undifferentiated above and Upper Cretaceous below.
The Double Trouble site (October–November 2008) was the thirteenth continuously cored borehole drilled as part of the New Jersey Coastal Plain Drilling Project (NJCPDP) and the tenth site drilled as part of Leg 174AX (Fig. F1). Located ~5 mi (8 km) updip from the Leg 150X Island Beach site, drilling at Double Trouble (39°53′44.732″N, 74°13′23.346″W; elevation 36.8 ft [11.2 m]; Toms River U.S. Geological Survey [USGS] 7.5 min quadrangle; Berkeley Township, Ocean County, New Jersey) targeted Oligocene and late to middle Eocene sequences and aquifers and the Cretaceous/Paleogene boundary. Recovery was good (mean recovery = 74%), ending at a total depth (TD) of 858 ft (261.5 m) in Upper Cretaceous sediments. A full suite of slimline logs was obtained on the formation to 848.8 ft (258.7 m), and a gamma log was obtained to 844.6 ft (257.4 m). A team of scientists from the New Jersey Geological Survey (NJGS), Rutgers University, the Delaware Geological Survey (DGS), and the USGS collaborated in drilling and stratigraphic studies of this corehole, which was funded by the NJGS. Onsite and postdrilling studies of lithology, sequence stratigraphy, biostratigraphy, hydrostratigraphy, and Sr isotopes comprise the basic data sets on which this site report is based. The scientific team provided onsite descriptions of sedimentary textures, structures, colors, and fossil content and identified lithostratigraphic units, lithologic contacts, and sequences (unconformity-bounded units).
Beneath a thin (25.2 ft; 7.7 m) fluvial surficial (?Pleistocene) section, nearshore deposits of the upper to upper middle Miocene Cohansey Formation are 140.3 ft (42.8 m) thick and are only dated by regional correlations. The Cohansey Formation represents deposition in shoreface, foreshore, lagoonal, and tidal flat/channel environments and likely represents two sequences. The lower Miocene Kirkwood Formation (165.1–293.8 ft; 50.5–89.6 m) is 128.2 ft (39.1 m) thick and is also only dated by regional correlations; it represents deposition in shelf, prodelta, and delta front environments and can be divided into two sequences likely correlative to the Kw1a and Kw1b sequences of Miller et al. (1997).
The upper middle Eocene Toms River Member of the Shark River Formation (293.8–475.7 ft; 89.6–145.0 m) was a major target of this corehole. It consists of slightly muddy, glauconitic quartz sand. The sands are poorly sorted, ranging from very fine to coarse grained with granules and generally coarsen upsection. We interpret the environment of deposition as a "dirty" shoreface that shallows from lower to upper shoreface and that was proximal to a coarse sediment source. The Toms River Member at Double Trouble comprises the highstand systems tract (HST) of Sequence E8 of Browning et al. (1997a, 1997b). Age control on the unit is provided by dinocysts that suggest it is ~37–43 Ma (i.e., equivalent to nannofossil Zones NP16–NP17) and by superposition over sediments assigned to planktonic foraminiferal Zone E10 and nannofossil Zone NP16, all of which indicate it is upper middle Eocene. Regional studies documented here show that the sands of the Toms River Member are diachronous in the New Jersey coastal plain, becoming older downdip (i.e., comprising the HST of Sequences E8, E9, and E10 progressively downdip). The Toms River Member is an important aquifer in the Toms River, New Jersey, area and the Double Trouble corehole confirms that it is a thick (~161 ft; 49.1 m) water-bearing unit.
The middle Eocene lower Shark River Formation (475.8–572 ft; 145.0–174.3 m) is 96.2 ft (29.3 m) thick and can be divided into three sequences. The upper part of the unit is a fossiliferous, slightly micaceous, quartzose, glauconitic clayey silt, with glauconite increasing downsection to a sequence boundary at 517.4 ft (157.7 m). A maximum flooding surface (MFS) is placed near the top of the unit at ~485 ft (147.8 m). The HST of this Sequence E8 comprises the top of the lower Shark River Formation and the Toms River Member. The bulk of the lower Shark River Formation consists of "ash colored marls": burrowed, very slightly glauconitic foraminiferal clays that become occasionally porcellanitic. A slightly sandy interval (517.4–541.1 ft; 157.7–164.9 m) marks the top of Sequence E6 or E6a, whereas a glauconitic interval (561–569.2 ft; 171.0–173.5 m) marks the base. Sequence E7 is not represented at Double Trouble. Sequence E6/6a is assigned to Zones E8–E9 (P10–P11) and NP15–N16. A thin Sequence E5 (570–572 ft; 173.7–174.3 m) consists of glauconitic clays assigned to Zone NP14a, which straddles the lower/middle Eocene boundary. Glauconitic clays are used to recognize the base of the formation.
The lower Eocene Manasquan Formation (572–706.5 ft; 174.3–215.3 m) is primarily a slightly glauconitic carbonate clay that can be divided into three sequences. A thin Sequence E4 (572–583.6 ft; 174.3–177.9 m) is slightly sandy (10% quartz) with a basal thin glauconitic clay and is assigned to Zone NP13. Sequence E3 (583.6–673.6 ft; 177.9–205.3 m) is thick (90 ft; 27.4 m), very slightly sandy at the top, and assigned to Zones NP11 and E4–E7 (P6b–P9). It overlies a sandier HST of Sequence E2 (673.6–706.5 ft; 205.3–215.3 m) assigned to Zones NP11 and E4–E5; Sequence E2 consists of carbonate clays with quartz sands decreasing downsection from ~20% to a clay peak interpreted as an MFS (~706 ft; 215.2 m) and a basal glauconite sand that is also the base of the Manasquan Formation.
The section from 706.5 to 741.9 ft (215.3 to 226.1 m) is a heavily bioturbated, slightly micaceous clayey silt to silt deposited in a delta-influenced shelf environment and is assigned to the Vincentown Formation. This unit has discrepant biostratigraphic assignments likely due to reworking of Paleocene planktonic foraminifers into the lower lower Eocene section. The Marlboro Clay, which represents the carbon isotope excursion (zones lower NP9b and E1) and subsequent recovery, is not represented at Double Trouble; it is similarly missing downdip at Island Beach but is otherwise well represented in other coastal plain coreholes. A sandy silt (741.9–751 ft; 226.1–228.9 m) may mark the HST of a sequence, with the contact at 741.9 ft (226.1 m) interpreted as a sequence boundary. A glauconitic-rich interval and surface at 810.3 ft (247.0 m) marks a basal sequence boundary. We tentatively interpret the entire section from 706.5 to 741.9 ft (215.3 to 226.1 m) and 741.9 to 810.2 ft (226.1 to 247 m) as two sequences correlated to Sequences E0 (defined herein) and Pa3a of Harris et al. (2010).
A thin sequence (810.3–818.8 ft; 247.0–249.6 m) straddles a contact with glauconite sands of the Hornerstown Formation (816–838.85 ft; 248.7–255.7 m), is assigned to Zone NP6, and is correlated with Sequence Pa2a of Harris et al. (2010). Below this, biostratigraphy suggests two thin Paleocene sequences: 818.8–822.95 ft (149.6–250.8 m), assigned to Zones P3 and NP5, and 822.95–832.65 ft (250.8–253.8 m), assigned to Zones P1c and NP3–NP4. A basal Paleocene sequence below 832.65 ft (253.8 m) straddles the Cretaceous/Paleogene boundary, with Zone P1b-P undifferentiated above and Upper Cretaceous below.
The Cretaceous/Paleogene boundary (838.35–838.65 ft; 255.5–255.6 m) appears to be biostratigraphically complete and has chalky clasts that may be carbonate accretionary lapilli and possible spherules, though a distinct spherule bed noted at Bass River (Olsson et al., 1997) is absent. Below the boundary are clayey glauconite sands of the Upper Cretaceous Navesink Formation.
The Double Trouble corehole penetrated several distinct water-bearing sands that comprise potential aquifers. Though no hydrologic studies were conducted at this site, sedimentological and log analyses suggest that the unconfined Kirkwood-Cohansey is shallow but a good aquifer (surface to ~185 ft; surface to 56.4 m). Prodelta fine silty sands and clayey silts (185–293.8 ft; 56.4–89.6 m) may confine the Toms River Member, the upper part of which comprises a major aquifer (293.8–~455 ft; 89.6–138.7 m).
