We used the planktonic foraminiferal zonation of Berggren and Miller (1988) for the Paleogene and that of Kennett and Srinivasan (1983) for the Neogene, the zonation of Martini (1971) for the Cenozoic nannofossils, the East Coast Diatom Zonation (ECDZ) of Andrews (1988) for the Neogene, and the Geomagnetic Polarity Time Scale (GPTS) and biostratigraphic ages of Berggren et al. (1985) for the Cenozoic. The GPTS has recently been revised (Cande and Kent, 1992); however, the biostratigraphic ages were not recalibrated to the new GPTS until Berggren et al. (1995). To maintain consistency of time scales with the previously published Island Beach and Atlantic City site reports (Miller et al., 1994a, 1994b), we report ages to the Berggren et al. (1985) time scale, realizing that the ages must be recalibrated.
The upper Eocene (1500-1360 ft, 457.3-414.6 m), the Oligocene (1360-1180 ft, 414.6-359.8 m), and the lowermost Miocene (1180-995.9 ft, 359.8-303.6 m) contain generally well-preserved and diverse planktonic foraminifer assemblages. The upper part of the lower Oligocene (1327-1270 ft, 404.6-387.2 m) contains low-diversity assemblages without diagnostic taxa in most cases. The interval above 920 ft (280.5 m) of the Miocene and younger sediments are largely barren of planktonic foraminifers; however, sporadic samples below 357.5 ft (109 m) contain characteristic Miocene taxa, including species of Globigerinoides, neogloborotaliids, tenuitellids, globigerinids, and globorotaliids. The presence of abundant and diverse planktonic foraminifers allows application of the zonation of Berggren and Miller (1988) to the Eocene and basal Oligocene. Planktonic foraminifer zonation for the rest of the Oligocene and younger sediments was not possible using primary zonal criteria because of the absence of marker taxa. However, we were able to zone the Oligocene to middle Miocene using secondary marker species of planktonic foraminifers as calibrated by Berggren et al. (1995).
The ?upper Miocene and younger sediments do not contain stratigraphically diagnostic planktonic foraminifer taxa, although sporadic samples may preserve a few specimens of Globigerina spp. The presence of benthic foraminifers provide paleoenvironmental constraints on the ?Pleistocene Cape May Formation (see "Lithostratigraphy" section, this chapter).
The upper Miocene cannot be directly recognized by planktonic foraminifer biostratigraphy in the Cape May borehole. However, it is possible that the Kirkwood-Cohansey sequence (357-432.2 ft) could be, in part, upper Miocene. It is also possible that some of the overlying clays and sands between 167 and 357 ft may be upper Miocene, although preliminary palynological studies at the nearby Cape May airport borehole indicate that this section is partly Pliocene. Circumstantial evidence for the presence of upper Miocene strata at Cape May include the following:
Between 357 and 615 ft, only four samples (485, 522, 563, and 600.1 ft) contain planktonic foraminifers. No zonal marker species were identified in this interval. However, occurrences of Neogloboquadrina mayeri, N. continuosa, Globoconella praescitula, Globi gerina brazieri, G. decoraptura, and Tenuitella spp. suggest that these samples are middle Miocene.
No detailed planktonic foraminiferal biostratigraphic zonation is possible for the upper part of the lower Miocene (615-1000 ft). The highest occurrence (HO) of G. incognita at 675 ft indicates that the section below is lower Miocene Zones N5-N7 (undifferentiated), whereas above this is Zones N7-N10 (Fig. 3). The interval from 1000 to 1045 ft contains a relatively diverse middle lower Miocene planktonic foraminifer assemblage containing Globigerinoides altiaperturus and 26 other taxa. Globigerinoides altiaperturus has its lowest occurrence at 1045 ft. This taxon appears near the base of middle lower Miocene Zone N5 (Berggren et al., 1995).
As a result of the absence of marker taxa, the Oligocene/Miocene boundary cannot be recognized based on planktonic foraminifers alone. The absence of Globorotalia pseudokugleri above the 1180-ft (359.7 m) unconformity and strontium isotopic age estimates (25.5 Ma below vs. 23.1 Ma above) place the Oligocene/Miocene boundary in a hiatus associated with the disconformity at 1180 ft (359.8 m).
The Oligocene in the Cape May borehole is the most fossiliferous of the three boreholes drilled during Leg 150X. Oligocene planktonic foraminiferal assemblages are characterized by relatively high diversity and most of the diagnostic taxa are present. Zonation is possible but should be used with caution due to rare occurrences of marker taxa.
Zone P22 spans approximately 1180 to 1249.7 ft. The base of Zone P22 is at 1249.7 ft based on the HO of Paragloborotalia opima opima at 1249.7 ft. The presence of Globorotalia cf. pseudokugleri at 1262 ft may represent an ancestral form, because Globorotalia pseudokugleri sensu stricto does not appear until well into Zone P22 (Berggren et al., 1995). The planktonic foraminiferal assemblage in Zone P22 is similar to that in Subzone P21b and is dominated by globigerinids, tenuitellids, and paragloborotaliids (Table 3).
Subzone P21b ranges from 1249.7 to 1270 ft. At 1270 ft, an unconformity separates Subzone P21b from Zone P20. The HO of Chiloguembelina cubensis is at 1294 ft and is clearly premature due to preservation because it occurs below the HO of Turborotalia ampliapertura (top of Zone P19; 1275.9 ft) at this site (Fig. 3). The interval from 1249.7 to 1270 ft probably belongs to Subzone P21b (basal upper Oligocene) because of the absence of C. cubensis. Preservation is good in this interval, and C. cubensis would be expected if this was Subzone P21a. (Note added in proof: Subsequent studies have shown that the upper/lower Oligocene contact is at 1304.8 ft [397.7 m]. Specimens of C. cubensis between 1294 and 1304.8 [394.4 and 397.7 m] are reworked. T. ampliapertura and S. angioporoides above 1304.8 ft [397.7 m] are reworked or misidentified.)
The lower Oligocene in the Cape May borehole ranges from 1270 to 1360 ft. Microfossil preservation in this interval is generally poor.
Zone P19 ranges from the HO of Pseudohastigerina spp. at 1351 ft to the HO of Turborotalia ampliapertura at 1275.9 ft. The diversity of the planktonic foraminiferal assemblage is relatively low, comprising subbotinids, globigerinids, tenuitellids, and chiloguembelinids (Table 3).
Zone P18 ranges from the HO of the Turborotalia cerroazulensis lineage (used along with Hantkenina spp. to recognize the top of Eocene and Zone P17) at 1360 ft to the HO of Pseudohastigerina spp. at 1351 ft (Fig. 6). Planktonic foraminifer diversity is higher in Zone P18 than in Zone P19 because of the presence of Pseudohastigerina spp. and more subbotiniid taxa (Fig. 3; Table 3).
Uppermost Eocene Zone P17 is defined as from the HO of Cribrohantkenina inflata to the HO of Turborotalia cerroazulensis spp. The HO of T. cerroazulensis cocoaensis and T. c. cunialensis is at 1360 ft (414.6 m) at Cape May, marking the top of Zone P17 and the Eocene/Oligocene boundary. As at Island Beach and Atlantic City (Miller et al., 1994a, 1994b), the Eocene/Oligocene boundary in the Cape May borehole coincides with a sharp lithologic contact at 1360 ft (414.6 m) and a hiatus. Cribrohantkenina inflata was not observed in the borehole and the base of Zone P17 is uncertain. The HO of Globigerapsis index, which approximates (0.3 m.y. before) the HO of Cribrohantkenina inflata (Berggren et al., 1995), is at 1392 ft (424.4 m), indicating the recovery of Zone P16 in the borehole. The upper Eocene contains diverse and well-preserved planktonic foraminifer assemblages (Table 3).
Calcareous nannofossils are present at most levels, but they are generally rare to scare and preservation is moderate to poor. The highest level with an age-diagnostic assemblage is at 675.0 ft (205.8 m). Helicosphaera ampliaperta (common) and Sphenolithus heteromorphus (very rare) characterize Zone NN4 (Fig. 3). Helicosphaera ampliaperta is present at 690.9-691 ft, but no Sphenolithus was encountered. Thus, this level may belong to Zone NN4 or older.
Samples between 700 and 822 ft (213.4 and 250.6 m) are barren or contain scarce low-diversity assemblages. Helicosphaera ampliaperta is present at 837 and 890.1 ft. Thus, these samples are assigned to the NN2-NN3 zonal interval (Fig. 4).
Calcareous nannofossils are common and moderately well preserved from 1020 to 1140 ft but lack age-diagnostic taxon. Triquetrorhabdulus carinatus occurs at 1157 ft (352.7 m), which indicates Zone NN2 or older (NP25-NN2), and the interval from 1157 to 1253 ft may be lower Miocene or upper Oligocene. The highest definite Oligocene assemblage is at 1300 ft (Zone NP24 or NP25 with R. bisecta and R. abisecta).
The interval between 1360 and 1377 ft may belong to Zone NP21. The sequential highest occurrences of D. saipanensis (1383 ft), D. barbadiensis (1412 ft), and R. reticulata (1436 ft) characterize a continuous upper Eocene Zone NP19-N20 interval.
Diatoms were present between 19.0 and 44.8 ft. No zonal indicators were observed. Samples between 54.2 and 84.0 ft had few diatoms. These samples contain Nitzschia granulata, a brackish water form. Diatoms are more common in samples from 91.9 to 131.9 ft. Again, no zonal indicators were observed; however, on the strength of the absence of species, these samples could be upper Miocene to Pleistocene. Samples between 161.9 and 391.6 ft contain few or no diatoms. Where diatoms are present, N. granulata, a brackish water indicator dominates.
Diatoms become more common in the Miocene section between 402.5 and 741 ft, although within this interval some levels contain no or very few diatoms. The zonal indicators Delphineis novaecaesaraea, D. penelliptica, and Denticulopsis hustedtii were found within this interval. The zonal marker Coscinodiscus lewisianus has its highest occurrence at 658.2 ft. These occurrences suggest that the levels above 658.2 ft belong to ECDZ 6 and 7. The last occurrence of Coscinodiscus lewisianus occurs in the lowermost part of ECDZ 6. Samples between 752.5 and 922 ft contain no or very few diatoms. The next underlying sample, 1045 ft, contains diatoms but no zonal markers were observed. No diatoms were noted between 1061 and 1247 ft. The next two samples below this (1253.9 and 1261.9 ft) contain Actinocyclus heliopelta and Sceptroneis caduceus. These two occurrences suggest that these samples belong to ECDZ 1 or older sediments. All samples below this level down to the sample at 1473 ft contain no diatoms.