LITHOSTRATIGRAPHY

Summary

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 (see "Visual Core Descriptions" for core images; Table T1; Figs. F2, F3, F4, F5, F6, F7, F8). Subsequent studies integrated preliminary descriptions with additional descriptions, biostratigraphy, biofacies studies, isotopic stratigraphy, and the gamma-ray log. 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. For the nonmarine and nearshore sections (primarily the Miocene and younger section), lithofacies interpretations provide the primary means of recognizing unconformities and interpreting paleoenvironments. For the neritic sections (primarily the Paleogene and Upper Cretaceous), 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 Ancora borehole.

Lithofacies changes within onshore sequences, particularly Upper Cretaceous sections, generally follow repetitive transgressive-regressive patterns (Sugarman et al., 1993, 1995) that consist of (1) a basal transgressive glauconite sand equivalent to the transgressive systems tract (TST) of Posamentier et al. (1988) and (2) a coarsening-upward succession of regressive medial silts and upper quartz sands equivalent to the HST of Posamentier et al. (1988). Lowstand systems tracts (LSTs) are usually absent in the coastal plain and the TSTs are generally thin. Because the TSTs are thin, maximum flooding surfaces (MFSs) are difficult to differentiate from unconformities. Both can be marked by shell beds and gamma-ray peaks. Flooding surfaces, particularly MFSs, may be differentiated from sequence boundaries by the association of erosion and rip-up clasts at the latter, lithofacies successions, and benthic foraminifer changes. The transgressive surface (TS) marking the top of a LST represents a change from generally regressive to transgressive facies; because LSTs are generally absent, these surfaces are generally merged with the sequence boundaries. Notable exceptions include the base of the Navesink Formation at outcrop (Miller et al., 1999) and the lower Marshalltown sequence described here.

Benthic foraminifer biofacies were used to recognize inner neritic (0-30 m), middle neritic (30-100 m), outer neritic (100-200 m), and upper bathyal (200-600 m) paleodepths. Cumulative percent plots of the sediments in the cores were computed from samples washed for paleontological analysis. 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 Sites), in which the samples were not dried before washing.

Surficial Deposits

Age: ?Pleistocene

Interval: 0.5-9.0 ft (0.15-2.74 m)

Gravels and sands were encountered from just below the soil horizon (0.5 ft [0.15 m] in a hand auger sample) to 9.0 ft (2.74 m), below which is a red clayey quartz sand. The gravels typically consist of rounded quartz pebbles up to 2 cm long. Sporadic chert fragments were noted. The age and lithologic assignment of this surficial unit are uncertain. Field studies of outcrops ~1 mi (1.61 km) north of the drill site (W. Newell, pers. comm., 1998) suggest that these surficial sediments are Bridgeton Formation (upper Miocene) gravels that were reworked by glacial Pleistocene streams.

Cohansey Formation

Age: ?early-?middle Miocene

Interval: 9.0-167.9 ft (2.74-51.18 m)

Red, yellow red, and yellowish to reddish brown quartz sands containing indurated zones up to 0.5 ft (0.15 m) thick occur between 9 and 29.25 ft (2.74-8.92 m). These variegated sands vary from fine- to very coarse-grained and have few opaque minerals. Obvious cross-bedding begins at 26 ft (7.92 m). Possible burrowing begins at 27 ft (8.23 m). The lithologic assignment of this variegated unit is uncertain; we tentatively place it in the Cohansey Formation. The environment of deposition is also unclear, and the upper part of the section may be fluvial. Bioturbation below 27 ft (8.23 m) may indicate shallow marine/nearshore deposition. The contact between indurated reddish gravelly sands above 29.25 ft (8.92 m) and yellow gravelly quartz sands below may merely reflect a diagenetic horizon.

Definite Cohansey Formation quartz sands appear at 29.25 ft (8.92 m) and continue to 167.9 ft (51.18 m). The lithology varies from fine to very coarse sand, with laminae of kaolinitic clays. Bedding is predominantly massive with occasional clay drapes; drapes are more common from ~38 to 90 ft (11.6-27.4 m). Coarsening-upward cycles are observed in the intervals 29.25-37, ~37-50, 50-70, 70-90, and 90-112 ft (8.92-11.28, 11.3-15.24, 15.24-21.34, 21.34-27.43, and 27.43-34.14 m). These cycles are also seen on the gamma-ray log (Fig. F2), although the coarse-fraction data show a generally fining-upward pattern from ~50 to 110 ft (15.24-33.53 m; Fig. F2). Medium-coarse sands predominate from ~112 to 145 ft (34.14-44.2 m), with interfingering organic-rich silts and sands at 138.0-138.5 ft (42.06-42.21 m). At 145.35 ft (44.3 m) there is a shift from fine and medium sands above to gravelly coarse sands below. Below this interval and down to 150.2 ft (45.78 m) are red to brownish yellow fine to coarse quartz sands with occasional pebbles; intercalations of medium and medium-coarse sands with clay laminations continue to the base of the Cohansey Formation (167.9 ft [51.18 m]). Cross-beds occur in the basal 3 ft (0.91 m). The quartz sands from 29.25 to 167.9 ft (8.92-51.18 m) were deposited in nearshore (beach, shoreface, and offshore sand ridge) environments. The absence of shell and calcareous plankton precludes the use of Sr isotopic or biostratigraphic ages for this unit.

Kirkwood Formation

Age: early middle to middle Miocene

Interval: 167.90-263.65 ft (51.18-80.36 m)

The Kirkwood Formation is distinguished from the Cohansey Formation at Ancora by its generally finer grain size, color (gray vs. yellow and variegated), and bedding (massive vs. massive and cross-bedded). It was deposited in (inner-middle?) neritic, prodelta, and delta-front environments. We tentatively recognize two Kirkwood sequences at Ancora (167.90-227.27 and 227.27-263.70 ft [51.18-69.27 and 69.27-80.38 m]). Based on Sr isotopic age estimates, the lower sequence correlates with the Kw1a sequence of Sugarman et al. (1993); based on superposition, the upper sequence may correlate with the Kw1b Sequence of Sugarman et al. (1993).

The top of the Kirkwood Formation (167.9-199.1 ft [51.18-60.69 m]) consists of a gray, massive, slightly micaceous, peaty, fine- to medium-grained quartz sand that fines downsection to a silty, very fine to fine sand. The coarsening reflects a shallowing upsection. We tentatively interpret these bioturbated, peaty sands as delta-front deposits. Kirkwood Formation silty clays begin at 199.1 ft (60.69 m) with a gradational contact. Laminated, occasionally lignitic, silty clays to clays containing shell impressions and shell debris were probably deposited in a prodelta environment (199.1-217.4 ft [60.69-66.26 m]). More massive (?burrowed) silty clays alternate with laminated silty clays between 220 and 226.2 ft (67.06 and 68.95 m). There is a probable sequence boundary at 227.2 ft (69.25 m), at the base of a prodelta clay that is associated with a sharp increase in gamma ray-log values (Fig. F2).

The section below the possible sequence boundary at 227.2 ft (69.25 m) shows a distinct shallowing-upward succession from neritic to delta-front environments:

1. Intensely micaceous, woody, cross-bedded silts (227.2-232.0 ft [69.25-70.71 m]) may indicate delta-front environments; on fresh exposure these sediments are dark gray, but they weather to yellowish brown.
2. Grayish brown ("milk chocolate") micaceous, laminated, woody clayey silts (232-238 ft [70.71-72.54 m]) are typical of a prodelta environment.
3. Silty, shelly, massive, slightly micaceous, very fine-grained quartz sands (238.0-262.7 ft [72.54-80.07 m]) were deposited in shelfal (probably inner neritic) environments. Benthic foraminifers indicate inner neritic paleodepths at 246 ft (74.98 m; Nonionellina pizzarensis fauna), and possibly middle neritic paleodepths at 261 ft (79.55 m; Buliminella fauna; see "Biostratigraphy"). The upsection facies shift is typical of Kirkwood sequences (Sugarman et al., 1993; Miller et al., 1997), reflecting a shallowing-upward succession from shelf to deep prodelta clay to delta front.

The base of the Kirkwood Formation at Ancora is a spectacular sequence boundary with a reworked lag zone (262.7-263.7 ft [80.07-80.38 m]), sharp gamma ray-log increase, and a basal phosphorite bed (263.7 ft [80.38 m]) overlying poorly sorted quartz sands of the Eocene Shark River Formation. Lowermost Miocene (Sequence Kw0) through uppermost Eocene strata are not represented at Ancora.

Shark River Formation

Middle to upper Eocene sands and clays (263.7-388.6 ft [80.38-118.45 m]) are assigned to the Shark River Formation. This formation is subdivided into an very sandy upper Toms River Member (Enright, 1969), an informal sandy upper Shark River Member, and a clayier lower Shark River Member (Miller et al., 1990).

Slightly shelly to shelly medium-grained quartz sands of the Toms River Member of the Shark River Formation appear below the unconformity at 263.7 ft (80.38 m; Fig. F3); this sandy unit is the HST of a sequence (263.7-359.8 ft [80.38-109.67 m]) that includes the upper Shark River Formation (Fig. F2). The dark greenish gray sands are massive with some evidence of burrowing, traces (<2%) of glauconite and brownish clay, occasional pebbles, shells, and rare to common foraminifers. The fairly uniform sands continue to 315.8 ft (96.26 m), thus providing a 50-ft (15.24 m) aquifer used by the Ancora hospital as a water supply. The section from 315.8 to 355.0 ft (96.26 to 108.20 m) generally coarsens upward (Fig. F3), with clayey medium-grained quartz sand (315.8-345.0 ft [96.26-105.16 m]) grading down to glauconitic clay at 345.0-359.8 ft (105.16-109.67 m).

Clays (345.0-359.8 ft [105.16 and 109.67 m]) comprise the lower part of the sequence between 263.7 and 359.8 ft (80.38-109.67 m). We interpret a lithologic contact at 359.8 ft (109.67 m) separating glauconitic clays above from glauconitic sandy clays below as a sequence boundary. The sequence from 263.7 to 359.8 ft (80.38-109.67 m) is probably equivalent to Sequence E9 of Browning et al. (1997a, 1997b), containing reworked middle Eocene foraminifers and in situ upper Eocene foraminifers (e.g., Globigerina praebulloides) and nannofossils.

A sequence between 359.8 and 388.6 ft (109.67-118.45 m) comprises most of the upper Shark River Formation. The upper part of this sequence is a HST (359.8-371.2 ft [109.67-110.64 m]) containing an admixture of glauconite and quartz sand, typical of HSTs of this age in New Jersey (Browning et al., 1997a, 1997b). Megafossils are common between 363.0 and 371.2 ft (110.64-113.14 m). The lower part of the sequence consists of glauconitic clay (371.2-388.6 ft [110.64 -118.45 m]). A distinct sequence boundary at 388.6 ft (118.45 m) separates glauconitic clay from the much brighter green clays of the underlying sequence. This sequence (359.8-388.6 ft [109.62-118.45 m]) is assigned to Zone NP16 (see "Biostratigraphy") and is, thus, equivalent to Sequence E8 of Browning et al. (1997a).

The top of the underlying sequence (388.6-427.6 ft [118.45-130.33 m]) consists of bioturbated, pale green, slightly sandy silty clay (lower Shark River Formation) that grades downsection to pale olive green clay (below ~410 ft [124.97 m]). Between 400 and 417 ft (121.92-127.10 m), the clay is slightly glauconitic, with glauconite increasing below 417 ft to a contact at 427.6 ft (130.33 m). Several 0.1- to 0.2-ft-thick (3-6 cm) indurated zones (porcellanites) occur from 427.0 to 427.9 ft (130.15-130.42 m). The bioturbated contact at 427.6 ft (130.33 m) separates very glauconitic porcellanitic clays from very slightly silty clays and is interpreted as a sequence boundary (E7/E6 of Browning et al., 1997a, 1997b).

Three thin cycles span the middle/lower Eocene boundary. These cycles consist of silty, pale olive clays grading down to glauconite-rich layers associated with gamma-ray peaks; the cycles are interpreted as sequences with sequence boundaries at the bases of the glauconite-rich layers:

1. A sequence from 427.6 to 443.0 ft (130.33-135.03 m) is assigned to Subzones NP15b-NP15a? and is, thus, correlative to Sequence E6 of Browning et al. (1997a, 1997b).
2. A sequence from 443.0 to 446.7 ft (135.03 -136.15m) is assigned to Subzone NP14a and is, thus, correlative to Sequence E5 of Browning et al. (1997a, 1997b).
3. A sequence from 446.7 to 448.7 ft (136.15-136.76 m) is assigned to Zone NP13 and Subzone NP14a and is, thus, correlative to Sequence E4 of Browning et al. (1997a, 1997b).

The contact at 448.7 ft (136.76 m) is a sequence boundary separating Sequence E4 from E3 of Browning et al. (1997a, 1997b).

The section from 388.6 to 448.7 ft (118.45-136.76 m) is assigned to the lower Shark River Formation (Fig. F3). In general, the Shark River Formation can be differentiated in fresh cores from the underlying Manasquan Formation by being less clay rich and darker green. However, grain size and color are not sufficient for differentiating these two formations in the field because both weather to "ash-colored marls" (Cook, 1868). We adopt the criteria of Enright (1969) and Owens et al. (1988) by placing the base of the Shark River Formation at a distinct glauconite bed (Browning et al., 1997a). This maintains the Manasquan Formation as primarily lower Eocene and the Shark River Formation as primarily middle Eocene.

Manasquan Formation

Immediately below the sequence boundary at 448.5 ft (136.70 m), there is a yellowish, weathered, ?kaolinitic clay (448.5-448.7 ft [136.7-136.76 m]). From 448.7 to 449.5 ft (136.76-137.01 m), glauconite is burrowed down from the sequence boundary above. Bioturbated, slightly glauconitic, fossiliferous, interbedded clays and silty clays extend to 451.6 ft (137.65 m); below this level, glauconite is less common and burrows are less visible. We interpret the glauconite as having been reworked into upper HST sands. Interbedded fossiliferous clay and silty clay grade downsection to clay at 458 ft (139.60 m). Glauconite and burrowing appear again at 459.8 ft (140.15 m) with increasing glauconite downsection to 461.2 ft (140.57 m), where there is an abrupt shift to very slightly glauconitic silty clay and a sharp gamma ray-log increase. This level is probably a sequence boundary separating Sequence E3 of Browning et al. (1997a) above from Sequence E2 below. However, there is ambiguity in the placement of the lower sequence boundary as a result of a coring gap between 462 and 470 ft (140.82-143.26 m). Nannofossils indicate that the section from 449 to 471 ft (136.86-143.56 m) is assigned to Zone NP12; Sequence E3 is contained entirely within this zone elsewhere in New Jersey (Browning et al., 1997a). This suggests either that there is contamination immediately below the coring gap or that the sequence boundary lies in, or just below, the coring gap.

Greenish gray silty clays extend from 461.2 ft to 517.4 ft (140.57-157.70 m). From 461.4 to 480.0 ft (140.63-146.30 m), these silty clays are slightly glauconitic. Below 480 ft (146.30 m) there are some finely laminated sections. The clay darkens and glauconite begins to increase below 496 ft (151.18 m). Glauconite increases in the silty clays from 517.4 to 519.2 ft (157.70-158.25 m). The sequence between 461.2 ft and 519.2 ft (140.57-158.25 m) correlates with Sequence E2 of Browning et al. (1997a).

A subtle sequence boundary is indicated by nannofossil biostratigraphy and a minor lithologic change at 519.2 ft (158.25 m). This level separates Subzone NP10d above (519 ft [158.25 m]) from NP10b below (519.9 ft [158.25 m]), with a glauconitic (~10%-20%) clay above and a very slightly glauconitic clay below that is associated with a gamma ray-log kick at about 518-519 ft (158.19-157.89 m). Clayey glauconite sand marks most of the sequence from 520.0 to 522.2 ft (158.50-159.17 m). Phosphorite pellets at 520.7 ft (158.71 m) probably mark the MFS and yield a sharp gamma-ray peak. A lithologic change associated with a sequence boundary occurs at 522.2 ft (159.17 m) from clayey glauconite sand above to a micaceous, very slightly glauconitic silty clay below. The sequence boundary shows a distinct irregular contact, with clay bioturbated ~0.5 ft (0.15 m) above and glauconite burrowed 0.5 ft (0.15 m) below. The sequence between 519.2 and 522.2 ft (158.25-159.17 m) correlates with Sequence E1 of Browning et al. (1997a).

The Manasquan Formation at Ancora displays larger lithologic variations than it does at Island Beach or Bass River, in part as a result from its more updip location. These lithologic and presumably attendant faunal variations should allow a finer evaluation of water depth and eustatic changes for this early Eocene "Greenhouse World."

Vincentown Formation

Age: late Paleocene

Interval: 522.2-604.5 ft (159.17-184.25 m)

The lithologic unit below the sequence boundary at 522.2 ft (159.17 m) is a dark greenish gray silty clay characterized by traces of mica and rare (<1%) to common (~5%) glauconite that continues to 543.4 ft (165.63 m). This unit is massive to laminated (laminae are alternating silt and clay) and contains sporadic shell material. Cross beds and possible lenticular beds are present. This lithologic unit is similar to the Vincentown equivalent at Island Beach (Miller et al., 1994b). At Island Beach, the Vincentown equivalent is sandy near the top, whereas at Bass River the unit is sandier below the CIE (Miller, Sugarman, Browning, et al., 1998). Although it is similar in color and grain size to the overlying Manasquan Formation, the Vincentown equivalent is differentiated at Ancora by its mica and cross-beds.

It appears that the Paleocene/Eocene contact is associated with the sequence boundary at 522.2 ft (159.17 m). Lower Eocene Subzone NP10a is extremely thin and found immediately above the 522.2 ft (159.17 m) disconformity (Sample 521.7 ft [159.01 m]), whereas the section immediately below (522.5 ft [159.26 m]) is assigned to upper Paleocene Subzone NP9b (see "Biostratigraphy").

We may have recovered the LPTM in an intriguing interval. Below slightly glauconitic, slightly micaceous laminated silty clay of the Vincentown equivalent (to 543.4 ft [165.63 m]), there is a section of clay that exhibits convoluted bedding, with mini-flame and mini-ball structures (543.5-545.5 ft [165.66-166.27 m]). Interbeds of clay and silty clay (550-560 ft [167.64-170.69 m]) have little mica, trace to 3% glauconite, abundant foraminifers (approaching a foraminifer clay), and unusual bedding; silty clay laminations in the clays show evidence of cross-bedding and possible rip-up clasts. Convoluted bedding (including flame structures) occurs again from 559.2 to 560.0 ft (170.44-170.69 m). Samples 545.5 and "560.15" ft (166.27 and "170.73" m; base of Core 89) contain Acarinina africana, a CIE species.³ This indicates that we have at least part of the LPTM represented at Ancora. There is a return to very slightly micaceous laminated silty clay (560-562 ft [170.69-171.30 m]). Based on lithologic correlations with Bass River and Clayton, it is likely that the CIE marking the LPTM occurs within the interval 561.5-562.5 ft (171.15-171.45 m), where there is an increase in glauconite and a decline in foraminifer preservation.

Glauconite increases downsection (562.1-570.0 ft [171.33-173.74 m]), bioturbation increases, bedding becomes more massive, and the lithology coarsens to glauconitic (up to 20%), micaceous, sandy, clayey silts. Benthic and planktonic foraminifers are rare. Covariance of quartz and glauconite sands indicates that the glauconite is reworked (Miller, Sugarman, Browning et al., 1998). The lithologic change from silty clay above to glauconitic clay below is associated with a sharp lithologic contact in Hole B at 562.1 ft (171.33 m); the contact is less distinct in Hole A at 563.7 ft (171.82 m), with glauconite burrowed up into the clays to 562.8 ft (171.54 m). Based on the sharp surface in Hole B, we tentatively identify the contact at 562.1 ft (171.33 m) as a sequence boundary (Fig. F4).

A classic transgressive-regressive sequence occurs between 562.1 and ~599 ft (171.33-182.58 m). Glauconitic, quartzose clays (562.1-566.0 ft [171.33-172.52 m]) with reworked glauconite constitute the upper HST; they grade downhole to micaceous silty clays (566-580 ft [172.52-176.78 m]). Slightly micaceous, silty clay comprises the lower HST. Glauconite increases in glauconitic clays from 589.0 to 595.5 ft (179.53-181.36 m), with an interval of nodules (?replaced shell) at 593.2 ft (180.81 m).

A clay interval at 596.8 ft (181.9 m) in Hole A appears to consist of replaced shell material (?siderite). In Hole B, shells of Gryphaea dissimilis are found with replaced shell material at 597.6 ft (182.15 m), suggesting either a 1-ft (0.30 m) offset or some relief on this shell bed.

Sequence boundaries are not readily observable in the lowermost Vincentown and Hornerstown Formations because the entire lower part of the Paleocene section is uniform clayey glauconite sands. Three tentative sequence boundaries (?599, ~606.5, and ~612.5 ft [?182.58, ~184.86, and ~186.69 m]) were inferred in the lowermost Vincentown and Hornerstown Formations based on biostratigraphic evidence (e.g., nannofossil Zones NP7 and NP2 and foraminifer Subzone P3a are missing, and Subzone P1b is less than 1 ft [0.30 m] thick), gamma ray-log kicks, and regional sequence stratigraphic relationships (e.g., the Zone NP7 hiatus is associated with a distinct sequence boundary at Island Beach; Miller et al., 1994b).

A sequence boundary is inferred between 597.5 ft (182.12 m; Zone NP8, with NP7 missing) and 600.0 ft (182.88 m; Subzone P4a), near a prominent gamma-ray peak/trough (596.5-600.0 ft [181.81-182.88 m]). This sequence boundary (?599 ft [?182.58 m] in Fig. F4) is indicated by regional relationships (i.e., Zone NP7 is missing in association with a clear erosional boundary; fig. 10D in Miller et al., 1994b), although lithologic evidence for a sequence boundary at Ancora is lacking. This sequence boundary separates Sequence Pa3 above from Pa2 of Liu et al. (1997a).

We use the criteria of Owens and Minard (1964) to place the contact between the Vincentown and Hornerstown Formations at the base of an Oleneothyris harleni shell bed (600.0-604.5 ft [182.88-184.25 m] in Hole A, 602.7-604.5 ft [183.70-184.25 m] in Hole B), where glauconite becomes subdominant. Alternatively, the formation boundary could be placed at a sequence boundary immediately below the O. harleni shell bed (Owens et al., 1997; see Liu et al. [1997a] for a discussion of the formation placement of similar green sands at Island Beach).

Hornerstown Formation

Age: early to earliest late Paleocene

Interval: 604.5-618.5 ft (184.25-188.52 m)

As noted above, the top of the Hornerstown Formation could be placed at 604.5 or 606.0 ft (184.25 or 184.71 m). Glauconite sands with clay burrows (600-610 ft [182.88-185.93 m] in Hole A) contain a shell bed (602.7-604.5 ft [183.7-184.25 m] in Hole A) including O. harleni. In Hole B, the shell bed occurs at 606.0-606.8 ft (184.71-184.95 m), thinner and ~2-3 ft (~0.60-0.91 m) lower than in Hole A, perhaps reflecting depositional relief. The shell beds appear to correlate with a gamma ray-log peak (604.5 ft [184.25 m] in Hole B; Fig. F4). Planktonic foraminifer biostratigraphy indicates that 600.4, 605.2-606.0, and 607.0 ft [183.00, 184.46-184.71, and 185.01 m] in Hole A correspond to Zones P4a, P3b, and P2 (see "Biostratigraphy"). The absence of Subzone P3a indicates a probable unconformity between 606 and 607 ft (184.71-185.01 m) in Hole A. There is no obvious physical break in either hole within the clayey sands.

Clayey glauconite sand continues below the inferred unconformity at ~606.5 ft (184.86 m) to another inferred unconformity at ~612.5 ft (~186.69 m). Subzone P1c (608.0-612.0 ft [185.32-186.54 m]) overlies a very thin Subzone P1b (Sample 613.0 ft [186.84 m]) that in turn overlies Subzone P1a (614.0-616.0 ft [187.15-187.76 m]; see "Biostratigraphy"). The thinness of Subzone P1b (which is absent at Bass River because of an unconformity; Miller, Sugarman, Browning, et al., 1998) indicates a break between either 612 and 613 ft or 613 and 614 ft (186.54-186.84 m or 186.84-187.15 m). A very subtle lithologic change at 612.5 ft (186.69 m) from slightly clayier glauconite sand above to slightly sandier glauconite sand below is 0.5 ft (0.15 m) below a major gamma ray-log kick (Fig. F4). The inferred sequence (606.5-612.5 ft [184.86-186.69 m]) is, thus, restricted to Subzone P1c. It shows an upsection increase of quartz sand in the coarse fraction (Fig. F4), consistent with an upsection change to a HST. In contrast, nannofossil studies indicate a hiatus between 617 and 615 ft (188.06-187.45 m), between Zones NP1 and NP3. Closer spaced samples are needed to verify the biostratigraphically inferred sequence boundaries and to resolve this discrepancy between foraminifer and nannofossil zonations in the lowermost Paleocene section.

Core 98 contains a change from glauconite sand (with occasional pyrite concretions) of the Hornerstown Formation (to 615.6 ft [187.63 m]) to clayey glauconite sand of the Navesink Formation (618.1 ft [188.40 m] and below). The intervening zone (615.6-618.1 ft [187.63-188.40 m]) is a bioturbated mixture of the two lithologies and is placed in the Hornerstown Formation. Sample 615.4 ft (187.57 m) is assigned to Subzone P1a.

Cretaceous/Tertiary Boundary in Hole A

Level: 618.5 ft (188.52 m)

Within Core 98, clay clasts are present at the top of the Navesink Formation at 618.1 ft (188.44 m), at the base of a bioturbated zone separating the Navesink from the Hornerstown Formation. A spherule layer is absent from Hole A. The clay clasts contain Cretaceous foraminifers; Heterohelix globulosa was observed protruding from the clay clasts. A similar clay-clast zone occurs at the K/T boundary at Parvin, New Jersey, and above the spherule layer at Bass River, New Jersey (Olsson et al., 1997). The clay clasts at the Bass River and Parvin boreholes yield numerous Cretaceous foraminifers, as is probably the case at Ancora judging by the readily observable foraminifers in the clasts. The origin of the clay clasts is probably from a deeper water bathymetric setting, judging from the clay lithology, which is not present at any of these boreholes in the underlying Cretaceous section, but is present in the more downdip Anchor Dickinson Gas #1 Well at Cape May (Petters, 1976). Cretaceous planktonic foraminifers are common to abundant and generally well preserved in the uppermost Maastrichtian interval from 618.10 to 618.95 ft (188.44-188.70 m).

Cretaceous/Tertiary Boundary in Hole B

Interval: 617.1-619.1 ft (188.09-188.70 m)

Two thin (2.6 cm total) layers occur toward the base of Core 9 at 617.1 ft (188.14 m) in Hole B. The upper layer is light gray, 1.1 cm thick, and consists of spherules (100-175 µm in diameter as well as some spherules up to 425 µm in diameter), grains of glauconite, and intermixed gray clay. Pyrite is present. The upper layer has a sharp upper boundary with the overlying sediments. The lower layer is 1.5 cm thick and is composed of fine-grained, rounded spherules. It has a sharp lower boundary. The spherule layer consists of a grayish tan interval comprised mostly of spherules (100-175 µm in diameter) with occasional glauconite grains and foraminifers (H. globulosa and Gavelinella). The presence of glauconite grains and foraminifers in both layers indicates that the original tektites were redeposited. The spherule layer is not continuous in the core as a result of its partial destruction by burrowing organisms. The interval below the spherule layer is intensely burrowed for at least 1 ft (0.30 m) and consists of a clayey glauconite sand. Hornerstown glauconite is seen in burrows for approximately another 0.7 ft (0.21 m) below this surface, before consistent Navesink lithology is encountered, thus blurring a definitive contact between the two formations. The contact is tentatively placed at an indistinct surface at 618.3 ft (188.51 m). Below 618.3 ft (188.51 m), Cretaceous planktonic foraminifers are abundant. The burrowed interval immediately above this level at 618.25 ft (188.49 m) contains numerous Cretaceous planktonic foraminifers that sharply diminish in number upward to 617.15 ft (188.16 m), where they become rare. Rarer Danian planktonic foraminifers are intermixed with the Cretaceous foraminifers. The Subzone P index species, Parvularugoglobigerina eugubina, occurs from 618.25 to 617.15 ft (188.49-188.16 m) below the spherule layer. The fragmentary occurrence of spherules between Subzones P and P1a in Hole B and their absence in Hole A are difficult to explain. The fact that they are redeposited suggests that they were derived from the K/T boundary tektite layer that was encountered in the Bass River borehole. Nearby exposure of the K/T tektite layer after deposition of Subzone P sediments at Ancora could have been facilitated by the relatively thin cover (~1.0 ft [0.30 m]) of sediments. Redeposition might indicate a hiatus between Subzones P and P1a.

Navesink Formation

Age: Maastrichtian

Interval: 618.3-651.3 ft (188.51-198.52 m)

Clayey glauconite sands to glauconitic clays of the Navesink Formation (Fig. F4) are found from 618.3 to 651.3 ft (188.51-198.52 m). The Red Bank Formation is not found in this area; the Navesink Formation represents the latest Cretaceous Period at Ancora. The lithology between 618.3 and 646.0 ft (188.51-196.9 m) consists of massive, clayey, burrowed glauconite sand to massive, glauconitic clays. This interval is slightly micaceous with shell fragments observed throughout. The carbonate content of the sand-sized fraction increases downsection below ~641 ft (~195.38 m), and the section below 647 ft (197.21 m) is light gray foraminifer glauconitic clay. We place the MFS at 646-647 ft (196.90-197.21 m), at the top of the carbonate-rich interval. Quartz sand is present in trace amounts above 646 ft (196.90 m), becomes common below 646 ft (196.90 m), and increases downsection to the Navesink/Mount Laurel contact at 651.3 ft (198.52 m). The increase in quartz sand below ~646 (~196.90 m) ft is consistent with deepening upsection in the TST. Sr isotopic analyses indicate that the Navesink Formation at Ancora is upper Maastrichtian (67.3 and 68.3 Ma at 645.0 and 649.2 ft [196.60 and 197.88 m], respectively).

Mount Laurel Formation

Age: late Campanian

Interval: 651.3-718.0 ft (198.52-218.85 m)

The Mount Laurel Formation (Fig. F5) extends from 651.3 to 714.9 ft (198.52-217.90 m). There is a burrowed contact between the Navesink and the Mount Laurel Formation. A bed of phosphate pebbles occurs between 650.7 and 650.9 ft (198.33-198.39 m) with phosphate pebbles up to 2 cm in diameter. Between 650.9 and 651.7 ft (198.39-198.64 m), there is a contact zone containing both Mount Laurel and Navesink Formation lithology. The sandier Mount Laurel lithology becomes dominant below 651.3 ft (198.52 m), where the lithology consists of pale olive, slightly clayey, glauconitic (~20%) fine- to medium-grained quartz sand, with ovoid phosphate grains throughout. A shell bed occurs at 681.0-682.0 ft (207.57-207.87 m). The Mount Laurel Formation generally fines downsection. From 690 to 695 ft (210.31-211.84 m), the quartz sand gradually becomes fine to very fine grained, and by 718 ft (218.85 m) the lithology consists mainly of dark greenish gray, (very fine) sandy, slightly micaceous, glauconitic (10%-15%) silts. Large shell fragments are observed at 712.4, 713.4, 715.1, 716.0, and 718.2 ft (217.14, 217.44, 217.96, 218.24, and 218.91 m). Sr isotopic analyses indicate that the Mount Laurel Formation is upper Campanian, with age estimates generally ranging from ~71 to 73.3 Ma (Fig. F5; Table T2). Age estimates for this unit correlate well with those from other boreholes and outcrops (Sugarman et al., 1995). Using an age of 71.3 Ma for the Campanian/Maastrichtian boundary (Gradstein et al., 1995), the uppermost Mount Laurel age estimate of 71.1 ± 1 Ma could be either earliest Maastrichtian or latest Campanian.

Wenonah Formation

The contact between the Mount Laurel and the Wenonah Formations (Fig. F5) is gradational, extending from 714.1 to 718.0 ft (217.66-218.85 m), with silty clay and mica increasing downsection in the transitional interval. The base of the Mount Laurel Formation is arbitrarily placed at the base of the transitional interval. Below the transition, the lithology consists of slightly glauconitic, micaceous, woody, clayey silty sand to sandy clayey silts. Shell fragments are observed throughout the formation. Glauconite increases downsection to >20% below ~735 ft (224.03 m).

Marshalltown Formation

Age: late Campanian

Interval: 742.0-757.2 ft (226.16-230.79 m)

The contact between the Wenonah and the Marshalltown Formations (Fig. F5) is gradational, occurring within the interval 730-742 ft (222.50-226.16 m). The lithology consists of very dark gray to very dark olive-gray, micaceous, glauconitic (<20%) clays. Glauconite increases downsection, becoming a shelly, pyritic glauconite sand (750-752 ft [228.60-229.21 m]). A peak in carbonate at 746 ft (227.38 m) may represent the MFS (Fig. F5). There is a sharp facies contact at 752 ft (229.21 m) in Hole A, with a shelly, micaceous glauconitic clay below that continuing down to the contact with the Englishtown Formation at 757.2 ft (230.79 m). Inoceramids and oyster shells occur in the basal Marshalltown Formation.

Burrowed clayey glauconite sand typical of the Marshalltown Formation is found down to 752.7 ft (229.42 m) in Hole B. At 752.7 ft (229.42 m), there is sharp facies change equivalent to that at 752 ft (229.21 m) in Hole A. This contact of glauconite sand above and glauconitic clay below could be interpreted as the MFS or TS. This occasionally lignitic lithology continues to 756.9 ft (230.70 m). Between 756.9 and 758.4 ft (230.79-231.16 m) the glauconitic clay lithology is reworked into the glauconitic micaceous, slightly lignitic quartz sand of the Englishtown Formation. We place the Marshalltown/Englishtown contact at 757.4 ft (230.86 m). Based on the overall lithologic change to glauconite above that is typical of TSTs, we interpret the 752.7-ft (229.42 m) surface as reflecting a TS and the basal 4.7 ft (1.43 m) as the LST. This is supported by the presence of common quartz and three-colored reworked glauconite (dark green, light green, and tan) in this lower unit. Alternatively, this basal unit may represent a thin sequence that was not previously recognized.

Upper Englishtown Formation

Age: Campanian

Interval: 757.2-792.3 ft (230.79-241.49 m)

Slightly clayey quartz sands assigned to the Englishtown Formation (Fig. F5) appear at 757.2 ft (230.79 m). The sands are greenish gray, fine-medium grained, and grains are subangular to rounded. The Marshalltown/Englishtown contact is similar in Hole B. The difference in the depth of the sequence boundary contact in the A and B holes is less than 2 ft (0.61 m), suggesting that the vertical deviation is <0.5° and the offset is <10 ft (30.5 m) at this depth.

The upper Englishtown Formation at Ancora is a sequence recording a coarsening- and shallowing-upward succession. Unconsolidated, poorly sorted, lignitic, fine- to medium-grained quartz sand with reworked glauconite sand at the top (758.1-765.2 ft [231.07-233.23 m]) grades downward to shelly, slightly sandy, micaceous silts (770.0-780.0 ft [234.70-237.74 m]). These sands comprise an aquifer. Heavy minerals are conspicuous in washed residues of the sand: Sample 760.5 ft (231.80 m) contains zircon, rutile, garnet, tourmaline, in addition to quartz, ironstone fragments (iron-cemented silt and very fine-grained sand), lignite, and traces of mica. The micaceous silts contain shell material (including corals) and are generally laminated below 777 ft (236.83 m) (often with thin micaceous sand cross-laminae). Between 780.0 and 788.3 ft (237.74-240.27 m), mica and lignite become especially abundant. The lignitic sands were deposited on a shallow shelf (probably nearshore bars), whereas the silts represent deeper water deposition (probably inner-middle neritic or prodelta).

At 788.3 ft (240.27 m), there is an abrupt facies change to a burrowed glauconite-rich silty clay, with a less glauconite-rich silty clay below 789.5 ft (240.64 m). This interval (788.3-789.5 ft [240.27-240.64 m]) is interpreted as the condensed section, with a MFS at 789.5 ft (240.65 m). Glauconitic silty clay continues down to 792.3 ft (241.49 m). A probable sequence boundary occurs at 792.3 ft (241.49 m), separating glauconitic silty clay above from shelly, micaceous, glauconitic, quartzose silty sand below. The sequence boundary is associated with a clear lithologic change and a minor gamma ray-log kick (Fig. F5), although the contact is not as obvious as others at Ancora (note that the coeval sequence boundary at Bass River has a distinct cemented zone). Thus, the upper Englishtown Formation represents a relatively complete sequence of lower glauconite sands/glauconitic clays, medial silts, and upper sands.

Lower Englishtown Formation

Age: Campanian

Interval: 792.3-797.6 ft (241.49-243.11 m)

Shelly, micaceous, glauconitic quartzose silty sands continue down to 797 ft (242.93 m), with several large clay nodules that react slightly with HCl (?replaced shell). We assign these sands to the lower Englishtown Formation (Fig. F6). Below 797 ft (242.93 m), the amount of glauconite in the core decreases down to the contact with the Woodbury Formation at 797.6 ft (243.11 m). The lower Englishtown Formation represents the HST of the Merchantville-Woodbury-lower Englishtown sequence at Ancora as it does at Bass River (Miller, Sugarman, Browning, et al., 1998).

Woodbury Formation

Age: early Campanian

Interval: 797.6-904.4 ft (243.11-275.66 m)

An indurated zone between 797.6 and 797.7 ft (243.11-243.14 m) marks the contact between the Woodbury and upper Englishtown Formations (Fig. F6). The Woodbury Formation consists of laminated to slightly burrowed, very micaceous, lignitic, slightly shelly very dark gray clay with occasional pyrite and pyrite nodules of replaced shell. The clays become glauconitic and more burrowed below 897 ft (273.41 m), with glauconite content reaching ~20% at 900 ft (274.32 m). Glauconite is common by 904.4 ft (275.66 m; >30%) and 40%-50% by 909 ft (277.06 m). Thus, the contact between the glauconitic clays of the lowermost Woodbury and the clayey glauconite sands of the Merchantville Formation is gradational; we place it at a visible increase in glauconite on the outside of the core at 904.4 ft (275.66 m).

Merchantville Formation

Age: early Campanian to Santonian

Interval: 904.4-945.3 ft (275.66-288.13 m)

Slightly lighter colored, more carbonate-rich glauconitic clays near the top of the Merchantville Formation (Fig. F6; 905-906 ft [275.84-276.15 m]) may represent a MFS of a sequence, similar to the MFS near the top of this formation at Bass River (Miller, Sugarman, Browning, et al., 1998). Below this, glauconite is typically 40%-60% in clayey glauconite sands to sandy glauconitic clays. Mica is less common (<1%) than in the overlying Woodbury Formation, there is extensive burrowing, and there are several intervals with shell concentrations. An indurated clayey glauconite sand (931.2-933.9 ft [283.83-284.65 m]) is cemented by a carbonate cement (?siderite); intervals of strong cementation in this interval contain bi-color "glauconite" pellets that are probably goethite. Clayey glauconite sand with clay burrows, clay laminae, and thin (1.5 cm thick) clay beds continues down to 944.5 ft (287.88 m), where there is a burrowed mixed interval with increasing quartz sand downsection.

Cheesequake Formation

Age: ?Santonian

Interval: 945.3-957.4 ft (288.13-291.82 m)

Silty, fine- to medium-grained, slightly pebbly quartz sand (Fig. F6) occurs below a distinct, irregular sequence boundary at 945.3 ft (288.13 m). Quartz sand is burrowed above the sequence boundary into the overlying clayey glauconitic sands. The quartz sands below the sequence boundary are lignitic, generally heavily bioturbated with large sand-filled burrows (up to 9 cm long), and contain shark teeth. They are marine (they also contain benthic foraminifers) and were deposited on a shallow (inner neritic?) shelf. These HST sands grade down to a distinct surface at 953.2 ft (290.54 m), which overlies slightly micaceous, slightly glauconitic, bioturbated, clayey, silty quartz sand (953.2-957.0 ft [290.54-291.69 m]). The surface is associated with a gamma ray-log peak and is tentatively interpreted as a MFS. The clayey, silty sands are marine, as indicated by the presence of echinoid spines and intense bioturbation. The interval from 956.9 to 957.4 ft (291.66-291.82 m) is a reworked zone with coarse clasts, phosphates, and lignite. A thin, discontinuous clay layer (957.0-957.2 ft [291.69-291.75 m]) within this reworked zone sits on top of a sequence boundary (957.4 ft [291.82 m]) separating marine sediments above from coarse- to very coarse-grained quartz sands of the Magothy Formation below. The sequence boundary is associated with a distinct gamma ray-log increase (Fig. F6). Thus, the gamma-ray log reflects an increase at the sequence boundary, maximum values at the MFS, and lower values in the sandy HST (Fig. F7). The low amounts of glauconite at the base of the sequence are attributed to the relatively shallow-water depositional environment. We tentatively assign the quartz sands and silts between 945.3 and 957.4 ft (288.13-291.82 m) to the Cheesequake Formation of Litwin et al. (1993).

Magothy Formation

Age: undifferentiated Santonian to late Turonian (?Coniacian)

Interval: 957.4-1062.5 ft (291.82-323.85 m)

Poorly sorted coarse- to very coarse-grained quartz sands of the Magothy Formation (Fig. F7) appear below a sequence boundary at 957.4 ft (291.82 m) and continue to 970 ft (295.66 m). A sequence is tentatively identified between 957.4 and 987.0 ft (291.82-300.84 m). Gravelly very coarse-grained sands to sandy gravels and interbedded well-sorted, medium- to coarse-grained quartz sand bracket a lignitic silty clay (962.6-962.7 ft [293.40-293.43 m]). The gravels and sands appear to be channel deposits of a delta plain; they represent the HST of a sequence. A major lithologic change occurs at 970 ft (295.66 m), with interbedded slightly sandy silty clay and lignitic sand below (970.0-984.9 ft [295.66-300.20 m]). These sandy clays appear to have been deposited in a delta-front or estuarine setting; pollen indicates a swamp/marsh, nonmarine environment (see "Biostratigraphy"). We tentatively place a MFS at a gamma ray-log peak at ~972 ft (~296.27 m), overlying an upsection increase in gamma ray-log values (Fig. F8), although this is speculative owing to the marginal to nonmarine environments represented by the sandy clays. We tentatively place a sequence boundary at a major gamma ray-log increase at 987 ft (300.84 m) in a coring gap (984.9-900.0 ft [300.20-274.32 m]) that encompasses a major facies change from sand below to sandy clay above.

Predominantly medium- to coarse-grained sand returns below a coring gap at 990 ft (301.75 m) and continues down to a sequence boundary at 1062.5 ft (323.85 m). The sand is massive, has occasional silty clay interbeds, and contains common interspersed lignite. The interval between 990 and 1010 ft (301.75-307.85 m) is generally coarser and more lignitic than below and is reminiscent of the delta-front sands at Bass River (1760-1780 ft [536.45-542.54 m]). At Ancora, between 990.0 and 1062.5 ft (301.75-323.85 m), there are several fining-upward successions consisting of a basal coarse to very coarse pebbly to gravely quartz sand (basal contacts at 1010.0, 1025.0, 1043.7, 1051.8, and 1062.4 ft [307.85, 312.42, 318.12, 320.59, and 323.82 m]), fining up to medium- to coarse-grained quartz sand, capped with a thin, sandy kaolinitic silty clay. Directly above the contact at the base of the Magothy Formation (1062.5 ft [323.85 m]), there is a 0.1-ft-thick (3 cm) lignite bed, overlain by a thin gravel bed (0.1 ft [3 cm]) that fines upsection to medium- to coarse-grained quartz sand. The environment of deposition between 1010.0 and 1062.5 ft (307.85-323.85 m) could be fluvial or marine channel (e.g., tidal delta). The paucity of fine sediments suggests that these fining-upward successions were deposited in a nearshore marine setting.

The section from 957.4 to 1062.5 ft (291.82-323.85 m) is assigned to the Magothy Formation. In outcrop, the Magothy Formation consists of sands and silty clays deposited in complex nonmarine to marginal marine environments (Owens and Gohn, 1985), similar to those observed at Ancora.

Bass River Formation

Age: Cenomanian to Turonian

Interval: 1062.5-1148.1 ft (323.85-349.94 m)

A spectacular contact occurs between the Magothy and Bass River Formations (Fig. F8) at 1062.5 ft (323.85 m), separating finer grained sediments below from coarser grained sediments above. Micaceous (including chlorite) silty clay of the Bass River Formation occurs below the contact. The clay has sandy silt laminae, is heavily bioturbated, and continues downsection to 1082.5 ft (329.95 m). The section from 1064 to 1066 ft (324.31-324.92 m) is darker (?higher organic-matter content) with a faint petroleum scent. We speculate that this interval correlates with the lowermost Turonian Bonarelli bed equivalent observed at Bass River (Sugarman et al., 1999). Glauconite is found in trace abundance from 1081.0 to 1082.5 ft (329.49-329.95 m). Common shells occur from 1062.5 to 1082.5 ft (323.85-329.95 m), indicating deposition on a marine shelf.

There is another spectacular contact at 1082.5 ft (329.95 m) that is interpreted as a sequence boundary. Below the contact is a 2.3-ft-thick (0.70 m) indurated shelly (including scaphopods) fine quartz sand. The indurated section overlies a fine quartz sand that fines downward, first to a clayey sand and then to a sandy clay by 1089 ft (331.93 m). The sands are interpreted as an upper HST. The sandy, micaceous clays continue to 1095.3-1095.4 ft (333.85-333.88 m), where another indurated zone (siltstone) was encountered. This zone overlies an irregular contact with rip-up clasts below. Another indurated zone with rip-up clasts below occurs at 1107.5-1107.8 ft (337.57-337.66 m), whereas the interval 1108.8-1108.9 ft (337.96-337.99 m) is partially indurated. The lithologies above and below these indurated zones are the same micaceous silty clays. Although the rip-up clasts may mark sequence boundaries, other evidence for interpreting these contacts as sequence bounding unconformities is lacking. The section from 1095.4 to 1107.5 ft (333.88-337.57 m) is a heavily bioturbated very micaceous (chloritic), slightly glauconitic silty clay with lignite, pyrite, and interspersed shells. Glauconitic clay to clayey glauconite sand (1107.50-1110.88 ft [333.88-338.60 m]) comprise the basal TST. An irregular, sharp contact (1110.9 ft [338.60 m]) that separates a pebbly shell bed above from a laminated shelly clay below is interpreted as a sequence boundary. The entire sequence from 1082.5 to 1110.9 ft (329.95-338.60 m) was deposited on a shallow shelf.

A shelly clay and silt unit (1110.9-1127.0 ft [338.60-343.51 m]) is characterized by laminations of slightly silty clays/clays and thin sand. Silt becomes dominant downsection (1120-1130 ft [341.38-344.42 m]), and the unit becomes more micaceous, glauconitic, bioturbated, less laminated, and shellier, with thin channels interpreted as storm beds. Lignite is common at 1123-1124 ft (342.29-342.60 m). A silty clay (1130.0-1144.6 ft [341.38-348.87 m]) contains varying amounts of glauconite. A nested shell bed (1144.6-1145.0 ft [348.87-349.00 m]) overlies a shelly glauconitic sandstone (1146.0-1148.0 ft [349.30-349.91 m]) with a basal shell bed (1147.7-1148.0 ft [349.82-349.91 m]). This overlies a distinct sequence boundary with slightly shelly clayey very fine sand below. We interpret the succession within the sequence as (1) a basal interfingering between middle shelf neritic glauconite and shell facies, (2) a medial prodelta silt and clay, and (3) an upper interfingering between storm-dominated shelly facies and prodelta sediments.

Pollen indicates that this section is primarily upper Cenomanian to ?lower Turonian Zone IV (1072, 1102, and 1138 ft [326.75, 335.89, and 346.86 m]; see "Biostratigraphy"). Planktonic foraminifers indicate that the early Turonian is represented at least at the top of the Bass River Formation at Ancora (see "Biostratigraphy").

Potomac Group

Age: ?Aptian to Cenomanian

Interval: 1148.1-1170.0 ft (total depth [TD]; 349.94-356.62 m)

Slightly shelly clayey very fine sands and clays encountered below the sequence boundary at 1148.1 ft (349.94 m) are probably the marine equivalent of the generally fluvial-deltaic Potomac Group (Fig. F8). Shelly clayey very fine sand at the top of the Potomac Group overlies a very lignitic clay (1150.0-1151.1 ft [350.52-350.86 m]), a poorly sorted medium- to very coarse-grained sand with rock fragments (1151.10-1151.55 ft [350.86-350.99 m]), and a mottled clay (1151.55-1154.50 ft [350.99-351.89 m]) with iron sand (1152.5-1152.9 ft [351.28-351.40 m]) and several very large pyritized burrows (1153.3-1153.8 ft [351.53-351.68 m]). This section is interpreted as marginal marine to estuarine. A sharp surface at 1154.5 ft (351.89 m) may be a sequence boundary with very shelly laminated brown clays below that grade down to a slightly glauconitic clay. The section below the sequence boundary was deposited in an inner-middle neritic setting.

A sharp facies change from neritic clays above to estuarine sands occurs at 1157 ft (352.65 m). The sands from 1157.0 to 1158.2 ft (352.65-353.02 m) are indurated to sandstone, very lignitic, clayey and faintly cross-bedded. A pebbly contact at 1158.2 ft (353.02 m) overlies a kaolinitic silty clay. This surface is probably a sequence boundary. Interbeds of sandy very lignitic, kaolinitic clay and clayey fine sand continue to 1163.5 ft (354.63 m), where there is a 1-ft (0.30 m) bed of lignitic, slightly glauconitic clay with large, reddish burrows (0.2 ft [5 cm] long). These clays are enigmatic because they occur sandwiched within estuarine sediments; they may represent a marine component within an estuary or marine interfingering. The base of the cored section (1164.5-1170.0 ft [354.94-356.62 m]) consists of highly bioturbated clayey silt, convoluted laminated lignitic silty sand, laminated silty clay, and flaser bedded silty clay and fine sand. The section from 1157 ft (352.65 m) to TD represents classic interbedded sand/clay facies deposited in an estuarine environment.

Pollen indicates that this section (samples at 1150 and 1165 ft [350.52 and 355.09 m]) is transitional between lower Cenomanian Zone III and upper Cenomanian to ?lower Turonian Zone IV (see "Biostratigraphy"). Nannofossils indicate that this section is upper Albian-lower Cenomanian Zone CC9 (see "Biostratigraphy"). Integration of pollen and nannofossil zonations indicates that the Potomac Group at Ancora is lower Cenomanian.

³Quotation marks indicate that the interval in question is from a core with >100% recovery. For example, "560.15" ft is from run 89 (550–560 ft) that had 102% recovery. Because run 90 also has an interval from 560.15 ft, we use the quotation marks to indicate that interval "560.15" ft is from run 89 and not run 90.