BIOSTRATIGRAPHY

Samples were examined qualitatively for planktonic foraminifer biostratigraphy at ~5-ft (1.52 m) intervals. Cenozoic and Maastrichtian samples were also examined for benthic foraminifers. Based on this qualitative examination, preliminary paleodepth estimates were made for Eocene (Browning) and Maastrichtian (Olsson) samples. The presence of ostracod taxa was noted for Upper Cretaceous samples from the Cheesequake to Mount Laurel Formations (Georgescu). Cenozoic foraminifer biostratigraphic resolution is generally limited at this updip location: only the Eocene (Zones P12-P14 undifferentiated, P11, P7-P10 undifferentiated, and P6b) and Paleocene (Zones P5, P4a, P3b, P2, P1c, P1b, P1a, and P) epochs could be subdivided. Three Maastrichtian planktonic foraminifer zones (Abathomphalus mayaroensis equivalent, Gansserina gansseri, and Globotruncana aegyptiaca) could be tentatively identified, although the shallow-water setting precludes most primary zonal markers. Biostratigraphic resolution is also limited by the shallow-water nature of the Santonian-Campanian section, although the Globotruncanella havanensis Zone (uppermost Mount Laurel Formation), Rugotruncana subcircumnodifer Zone (Mount Laurel and Wenonah Formations), Globotruncanita elevata Zone (Woodbury Formation), and the Santonian Dicarinella asymetrica Zone (Merchantville Formation) could be identified. Planktonic foraminifers were not found in the Cheesequake and Magothy Formations. Planktonic foraminifers are rare to common in the Bass River Formation; the presence of Rotalipora cushmani indicates definite Cenomanian strata below 1101.0 ft (335.67 m). Planktonic foraminifers were not found in the Potomac Group.

There are no planktonic foraminifers in the Miocene samples examined. Two samples from the lower part of the Kw1a sequence contain inner neritic benthic foraminifers. At 246 ft (74.98 m), benthic foraminifers are common and include Nonionellina pizarensis, Buliminella elongata, Glandulina, Lenticulina, Guttulina, and Cibicidina. A sample at 261 ft (79.55 m) contains rare specimens of Buliminella elongata.

Biostratigraphy in the Toms River Member of the Shark River Formation is difficult because of widespread mixing of middle and upper Eocene microfossils (Liu et al., 1997b; Poore and Bybell, 1988). In the Ancora borehole (263.7-359.8 ft [72.15-109.67 m]), planktonic foraminifers are rare, especially at the top of the unit, and are not age diagnostic to the zonal level. All samples in this unit up to 281 ft (85.65 m) contain Acarinina, equivalent to middle Eocene Zone P14 or older. However, these samples also contain Globigerina praebulloides that has been used to infer a late Eocene age and that the middle Eocene fossils are reworked. Nannofossils indicate that the section from 306 to 266 ft (93.29-81.10 m) is equivalent to upper Eocene Zone P15.

Benthic foraminifers are generally common and well preserved in the Toms River Member. Common taxa include Cibicidina, Gyroidinoides octocamerata, Epistominella minuta, Pararotalia stellata, Uvigerina elongata, Cibicidoides pippeni, Hanzawaia mauricensis, and Valvulineria texana. In other boreholes on the New Jersey Coastal Plain, these taxa have been interpreted to have inhabited water depths of ~50 m (Olsson and Wise, 1987; Browning et al., 1997a).

The upper Shark River Formation (359.8-388.6 ft [109.67-118.45 m]) contains rare but well-preserved planktonic foraminifers. The samples within this unit contain Morozovella lehneri, Subbotina frontosa, and abundant small acarininas and pseudohastigerinids. The co-occurrence of M. lehneri and S. frontosa places this unit within Zones P12 to mid-P14.

Benthic foraminifers are abundant and show a shallowing-upward trend within the upper Shark River Formation. Samples from the base of the section contain common Cibicidoides pippeni, C. cf. pseudoungerianus, Kolesnikovella elongata, Trifarina wilcoxensis, Discorbis huneri, and Alabamina, indicative of water depths of 75 to 100 m. Samples at the top of the unit contain common Cibicidina, Epistominella minuta, Pararotalia stellata, indicative of water depths of 50 to 75 m (Browning et al., 1997a; Olsson and Wise, 1987).

Planktonic foraminifers from the lower Shark River and Manasquan Formations are common, but age-diagnostic taxa are restricted in these shallow-water environments and highest and lowest occurrences are not reliable. In addition, many samples in these units were difficult to disaggregate. The lowest occurrence of Morozovella lehneri at 387.5 ft (118.11 m) is interpreted to mark the boundary between Zones P11 and P12. The lowest occurrence of Globigerinitheka subconglobata at 420.5 ft (128.17 m) is interpreted to mark the boundary between Zones P10 and P11. Zones P7 through P10 cannot be readily distinguished because (1) Hantkenina (zonal criterion for the base of Zone P10) is absent from the borehole, (2) Planorotalites palmerae (zonal criterion for the base of Zone P9) is absent from the borehole, and (3) Morozovella formosa is only found in two samples (471 and 476 ft [143.56 and 145.08 m]), and it is not clear that these samples represent either its correct highest or lowest occurrence. The top of Subzone P6b is at 471 ft (143.56 m), a level containing M. formosa before the first occurrence of M. aragonensis at 460.4 (140.33 m). Planktonic assemblages between 471 ft (143.56 m) and the base of the Manasquan Formation are similar; therefore, the base of the formation is interpreted to be Subzone P6b.

Benthic foraminifers in the lower Shark River and Manasquan Formations indicate deposition in middle to outer neritic paleodepths. The lower part of the Manasquan Formation (Sequence E2; 506-471 ft [154.23-143.56 m]) was deposited in the deepest water, as indicated by diverse and abundant planktonic foraminifers as well as benthic biofacies dominated by Gavelinella capitatus, Eponides, and Cibicidoides eocenus (Browning et al., 1997a). Samples at the top of Sequence E2 are dominated by C. eocenus, Anomalinoides acuta, and Cibicidoides cf. pseudoungerianus that may indicate a shallowing of 30-50 m through this sequence. Benthic foraminifers between 461.2 and 448.0 ft indicate a shallowing from biofacies dominated by Cibicidoides aff. subspiratus and Anomalinoides acuta (~155 m) to one dominated by Siphonina claibornenesis (~125 m). Samples in the sequence between 443.0 and 427.6 ft did not disaggregate well enough to recognize trends but benthic foraminifers indicate deposition in >100 m paleodepth. Samples at the bottom of the sequence between 427.6 and 388.6 ft (E6 of Browning et al., 1997a) are dominated by the benthic foraminifers Cibicidoides subspiratus, Gyroidinoides, and Melonis. Those at the top contain relatively higher percentages of Cibicidoides pippeni and C. cf. pseudoungerianus. This change in dominance may reflect a shallowing upward from ~140 to 110 m paleodepth.

The top of the Paleocene is at 522.2 ft (159.17 m) in Hole A, at the contact between the glauconitic clays of the Manasquan Formation and the green clays of the Vincentown Formation (Fig. F4). Foraminifers are poorly preserved in the uppermost part of this unit. Sample 530.3 ft (161.64 m; base of Core 86) contains Morozovella occlusa (a late Paleocene species), M. aequa, M. gracilis, M. subbotinae, Acarinina soldadoensis, Subbotina patagonica, and S. velascoensis. From 539.60 to 560.15 ft (164.47-170.73 m), abundant well-preserved foraminifers are present. This interval is placed in the Morozovella velascoensis Zone (P5) and contains M. occlusa, M. aequa, M. subbotinae, M. acuta, M. gracilis, Globanomalina chapmani, G. elongata, G. ovalis, Parasubbotina varianta, Subbotina patagonica, S. triangularis, and Acarinina soldadoensis. Acarinina africana, a LPTM species, occurs in Samples 545.50 and 560.15 ft (166.27 and 170.73 m). Zone P5 also contains middle neritic benthic foraminifers similar to those encountered in the Bass River borehole (e.g., Bolivina, Bulimina, Cibicides, Gyroidinoides, Pulsiphonina, and Gyroidinoides).

The interval from 560.15 to 595.40 ft (170.73-181.48 m) contains sparse, poorly preserved foraminifers. Rare occurrences of Morozovella aequa and Parasubbotina varianta are noted at 570.3 ft (173.87 m), and of Igorina tadjikistanensis at 595.4 ft (170.73 m). Benthic foraminifers are sparse throughout the interval, and at the base of the interval only small specimens are noted.

Globanomalina pseudomenardii was found only in Sample 600.4 ft (183.00 m). The association of Acarinina subsphaerica, A. mckannai, G. chapmani, G. imitata, M. angulata, Subbotina triangularis, S. velascoensis, and I. tadjikistanensis places this sample in Subzone P4a. The interval from 600.4 to 606.0 ft (183.00-184.76 m) is placed in Subzone P3b based on the occurrence of Acarinina strabocella, Globanomalina ehrenbergi, G. imitata, Igorina pusilla, Morozovella acutispira, M. angulata, M. apanthesma, M. conicotruncana, Parasubbotina varianta, and Subbotina triloculinoides. Sample 607.0 ft (185.06 m) is placed in Zone P2 based on the occurrence of Eoglobigerina spiralis, Morozovella praeangulata, Parasubbotina pseudobulloides, Praemurica inconstans, and Subbotina triloculinoides.

Foraminifers are abundant, diverse, and generally well preserved in the section from 607.0 to 612.0 ft (185.06-186.58 m). This section is placed in Subzone P1c based on the occurrence of Eoglobigerina edita, Globanomalina compressa, G. planocompressa, Globoconusa daubjergensis, Parasubbotina pseudobulloides, Praemurica inconstans, Subbotina triloculinoides, and S. trivialis. Sample 613.0 ft (186.89 m) is assigned to Subzone P1b. Characteristic taxa that occur in Subzone P1b include Eoglobigerina edita, E. eobulloides, Globoconusa daubjergensis, Praemurica pseudoinconstans, P. taurica, and Subbotina triloculinoides.

The section from 613.0 to 616.0 ft (186.89-187.80 m) is assigned to Subzone P1a based on the occurrence of Eoglobigerina eobulloides, Globoconusa daubjergensis, Guembelitria cretacea, Parasubbotina pseudobulloides, Praemurica pseudoinconstans, P. taurica, and Woodringina hornerstownensis. Parvularugoglobigerina eugubina, the index species for Subzone P, occurs in Sample 617.0 ft (188.11 m) along with E. eobulloides, G. cretacea, P. taurica, Woodringina claytonensis, and W. hornerstownensis. Because Danian planktonic foraminifers are relatively rare in the basal Hornerstown interval, Sample 617.5 ft (188.26 m) may also belong in Subzone P, although P. eugubina was not identified. Species identified in this sample include E. eobulloides, G. cretacea, Parvularugoglobigerina extensa, and Praemurica taurica. Alternatively, this sample could be regarded as upper Zone P0. Sample 617.9 ft (188.38 m) is assigned to Zone P0 based on the range of Guembelitria cretacea above the K/T boundary, which is placed at the top of the Navesink Formation at 618.1 ft (188.44 m), and the first occurrence (FO) of P. eugubina. Cretaceous planktonic foraminifers are intermixed in the Danian section through Subzone P1a, but are less abundant, rapidly decrease in numbers upsection, and are represented almost entirely by the species Heterohelix globulosa.

Only samples from the Hornerstown Formation were examined in Hole B. Sample 608.0 ft (185.36 m) at the top of the Hornerstown Formation is assigned to Subzone P4a based on the occurrence of Acarinina mckannai, Globanomalina pseudomenardii, Morozovella angulata, Subbotina triangularis, S. triloculinoides, and S. velascoensis. Sample 609.5 ft (185.82 m) contains a mixed assemblage. Subzone P3b species include Acarinina strabocella, Globanomalina ehrenbergi, and Morozovella angulata. Morozovella praeangulata and Praemurica uncinata are species indicative either of Zone P2 or lowermost Subzone P3a, suggesting that this sample is close to an unconformity. In contrast, at Ancora Hole A, Subzone P3b lies above Zone P2.

The section from 609.5 to 612.5 ft (185.82-186.74 m) is placed in Subzone P1c based on the occurrence of Eoglobigerina edita, Globanomalina compressa, Globoconusa daubjergensis, Parasubbotina pseudobulloides, Praemurica inconstans, P. pseudoinconstans, Subbotina triloculinoides, and S. trivialis. Sample 613.0 ft (186.89 m) is assigned to Subzone P1b based on the occurrence of Eoglobigerina edita, Globoconusa daubjergensis, P. pseudobulloides, Praemurica taurica, and S. triloculinoides. The interval from 613.0 to 616.4 ft (186.89-187.93 m) contains E. edita, G. daubjergensis, Guembelitria cretacea, P. pseudobulloides, and P. taurica and is assigned to Subzone P1a.

Planktonic foraminifer biostratigraphic results from the K/T boundary in both Ancora holes are integrated into "Lithostratigraphy."

Interval: 618.1-651.3 ft (188.40-198.52 m)

Age: Maastrichtian

The Navesink Formation (618.3-651.3 ft [188.51-198.52 m]) contains common to abundant foraminifers, but planktonic foraminifers are less abundant and diverse and, in general, smaller in size than at the Bass River borehole, reflecting the shallower paleodepths updip at Ancora. Because of the scattered occurrences of planktonic species, the highest occurrences (HOs) and lowest occurrences (LOs) of marker species should be considered tentative. The HO of Globotruncana linneiana, which occurs at the base of the Gansserina gansseri Zone, is at 646 ft (196.95 m), indicating that the base of the Navesink Formation lies within the Globotruncana aegyptiaca Zone as is the case at the Bass River borehole. The HO of G. gansseri is at 630.5 ft (192.22 m), which is probably too low in comparison to its HO at the downdip Bass River borehole. Nevertheless, it suggests that the upper part of the Navesink Formation at Ancora lies within the Abathomphalus mayaroensis Zone (see Miller, Sugarman, Browning, et al., 1998, for comments on the paleoecology of A. mayaroensis). Species typical of the A. mayaroensis Zone at Bass River that occur at Ancora include Globotruncana aegyptiaca, Hedbergella monmouthensis, Laeviheterohelix dentata, Planoglobulina acervulinoides, Racemiguembelina powelli, and Rugoglobigerina scotti.

Except for its more glauconitic facies, the Navesink section at Ancora is identical to the Navesink-New Egypt sequence at Bass River. The two sections are nearly identical in thickness (33.00 and 34.25 ft [10.06 and 10.44 m] at Ancora and Bass River, respectively). As at Bass River, the Navesink sequence at Ancora was deposited in a gradually shallowing sea-level cycle from middle to inner neritic paleodepths. Some deeper water benthic foraminifer taxa that occur in the basal part of the Navesink section include Arenobulimina subsphaerica, Bolivinoides giganteus, Eggerella trochoides, and Gavelinella spissocostata. Species typical of the shallowing trend include Anomalinoides midwayensis, Globulina gibba, Gyroidinoides imitata, Pseudoclavulina clavata, Pullenia americana, Pulsiphonina prima, Stilostomella pseudoscripta, Tappanina selmensis, and Valvulineria depressa. As at Bass River, an abrupt shallowing is evident just before the K/T boundary in the appearance of a typical Danian assemblage, characterized by Alabamina midwayensis, Angulogerina naheolensis, Anomalinoides acuta, and Gavelinella neelyi. This assemblage continues into the Danian section above.

Interval: 651.3-715.0 ft (198.52-217.93 m)

Age: late Campanian

Planktonic foraminifers are generally present throughout the Mount Laurel Formation (666.0-711.0 ft [203.00-216.71 m]) and the assemblages resemble those in the underlying Wenonah Formation. Planktonic foraminifer specimens increase in abundance in the uppermost part of the Mount Laurel section (656.0-661.0 ft [199.95-201.47 m]), where some specialized taxa are recognized: Pseudoguembelina excolata and Rugotruncana subcircumnodifer. According to Nederbragt (1991), the FO of P. excolata is placed at the top of the Globotruncanella havanensis Zone (late Campanian according to the Gradstein et al. [1995] time scale). The Mount Laurel Formation is assigned to the Campanian (defined using the Gradstein et al. [1995] time scale as older than 71.3 Ma) based on these taxa and the persistent presence of Globigerinelloides volutus. Ostracods are numerous and species of the genera Asciocythere, Cytherella and Escharacytheridea are common, in particular.

Interval: 715.0-735.0 ft (217.93-224.03 m)

Age: late Campanian

Planktonic foraminifers are not common in the Wenonah Formation. Most species are typical constituents of epicontinental sea and shallow-water faunas belonging to Heterohelix, Globigerinelloides, and Hedbergella. The presence of Globigerinelloides volutus indicates that these are upper Campanian sediments (probably belonging in the Rugotruncana subcircumnodifer Zone). Keeled taxa, present mostly as fragmentary shells, are small in size and rare.

Large-sized oyster fragments, persistent in the interval 721.0-731.0 ft (219.76-222.81 m) suggests shallower water depositional environments.

Interval: 735.0-797.2 ft (224.03-242.99 m)

Age: Campanian

Planktonic foraminifers are absent in the lower part of the interval (below 754.0-756.0 ft [229.82-230.43 m]). Specimens above this level belong to the globular morphotypes, such as Heterohelix globulosa, Globigerinelloides prairiehillensis, and Hedbergella. Archaeoglobigerina cretacea is present, although specimens are generally small. Keeled species are rare and specimens are generally broken; most belong to the genus Globotruncana (i.e., G. arca, G. bulloides, and G. linneiana). The scarcity of highly specialized taxa was previously noted in the sediments of the Marshalltown Formation in the Bass River borehole (Miller, Sugarman, Browning, et al., 1998). The age of the Marshalltown Formation is Campanian based on superposition, consistent with the results from other boreholes and outcrops (Olsson, 1964; Petters, 1977; Miller, Sugarman, Browning, et al., 1998).

Interval: 757.2-797.2 ft (230.79-242.99 m)

Age: Campanian

Planktonic foraminifers are very rare in the Englishtown Formation, consisting of fragmentary tests and abraded surfaces. This may be the result of dissolution and/or transport. Ostracods are rare but, when present, show larger shells with smooth, polished surfaces (e.g., Asciocythere).

Interval: 797.2-903.0 ft (242.99-275.23 m)

Age: Campanian

At the top of this unit (801.0-861.0 ft [244.14-262.43 m]), all morphologically advanced taxa are absent and only taxa with simple test morphology (e.g., Heterohelix globulosa [smooth to fine striated tests], Globigerinelloides, and Hedbergella) are present. The presence of Globigerinelloides bollii indicates a late Santonian-early Campanian age. At the base of the unit (881.0-901.0 ft [268.53-274.62 m]), planktonic foraminifer assemblages are rather rich. The dominant taxa are primitive, globular chambered species of the genera Heterohelix, Globigerinelloides, and Hedbergella. In contrast with the Merchantville Formation, double-keeled species (belonging to the genera Globotruncana [i.e., G. arca and G. bulloides], Marginotruncana [i.e., M. marginata and M. pseudolinneiana], and Contusotruncana [i.e., C. fornicata and C. plummerae]) are numerous. The complete absence of Marginotruncana sinuosa suggests that the sediments are younger than Santonian (i.e., the G. elevata Zone).

The ostracod assemblages change through the Woodbury Formation. Towards the top (816.0-826.0 ft [248.72-251.76 m]) they are rare and assemblages are dominated by smooth shelled forms (e.g., Cythereis, Cytherella, and Cytheropteron). At the base, they are numerous, locally abundant (891.3-891.4 ft [271.67-271.70 m]), and dominated by ornamented forms. This suggests a shallowing upsection that is also indicated by an upsection decrease in marine microfossils.

Interval: 903.0-944.5 ft (275.23-287.88 m)

Age: late Santonian to earliest Campanian

Planktonic foraminifer assemblages become more abundant and diverse upsection in the Merchantville Formation, indicating transgression. Planktonic foraminifers are absent at the base of the Merchantville Formation (926.0-941.0 ft [282.24-286.82 m]). The first planktonic foraminifers are recorded beginning with Sample 921.0 ft (280.72 m), with mostly single-specimen occurrences of the primitive species Heterohelix globulosa, Hedbergella bassriverensis, and H. sp. They become more numerous upsection, with a peak in abundance at the top of the Merchantville Formation, supporting the placement of the MFS at this level (Fig. F6). Most of the specimens belong to the globular chambered Heterohelix globulosa, Globigerinelloides prairiehillensis, Hedbergella div. sp., Archaeoglobigerina blowi, A. cretacea, and Rugoglobigerina rugosa. Morphologically advanced species belonging to the genera Globotruncana (i.e., G. arca, G. bulloides, and G. linneiana), Marginotruncana (i.e., M. marginata, M. pseudobulloides, and M. sinuosa), and Contusotruncana (i.e., C. fornicata) are rarely seen in the samples collected from the top part of the formation. The FO of Globotruncana arca typically occurs in the upper Santonian section; however, a latest Santonian age is suggested by the dominance of specimens of Marginotruncana over those of Globotruncana.

Ostracods are present in varying numbers at the top of the Merchantville Formation. Spinose valved types are dominant over smooth valved types. Ostracod genera include Bythocypris, Cytherella, Veenia, and Xestoleberis (906.0-916.0 ft [276.15-279.20 m]).

Interval: 944.5-957.2 ft (287.88-291.75 m)

Age: ?Santonian

No planktonic foraminifers were found in these sediments. The only fossil material found belongs to small-sized benthic foraminifers and indeterminate mollusks. All the microfossils present are fragmentary, suggesting transportation.

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

Age: Undetermined

The Magothy Formation consists of fine-, medium-, and coarse-grained sands and some gravel. Lignitic intervals were noted in Samples 961.0 ft (292.99 m), 971.0-981.0 ft (296.04-299.08 m), 1006.0 ft (306.71 m), 1021.0 ft (311.28 m), 1046.0 ft (318.90 m), and 1056.0 ft (321.95 m). Occasional glauconite grains were noted in Samples 961.0 ft (292.99 m), 996.0 ft (303.66 m), and 1041.0 ft (317.38 m). The entire formation is barren of foraminifers, other calcareous microfossils, and shell material.

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

Age: Cenomanian to Turonian

Foraminifers are less abundant and diversified in the Bass River Formation (1062.5-1148.1 ft [323.85-349.94 m]) at Ancora than in the Bass River borehole. Planktonic foraminifers are very rare to common and are absent in some intervals as a result of the shallow paleodepth updip position of Ancora. Foraminifers are in general well preserved. A single occurrence of Rotalipora cushmani, an upper Cenomanian index species, is noted in Sample 1101.0 ft (335.67 m). Above this level, from 1076.0 to 1075.2 ft (328.05-327.80 m), common occurrences of Hedbergella delrioensis, H. planispira, H. simplex, Whiteinella archeocretacea, W. baltica, and W. inornata are probably indicative of the Whiteinella archeocretacea Zone.

The shallow inner neritic benthic foraminifer assemblages are low in diversity and are dominated in several intervals by species of the genus Epistomina that are also common to abundant in the downdip Bass River borehole. Epistomina stelligera ranges to the top of the Bass River Formation at Ancora; this, together with the absence of E. lenticularia and E. sliteri, suggests that the upper part of the Bass River Formation at the Bass River borehole is either missing or is replaced by a nonmarine facies at Ancora. Gavelinella cenomana, a diagnostic Cenomanian benthic species, is frequent in the interval from 1096.0 to 1101.0 ft (334.15-335.67 m).

The Potomac Group (1148.1-1170.0 ft [TD; 349.94-356.62 m]) consists of alternating beds of very fine- to fine-grained sand with intervals of lignite and pelecypod shell material. Sample 1156.0 ft (352.44 m) consists almost entirely of micropelecypod shell fragments, whereas Sample 1161.0 ft (353.96 m) is dominated by lignite. Other intervals consist of very fine- to fine-grained sand with varying amounts of lignite and occasional shell fragments. Foraminifers and ostracods are absent.

Cenozoic Calcareous Nannofossils

Except for a thick stratigraphic interval (575.0-589.0 ft [175.26-179.53 m]) that is barren as a result of secondary silicification, the Paleogene formations recovered from the Ancora borehole yield abundant, generally well-preserved calcareous nannofossils with a high diversity. There are floods of tiny coccoliths at most levels, indicating good preservation and a quiet depositional environment. The biozonal scheme used below is that of Martini (1971) and the subzones are those defined by Bukry (1973, 1975), as codified by Okada and Bukry (1980) and Berggren et al. (1995).

The youngest calcareous nannofossil-bearing beds in the Ancora borehole are at 266.0 ft (81.08 m), 3 ft (0.91 m) below the Shark River/Kirkwood Formation contact, and belong to the lower upper Eocene Zone NP18. This firmly establishes the age of the uppermost levels of the Shark River Formation. The oldest Cenozoic calcareous nannofossil-bearing beds occur at 617.5 ft (188.21 m), and possibly belong to Zone NP1. In the intervening interval (between 266.0 and 617.5 ft [81.08-188.21 m]), almost all calcareous nannofossil biozones have been identified, although many are extremely thin. The only zones that are absent are the Paleocene Zones NP2, NP5, and NP7.

The Ancora borehole provides two exceptionally thick and interesting stratigraphic intervals. The NP15-NP16 zonal interval is 125 ft (38.10 m) thick; this greatly contrasts with the thin Zones NP14 and NP17 (~5 ft [1.52 m] or less, and ~10 ft [3.05 m] or less, respectively). However, as is often the case, it is difficult to delineate zonal/subzonal boundaries within Zones NP15-NP16 because of the scarcity or inconsistent occurrences of the marker species. A thick (77 ft [23.47 m]) NP9-NP10 zonal interval provides a remarkable record of the LPTM that is partly complementary of the Bass River record.

Interval: 263.7-448.5 ft (80.38-136.70 m)

The Shark River Formation extends from Zone NP18 to ?Subzone NP14a (lower upper Eocene to lower middle Eocene). Zone NP18 extends from 266.0 to 286.0 ft (81.08-87.17 m). Discoasters are rare in this interval, and preservation is poor as a result of secondary silicification. Zone NP17 is characterized well in Sample 296 ft (90.22 m) and, possibly, Sample 306 ft (93.27 m). The interval between 316.8 and 391.0 ft (96.56-119.18 m) is confidently assigned to Zone NP16. Reticulofenestra reticulata and R. floridana co-occur at 391.0 ft (119.18 m), which indicates a level in approximately mid-Zone NP16. Reticulofenestra reticulata, a species that is usually common in upper middle and upper Eocene assemblages, is very rare in the Ancora borehole. There is a sharp change in species dominance in the lower part of this interval. At 385.0 ft (117.35 m) and above, representatives of Reticulofenestra are dominant. At 387.5 ft (118.11 m), representatives of Reticulofenestra and Chiasmolithus are equally abundant. At 391 ft (119.18 m), representatives of Chiasmolithus are dominant and those of Reticulofenestra are much fewer.

Biozonal determination in the interval between 391.0 and 428.6 ft (119.18-130.64 m) is uncertain because of poor preservation and lack of biozonal markers. Sample 430.5 ft (131.22 m) belongs to Subzone NP15b, characterized by Nannotetrina fulgens and Chiasmolithus gigas, whereas Sample 433.5 ft (132.13 m), which yields N. fulgens and Cruciplacolithus staurion but no C. gigas, probably belongs to Subzone NP15a. The zonal assignment of level 441.0 ft (134.42 m) is uncertain. Sample 446.0 (135.94 m) belongs to Subzone NP14a, as indicated by the co-occurrence of Discoaster sublodoensis and Discoaster lodoensis and the absence of Blackites inflatus. Sample 447.9 ft (136.52 m) yields one of the richest and best preserved assemblage of the Paleogene section recovered from the Ancora borehole. However, its zonal position is difficult to determine; Discoaster lodoensis (five- and six-rayed) is common as is Discoaster kuepperi. A few characteristic Discoaster cruciformis as well as very rare Tribrachiatus orthostylus that are probably reworked are present. The co-occurrence of D. lodoensis, D. kuepperi, and D. cruciformis would be indicative of lower Zone NP13. However, a couple of poorly preserved discoasters may be assignable to D. sublodoensis, and an NP14a zonal assignment (with D. cruciformis reworked) cannot be excluded.

The rapid zonal succession NP15b-NP15a-NP14a (or -NP13) is suggestive of a succession of unconformable surfaces and dates successive sequences. Unconformable units of these ages have been recognized on the New Jersey margin and are discussed in Aubry (1991, 1995).

Interval: 448.5-522.2 ft (136.70-159.17 m)

The Manasquan Formation comprises Zones NP12, NP11, and NP10. Zone NP12 extends from 448.8 to 471.0 ft (136.79-143.56 m). Tribrachiatus orthostylus is very common at 476 ft (145.08 m), together with Imperiaster obscurus. With the exception of Discoaster binodosus, discoasters are very rare at this level. It is possible that the absence of D. lodoensis reflects the paucity in discoasters. However, D. lodoensis was not encountered at any level below 471 ft (143.56 m). Thus, the NP11/NP12 zonal boundary is located between 471 and 476 ft (143.56-145.08 m). Assemblages are very diverse and well preserved throughout this NP12-NP11 zonal interval; Rhomboaster bitrifida and Rhomboaster intermedia occur at several levels (e.g., at 496.0 and 501.0 ft [151.18 and 152.70 m]). The HO of Tribrachiatus contortus at 519 ft (158.19 m) places the NP11/NP10 zonal boundary between 516.3 and 519.0 ft (157.37-158.19 m).

The subzonal zonation of Aubry (1996) is easily applied to the NP10 interval in the Ancora borehole. Subzone NP10d is identified at 519 ft (158.19 m). Unless reworked, very rare specimens of T. bramlettei at this level may indicate the lower part of the subzone (Aubry, 1996). Based on the occurrence of Tribrachiatus digitalis, Subzone NP10b is identified between 519.9 and 521.0 ft (158.47-158.80 m). The occurrence of Tribrachiatus bramlettei and the absence of T. digitalis at 521.7 ft (159.01 m) indicate Subzone NP10a.

There is no record of Subzone NP10c, and the NP10b/NP10d subzonal contact between 519.0 and 519.9 ft (158.19-158.47 m) is unconformable.

Calcareous nannofossil assemblages are very diverse in the NP10 zonal interval. Hornibrookina australis occurs in the lower part of the zone.

Interval: 522.2-596.6 ft (159.17-181.84 m)

The Vincentown Formation essentially belongs to Zone NP9, except for its lowermost part which belongs to Zone NP8. The boundary between the two zones is located between 594.0 and 596.2 ft (181.05-181.72 m).

The unconformable Vincentown/Manasquan contact at 522.2 ft (159.17 m) coincides with the NP9b/NP10a subzonal contact. Subzone NP10a is extremely thin in the Ancora borehole, suggesting a stratigraphic gap corresponding to most of the subzone. The gap is also indicated by the simultaneous HOs of F. tympaniformis and Discoaster mahmoudii at 522.6 ft (159.29 m) and the LO of T. bramlettei at 521.7 ft (159.01 m).

It appears possible to subdivide Zone NP9 into two subzones, with the younger subzone distinguished by the occurrence of Rhomboaster (R. bitrifida and R. calcitrapa) and Tribrachiatus spineus in the upper part of the zone. However, it remains unclear which criteria would constitute the best means for global correlation of the NP9a/NP9b subzonal boundary. Several criteria are possible: the HO of Fasciculithus alanii and the LOs of Rhomboaster calcitrapa, Discoaster anartios, and Discoaster araneus. In several sections, Aubry et al. (M. Aubry, pers. comm., 1999) have observed that these events are stratigraphically coincident. This is not the case at Ancora, suggesting that this section is more complete across the NP9a/NP9b subzonal boundary. In the Ancora borehole, the boundary would be placed between 559.75 and 555.90 ft (170.61-169.44 m) depending on which criterion is selected. As indicated by Cramer et al. (in press) and Aubry et al. (M. Aubry, pers. comm., 1999), the NP9a/NP9b subzonal boundary is associated with the LPTM. Thus, the LO of these taxa in the Ancora section allows us to predict the location of the CIE in the interval 563.00-559.75 ft (171.60-170.61 m).

Calcareous nannofossil assemblages are poorly preserved in Samples 561 and 562 ft (170.99 and 171.30 m) as a result of secondary silicification, and discoasters are rare. The occurrence of Discoaster sp. aff. D. mediosus at 559.75 ft (170.61 m) is the lowest indication in the Ancora borehole of the proximity of the LPTM. Discoaster sp. aff. D. mediosus differs from D. mediosus by its long slender arm tips, which in some specimens are irregularly spaced (but located in the same plane, unlike the arms of D. araneus). Discoaster sp. aff. D. mediosus is a form reminiscent of the late Eocene Discoaster levini (Hay, 1967). This is followed by the LO of D. anartios at 557.0 ft (169.77 m) and the LOs of D. araneus, Tribrachiatus spineus, Rhomboaster bitrifida, and R. calcitrapa at 556.0 ft (169.47 m).

A thick interval (575-589 ft [175.26-179.53) in Subzone NP9a is barren, as a result of secondary silicification.

Diversity increases progressively through Subzone NP9a (perhaps as a result of increasingly better preservation), and is very high in Subzone NP9b. The "LPTM calcareous nannofossil taxa" do not range throughout Subzone NP9b but are most abundant in its lower part between 539.6 and 556.0 ft (164.47-169.47 m). Discoaster anartios and Rhomboaster calcitrapa were not encountered above this level, whereas T. spineus is rare, and D. araneus is occasional up to 522.6 ft (159.29 m). A marked decrease in diversity among fasciculiths occurs at 542.5 ft (165.35 m), but the genus is represented (common) up to the top of the Vincentown Formation. The bulk of the assemblage in Subzone NP9b consists of Toweius pertusus and Hornibrookina australis (=Hornibrookina arca).

Sample 596.2 ft (181.72 m) belongs to Zone NP8. Sample 594.0 ft (181.05 m) yields few multi-rayed rosette-shaped discoaster that are early morphotypes of D. multiradiatus. In both samples, Heliolithus riedelii is common and characteristic.

Interval: 596.6-618.5 ft (181.84-188.52 m)

The Hornerstown Formation extends from Zone NP8 to ?Zone NP1, and includes several large stratigraphic gaps with Zones NP7, NP5, and NP2 absent.

Sample 597.5 ft (182.12 m) belongs to Zone NP8. Sample 602.5 ft (183.64 m) belongs to Zone NP6, characterized by Heliolithus kleinpelli (rare) and H. cantabriae (common). Sample 607.5 ft (185.17 m) belongs to Zone NP4, characterized by the presence of Ellipsolithus macellus and the absence of Sphenolithus primus. Samples 612.0 and 614.9 ft (186.54 and 187.42 m) belong to Zone NP3, with Chiasmolithus danicus very common, but this species was not observed in Sample 614.0 ft (187.15 m). Sample 616.0 ft (187.76 m) is essentially barren. Cretaceous taxa are abundant in Samples 617.0 and 617.5 ft (188.06 and 188.21 m). The scarcity of small coccoliths (genus Prinsius in particular) is surprising and may reflect poor preservation. These levels are tentatively assigned to Zone NP1.

The rapid succession of biozones in the Hornerstown Formation is strongly suggestive of successive unconformities (sequence boundaries) between 597.5 and 602.5 ft (182.12-183.64 m), 602.5 and 607.5 ft (183.64-185.17 m), 607.5 and 612.0 ft (185.17-186.54 m), and possibly 615 and 616 ft (187.45-187.76 m), some of which intervals are delineated on the basis of lithologic changes (see "Lithostratigraphy").

Cretaceous Calcareous Nannofossils

Samples were taken at 2-ft (0.61 m) intervals except near the K/T boundary where sampling density was increased. Smear slides were prepared using standard techniques and examined under the light microscope at a magnification of 1250×.

Calcareous nannofossil abundance and diversity are high and preservation is generally good to excellent in samples from the Navesink, Mount Laurel, and Wenonah Formations, and from most of the Marshalltown Formation. Below 753.5 ft (229.67 m), near the base of the Marshalltown Formation and continuing through the Englishtown and upper Woodbury Formations down to 851.5 ft (259.54 m), nannofossils are less abundant with poor to fair preservation. Barren intervals are common in the Englishtown Formation. In the lower Englishtown Formation (851.5-943.0 ft [259.54-287.43 m]), nannofossil abundance increases and preservation improves. Below this, the Cheesequake, Magothy and uppermost Bass River Formations are barren of nannofossils. The Bass River Formation nannofossils are mostly well preserved with low abundance and high diversity. Throughout the core, nannofossil assemblages include both high- and low-latitude species. Holococcoliths are generally common to abundant.

The nannofossil zonation and CC terminology of Sissingh (1977) were used to subdivide the section. Several of the Sissingh (1977) zones have been modified by Perch-Nielsen (1985) based largely on reclassification of the names of original species and genera. Perch-Nielsen (1985) also defined several subzonal units, and these are also applied here. Zones defined by Bralower (1988) have been applied to the Cenomanian/Turonian boundary interval. All zones are correlated to stages according to the scheme of Gradstein et al. (1995). Table T3 lists the zonal definitions and assigned intervals in the Ancora borehole.

The precise position of the K/T boundary is difficult to determine using nannofossil stratigraphy because of substantial mixing of Upper Cretaceous and lower Paleocene assemblages between 617.1 and 618.0 ft (188.09-188.37 m). Nannofossil assemblages in this interval are rare, poorly preserved, and dominated by Cretaceous taxa and the disaster genus Throracosphaera. Paleocene taxa, including Cruciplacolithus primus, extend down into the upper Maastrichtian section. Other taxa diagnostic of lower Paleocene Zone NP1, including Biantholithus sparsus and Neobiscutum romeinii, are rare. The boundary interval appears to be complicated by slumping. For example, a sample that belongs to Zone NP2 (617.7 ft [188.27 m]) appears to lie below a sample that belongs to Zone NP1 (617.4 ft [188.18 m]). Reworking of Cretaceous nannofossils into the Tertiary section is pervasive as in many other sections (e.g., Pospichal, 1996). Our tentative placement of the K/T boundary at 618.0 ft (188.37 m) is based on a dramatic increase in the relative proportion of Cretaceous nannofossils below this level. Clearly, more detailed investigations of the boundary interval, including sampling at the centimeter scale, are warranted.

Interval: 618.1-651.3 ft (188.40-198.52 m)

The Navesink Formation is assigned to upper Maastrichtian Zones CC26 to CC25. Calcareous nannofossils are abundant. Preservation is excellent in the upper part of the formation and decreases to good in the lower part of the formation because of overgrowth.

The upper and lower boundaries of Zone CC26 are precisely identified by the HO and LO of Nephrolithus frequens (618.1 and 631.1 ft [188.40 and 192.36 m]), respectively. Subzones CC26a and CC26b cannot be identified because of the absence of Micula prinsii.

The interval between 631.1 and 651.3 ft (192.36-198.52 m) is assigned to Zone CC25. Evidence of mixing between Zone CC25 and the zone that lies unconformably below it (CC23 or possibly CC22) in the interval 650.7-651.6 ft (198.33-198.61 m) makes it difficult to determine the lower boundary of Zone CC25. This interval includes the base of the Navesink Formation and the top of the Mount Laurel Formation.

The only specimen of Micula murus observed in the Ancora borehole was found at 618.83 ft (188.62 m) in Zone CC26. Thus, it is not possible to determine the boundary between Subzones CC25b and CC25c (Table T3). The top of Subzone CC25a is precisely identified by the LO of Lithraphidites quadratus at 647.8 ft (197.45 m).

Interval: 651.3-715.0 ft (198.52-217.93 m)

The Mount Laurel Formation is assigned to upper-middle Campanian Zones CC22-CC21, and possibly Zone CC23. It may extend into the lower Maastrichtian, as Zone CC23 spans the Campanian/Maastrichtian boundary (Gradstein et al., 1995). Nannofossil preservation is good to fair. Species identification is occasionally difficult because of overgrowth. Abundance and diversity are high, particularly among the holococcoliths.

Coincidence of the HOs of Reinhardtites levis, Aspidolithus parcus, Calculites obscurus, Quadrum gothicum, and Tranolithus phacelosus in the transition between the Navesink and Mount Laurel Formations suggests the presence of an unconformity that spans Zone CC24 and maybe the lower part of Zone CC25 and upper part or all of Zone CC23. The presence of Zone CC23 is questionable because of a lack of consensus on making a diagnosis between Reinhardtites levis and R. anthophorus (Bralower and Siesser, 1992; J. Bergen, pers. comm., 1999; J. Self-Trail, pers. comm., 1999). The interval 678.8-709.5 ft (206.90-216.26 m) belongs to Subzone CC22a based on the HO of Lithastrinus grillii and the LO of Quadrum trifidum. It is difficult to determine the top of the subzone with certainty because of the sporadic occurrence of Lithastrinus grillii. The interval 709.5-714.9 ft (216.26-217.90 m) is assigned to the top of Zone CC21 based on the absence of Quadrum trifidum and the presence of Quadrum sissinghii.

Interval: 715.0-735.0 ft (217.93-224.03 m)

The Wenonah Formation is assigned to middle Campanian Zone CC21. Nannofossils are abundant with high diversity, although the abundance of holococcoliths is lower than in overlying units. Preservation is good to excellent. Quadrum sissinghii continues to be present throughout the Wenonah Formation, indicating that it belongs to Zone CC21.

Interval: 735.0-757.2 ft (224.03-230.79 m)

The Marshalltown Formation is assigned to middle Campanian Zone CC21 and possibly the upper part of Zone CC20. From 735.0 to 753.5 ft (224.03-229.67 m), nannofossil abundance is high and preservation good to excellent, with dissolution increasing downhole. Samples in the interval from 753.5 to 757.5 ft (229.67-230.79 m) are barren.

Based on the continued presence of Quadrum sissinghii throughout the fossiliferous part of the formation, the interval 735.0-753.5 ft (224.03-229.67 m) is assigned to Zone CC21. The base of the Marshalltown Formation (753.5-756.5 ft [229.67-230.79 m]) is assigned with some uncertainty to Zone CC20 based on the LO of Q. sissinghii at 753.5 ft (229.67 m); however, it is plausible that Zone CC21 continues through this barren interval.

Interval: 757.2-797.2 ft (230.79-242.99 m)

The Englishtown Formation is assigned to middle Campanian Zone CC19 and possibly part of Zone CC20. Much of the formation is barren of nannofossils. In fossiliferous samples, nannofossils are scarce and poorly preserved. Dissolution is common and many specimens are broken.

Identification of Zone CC20 is uncertain. The uppermost sample in the Englishtown Formation at 758.5 ft (231.19 m) is tentatively assigned to Zone CC20 based on the occurrence of Ceratolithoides aculeus. However, preservation is poor and diversity low and only one specimen of this species was found in the sample. A 4-ft (1.23 m) barren interval lies below this sample (759.5-763.5 ft [231.5-232.72 m]). Part or all of the barren interval may also belong to Zone CC20. On the other hand, given the poor preservation, it is also possible that specimens of Q. sissinghii have been dissolved and Zone CC21 extends down to 763.5 ft (232.71 m). If so, an unconformity must lie at the base of Zone CC21. If not, Zone CC20 probably represents a condensed section or deposition at a diminished sedimentation rate.

On the basis of the absence of Ceratolithoides aculeus, the interval between 763.5 ft (232.71 m) and the base of the formation (792.2 ft [242.99 m]) is assigned to Zone CC19. The barren interval above, from 759.5 to 763.5 ft (231.50-232.71 m), may also belong to this zone.

Interval: 797.2-903.0 ft (242.99-275.23 m)

The Woodbury Formation is assigned to lower-middle Campanian Zone CC18. Nannofossils are rare and their preservation poor to fair to a depth of 851.5 ft (259.54 m) in the upper Woodbury Formation. Preservation improves to good below this level. The entire Woodbury Formation is assigned to Zone CC19 based on the absence of Ceratolithoides aculeus and Marthasterites furcatus.

Interval: 903.0-944.5 ft (275.23-287.88 m)

The Merchantville Formation is assigned to upper Santonian to lower Campanian Zones CC18-CC17. Calcareous nannofossil abundance is high and preservation good to very good in most of the formation. Preservation diminishes to fair because of dissolution in samples from 939.5 and 941.5 ft (286.36 and 286.97 m). Below this level, sediments are barren of nannofossils.

The top of Zone CC18 is precisely defined at 903.0 (275.23 m) by the HO of Marthasterites furcatus. The LO of Aspidolithus parcus defines the top of Zone CC17 at 918.5 ft (279.96 m), indicating that strata below this level can be dated as Santonian based on nannofossil correlations. Zonal assignment of the interval 940.5-943.0 ft (286.70-287.43 m) is uncertain as the holococcolith C. obscurus, the major marker species for the base of Zone CC17, is absent. However, holococcoliths are rare in Zone CC17 and none are found in the Merchantville Formation below the LO of C. obscurus. The lack of holococcoliths in the interval 940.5-943.0 ft (286.70-287.43 m) is possibly a result of changing environmental conditions. Parhabdolithus regularis, the LO of which lies in the middle of combined Zones CC16 and CC17 (Bralower and Siesser, 1992), is found throughout this interval. Thus, this interval belongs to either Zone CC17 or CC16. The zonal correlation of the barren section from 943.0 to 944.5 ft (287.43-244.5 m) is uncertain.

Interval: 944.5-1062.5 ft (287.88-323.85 m)

All samples examined from these formations are barren of calcareous nannofossils. The Cheesequake and Magothy Formations lie somewhere in the interval comprising middle Santonian Zone CC16 to lower Turonian Zone CC11.

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

The interval from 1061.9 to 1074.5 ft (323.67-327.51 m) is barren of nannofossils. Abundance varies from low to high and preservation from poor to good in the interval below, which ranges from the upper Cenomanian Parhabdolithus asper Zone (Microstaurus chiastius Subzone) to the lower Cenomanian Axopodorhabdus albianus Zone (Zones CC10-CC9 of Sissingh [1977]).

The interval between 1074.5 and 1076.4 ft (327.51-328.09 m) is assigned to the Parhabdolithus asper Zone, Microstaurus chiastius Subzone. Microstaurus chiastius is not found in this interval. However, we have identified this subzone using the HO of the secondary marker, Lithraphidites acutum, which lies near the base of the Microstaurus chiastius Subzone in several sections (Bralower, 1988). The Axopodorhabdus albianus Zone is precisely identified from 1076.4 to 1146.7 ft (328.09-349.51 m), between the HO of Axopodorhabdus albianus and the FO of Vagalapilla octoradiata.

Although the Sissingh (1977) zonation scheme has been shown to be inapplicable in the Cenomanian/Turonian boundary interval (Bralower, 1988), we show the CC zonation in the Bass River Formation for reference. The coexistence of M. decoratus and Lithraphidites acutum, whose range is restricted to the Cenomanian (Perch-Nielsen, 1985), indicates that the interval between 1074.5 and 1128.5 ft (327.51-343.97 m) lies in Zone CC10. Quadrum gartneri, the principal marker for the top of Zone CC10, is not present in the Ancora borehole. Subzone CC10b is considered to extend to 1101.7 ft (335.80 m). As Microstaurus chiastius is not present, the LO of Corollithion exiguum was used as a secondary marker for the base of this subzone (Self-Trail and Bybell, 1995). The interval between 1101.7 and 1128.5 ft (335.80-343.97 m) belongs to Subzone CC10a, with the LO of Microrhabdulus decoratus at 1128.5 ft (343.97 m) marking the base of the subzone and the top of Zone CC9.

Interval: 1148.1-1170.0 ft (TD; 349.94-356.62 m)

The top of the Potomac Group is assigned to Zone CC9 (upper Albian to lower Cenomanian). Nannofossil preservation is fair and abundance is scarce in the uppermost sample at 1149.0 ft (350.22 m). Below this, all samples are barren and no zonal correlation is possible. The uppermost sample is assigned to Zone CC9 based on the co-occurrence of Lithraphidites alatus and Eiffellithus turriseiffelii.

Pollen

The upper part of the Magothy Formation at Ancora is assigned to pollen Zone V (samples at 980.9 and 983.6 ft [299.05 and 299.88 m]) of Christopher (1982), which is generally correlated to the upper Turonian-Santonian (Fig. F7). The lower part of the Magothy Formation at Ancora (1028.9 ft [313.7 m]) is tentatively assigned to pollen Zone V (Fig. F7), consistent with previous studies (Christopher, 1982). Three Bass River Formation samples (1072.0, 1102.0, and 1138.0 ft [326.82, 335.98, and 246.95 m]; Fig. F8) are assigned to upper Cenomanian to lowermost Turonian pollen Zone IV of Christopher (1982). Two Potomac Group samples (1150.5 and 1165.0 ft [350.76 and 355.18 m]) are assigned to the pollen Zone III/IV transition; this interval is lower-middle Cenomanian.