented fragments (siderite?). From 1245 ft (379.48 m) to the contact, there are scattered granules and shell fragments as large as 2 cm; this section is browner than above and reflects reworking of Cheesequake sediments into the overlying Merchantville Formation. The darker Merchantville lithology is burrowed down to 1247 ft (380.09 m).
The Cheesequake Formation is a cross-bedded to homogeneous lignitic glauconitic (few percent) fine- to medium-grained quartz sand with thin interbedded clays. There are thin shells throughout (Fig. F6). There is a facies shift at 1250–1251.4 ft (381.00–381.43 m) to a shelly, slightly muddy fine quartz sand with traces of mica that grades into a slightly micaceous, finer-grained muddy sand to 1254.4 ft (382.34 m). The environment of deposition of the Cheesequake Formation at Millville is interpreted as delta front.
A spectacular contact (Fig. F10) is present at 1254.4 ft (382.34 m), with darker muddy sand above (Cheesequake Formation) and a pinkish gray fine sand with lignite below (Magothy Formation) (Fig. F7). There are rip-up clasts (up to 4 mm) of the Magothy Formation from 1253.0 to 1254.0 ft (381.91 to 382.22 m). The light sand (1254.4–1256.6 ft; 382.34–383.01 m) ranges from very fine sand below the contact to fine and very fine sand at 1255–1256.6 ft (382.52–383.01 m). The sands contain sphaerosiderite nodules (1254.8–1255.2 ft; 382.46–382.52 m) with hematite rinds. A dark clay clast occurs at 1255.3 ft (382.62 m). The sands were deposited in an alluvial plain and may represent crevasse splay or levee subenvironments and incipient soil formation exemplified by sphaerosiderite. The underlying section consists of lignitic, pyritic silt (1256.6–1257.0 ft; 383.01–383.13 m), an irregular contact with rip-up clasts at 1257 ft (383.13 m), and white clay (1257–1257.9 ft; 383.13–383.41 m). The environment of deposition of the silts and clays was a subaqueous alluvial plain with a soil profile at the top.
Below an interval of no recovery (1257.0–1260 ft; 383.13–384.05 m), mottled white and red clays with red root zones were deposited as soils in an interfluvial mudplain environment. The mottled facies are typical of the Potomac Group and have not previously been reported from the Magothy Formation. The shift from the intense alternating wet–dry soil forming white and red clays below 1260 ft (384.05 m) to subaqueous silts and clays above 1257 ft (383.13 m), may reflect a sequence boundary or a shift in depositional systems from marginal to more proximal alluvial plain (Fig. F7).
From 1260 to 1274.3 ft (384.05 to 388.41 m), a mottled red, dusky red, and white silty clay with rootlike traces (up to 2–3 cm) and drab halos is present; these clays are soils deposited in highly weathered, well-drained alluvial plain. An irregular contact at 1274.3 ft (388.41 m) may be a soil surface or a sequence boundary (Fig. F7). Root traces near the bottom of this interval are smaller (a few millimeters). Sphaerosiderite appears at 1272 ft (388.32 m) and becomes common at 1273–1274.3 ft (388.01–391.24 m). Light gray silty clay (1274.3–1283.6 ft; 391.24–391.24 m) changes downsection to a light gray, slightly clayey silty very fine sand and sandy silt (1283.6–1286.25 ft; 391.24–392.05 m) that becomes increasingly coarser with lignite fragments down to 1283.6 ft (391.24 m). Cracks and root traces are more common from 1274.3 to 1276 ft (388.41 to 388.92 m). From 1283.6 to 1286.25 ft (391.24 to 392.05 m), the sand increases to a silty fine- to very fine grained sand with abundant lignite and pyrite nodules; lignite is ~25% of the volume from 1285 to 1286.25 ft (391.67 to 392.05 m). Clay rip-up clasts are found from 1286.1 to 1286.25 ft (392.00 to 392.05 m). Thus, from 1274.3 to 1286.25 ft (388.41 to 392.05 m), a fining upward succession from lignitic silty sand at the base to silty clay at the top represents deposition in an alluvial overbank environment and with a surface of soil formation at the top.
There is a contact at 1286.25 ft (392.05 m) with a light gray clayey silt below (1286.25–1292 ft; 392.05–393.80 m), also deposited in an alluvial overbank environment (Fig. F7). Slightly silty clay to clayey silt below the contact becomes increasingly dark, lignitic, and sandy down to 1292.3 ft (393.89 m). The surface at 1286.25 ft (392.05 m) is marked by some degree of soil formation (gleying) with subtle mottling and cracking down to 1289 ft (392.89 m). Thus, there are two upward-fining packages (1274.3–1285.25 and 1286.25–1292.2 ft; 388.41–391.74 and 392.05–393.86 m), probably with more weathering in the upper part of the cycles. The only sediment recovered from 1292.2 to 1300 ft (393.86 to 396.24 m) was a medium–coarse lignitic sandstone (1292.0–1292.2 ft; 393.80–393.86) that appears to be cemented (?hematite) Magothy lithology. Below the coring gap is another lignitic poorly sorted, poorly cemented fine to medium sandstone containing abundant pyrite and pyrite weathered to hematite between 1300 and 1300.2 ft (396.24 and 396.30 m). From 1300.2 to 1300.6 ft (396.30 to 396.42 m), a mixture of muddy fine-grained sand, silty clay, and lignite fragments is present. The silty clay may be rip-up clasts from below. At 1300.5 ft (396.39 m), a large (up to 3 cm diameter) iron-cemented concretion around a pyrite-cemented sand (2 cm), which might be a rip-up clast or burrow fill, is present. A contact at 1300.6 ft (396.42 m) is very abrupt.
Below the 1300.6 ft (396.42 m) contact is silty, shelly, micaceous (including chlorite) clay of the Bass River Formation (Fig. F7). Sandy silt-filled burrows are common at the top of the formation. There is a coring gap from 1301.7 to 1310 ft (396.76 to 399.29 m). Between 1312.5 and 1313 ft (400.05 and 400.20 m), the lithology grades down to slightly silty clay below and sandy filled burrows become less conspicuous. At 1318.4 ft (401.85 m), shells are more common; between 1318.5 and 1318.9 ft (401.88 and 402.00 m), a calcite-cemented shelly, slightly siltier and sandier interval is present. A whole ammonite shell occurs at 1319.4 ft (402.15 m). Below the sandier interval, the sediments return to shelly clay, slightly siltier than above with slight shell concentrations at 1320, 1320.7, 1320.9, 1323.1, 1323.7, and 1324.2 ft (402.34, 402.55, 402.61, 403.28, 403.46, and 403.62 m). This unit represents storm-dominated shallow shelf deposition (outer inner to middle neritic, near storm-wave base). A dark greenish black clay (1324.95–1325.25 ft; 403.84–403.94 m) may be more organic rich. From 1331.7 to 1332.4 ft (405.90–406.12 m), a shell hash in a slightly sandy (very fine), slightly clayey silt matrix is present.
Shelly, slightly silty to silty clay with traces of glauconite continues to 1340.4 ft (408.55 m). From 1340.4 to 1340.9 ft (408.55 to 408.71 m), a slightly indurated shell concentration/bed (including corals) is sandier and has less clay than above. There is a contact at 1340.9 ft (408.71 m) with shelly, slightly clayey silty glauconitic fine-grained sand below that fines downsection to a slightly clayey sandy silt with common small shells and shell fragments (1340.9–1342.55 ft; 408.71–409.21 m). The contact at 1340.9 ft (408.71 m) may mark a sequence boundary, with an admixture of quartz and glauconite sand (1340.9–1342.55 ft; 408.71–409.21 m) in the HST below. Alternatively (and preferred), this surface is a MFS and there is a sequence boundary at an irregular contact at 1342.55 ft (409.21 m) (Fig. F10). The 1342.55-ft (409.21 m) contact has micaceous slightly glauconitic muddy sand above and very micaceous silty clay below (Fig. F7). Shelly sands are burrowed down from 1342.55 to 1343.1 ft (409.21 to 409.38 m), consistent with 1342.55 ft (409.21 m) as a sequence boundary. The sequence boundary separates the Bass River III sequence above from the Bass River II sequence below (Miller et al., 2004).
Very micaceous silty clay is found from 1342.55 to 1344 ft (409.21 to 409.65 m), with thin wispy micaceous silty sands to sandy silts (Fig. F7). The interval 1344–1348.1 ft (409.65–410.90 m) is very micaceous and alternates between very micaceous clay and subordinate wispy beds of very micaceous slightly sandy silt and shell concentrations. Scattered burrows are present at 1346.5, 1346.7, and 1347.2 ft (410.41, 410.47, and 410.63 m). There is a coring gap (1348.1–1350 ft; 410.90–411.48 m) with silty micaceous clay (1350–1351 ft; 411.48–411.78 m) below with less mica and sand. From 1351 to 1360 ft (411.78 to 414.53 m), the section consists of micaceous very silty clay with pyritic burrows and scattered small shells and small shell debris. The section becomes sandier at 1360–1360.3 ft (414.53–414.62 m) with a clayey sandy silt with fine glauconite sand, mica, and shell debris. From 1360.3 to 1360.75 ft (414.62 to 414.76 m), the section becomes more indurated micaceous glauconitic sandy silt with carbonate fossils. There is a contact at 1360.75 ft (414.76 m) where the lithology changes below to slightly micaceous silty clay. There is little irregularity across the contact and little evidence of reworking, and we interpret it as a flooding (probably MFS) surface (Fig. F7).
From 1360.75 to 1365.95 ft (414.76 to 416.34 m), slightly micaceous silty clay contains subordinate wispy silty laminated beds (1–2 cm), small shell fragments, and sulfur-rich burrows altered from pyrite. From 1365.5 to 1365.95 ft (416.20 to 416.34 m), the lithology becomes sandier, shellier, and more glauconitic. Below a coring gap (1365.95–1370 ft; 416.34–417.58 m), a micaceous shelly sandy slightly clayey silt (1370–1371.7 ft; 417.58–418.09 m) with glauconite dominating the sand fraction (~25% of total) is present (Fig. F7). From 1371.7 to 1372.9 ft (418.09 to 418.46 m), a more indurated (calcite cemented) silty glauconite-quartz sand with fewer shell fragments, more whole shells, and thin clay laminae is present. From 1372.9 to 1373.4 ft (418.46 to 418.61 m), the shelly silty glauconite-quartz sand continues, although it is not as indurated and clayier and contains clay laminae. From 1373.4 to 1373.7 ft (418.61 to 418.70 m), the section returns to an indurated dirty quartz-glauconite sand with abundant shells. From 1373.7 to 1374.4 ft (418.70 to 418.92 m), a slightly clayey, shelly, glauconite-quartz sand with decreasing shell debris downsection and scattered pyrite is present; this is a lag deposit. There is a sequence boundary at 1374.4 ft (418.92 m) associated with a facies shift from glauconite-quartz sand above to a very sandy silty clay below and a major gamma log increase. The contact is irregular with the lag deposit above and heavy burrows continuing down to 1375.0 ft (419.10 m). The sequence boundary separates the Bass River II sequence above from the Bass River I sequence below (Miller et al., 2004).
The lower part of the Bass River Formation (1374.4–1422 ft; 418.92–433.43 m) is generally sandier than above (Fig. F7). Sandier intervals alternate with finer-grained intervals, perhaps reflecting thin parasequences that are also visible on the gamma log (Fig. F7). Most of the section was deposited in inner–middle neritic environments near or just below storm-wave base, although some of the sandier units may have been deposited in a lower shoreface environment. The interval 1374.4–1376.1 ft (418.92–419.44 m) consists of a slightly micaceous, very sandy silty clay with abundant glauconite-quartz sand and shell debris. An indurated shelly glauconite-quartz sand (1376.1–1376.9 ft; 419.44–419.68 m) contains mainly whole and some articulated bivalve shells (to 2 cm diameter). A shelly very sandy clay to clayey silty glauconitic quartz sand (1376.9–1377.4 ft; 419.68–419.83 m) with common shell fragments overlies a very micaceous clayey slightly glauconitic sandy silt (1377.4–1379 ft; 419.83–420.32 m) with very fine sand and shell fragments. Very micaceous silty very fine to fine quartz sand (1380–1380.5 ft; 420.62–420.78 m) is muddy at the top and clean at the bottom. Very sandy micaceous silty clay (1380.5–1387.75 ft; 420.78–422.99 m) with scattered shells, pyrite/sulfur-filled burrows, and small shell fragments become slightly less micaceous below a coring gap (1387.75–1390 ft; 422.99–423.67 m). The interval 1390–1394 ft (423.67–424.89 m) is a sandy slightly micaceous silty clay. From 1394 to 1394.4 ft (424.89 to 425.01 m), there is a micaceous glauconitic siltstone with abundant sand-sized shell debris. This lithology is present from 1400 to 1400.65 ft (426.72 to 426.92 m), sandwiched between coring gaps (1394.4–1400 and 1400.65–1410 ft; 425.01–426.72 and 426.92–429.77 m). From 1410 to 1412.3 ft (429.77 to 430.47 m), a micaceous silt with some very fine sand and thin shells is underlain by an intensely bioturbated silty glauconite sand (1412.3–1414.2 ft; 430.47–431.05 m) that contains large shells and a concretion. Burrowed to laminated very micaceous, slightly clayey silty very fine sand is found from 1414.2 to 1416.35 ft (431.05 to 431.70 m), with common small shell fragments and burrows disrupting laminae. There is a pyritic burrow at 1416 ft (431.60 m) and a shell concentration at 1416.15–1416.35 ft (431.64–431.70 m). The facies from 1414.2 to 1416.35 ft (431.05 to 431.70 m) was probably deposited in a lower shoreface environment, although a lower estuarine environment cannot be excluded. The facies shift at 1414.2 ft (431.05 m) could be a sequence boundary, and there is a minor gamma kick at this level. There is a facies shift at 1416.35 ft (431.70 m) to a slightly silty, slightly micaceous dense clay (1416.35–1416.8 ft; 431.70–431.84) with common small shell fragments. There is a coring gap (1416.8–1420 ft; 431.84–432.82 m) and an interesting interval from 1420 to 1422.1 ft (432.82 to 433.46 m). From 1420 to 1420.5 ft (432.82 to 432.97 m) a lignitic silty clay is present. From 1420.5 to 1421.9 ft (432.97 to 433.40 m) is silty clay with scattered shell fragments. Glauconite appears at 1420.5 ft (432.97 m) and increases downsection to a few percent at 1421.9 ft (433.40 m). Lignite is common at 1421.8 ft (433.36 m). The section from 1421 to 1421.9 ft (433.12 to 433.40 m) is burrowed with reddish clay in the burrows. The environment of deposition of the section from 1420 to 1421.9 ft (432.82 to 433.40 m) is probably shallow marine influenced by a terrestrial source of lignite (delta?). From 1421.9 to 1422.1 ft (433.40 to 433.16 m) is a thin iron-cemented dirty sand with lignite fragments. A sequence boundary marking the contact with the Potomac Formation is present at 1421.9 ft (433.40 m), separating the indurated sand below from the shelly glauconitic silty clay above.
The nonmarine Potomac Formation was encountered at 1421.9 ft (433.40 m) (Fig. F7). The top of the formation (1421.9–1450.2 ft; 433.40–442.02 m) is mostly gray clay with minor mottling, some lamination/banding and scattered pyrite, occasional microsphaerosiderite, and plant debris/charcoal. There are alternations between darker gray silty clays and lighter gray silty clays and very fine sands, reflecting changes between unaltered alluvial plain/swamp deposits and immature (gleyed) paleosols.
A slightly lignitic gray silty clay (1422.0–1422.2 ft; 433.43–433.49 m) is sulfur rich in the lower part and overlies a lignite bed (1422.2–1422.25 ft; 433.49–433.50 m). From 1422.2 to 1423.0 ft (433.49 to 433.73 m) is a very stiff, very silty, very fine sand with abundant lignite fragments and small holes (?root casts) filled with clean quartz sand. This upper interval was deposited in a swamp. From 1423 to 1425.6 ft (433.73 to 434.52 m) is a succession of silty, slightly sandy clay that transitions from very sandy at the top to silty clay to a thin (0.1 ft; 3 cm) lignite bed at the base; the color changes from medium light gray to dark gray at the bottom with a corresponding increase in lignite. This succession was deposited in an overbank/swamp environment with an incipient soil at the top. The next succession (1425.6–1426.6 ft; 434.52–434.83 m) ranges from a light gray silty clay at the top to a slightly silty light gray sand at the bottom, yielding a typical upward-fining overbank succession. From 1426.6 to 1427.6 ft (434.83 to 435.13 m), the core consists of dark gray sandy silty clay with small root fills and sandy cross lamination. From 1427.6 to 1433.5 ft (435.16 to 436.93 m), the core consists of slightly sandy light gray clay that darkens downsection with remnants of plant debris. Sphaerosiderite is found from 1430.4 to 1431.2 ft (435.99 to 436.23 m). The section from 1433.5 to 1435 ft (436.93 to 437.39 m) is similar in lithology although darker in color.
A more significant paleosol from 1435 to 1442.6 ft (437.39 to 439.72 m) consists of a hard light gray to medium gray to olive-colored silt with some banding, mottling, and soil cracks; this section has been subjected to significant soil formation, mostly through gleying. Sphaerosiderite is found from 1442.0 to 1442.5 ft (439.52 to 439.67 m). Below a coring gap (1442.6–1450 ft; 439.72–441.96 m), there is a dark gray laminated slightly silty clay (1450.0–1450.25 ft; 441.96–442.04 m). A silty, very fine sand (1450.25–1451.3 ft; 442.04–442.36 m) has a pock-mocked appearance due to rooting on the upper surface; the upper part of this interval has sphaerosiderite that decreases downsection. From 1451.3 to 1454.3 ft (442.36 to 443.27 m) is an interval of clayey silt/silty clay that changes from light gray at the top to medium gray, more carbonaceous, and sulfur bearing at the bottom. The intervals 1452.0–1452.15 ft (442.57–442.62 m) and 1452.7–1452.9 ft (442.78–442.84 m) contain sphaerosiderite. From 1460 to 1462.2 ft (445.01 to 445.68 m), a dark gray clay with scattered sulfur blooms and iron concretions is present; there is a concretion at 1462.1–1462.2 ft (445.65–445.68 m). Below a coring gap (1462.2–1470 ft; 445.68–448.06 m), the section from 1470 to 1475 ft (448.06 to 449.58 m) consists of a dark gray slightly sandy clayey silt at the top that transitions to a dark gray silty clay at the bottom. The upper 1 ft (1470–1471 ft; 449.58–448.36 m) includes mica, small lignite fragments, pyrite, and sand-filled root holes. From 1475.0 to 1481.05 ft (449.58 to 451.42 m) is a micaceous fine to very fine sand; the grains have a rusty coating and there is scattered lignitic debris in the sand. The interval 1481.05 to 1481.5 ft (451.42 to 451.56 m) is dark gray sandy lignitic clay with iron concretions. From 1481.5 to 1482.9 ft (451.56 to 451.99 m) is a slightly sandy, slightly clayey silt with microsphaerosiderite. From 1482.9 to 1483.0 ft (451.99 to 452.02 m) is a sliver of clay. Below a coring gap (1483.0–1490.0 ft; 452.02–454.15 m), the section from 1490 to 1491.2 ft (454.15 to 454.52 m) is a silty, very fine sand with pockmarks suggesting rooting. It is possible that this sand correlates with the sand at the base of Potomac sequence III at Fort Mott (Chap. 4, this volume) (Fig. F7).
The interval 1491.2 to 1492.35 ft (454.52 to 454.87 m) is light medium gray, slightly clayey, slightly sandy silt with scattered lignite fragments and pyrite. A lignitic sandy silt (1492.35–1493.1 ft; 454.87–454.10 m) overlies a large lignite chunk at the base. From 1493.1 to 1495.5 ft (454.10 to 455.83 m; TD), the core consists of a mottled dark gray to reddish gray silty clay with scattered lignite.
Pollen from the very bottom of the core (1495.5 ft; 455.83 m) was assigned to the Zone III/IIC boundary (Table T9). In the Fort Mott borehole, Potomac Unit 3 is 222.5 ft (68.58 m) thick (Chap. 4, this volume). The Potomac Unit 3 should be thicker in the downdip Millville borehole than at Fort Mott. We thus favor the Zone III assignment and interpret the entire Potomac Formation in this borehole as Unit 3.
