The Cape May Zoo site (September and October 2004) was the eleventh continuously cored borehole drilled as part of the New Jersey Coastal Plain Drilling Project (NJCPDP) and the eighth site drilled as part of Ocean Drilling Program (ODP) Leg 174AX. Located between the Leg 174AX Ocean View and Leg 150X Cape May sites, drilling at Cape May Zoo (39°06´16.9N, 74°48´52.6W; elevation = 19.4 ft; Stone Harbor Quad, USGS 7.5 minute quadrangle; Middle Township, Cape May County, New Jersey) targeted lower Miocene through Pleistocene sequences. Recovery was good (mean recovery = 70.3%) and ended at a total depth (TD) of 720 ft (219.46 m) in lower Miocene sediments. A full suite of slim-line logs was obtained to 708.3 ft (215.89 m), and a gamma log was obtained to 711.3 ft (216.8 m). A team of scientists from the New Jersey Geological Survey (NJGS), Rutgers University, the Delaware Geological Survey (DGS), and the U.S. Geological Survey (USGS) collaborated in drilling and stratigraphic studies of this corehole that was funded by the NJGS. The scientific team provided descriptions of sedimentary textures, structures, colors, and fossil content and identified lithostratigraphic units, lithologic contacts, and sequences (unconformity-bounded units). On-site and postdrilling studies of lithology, sequence stratigraphy, biostratigraphy, Sr isotopes, and aminostratigraphy comprise the basic data sets on which this site report is based.
The Cape May Formation (?Holocene–Pleistocene) is 93.6 ft (28.53 m) thick and can be divided into at least two sequences. Nearshore sand and thin gravel beds (0–20.5 ft; 0–6.25 m) form the upper part of Sequence Cm2, whereas tidal channel and foreshore sand and gravel with clay laminae form the lower part from 20.5 to 37 ft (6.25 to 11.28 m). The lower and older Sequence Cm1 (37–93.6 ft; 11.28–28.53 m) is a slightly deeper water deposit (estuary/bay/inner shelf) consisting of varying size sand with occasional shell beds above to finer grained very fine sand and sandy silty clay to clayey silt to clay below. Amino acid racemization (AAR) age estimates for this interval are middle Pleistocene (300–400 ka), suggesting correlation with marine isotope Chron (MIC) 9e or 11.
The ?upper Miocene sequence from 93.6 to 180.4 ft (28.53 to 54.99 m) is tentatively assigned to Sequence Ch4 of de Verteuil (1997) and placed in the newly named Stone Harbor Formation. The age and sequence assignment are provisional, as no datable material was obtained between 93.6 and 180.4 ft (28.53 and 54.99 m). The upper part from 93.6 to 113 ft (28.53 to 34.44 m) is fluvial coarse to very coarse pebbly sand. Below this are barrier beach deposits with generally finer grained sand, silty sand, sandy silt, and organic-rich clay and occasional lignite.
An upper Miocene sequence (180.4–231.4 ft; 54.99–70.53 m) contains mostly lower and some upper estuarine deposits and is tentatively correlated to Sequence Ch3 of de Verteuil (1997). Variegated lignitic sandy clay and poorly sorted sand with lignite and pebbles dominate this sequence, which is also placed in the Stone Harbor Formation.
A middle Miocene (~12 Ma) Kirkwood-Cohansey sequence (Kw-Ch2), from 231.4 to 293.3 ft (70.53 to 89.40 m), is a classic "New Jersey" coarsening-upward sequence with deeper water (shelf and prodelta) facies at the base of the sequence and shallow-water (shoreface) facies toward the top. Laminated to interbedded shelly sand and clayey silt (shelf deposits) from 283.5 to 293.3 ft (86.41 to 89.40 m) grade upward into laminated, slightly micaceous, slightly silty clay (prodelta deposits) from 261.2 to 283.5 ft (79.61 to 86.41 m). Interbedded silty fine to medium sand with thin clay beds (250–261.2 ft; 76.20–79.61 m) were deposited as lower shoreface deposits, coarsening upward to upper shoreface medium to coarse sand (231.4–248.7 ft; 70.53–75.80 m). We correlate this sequence with Sequence Ch2 of de Verteuil (1997).
An upper middle Miocene sequence (Sr isotope ages of 12.7 and 13.1 Ma; East Coast Diatom Zone [ECDZ] 7) is also a classic New Jersey coarsening-upward sequence at Cape May Zoo. The sequence was poorly recovered from 293.3 to 325 ft (89.40 to 99.06 m). This sequence is ~0.7 m.y. older than the overlying Kirkwood-Cohansey sequence and has a thinner upper highstand systems tract (HST). This sequence correlates in age with the lower Kirkwood-Cohansey sequence (Kw-Ch1; Miller et al., 1997, 1998) and is equivalent to Sequence Ch1 of de Verteuil (1997). Offshore deposits from 323.7 to 324.6 ft (98.66 to 98.94 m) contain very shelly, silty clayey sand with medium to fine sand laminae. These deposits grade into slightly micaceous sandy silty clay with rare shells, representing prodelta and distal delta front environments. The thin upper HST (293.3–304 ft; 89.40–92.66 m) contains delta front deposits consisting of cross-bedded to laminated, fine to very fine, silty, slightly micaceous quartz sand with silt and clay laminae and beds, and slightly micaceous, slightly silty, clay with thin sand and organic-rich laminae from 302 to 304 ft (92.05 to 92.66 m).
Sequence Kw3 (325–415.7 ft; 99.06–126.71 m) is thick with two flooding surfaces in the HST. This sequence contains diatoms assigned to ECDZ 6 and has Sr isotope age estimates between 14 and 13 Ma. The base of this sequence (406–415.7 ft; 123.75–126.71 m) contains bioturbated, slightly silty fine to medium sand with scattered shell fragments and numerous granules deposited in lower shoreface environments representing the transgressive systems tract (TST). Above this, the offshore facies from 368.5 to 406 ft (112.32 to 123.75 m) is gray clayey silt (369–370.2 ft; 112.47–112.84 m) with common sulfur, tight clay (370.2–371.1 ft; 112.84–113.11 m), and bioturbated, shelly, slightly silty clay (371.1–400 ft; 113.11–121.92 m) that contains the maximum flooding surface (MFS) (395 ft; 120.40 m). The HST occurs from 325 to 395 ft (99.06 to 120.4 m) and is punctuated by two flooding surfaces (FS) at 352.8 and 368.5 ft (107.53 and 112.32 m). It is dominated by shoreface environments and shallows from a finer grained lower shoreface environment in the lower part to a coarser grained upper shoreface environment above. Bioturbated, slightly shelly sandy silt (360–368.6 ft; 109.73–112.35 m) coarsens upward to bioturbated silty, slightly shelly fine sand (355–360 ft; 108.20–109.73 m) deposited in the upper shoreface. The HST from 325 to 352.8 ft (99.06 to 107.53 m) is also composed of sediments deposited in dominantly lower shoreface environments. From 351.7 to 352.8 ft (107.20 to 107.53 m) is shelly clayey silt. Clayey silt grades to sandy silt from 332.7 to 351.7 ft (101.41 to 107.20 m). An abrupt facies change occurs at 332.7 ft (101.41 m), with the section coarsening upward to burrowed, silty fine sand with traces of mica, wood, and shell from 325.5 ft (99.21 m). This distal upper to lower shoreface deposit represents the upper part of an HST.
Sequence Kw2b (16.7 Ma based on Sr isotope age estimates; ECDZ 3–4) is a coarsening-upward New Jersey sequence (415.7 5–15.7 ft; 126.71–157.19 m), which may have a thin lowstand systems tract (LST) at its base. This potential LST (510.4–515.7 ft; 155.57–157.19 m) is a medium–coarse, bioturbated, granuliferous shelly muddy sand deposited in a proximal upper shoreface environment. Above the LST is the lower part of the TST, comprised of slightly clayey silt (500–510.4 ft; 152.40–155.57 m) with shell fragments deposited in offshore environments. The lower HST deposited in prodelta environments consists of predominantly laminated organic-rich clay with thin sand laminae and sand beds from 483.7 to 493.7 ft (147.43 to 150.48 m). There is a transition to upper HST muddy cross-bedded sand with interbedded clean sand, lignite clay, and silty brown organic-rich clay (479.2–483.7 ft; 146.06–147.43 m) deposited in delta front environments. Above a flooding surface or autocyclical change, thick upper shoreface, bioturbated, muddy, very shelly fine–medium sand is found from 442.9 to 479.2 ft (135.00 to 146.06 m). Above this is heavily bioturbated, shelly, fine–medium sand (430.0–438.5 ft; 131.06–133.65 m) that is interpreted as part of a general stillstand from 424 to 442 ft (129.24 to 134.72 m). The upper part of the Kw2b sequence (415.7–424 ft; 126.71–129.24 m) consists of slightly shelly, silty fine–medium sand deposited in wave-dominated shoreface environments.
The early Miocene Kw2a sequences (Kw2a1, Kw2a2, and Kw2a3) are assigned to ECDZ 2 and have Sr isotope age estimates from 17.8 to 17.0 Ma. These Kw2a sequences, from 515.7 to 630.7 ft (157.19 to 192.24 m), are dominated by offshore and prodelta clay and silt, except for the coarser grained Sequence Kw2a2 (529–549.5 ft; 161.24–167.49 m).
Sequence Kw2a1 is the thickest (81.2 ft; 24.75 m) of the Kw2a sequences (549.5–630.7 ft; 167.49–192.24 m). We interpret a thin LST from 625 to 630.7 ft (190.50 to 192.24 m). Above this is a thin TST (620.1–625 ft; 189.01–190.50 m) composed of interbedded very fine sand and silty clay deposited in prodelta environments. The unit from 549.5 to 620.1 ft (167.49 to 189.01 m), a thick HST, is generally fine-grained, laminated clayey silt with very fine sand laminae (549.5–558.5 ft; 167.49–170.23 m), silty very fine sand (558.5–561.7 ft; 170.23–171.21 m), laminated silty clay with very fine sand laminae (561.7–586 ft; 171.21–178.61 m), and shelly laminated silty clay with very fine sand laminae (586–620.1 ft; 178.61–189.01 m) deposited in offshore (probably inner neritic), prodelta, and lower shoreface environments. The thin Kw2a2 sequence, from 529 to 549.5 ft (161.24 to 167.49 m), is a slightly clayey, shelly medium sand with a trace of mica and glauconite deposited in lower shoreface to offshore environments. The thinnest of the Kw2a sequences, Sequence Kw2a3 (13.3 ft [4.05 m]; 515.7–529 ft [157.19–161.24 m]), is a micaceous, organic-rich laminated clay to thin bedded silty clay with occasional fine sand beds and shell fragments, interpreted as a prodelta deposit.
The lower Miocene Kw1c sequence (Sr isotope age estimates of 18.8–19.2 Ma) is much thinner at this site (25.8 ft [7.86 m]; 630.7–656.5 ft [192.24–200.10 m]) than at the Leg 150X Cape May site to the south. Sequence Kw1c at Cape May Zoo consists of slightly muddy, fine–medium sand with shell fragments toward the base deposited in distal upper and lower shoreface environments. A thin, indurated, medium-grained sandstone (643.0–643.5 ft; 195.99–196.14 m) with pebbles and large shells (including oysters) marks either a flooding surface or an autocyclical change. Above the surface the sequence is laminated silty clay with thin, interbedded, fine, organic-rich, slightly shelly sand (prodelta environments) grading upward to black, organic-rich, shelly, silty, fine–medium sand interbedded with organic-rich sandy clayey silt deposited in delta front environments. Based on Sr isotope age estimates, its age ranges from 18.8 to 19.2 Ma, though reworking in the lower part of the section yields older ages.
The hole bottomed in the HST of the lower Miocene (Sr isotope age estimates of 19.2–20.0 Ma) Kw1b sequence. Sequence Kw1b is dominated by lower and distal upper shoreface deposits characterized by bioturbated, shelly, slightly silty, fine–medium sand with occasional coarser sand beds.
The Miocene sequences recovered at the Cape May Zoo site not only verify sequences found at the Cape May site (especially Sequence Kw1c), they also compliment sequences that will be divided by Integrated Ocean Drilling Program Expedition 313 in summer 2007. The section also provides insights to the hydrostratigraphy of the Cape May peninsula and aquifer distribution.