BIOSTRATIGRAPHY

Planktonic Foraminifers

Cenozoic

Planktonic foraminifers were only locally abundant through most of the Cenozoic section at Millville (Table T3). For the most part, the shallow-water sections here did not preserve important index species. Where found, planktonic foraminferal assemblages are dominated by morphologically simple and long-ranging forms. Age determinations can only be reliably assigned in part of the lower middle and upper lower Eocene and in the lower Paleocene.

The Miocene section at the Millville borehole was only fossiliferous in the lowermost section (360–406 ft; 109.73–123.75 m) and yielded a sparse planktonic fauna including Globoquadrina dehiscens and large Globigerinoides trilobus with well-developed supplementary apertures. This indicates an assignment to Subzone M1b (= upper N4b).

The highest occurrence (HO) of Turborotalia cerroazulensis at 451 ft (137.46 m) marks the top of the known Eocene sediments. The section above 451 ft (137.467 m) to the sequence boundary at 407.95 ft (124.34 m) is barren of planktonic foraminifers and cannot be zoned. The section between 451 and 620 ft (137.46 and 188.98 m) is mostly barren of plankton. Where plankton are present, members of the genera Acarinina, Morozovella, and Truncorotaloides are absent, indicating assignment to undifferentiated Zones P15–P17. These zones cannot be differentiated in the Millville borehole because of the absence of the marker species Cribrohantkenina inflata and Porticulasphaera semiinvoluta.

The HO of Morozovella spinulosa and the absence of Morozovella aragonensis at 626 ft (190.80 m) indicates that the sequence between 620 and 640.35 ft (188.98 and 195.18 m) is assigned to undifferentiated Zones P12–P14. The boundary between Zones P11 and P12 is placed at the highest occurrence in the corehole of M. aragonensis between 666 and 676 ft (203.00 and 206.04 m), and the section between 640.35 ft (195.18 m) and the sequence boundary at 666 ft (203.00 m) is assigned to Zone P12. The base of Zone P11 is approximated between 691 and 701 ft (210.62 and 213.66 m) by the lowest occurrence (LO) of Turborotalia pomeroli because Globigerapsis is not found in the borehole. The base of Acarinina bullbrooki approximates the base of Zone P9, and the section between 701 and 722.5 ft (213.66 and 220.22 m) is assigned to undifferentiated Zones P9 and P10. Samples 731 to 761 ft (222.81 to 231.95 m) are assigned to Zone P8 based on the presence of M. aragonensis and the absence of A. bullbrooki and Morozovella formosa. Samples between 771 and 741 ft (235.00 and 225.86 m) are assigned to Subzone P6b based on the presence of M. formosa and the absence of M. aragonensis. Note that Zone P7 is apparently absent in the core; however, M. formosa is very rare and may range higher. The sample at 846 ft (257.86 m) is assigned to Subzone P6a based on the absence of M. formosa.

Samples at 866 and 891 ft (263.96 and 271.58 m) are assigned to Zone P5. A sample from 866 ft (263.96 m) contains members of the Paleocene/Eocene Thermal Maximum "excursion fauna." Samples between 899 and 956 ft (274.02 and 291.39 m) are either barren or unzoned because of very poor preservation. Samples at 961 ft (292.91 m) contain Globanomalina pseudomenardii and Morozovella angulata and are assigned to Subzone P4a. Samples from 970–976 ft (295.66–297.48 m) may be assigned to Subzone P3b based on the presence of Acarinina strabocella and Igorina tadjikistanensis.

Cretaceous/Paleogene Boundary

Samples from 981.0 to 983.5 ft (299.08 to 299.85 m) in a glauconitic clay interval were processed for planktonic foraminifers to identify the Cretaceous/Paleogene boundary (Table T5). Planktonic foraminifers from the lower Danian were sparse and moderately preserved, whereas those from the Cretaceous were more numerous and better preserved. The Cretaceous/Paleogene boundary is placed between samples from 983.0 ft (299.70 m) and 983.05 ft (299.71 m). The presence of P. eugubina in the sample at 983.0 ft (299.07 m) identifies lower Danian Zone P. Basal Danian Zone P0 may lie just below this. Our experience shows this zone to be a centimeter or so in the New Jersey Coastal Plain boreholes. Danian Subzone P1a is identified from samples at 982.95–982.0 ft (299.68–299.39 m) and on the occurrence of E. edita, E. eobulloides, G. cretacea, and P. taurica. The identification of S. triloculinoides in the sample at 981.0 ft (299.08 m) indicates Danian Subzone P1b.

The Cretaceous samples at 983.05–983.5 ft (299.85–299.85 m) are placed in the uppermost Maastrichtian on the occurrences of H. monmouthensis, P. hariaensis, R. macrocephala, R. reicheli, and G. cretacea. The environment of deposition was too shallow to allow a full complement of deeper-dwelling planktonic foraminiferal species to occur. For instance, the genus Globotruncana is very rare. The range of P. hariaensis falls within the uppermost Maastrichtian A. mayeroensis Zone.

Maastrichtian

The Maastrichtian occurs from samples at 1032.9–983.05 ft (299.85–314.91 m) that include the Navesink and New Egypt equivalents (Table T5). The HO of Gansserina gansseri is in the sample at 996.0 ft (303.66 m) and may indicate the top of the G. gansseri Zone, although the top occurrence may have been depressed due to shallow-water environments of deposition. The HOs of Globotruncana linneiana and Rosita fornicata identify the top of the lower Maastrichtian Globotruncana aegyptiaca Zone.

Campanian

Low diversity and a scarcity of marker taxa characterize the Campanian formations in the Millville borehole. The occurrence of Globotruncana ventricosa in a sample at 1036 ft (315.77 m) indicates the section above 1036 ft (315.77 m) is middle or upper Campanian. Samples at 1036 and 1041 ft (315.77 and 317.30 m) from the Mount Laurel/Wenonah Formations contain Marginotruncana marginata, which is typically confined to the Santonian. R. Olsson has observed such occurrences in other wells on the New Jersey coastal plain. We interpret the M. marginata to be reworked into these samples. A specimen of Ventilabrella browni at 1220 ft (371.86 m) indicates the section below to be lower Campanian or older. No Santonian marker species were found.

Cenomanian–Turonian

The Bass River Formation contained a sparse planktonic foraminiferal fauna. The HO of Rotaliapora cushmani, a marker for the top of the Cenomanian, was found in a sample at 1371 ft (417.88 m). Calcareous nannofossils indicate that the Cenomanian section continues to 1354 ft (412.7 m), and we believe the HO of R. cushmani is premature.

Benthic Foraminifers

Benthic foraminifers were locally abundant in the Miocene–Eocene section (Table T4). Most samples had five to ten species of benthic foraminifers that allowed preliminary paleodepth estimates. Specimens were picked from the >63-µm size fraction that was also used for sedimentological analysis.

The Miocene Kirkwood Formation contains sparse benthic foraminiferal assemblages. The average sample contained five species. The two most common species are Nonionellina pizarrensis and Caucasina elongata. N. pizarrensis dominates samples at 356 ft (108.51 m) and from 406 to 381 ft (123.75 to 116.13 m). C. elongata is approximately equally present in samples at 361 and 366 ft (110.03 and 111.56 m). N. pizarrensis characterizes the N. pizarrensis biofacies of Miller et al. (1997). This biofacies is interpreted to represent 25–50 m paleowater depths (Miller et al., 1997). C. elongata characterizes the Bulimina gracilis biofacies of Miller et al. (1997). This biofacies is interpreted by Miller et al. (1997) to represent 50–80 m paleowater depths. The biofacies are interpreted to represent paleowater depths of 25–50 m at the base of the sequence. The section deepens to 50–80 m between 361 and 366 ft (110.03 and 111.56 m) and shallows to 25–30 m above 356 ft (108.51 m). This is in agreement with lithofacies analysis that places the maximum flooding surface at 372 ft (113.39 m).

The Eocene benthic foraminifers are generally well preserved, although there is some overprinting of the biofacies by dissolution. Paleowater depths were assigned using the benthic foraminiferal biofacies defined by Browning et al. (1997b). Three sequences between 640.35 and 410 ft (195.18 and 124.97 m) contain a middle neritic fauna dominated by Cibicidoides cf. pseudoungerianus and were deposited at paleowater depths of ~100 m. Sequence E7 (698.85–640.35 ft; 213.01–195.18 m; lower Shark River Formation) contains abundant Cibicidoides subspiratus and was deposited at paleowater depths of ~135 m. Sequence E6 (722.5–698.85 ft; 220.22–213.01 m) is dominated by Cibicidoides aff. subspiratus and was deposited in ~155 m paleowater depth. Sequence E4 (731.9–722.5 ft; 223.08–220.22 m) is dominated by C. cf. pseudoungerianus and was deposited in ~100 m paleowater depth. Sequence E3 (756–731.9 ft; 230.43–223.08 m) from the Manasquan Formation is dominated by C. aff. subspiratus at the base and Siphonina claibornensis on top. This represents paleowater depths of ~155 m at the base shallowing to paleowater depths of ~125 m on top. Sequence E2 (836–756 ft; 254.81–230.43 m), though affected by dissolution through the middle part of the sequence, is dominated by Cibicidoides eocena and Eponides jacksonensis and was deposited in paleowater depths of ~185 m. Sequence E1 (847–836 ft; 258.17–254.81 m) is dominated by Cibicidoides mimulus and was deposited in paleowater depths of ~135 m.

Cretaceous benthic foraminifers are only locally abundant, probably because of dissolution and shallow paleowater depths. Maastrichtian samples are dominated by Buliminella carseyae, Coryphostoma plaitum, Pseudouvigerina seligi, and Gavelinella. This indicates outer inner to inner middle neritic paleowater depths. The dominance of species of Gavelinella in Campanian samples indicates mostly inner neritic paleowater depths. Bass River Formation samples are dominated by species of Epistomina, indicating inner neritic paleowater depths. A sample at 1371 ft (417.88 m) contains a much more abundant and diverse fauna and was likely deposited in middle neritic paleowater depths.

Calcareous Nannoplankton

Cenozoic

The calcareous nannoplankton biozonal subdivision of the Cenozoic section in the Millville corehole is difficult because of pervasive dissolution throughout the middle Eocene–Paleocene interval. Assemblages are thus impoverished, discoasters are few to extremely rare, and markers may be absent. The zonal scheme used below is that of Martini (1971) and Martini and Müller (1986).

The section from 572 to 595.9 ft (174.35 to181.63 m) is assigned to Zones NP19–NP20a based on the occurrence of Isthmolithus recurvus, Discoaster saipanensis, Discoaster barbadiensis, and Reticulofenestra reticulata. The section from 601.0 to 626.0 ft (183.18 to 190.80 m) contains Chiasmolithus oamaruensis without I. recurvus and is assigned to Zone NP18. A sample at 631.0 ft (192.33 m) is tentatively assigned to Zone NP17 based on the HO of Chiasmolithus grandis.

Samples through most of the middle Eocene are poorly preserved and are only provisionally zoned at this time. Samples at 636.0–641.0 ft (193.85–195.38 m) contain a mixture of fossils and cannot be zoned. Samples at 656.0 and 656.5 ft (199.95 and 200.10 m) yield Chiasmolithus solitus, R. reticulata, and Reticulofenestra floridana and belong to the upper part of Zone NP16 (Subzone NP16b). The HO of Discoaster distinctus in the sample at 661.5 ft (201.63 m) indicates mid-Zone NP16. Samples at 691.0 and 696.0 ft (210.62 and 212.14 m) are assigned to Zone NP15 based on the occurrence of Nannotetrina quadrata. The interval between the samples at 706.0 and 711.0 ft (215.19 and 216.71 m) may belong to Zone NP14 or NP15. Discoaster sublodoensis is rare in this interval with poor preservation, which is further characterized by the occurrence of Nannotetrina cristata.

The lowermost middle Eocene and lower Eocene has a better preserved flora and biozonal interpretations are more confident. Samples between 717.0 and 722.5 ft (218.54 and 220.22 m) contain D. sublodoensis and Blackites inflatus (717.0 ft; 218.54 m) and lack Discoaster lodoensis and Discoaster kuepperi, indicating assignment to Subzone NP14b. A sample at 731.0 ft (222.81 m) is assigned to Zone NP13 based on the occurrence of D. lodoensis and a diverse, well-preserved, typical lower Eocene assemblage. Samples between 734.0 and 767.0 ft (223.72 and 233.67 m) are assigned to Zone NP12 based on the co-occurrence of D. lodoensis and Tribrachiatus orthostylus. Samples between 771.0 and 831.1 ft (235.00 and 253.29 m) are assigned to Zone NP11 based on the occurrence of T. orthostylus. Dissolution in this interval is pervasive, and the nannofossil assemblages are considerably impoverished. Location of the NP11/NP12 zonal boundary is provisional because dissolution is strong throughout the Zone NP11–NP12 interval and D. lodoensis is fragmented to completely dissolved. A sample at 841.0 ft (256.34 m) containing Tribrachiatus contortus is assigned to Subzone NP10d, and samples at 846.0–851.0 ft (257.86–259.38 m) are provisionally assigned to either Subzone NP10a or NP10c.

Heavy dissolution in much of the Paleocene section makes it difficult to zone. Samples between 856.0 and 891.0 ft (260.91 and 271.58 m) are assigned to Subzone NP9b. Assemblages in this interval are characterized by Fasciculithus tympaniformis, Discoaster multiradiatus, Discoaster araneus, Discoaster anartios (891.0 ft; 271.58 m), Rhomboaster spineus, and Rhomboaster cuspis (the latter four taxa representing the Rhomboaster spp.-D. araneus [or RD] assemblage). D. araneus is rare in this interval, and there is no clear acme of Rhomboaster spp. The sample at 891.0 ft (271.58 m) is younger than the acme of the Rhomboaster-Discoaster assemblage. The HO of Fasciculithus alanii in a sample at 896.0 ft (273.10 m) and the LO of the RD in a sample at 891.0 ft (271.58 m) marks the NP9a/NP9b subzonal boundary. Subzone NP9a extends down to 946.0 ft (288.34 m). The interval between 921.0 and 941.0 ft (280.72 and 286.82 m) is barren. Samples between 951.0 and 966.0 ft (289.86 and 294.44 m) are assigned to Zone NP8 based on the abundant occurrence of Heliolithus riedelii; however, there are almost no discoasters preserved to either refine the position within the biozone or exclude the occurrence of the Zone NP9 marker D. multiradiatus. A sample at 971.0 ft (295.96 m) with Heliolithus cantabriae is assigned to either Zone NP6 or NP7. A sample at 976.0 ft (297.48 m) with Ellipsolithus distichus, Sphenolithus primus, Fasciculithus janii, and without F. tympaniformis is assigned to upper Zone NP4. A sample at 981.0 ft (299.01 m) just above the K/P boundary contains Cruciplacolithus tenuis and Chiasmolithus danicus and is assigned to Zone NP3.

Cretaceous

Cretaceous coccolith slides from the Millville corehole reflect a coccolith-rich environment with only one barren sample. Maastrichtian floras at 986 and 991 ft (300.53 and 302.06 m) are similar, but the floras at 986 ft (300.53 m) are more abundant. These samples are assigned to Zone CC26 based on the presence of Micula prinsii and Nephrolithus frequens. Samples from 996 to 1020.1 ft (303.58 to 310.93 m) are assigned to Subzone CC25c, based on the occurrence of Arkhangelskiella cymbiformis, Lithraphidites grossopectinatus, Lithraphidites quadratus, Micula murus, and Micula praemura. The sample at 1021.9 ft (311.48 m) contains A. cymbiformis and no other marker species and is assigned to Zone CC25.

The Campanian is identified in the corehole between 1026 and 1086 ft (312.72 and 331.01 m). Samples between 1026 and 1036 ft (312.72 and 315.77 m) are assigned to Subzone CC23a based on the presence of Broinsonia parca, Reinhardtites levis, and Tranolithus phacelosus and the absence of Reinhardtites anthophorus. Coccoliths show no age difference across the Navesink/Mount Laurel contact at 1032.9 ft (314.83 m) based on the floral similarities in samples at 1031 and 1036 ft (314.25 and 315.77 m). This reflects extensive reworking of the Campanian Mount Laurel Formation lithology in the Maastrichtian Navesink Formation lithology. The higher sample at 1031 ft (314.25 m) has much more abundant coccoliths. Both contain B. parca and R. levis, typical of late Campanian to early Maastrichtian floras. The sample at 1041 ft (317.30 m) contains B. parca and R. anthophorus and is assigned to Zone CC22. The sample at 1041 ft (317.30 m) has a distinctive shallow-water flora with Braarudosphaera and abundant Lucianorhabdus. The presence of R. anthophorus between 1071 and 1086 ft (326.44 and 331.01 m) suggests this section is Campanian. Samples from 1071 to 1075.9 ft (326.44 to 218.54 m) are assigned to Zone CC20–CC21 undifferentiated based on the presence of B. parca and Calculites obscurus and the absence of R. levis. A sample at 1086 ft (331.01 m) lacks C. obscurus and is assigned to CC19–CC21.

A sample at 1251.9 ft (381.589 m) is assigned to Santonian Zone CC15 based on the occurrence of Calculites ovalis, Lithastrinus septenarius, and R. anthophorus. A sample at 1344 ft (409.65 m) is assigned to lower Santonian/upper Coniacian Zone CC14 based on the occurrence of L. septenarius and Micula decussata. This is different from the Turonian age assigned using Sr isotopes and regional correlations of the Bass River Formation to the Cenomanian–lower Turonian and must reflect either downhole or laboratory contamination.

The sample at 1354 ft (412.70 m) is surprising for the abundant and well-preserved coccoliths. The sample contains Gartnerago obliquum and Lithraphidites acutus and is assigned to Zone CC10. Samples from 1386 to 1412 ft (422.45 to 430.38 m) are etched and have low diversity, making zonal determination difficult. These samples contain Eiffellithus turriseiffelii and are assigned to Zone CC9–CC10 undifferentiated. The sample at 1416.7 ft (431.81 m) is barren.

Diatoms

Fourteen Miocene samples were processed for diatoms from the Millville borehole. Diatoms were generally rare to absent in these samples. A sample at 374.4 ft (114.15 m) contains common diatoms assignable to East Coast Diatom Zone 1 (ECDZ 1) of Andrews (1988). Two samples at 249.9 and 250.0 ft (76.17 and 76.20 m) contain a fragmented, poorly preserved diatom assemblage. Diatoms include Paralia sulcata, Biddulphia tuomeyi, Melosira westii, Coscinodiscus sp., and Goniothecium rogersii. The assemblage is similar to that of the ECDZ 1 diatom assemblage at 374.7 ft (114.15 m) but it lacks marker species A. heliopelta. A. heliopelta is reported at 249.5 ft (76.05 m) by R. Benson (pers. comm., 2003) of the Delaware Geological Survey. Therefore, the section between 249.5 and 374.4 ft (76.05 and 114.15 m) is assigned to ECDZ 1.

Pollen

Thirteen samples were analyzed from the Millville corehole for palynomorphs, pollen, and spores (Table T9). All but one sample contained biostratigraphically useful specimens, although specimen recovery was generally poor to very poor (Table T9). Preservation in the Potomac Formation was generally better than samples higher upsection. Samples are assigned ages using the zonations of Brenner (1967) and Doyle and Robbins (1977).

Four samples taken from the Magothy Formation (between 1249.4 and 1291.8 ft; 380.82 and 393.74 m) contain several species of triporates of the genera Complexipollis and Porocolpopollenites and lack triporates typical of the middle and upper Magothy Formation. This strongly suggests Zone V (late Turonian) for the Magothy Formation at Millville, which is stratigraphically equivalent to the South Amboy Fire Clay. Samples in the Bass River Formation between 1320.0 and 1354.0 ft (402.40 and 412.70 m) contain either the Atlantpollis complex or Complexipollis sp. A, a triporate-Normapolle type very similar to similar to the Atlantpollis complex, and are assigned to Zone IV (late Cenomanian). This is stratigraphically equivalent to the Raritan Formation. A sample at 1384.0 (421.84 m) contains Ajatipollis sp. A, which is common in Zone III. The stratigraphic range of Ajatipollis sp. A is not well known, and it may extend into Zone IV. If Ajatipollis sp. A does extend into Zone IV, then, given the paucity of palynomorphs in this sample, dating is uncertain and the boundary between Zones IV and III is approximate. Three samples between 1411.2 and 1473.7 ft (430.13 and 449.18 m) contain several species of Tricolporopollenites that are indicative of Zone III (early Cenomanian). A sample at 1495.5 ft (455.83 m) contains both Subzone IIC and Zone III forms. The abundance of bisaccate coniferous pollen is a very common aspect of the upper Patapsco. This most likely reflects cooler paleoclimatic conditions at this time. The boundary between Subzone IIC and Zone III have not been well defined; this, together with the mixture of taxa, results in an uncertain assignment of the base of the borehole.

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