The on-site scientific team provided preliminary descriptions of sedimentary texture, structure, color, fossil content, identification of lithostratigraphic units (New Jersey Division of Water Resources, 1990), and lithologic contacts (Table T1; Figs. F2, F3, F4, F5, F6, F7). Subsequent studies integrated preliminary descriptions with additional descriptions, biostratigraphy, biofacies studies, isotopic stratigraphy, and the downhole gamma log. Unconformities were identified on the basis of physical stratigraphy, including irregular contacts, reworking, bioturbation, major facies changes, and gamma ray peaks. Paraconformities were inferred from biostratigraphic breaks. Core photographs (Figs. AF1, AF2, AF3, AF4, AF5) illustrate sequence-bounding unconformities and facies variation within sequences.
For the nonmarine and nearshore sections, lithofacies interpretations provide the primary means of recognizing unconformities and interpreting paleoenvironments and systems tracts. For the neritic sections, biostratigraphic studies and Sr isotopes provide an additional means of recognizing unconformities and interpreting paleoenvironments and systems tracts.
Cumulative percent plots of the sediments in the cores were computed from washed samples (Table T2). Each sample was dried and weighed before washing, and the dry weight was used to compute the percentage of sand.
Facies changes within onshore sequences generally follow repetitive transgressive–regressive patterns (Sugarman et al., 1993, 1995) that consist of (1) a basal transgressive glauconite (particularly Paleogene–Upper Cretaceous sections) or quartz sands (particularly Miocene sections) equivalent to the transgressive systems tract (TST) of Posamentier et al. (1988) and (2) a coarsening-upward succession of regressive medial silts and upper quartz sands on top equivalent to the HST of Posamentier et al. (1988). Lowstand systems tracts (LSTs) are usually absent in the coastal plain and the TSTs are generally thin. Because the TSTs are thin, MFSs are difficult to differentiate from unconformities. Shell beds and gamma ray peaks can mark both TSTs and MFSs. Flooding surfaces, particularly MFSs, may be differentiated from sequence boundaries by the association of erosion and rip-up clasts at the latter, lithofacies successions, and benthic foraminiferal changes. The transgressive surface (TS), marking the top of the LST, represents a change from generally regressive to transgressive facies; because LST are generally absent, these surfaces are generally merged with the sequence boundaries. Where present, LSTs are recognized as generally thin, regressive, fluvial-estuarine sediments underlying TSTs and overlying sequence-bounding unconformities.
The upper 25.2 ft (7.7 m) is a fining-upward succession based on the on the gamma log, general core descriptions, and washed samples (Fig. F2). From 5 to 5.3 ft (1.5 to 1.6 m) is a gravelly sand (5%–10% very coarse sand and granules) that might represent slump into the hole or a lag gravel deposited as colluvium. From 5.3 to 25.2 ft (1.6 to 7.7 m) is a reddish yellow medium- to coarse-grained sand with 1%–2% opaque heavy mineral that fines upsection. No bedding is evident. The unit from 5 to 25.2 ft (1.5 to 7.7 m) was deposited in a channel, likely a fluvial one. The absence of clay and silt is likely due to the source being reworked from the marine Cohansey Formation sands below. The base of the unit is associated with a large gamma kick and an interval of no recovery (21.7–25.0 ft; 6.6–7.6 m); the contact is tentatively placed at 25.2 ft (7.7 m) at a change from fine sands above to gravely sands below. This surficial deposit is assigned to the upper stream terrace deposits with a likely age of ?125 ka (Newell et al., 2000).
The Cohansey Formation in the Double Trouble corehole (Fig. F2) is an aquifer sand deposited in inner neritic to nearshore (including shoreface and intertidal) environments. The Cohansey Formation is dominated by water-saturated medium to coarse quartz sand with gravel. Poor recovery (Fig. F2) of these unconsolidated sands makes detailed paleoenvironmental interpretation difficult. From 25.2 to 25.4 ft (7.68 to 7.74 m) is poorly sorted medium to coarse sand with abundant gravel (up to 14 mm) and 4% opaque heavy minerals. From 25.4 to 40.25 ft (7.74 to 12.3 m) the gamma log (Fig. F2) shows two coarsening-upward successions (the contact between the two was lost in a coring gap). The upper succession extends from 25.4 to 34 ft (7.74 to 10.4 m); the lower succession extends from 34 to 40.25 ft (10.4 to 12.3 m). From 25.4 to 27.3 ft (7.74 to 8.3 m) is coarse to very coarse sand with granules; 26.3–26.9 ft (8.0–8.2 m) has a concentration of granules and pebbles (up to 10 mm). Hints of bedding are defined by grain size differences. From 27.3 to 28.3 ft (8.3 to 8.6 m) there is a bedded interval with beds to 2 cm in thickness. This is mostly medium to very coarse sand that fines downward. Some of the beds are thin and dusky red with more common granules. The coarse beds from 25.4 to 28.3 ft (7.74 to 8.6 m) have a dusky red staining on coarser interbeds. From 28.3 to 31 ft (8.6 to 9.4 m) is medium to very coarse poorly sorted sand; there is a coring gap from 31.0 to 35.0 ft (9.4 to 10.7 m). There is an opaque heavy mineral concentration from 28.7 to 28.85 ft (8.7 to 8.8 m) in a finer grained bed. Another opaque heavy mineral concentration is in a coarser grained bed at 30.25–30.35 ft (9.2–9.3 m). There appears to be some bedding changes based on grain size changes. From 34 to 37.5 ft (10.4 to 11.4 m) is a better sorted medium to coarse sand dominated by quartz with few opaque heavy minerals. From 37.5 to 40.25 ft (11.4 to 12.3 m) the core is finer grained silty fine to medium sand and it gets slightly finer toward the base with more opaque heavy minerals. This unit appears to represent an upper shoreface at the base overlain and prograded over by foreshore deposits.
A surface at 40.25 ft (40.25 m) separates silty fine sand above from a sandy gravel bed (40.25–40.55 ft; 12.3–12.4 m) below which in turn overlies a medium-coarse sand with more opaque heavy minerals below (Fig. F2). The gravel bed might be placed as a basal lag of the overlying succession or the top of the underlying succession; a sharp gamma log kick at 40 ft (12.2 m) suggests the latter.
The section from 40.55 to 41.1 ft (12.4 to 12.5 m) goes from gravelly very coarse sand at the base to medium sand at top. The unit is vaguely bedded with ~4–6 cm thick beds. From 41.1 to 43.1 ft (12.5 to 13.1 m) the core changes from medium on top to coarse to very coarse sand at the base with the boundary between the two lithologies at 42.2 ft (12.9 m). There is a coring gap from 42.2 to 50 ft (12.9 to 15.2 m). From 50 to 53.2 ft (15.2 to 16.2 m) is coarse to very coarse sand with a little fine sand matrix. At 53.2–53.5 ft (16.2–16.3 m) there is a change to a silty fine to medium sand with a possible silty burrow. There is a coring gap from 53.5 to 60 ft (16.3 to 18.3 m). The section from 60 to 72.75 ft (18.3 to 22.2 m) consists of alternating thinly bedded medium to medium-coarse sands with granuliferous zones; it is generally finer grained than above (Fig. AF1). We interpret this unit as foreshore/swash zone deposits representing a regressive foreshore barrier beach succession (succession A of Carter, 1978).
The section from 72.7 to 120 ft (22.2 to 36.6 m) is lithologically distinct from the section above and is interpreted to represent subtidal/intertidal environments (Fig. F2). A sharp surface at 72.7 ft (22.2 m; Fig. AF1) separates the nearshore sands with a thin gravel (as much as 10 mm in diameter) basal laminae (~2.5 cm thick) from a predominantly whitish gray clay with orangish laminae (liesegang banded) and areoles that might represent soil environments (72.5–75.2 ft; 22.1–22.9 m). The clay contains silty lenses 1–2 cm thick that are occasionally iron cemented. This was deposited in a protected nearshore environment behind a barrier island. Sand between 75.2 and 77.1 ft (22.9 and 23.5 m) is finely laminated with cross-laminae and may represent tidal environments. There seems to be two cycles of development in this interval. The top of the cycles consists of 0.2 ft of laminated fine sand with rare burrows. Sand from 77.1 and 95 ft (23.5 and 29 m) is bedded coarse to very coarse sand with rare granules. The sand is dominantly cross-bedded to 80.8 ft (24.6 m). Clay laminae are found at 77.65, 82.15, and 83.15 ft (23.7, 25.0, and 25.3 m). There is an ironstone concretion at 83.5–83.6 ft (24.45–25.48 m). The lower contact is missing in a coring gap between 89.7 and 95 ft (27.3 and 29.0 m). The entire unit from 72.7 to 95 ft (22.2 to 29.0 m) is interpreted to represent a tidal channel filling in to a tidal flat on top. These facies are similar to the tidal flat model of Carter (1978). Bidirectional cross beds within a core (e.g., 80–82 ft; 24.4–25.0 m) argue against a fluvial environment of deposition for this section.
The interval between 95 and 120 ft (29.0 and 36.6 m) is lithologically distinct from the section above (Fig. F2). The contact between the two units is lost in a coring gap between 89.7 and 95 ft (27.3 and 29.0 m). The gamma log has a positive inflection at 95 ft (29.0 m), where we placed the contact. From 95 to 96.3 ft (29.0 to 29.4 m) is laminated, kaolinitic clayey, silty fine to very fine sand with rare burrows. Laminations are highlighted by yellow iron staining, with thin and one thicker cross-laminae of medium-coarse sand. We interpret this as a tidal flat environment. The section grades down to 96.3–97.4 ft (29.4–29.7 m); it is kaolinitic at the top with kaolinite decreasing and grain size increasing to coarse downsection. From 97.4 to 101.35 ft (29.7 to 30.9 m) is a silty, clayey medium to coarse quartz sand that coarsens downsection. These two sections are interpreted as two fining-upward tidal channels well displayed on the gamma log (Fig. F2). From 101.35 to 101.7 ft (30.9 to 31.0 m) is a yellowish, laminated clayey, silty very fine sand. From 101.7 to 106.2 ft (31.0 to 32.4 m) is a micaceous yellowish clayey, sandy silt with organic-rich clay rip-up clasts (105.3 ft; 32.1 m); it is generally laminated with slight bioturbation. From 106.2 to 107.8 ft (32.4 to 32.9 m) is a gray micaceous, structureless, silty, very fine sand; there is an organic-rich layer from 106.45 to 106.6 ft (32.4 to 32.5 m; Fig. AF1). The unit appears gleyed. From 107.8 to 108.6 ft (32.9 to 33.1 m) is a gray, gleyed clay. From 108.6 to 110.75 ft (33.1 to 33.8 m) is a gray to blackish gray, organic-rich (?), well-sorted, fine–medium quartz sand with a few opaque heavy minerals. There is a coring gap from 110.75 to 120 ft (33.8 to 36.6 m). We interpret the section from 101.35 to 110.75 ft (30.9 to 33.8 m) as a lagoon environment (Fig. AF1). The lagoonal sediments have high but variable gamma log values. The gamma log suggests a change at ~112–113 ft (34.1–34.4 m) to more serrated log values of the sands below.
Sands from 120 to 140.4 ft (36.6 to 42.8 m) were deposited in foreshore (beach) environments, though the lower part may represent proximal upper shoreface environments (Figs. F2, AF1). The facies consist of laminated to cross-laminated medium sands with distinct dark ilmenite-rich laminae at 121.15, 126.8–127.9, 128.8–129.5, 130.9–131.9, and 132.4–132.6 ft (36.9, 38.6–39.0, 39.3–39.5, 39.9–40.2, and 40.4–40.4 m). The ilmenite-rich zones yield high gamma log values and a serrated log pattern. There are heavy mineral laminations in the section. The section is generally yellow, along with white, gray, and red (below 135 ft; 41.1 m) zones that may reflect minor grain size/sorting differences. There are some intensely burrowed (e.g., 120–120.3 ft; 36.6–36.7 m) intervals, but in general the section is laminated to cross-laminated, with some larger, spectacular cross-beds (e.g., 124.6 and 128.4 ft; 38.0 and 39.1 m). Ilmenite is less observable below 135 ft (41.1 m), and the log values are low and constant. This section below 135 ft (41.1 m) may represent a proximal shoreface environment. There is a coring gap from 140.4 to 150 ft (42.8 to 45.7 m).
The lower part of the Cohansey Formation (150–162.05 ft; 45.7–49.4 m) consists of yellow structureless, moderately to poorly sorted medium to coarse sand. There is a yellow-white well-sorted, cross-laminated fine sand bed from 162.05 to 162.35 ft (49.4 to 49.5 m) and a yellowish fine–very coarse poorly sorted sand (162.35–162.7 ft; 49.5–49.6 m). These sediments (150–162.7 ft; 45.7–49.6 m) may represent an offshore bar in a proximal upper shoreface environment. There is a coring gap from 162.7 to 165.0 ft (49.6 to 50.3 m). Thus, the section from 162.7 to 120 ft (49.6 to 36.6 m) appears to shallow upsection.
From 165.0 to 165.1 ft (50.3 to 50.4 m) is a yellow sand (Fig. F2). This may be caved but appears to mark the base of the Cohansey Formation. There is a major sequence boundary at 165.1 ft (50.4 m) with a gray sand below to 165.55 ft (50.5 m). This sand is gray and medium-coarse with a few lithic fragments tentatively assigned to the Kirkwood Formation. Below 165.1 ft (50.4 m) appears fine–very fine lignitic sands typical of distal delta front deposits of the Kirkwood Formation.
There are two general trends in the Cohansey Formation at Double Trouble. First is a generally shallowing upward trend from the base to 110/120 ft (33.5/36.0 m), suggesting interpretation as an HST. The second is a retrogradational succession (tidal channel to foreshore to upper shoreface) from 25.2 to 95 ft (7.7 to 29.0 m; Fig. F2), suggesting interpretation as a TST. This change from progradational to retrogradational facies suggest a possible sequence boundary in the coring gap from 110 to 120 ft (33.5 to 36.6 m) or at the top of the kaolinite clays at 95 ft (29.0 m).
The upper part of the Kirkwood Formation (Fig. F3) is characterized by sharply changing lithologies deposited in deltaic environments. From 165.1 to 165.55 ft (50.3 to 50.5 m) is a bed of poorly sorted, medium to very coarse quartz sand with minor amounts of silt and fine sand (Fig. AF2). The sediments are grayer than the yellowish brown sands of the Cohansey above. From 165.55 to 166.75 ft (50.5 to 50.8 m) is a darker silty, micaceous fine sand to very fine silt with abundant disseminated lignite within the sand and cross-laminations (to 1 cm) of lignite. From 166.75 to 168.15 ft (50.8 to 51.3 m) is laminated (0.25 cm) to thin bedded (1 cm) silty fine to medium sand. From 168.15 to 177.8 ft (51.3 to 54.2 m) is very micaceous, silty fine sand with some medium sand. The sand contains laminations (0.1–1 cm thick) to thin beds of silty clay and rare lignite laminations. The facies from 165.1 to 177.8 ft (50.3 to 54.2 m) again suggests deposition in a nearshore delta-influenced/delta front environment.
A gradational contact from 177.8 to 178.8 ft (54.2 to 54.5 m) contains brown slightly organic-rich, slightly granuliferous muddy sand (Fig. F3). Below 177.8 ft (54.5 m) the lithology changes to a slightly micaceous silty, gravelly, very poorly sorted sand. The amount of gravel and the size of the gravel (as large as 1 cm) increases to 182.7 ft (55.7 m). The interval from 182.7 to 190 ft (55.7 to 57.9 m) was lost. Gravel was screened from the drilling mud in this interval. The gamma log suggests that the base of the gravel is at 182.7 ft (55.7 m), with the sediments becoming increasingly clayey below. A gamma log minimum at ~180–183 ft (54.9–55.8 m) indicates the base of the fining-upward gravelly succession is at 182.7 ft (55.7 m) and the gravel found below was caved into the hole. The gravels (177.8–182.7 ft; 54.2–55.7 m) probably represent the base of a delta front channel. The section from 190 to 191.2 ft (57.9 to 58.3 m) is interlaminated (with numerous burrows interrupting laminations) lignitic and micaceous silty sand and medium sand deposited in a delta front environment. This finer grained material is associated with a major inflection in the gamma log that represents an important facies change that might be a sequence boundary or a change in environment in a delta front environment. The lack of evidence for deepening associated with the clays suggests a change in facies unrelated to sea level change.
The section from 192 to 205.95 ft (58.5 to 62.8 m) consists of structureless, well-sorted, silty fine sand (Fig. F3). The section from 205.95 to 210 ft (62.8 to 64.0 m) is muddier than above, consisting of micaceous clayey silty fine sand that appears bioturbated. The sand (192–210 ft; 58.5–64.0 m) contains fine lignite and abundant mica and may represent bay filling in a river-dominated delta. From 210 to 210.4 ft (64.0 to 64.1 m) there is a poorly sorted, clayey to granuliferous very coarse sand with possible phosphatic granules. A sequence boundary at 210.4 ft (64.1 m) separates the poorly sorted sand above from medium lignitic, micaceous sand below. The surface at 210.4 ft (64.1 m) is burrowed with burrows (0.4–1 cm in diameter) extending ~1 ft below the contact. The poorly sorted sand from 210 to 210.4 ft (64.0 to 64.1 m) is interpreted as a lag deposit on the sequence boundary. The lag deposit may be thicker, but the top of the lag was not recovered.
The section from 210.4 to 241.2 ft (64.1 to 73.5 m) is dominated by well-sorted medium to fine sand (Figs. F3, AF2). The section from 210.4 to 212.8 ft (64.1 to 64.9 m) is slightly micaceous, slightly sandy silty clay. From 212.8 to 230 ft (64.9 to 70.1 m) is a well-sorted micaceous fine sand with increasing medium sand downsection. Possible channel bases occur at 221.1 and 222.9 ft (67.4 and 67.9 m) where there is slightly cemented coarse sand. Below an unrecovered interval (230–231.3 ft; 70.1–70.5 m) is a change to laminated muddy fine sand (231.3–241.2 ft; 70.5–73.2 m). The sands are interpreted as delta front transitioning down to prodelta.
Fine-grained prodelta deposits appear at 241.2 ft (73.5 m; Fig. F3). From 241.2 to 245 ft (73.5 to 74.7 m) is slightly micaceous very fine sandy mud, which is laminated to thinly bedded (to 2.5 cm). Beds are disrupted by occasional burrows. From 245 to 260 ft (74.7 to 79.2 m) is dark gray to black, laminated to thin-bedded micaceous silty fine sand and clay silt deposited in a prodelta setting. At ~254 ft (77.4 m; Fig. AF2) clay content reaches a maximum. From 260 to 263.7 ft (79.2 to 80.4 m) is silty fine to medium sand representing a shelf environment. There is coring gap from 263.7 to 270 ft (80.4 to 82.3 m), below which the sediments (270–278.8 ft; 82.3–85.0 m) change back to laminated to thin-bedded, slightly burrowed, micaceous silty fine sand probably representing environments transitional between a shelf and a prodelta (Fig. AF2). Below a minor coring gap, the sediments change from 280 to 285 ft (85.3 to 86.9 m) to laminated slightly micaceous clayey silt with burrows containing micaceous very fine sand (Fig. AF2). Glauconite sand beds occur at ~285 ft (86.9 m; Fig. F3). Slightly micaceous, slightly glauconitic, slightly sandy muddy silt appears from 285 to 285.7 ft (86.9 to 87.1 m). From 285.7 to 293.8 ft (87.1 to 89.6 m) is interbedded dark gray silty quartz glauconite sand, with glauconite sand likely reworked from the sequence below. We interpret the environments as delta front (210–231 ft; 64.0–70.4 m), distal delta front (231–241 ft; 70.4–73.5 m), prodelta clays (241–260 ft; 73.5–79.2 m), transitional between shelf and prodelta (260–280 ft; 79.2–85.3 m), and shelf sand (280–285 ft; 85.3–86.9 m) (Fig. AF2). We place the TST from 285 to 293.8 ft (86.9 to 89.6 m), the MFS at ~285 ft (86.9 m) at the glauconite sands, and an HST from 165.1 to 285 ft (50.3 to 86.9 m).
There is no age control on the Kirkwood Formation at Double Trouble. Regional correlations suggest that the sequences from 165.1 to 210.4 and 210.4 to 293.8 ft (50.3 to 64.1 and 64.1 to 89.6 m) correlate with the Kw1b (Shiloh Marl Member) and Kw1a (Brigantine Member) sequences of Miller et al. (1997), respectively. This is similar to the Miocene sequence stratigraphy at Island Beach, although the Kw3 sequence is represented there, but not at Double Trouble.
A sharp contact at 293.8 ft (89.6 m; Fig. AF3) separates the shelfal facies of the Kirkwood Formation above from dark green slightly glauconitic quartz sand of the Shark River Formation, Toms River Member, below. The sands oxidize to brown. The facies from 293.8 to 350 ft (89.6 to 106.7 m) are an interesting mix of glauconitic poorly sorted quartz sand ranging from very fine to coarse grained with granules.
The section generally coarsens up from 350 ft (106.7 m) and consists of thick beds of glauconitic medium–very coarse quartz sand (up to 30 cm thick). There are indurated (iron-cemented) zones (Fig. F4) starting at 309 ft (94.2 m) that are a maximum of 20 cm thick and consist of siltstones with some sandy matrix (e.g., 317.0–317.9, 325.6–325.9, 332.9–333.1, and 341–341.1 ft; 96.6–96.9, 99.2–99.3, 101.47–101.53, and 103.9–104.0 m). These punctuations of finer, indurated beds may signify minor flooding surfaces. There are rare shell molds (e.g., 350.7 ft; 106.9 m), though there does not appear to be primary shell material. Some of the section is heavily burrowed (e.g., 312–314 ft; 95.1–95.7 m), indicating likely marine deposition. Below 350 ft (106.7 m) there are distinct thin brown clay beds (2–7 cm thick) and overall sand size decreases and the section is slightly better sorted. The environment of deposition of the section from 293.8 to 350 ft (89.6 to 106.7 m) is uncertain but appears to be a generally coarsening-upward succession on top of lower shoreface shelf clays, and thus the shallower, higher energy marine section above is interpreted as deposited in upper shoreface environments (Fig. AF3).
Mud increases generally downsection from 360 to 466.75 ft (109.7 to 142.3 m), and there are more clay beds (as thick as 30 cm; Fig. F4). Clays with thin interbedded sands occur from 366.4 to 371.4 ft (111.7 to 113.2 m) and represent the transition from distal lower shoreface to offshore deposits. There are common gypsum needles (e.g., 365.1–367.9 ft; 111.3–112.1 m), possibly carbonate. There is a return to glauconitic granuliferous medium to coarse quartz sand from 371.4 to 410 ft (113.2 to 125.0 m), with a granule-rich coarse sand bed from 371.8 to 372.1 ft (113.3 to 113.4 m). The section from 385.1 to 385.5 ft (117.4 to 117.5 m) is clearly bioturbated, though bioturbation in much of the section is not clear. A sand bed from 410 to 415.4 ft (125.0 to 126.6 m) consists of cleaner glauconitic medium to coarse quartz sand that coarsens upsection. Clayey, slightly granuliferous cross-bedded glauconitic quartz occurs from 415.4 to 420 ft (126.6 to 128.0 m). From 420 to 421.5 ft (128.0 to 128.5 m) is bioturbated glauconitic medium to coarse quartz sand with clay-lined burrows. The interval from 421.5 to 454.8 ft (128.5 to 138.6 m) consists of slightly granuliferous clayey glauconitic medium-coarse quartz sand with sandy clay interbeds up to 5 cm thick. There is an indurated siltstone at 426.4–426.6 ft (129.97–130.03 m). The section from 454.8 to 466.75 ft (138.6 to 142.3 m) is also slightly granuliferous clayey glauconitic medium-coarse quartz sand, but is more clay-rich, heavily bioturbated, and very slightly shelly, with a downsection decrease in quartz grain size and increase in glauconite to ~25%. There is a large pyrite nodule at the base of the section, and there is a faint contact at 466.75 ft (142.3 m) with Thalassinoides burrows from ~466.9 to 467.9 ft (142.3 to 142.6 m). Common gypsum occurs on the core surface below 465 ft (141.7 m), and planktonic foraminifers occur in a sample at 466 ft (142.0 m). Below the interbedded sand/clay contact is a heavily bioturbated, slightly micaceous, clayey, silty, slightly shelly, glauconitic quartz sand. Silt and clay increase downsection to 476 ft (145.1 m). Below a minor coring gap (476–480 ft; 145.1–146.3 m), the section is sandy silt to clayey silt with 5%–10% glauconite, thin shells, and shell fragments. We place the base of the Toms River Member at 475.7 ft (145.0 m) at a transition from the sand above to more carbonate-rich clay below (Fig. F4); there is also a downhole increase in gamma log values at this depth.
The depositional environment of the section from 360 to 475.7 ft (109.7 to 145.0 m) is enigmatic. The co-occurrence of quartz and glauconite argues for recycled glauconite, and the coarseness of the quartz sand argues for a fairly high-energy environment (shoreface or estuarine). Cross-beds (e.g., 380–380.6 and 416–418 ft; 115.8–116.0 and 126.8–127.4 m) and clay beds are common, though wood/lignite is generally absent and mica, though present, is rare. Bioturbation varies from extensive to obscure. One tentative interpretation is lower shoreface on a muddy shelf. Another interpretation is an estuary, with numerous thin clays, channels, and cross-beds. We favor the former, with the sequence from 293.8 to 517.5 ft (89.6 to 157.7 m) comprising one thick sequence comprising all of the Toms River Member and the upper part of the lower Shark River Member.
The unusual nature of the Toms Rivers Member warrants discussion. It is a very poorly sorted unit with reworked acarininids at the ACGS#4 corehole (Poore and Bybell, 1988; Miller et al., 1990); at that site it is essentially the same age as the Exmore Breccia in the Chesapeake Bay Impact Structure (CBIS) (35.4 Ma; Pusz et al., 2009) that results from resurge and tsunamis associated with impact. However, there is evidence that the Toms River Member is not a tsunamite or resurge deposit at Double Trouble: (1) we note that burrowing occurs throughout; (2) there are repetitive patterns of lithologies that can best be ascribed to normal marine processes; (3) there are no reworked taxa other than the acarininids and other uppermost middle Eocene forms (i.e., tsunamites and resurge deposits in the CBIS represent a full Cretaceous through middle Eocene suite of fossils); and (4) the unit is clearly older at Double Trouble (>37 Ma) than it is at ACGS#4 and is thus older than the CBIS (see "Regional Correlations of the Toms River Member," below).
The middle Eocene lower Shark River Formation is first encountered at 475.8 ft (145.0 m), immediately below a minor coring gap (Fig. F4). The top of the lower Shark River Formation consists of very fossiliferous and heavily bioturbated, slightly micaceous, quartzose, glauconitic clayey silt. Glauconite is more concentrated between 495 and 500.8 ft (150.9 and 152.6 m). An MFS is placed at ~485 ft (147.8 m) at a clay peak associated with high gamma log values (Fig. F4). Below a coring gap (497.1–500 ft; 151.5–152.4 m), the section returns to slightly glauconitic silt (500.8–505.6 ft; 152.6–154.1 m). Glauconite increases downsection at 505.6 ft (154.1 m). There is a large sandy, pyritized burrow from 506 to 506.4 ft (154.2 to 154.4 m) that may mark a sequence boundary. An alternate interpretation is that this is a TS, with a coarsening upward LST from 506 to 517.4 ft (154.2 to 157.7 m; Fig. F4). Glauconitic shelly silty clay returns from 506.4 to 513 ft (154.4 to 156.4 m). Glauconite and shells increase downsection to an irregular contact and major sequence boundary at 517.4 ft (157.7 m). The sequence above 517.4 ft (157.7 m) is assigned to Zone NP16 (511 ft; 155.8 m) and Zone E10 (P12) above 506 ft (154.2 m) and Zone E8–E9 (P10–P11) below 511 ft (155.8 m). It is possible that there is a thin sequence between 506.4 and 517.4 ft (154.4 and 157.7 m) that is Zones E8–E9 (P10–P11), though regional correlations suggest that there is one sequence, E8 of Browning et al. (1996), from 293.8 to 517.4 ft (89.6 to 157.7 m).
The top of the sequence below 517.4 ft (157.7 m; Figs. F5, AF4) contains a subequal mixture of ~20% fine–very fine quartz sand, with glauconite (~15%), shells, and rare wood to 524.1 ft (159.7 m) that all sharply decrease in abundance below 524.1 ft (159.7 m). This thin section (517.4–524.1 ft; 157.7–159.7 m) is a slightly sandier HST of the E6/E6a sequence (Fig. F5) deposited in offshore-distal lower shoreface environments.
The section from 524.1 to ~560 ft (159.7 to 170.7 m) is an "ash-colored marl" (5GY4/1): burrowed, very slightly glauconitic, foraminiferal clay typified by "wormy" horizontal burrows and generally uniform except as follows. There a slightly sandy bed from 525.6 to 525.9 ft (160.2 to 160.3 m; Fig. F5). Porcellanitic zones appear at 534.4 ft (162.9 m) and continue downsection (e.g., 549.2–549.3 ft; 167.40–167.43 m). A slightly sandy (10%) bed observed in the washed samples and single-point resistivity at 541 ft (164.9 m) is associated with a slightly sandy interval from 540.8 to 541.5 ft (165.0 m) and a slight difference in bioturbation (not as "wormy"). The interval from 541.5 to 551.4 ft (165.0 to 168.1 m) shows a low in single-point resistivity values. Washed samples show a clear change in glauconite; though low in abundance, glauconite shows a distinct, progressive decrease downsection from ~2% at 526 ft (160.3 m) to 0% at 550 ft (167.6 m), increases to 3% at 561 ft (171.0 m), and then shows a sharp, large (>10%) increase at 566 ft (172.5 m). We identify a surface at 551.4 ft (168.1 m) as the MFS, with interbedded dark green wormy burrowed clays above with whiter clay with larger burrows below. A major increase in glauconite occurs from 561 to 562 ft (171.0 to 171.3 m; Fig. AF4). The "ash-colored marls" below 562 ft (171.3 m) consist of highly bioturbated silty clay that slightly coarsens downsection to clayey silt at 569 ft (173.4 m; Fig. AF4), with intervals of fine glauconite sand-filled burrows. The clay contains thin porcellanitic zones. A sequence boundary occurs in a coring gap between 569.2 and 570 ft (173.5 and 173.7 m), with a heavily burrowed zone containing up to 50% glauconite immediately above the coring gap.
The base of the Shark River Formation represents another sequence. The section from 570 to 570.8 ft (173.7 to 174.0 m) is an indurated, slightly glauconitic, very fine quartz sand that represents a thin HST (Fig. F5). Glauconite increases from 570.8 to 571.9 ft (174.0 to 174.3 m) and is concentrated in burrows, with a hard nodule at 571.9–572.0 ft (174.3–174.3 m). There is another sequence boundary at 572 ft (174.36 m) at the top of a bed of light brown clay. Thus, there are two sequence boundaries associated with the glauconite sands at 569.2/570.0 and 572 ft (173.5/173.7 and 174.3 m). Nannofossils date the thin sequence between these levels as Zone NP14a in Samples 570.3 and 571 ft (173.8 and 174.0 m); nannofossils confirm the interpretation of the two sequences boundaries by the absence of Zone NP14b and the presence of Zone NP13 at 574 ft (175.0 m). The sequence above 569.2 ft (173.5 m) is correlated to Sequence E6 or E6a of Browning et al. (1996), the thin sequence from 570 to 572 ft (173.7 to 174.3 m) to Sequence E5, and the sequence below 572 ft (174.3 m) to Sequence E4.
We place the top of the Manasquan Formation at the base of the glauconite bed at 572 ft (174.3 m; Fig. F5). The Manasquan Formation at the Double Trouble corehole consists of yellowish greenish gray, very slightly glauconitic, carbonate-rich (average ~9% of sand fraction), very slightly sandy silty clay to clay, with occasional thin silty and sandy beds and porcellanitic zones. Quartz sand is particularly low from 572 to 671 ft (174.3 to 204.5 m) (0.3%–15%; average = ~5%) and is higher (average = ~20%) from 675.3 to 706.5 ft (205.8 to 215.3 m; Table T2). Glauconite is generally rare in the formation (0%–4%, average and median 2%, including several zones with no glauconite) (Table T2).
Sequences and lithologic changes are subtle in the Manasquan Formation at Double Trouble (Fig. F5). The top of the formation is slightly sandier, with ~10% fine quartz sand above 600 ft (182.9 m). Glauconite content is higher in burrows from 578 to 580.6 ft (176.2 to 177.0 m) and there is a burrowed contact at 581.5–583.6 ft (177.2–177.9 m; Fig. AF5) with glauconite infilled burrows. This level is associated with a major gamma log kick and is possibly a sequence boundary separating Sequence E4 from E3 of Browning et al. (1996).
The section from 583.6 to 675.3 ft (177.9 to 205.8 m) is relatively uniform silty clay to clay, occasionally porcellanitic with traces of glauconite, sparse fine quartz sand, and common porcellanitic zones (notably 620–626 and 660–670 ft; 189.0–190.8 and 201.2–204.2 m). Downhole log resistivity peaks at ~595, ~610, ~630, and ~650 ft (~181.4, ~185.9, ~192.0, ~198.1 m; Fig. F5) appear to correspond to minor peaks (~10%) in quartz sand. The section from 583.6 to 675.3 ft (177.9 to 205.8 m) appears to be one sequence assigned to Zones NP12 and E4–E7 (P6b–P8) and thus correlates with Sequence E3 of Browning et al. (1996). Slightly sandy clays above 600 ft (182.9 m) are likely the HST. The MFS might be in the finest grained sediments at 666 ft (203 m; Fig. F5).
There is a contact at 673.3–673.6 ft (205.2–205.3 m) with porcellanitic silty clay above and a sandy clayey silt below associated with a minor gamma ray peak. The contact is subtle and is recognized as a possible sequence boundary by the change from progradational facies below to retrogradational facies and a change to deeper water facies above and a nannofossil boundary between Zones NN11 and NN12 (see "Calcareous Nannofossils"; Fig. F5). This change suggests correlation of the section from 673.6 to 706.5 ft (205.9 to 215.3 m) with Sequence E2 of Browning et al. (1996). Quartz sand is higher (average = ~20%) in Sequence E2 than other Manasquan Formation sequences in the Double Trouble corehole (Table T2). It is particularly high from 675.6 to 689.7 ft (205.9 to 210.2 m) and drops off below this interval at a downhole increase in gamma log values. Sand occurs in burrows from 689.5 to 695 ft (210.2 to 211.8 m), though the section is primarily silty clay. Clay generally increases downsection from 689.5 to ~706 ft (210.2 to ~215.2 m). Glauconite appears at 704.5 ft (214.7 m), becomes prominent at 705 ft (214.9 m), and increases to a glauconite sand down to a contact at 706.5 ft (215.3 m; Fig. AF5). The contact is sharp and abrupt, with a few small circular burrows just below the contact. Thus, 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.
The Vincentown Formation contains several sequences. The section from 706.5 to 735 ft (215.3 to 224.0 m) is a heavily bioturbated, slightly micaceous, heavily burrowed clayey silt (to 719 ft; 219.2 m) and silt (719–735 ft; 219.2–224.0 m; Fig. F6). Calcispheres are found in abundance between 711 and 731.4 ft (216.7 and 222.9 m) (Table T3). Silty glauconitic clay (735–736 ft; 224.0–224.3 m) overlies glauconitic silt (736–741.9 ft; 224.3–226.1 m) and clayey, slightly glauconitic sandy silt that is heavily burrowed (743.8–769.5 ft; 226.7–234.5 m). This silty unit represents shelf deposits with a deltaic influence. Lithologically it differs from the "ash marls" of the Eocene above and is assigned to the Paleocene Vincentown Formation. The age assignment of this unit is uncertain. Foraminifers (e.g., Globanomalina pseudomenardii, found at 714.6 ft; 217.8 m) assign it to Paleocene Zones P5 and P4c (Berggren and Pearson, 2005), suggesting that the unit predates the carbon isotope excursion (CIE). Nannofossils assign it to the post-CIE portion of Eocene Zone NP9b and Zone NP10. Two possibilities exist: (1) it correlates with the Eocene, indicating Paleocene planktonic foraminifers are reworked, or (2) it correlates with the upper Paleocene Vincentown Formation, indicating the calcareous nannoplankton are contaminated. In either case, it appears that the CIE and carbon isotope recovery section associated with kaolinite-rich clays (Marlboro Clay) is missing from Double Trouble as it is at Island Beach (Pak et al., 1997). The absence of the Marlboro Clay appears to be restricted to the region between this updip-downdip pair of sites because it is well-represented at Sea Girt to the north (Miller et al., 2006) and Bass River to the south (Cramer et al., 1999). We favor an interpretation of the section from 706.5 to 816 ft (215.3 to 248.7 m) as a lower lower Eocene sequence that we name E0. It postdates the PETM and predates the basal Manasquan E1 sequence boundary, which is younger than 54.6 Ma.
There is a contact at 741.9 ft (226.1 m; Fig. AF5) with a glauconitic clayey slightly sandy silt above and slightly clayey, slightly glauconitic sandy silt below (Fig. F6). The contact has glauconite sand concentrated (up to 20%) in burrows and no evidence of rip-up clasts. Quartz sand peaks below the contact at 751 ft (228.9 m; up to 30% in burrows) and decreases below this. This pattern looks like a regressive HST to a sequence boundary at 741.9 ft (226.1 m), but the similarities of lithologies above and below and lack of evidence for erosion at the contact could indicate a flooding surface rather than a sequence boundary. Nannofossils suggest a hiatus, and thus we interpret this contact as a sequence boundary with Sequence E0 above and Sequence Pa3a (Harris et al., 2010) below. The Marlboro Clay is cut out by this unconformity at 741.9 ft (226.1 m).
Below 741.9 ft (226.1 m) the section fines down to slightly micaceous, slightly glauconitic clayey silt and silty clay (to 785 ft; 239.3 m) and coarsens again to very micaceous very fine sandy glauconitic clayey silt (to 792 ft; 241.4 m; Fig. F6). The section fines again to silty clay (792–799.4 ft; 241.4–243.7 m), with slightly sandy, slightly silty, slightly glauconitic clay (800–803 ft; 243.8–244.8 m) and glauconite increasing downsection to ~30% from 806 to 810.3 ft (245.7 to 247.0 m; note that there appears to be a registry issue on the gamma log of 2.5 ft; 0.8 m). The peak in clay content at 796–801 ft (242.6–244.1 m) may be the MFS. There is a sideritized shell at 805 ft (245.4 m) and a large burrow from 807.5 to 807.55 ft (246.13 to 246.14 m), filled with glauconitic, silty very fine quartz sand. There is a sequence boundary at 810.3 ft (247 m), with a shift from the glauconite clay to a slightly silty, sandy glauconitic clay; the contact is heavily burrowed with clay chips (2 mm from Zone NP6 (811 ft; 247.2 m) to Zone NP8 (801.9 ft; 244.4 m), which correlates the sequence below 810.3 ft (247.0 m) with Pa2a of Harris et al. (2010). The section from 810.3 to 814 ft (247.0 to 248.1 m) is glauconitic, quartzose sandy clayey silt that is heavily bioturbated, with sand concentrated in burrows. Glauconite increases downsection to 814–816 ft (248.1–248.7 m).
We place the top of the Hornerstown Formation at 816 ft (248.7 m) where glauconite becomes dominant in a sandy, clayey, silty glauconite sand, with scattered shells and shell fragments (Fig. F6). Shell beds occur at 817.7–817.85, 818.1–818.2, 820–820.1, 820.3–820.4, 820.5–820.6, and 821.55–821.6 ft (249.23–249.28, 249.36–249.39, 249.94–249.97, 250.03–250.06, 250.09–250.12, and 250.41-250.42 m). As at other New Jersey coastal plain sites, there are several closely spaced sequences in the Hornerstown Formation. We place a sequence boundary at 818.5 ft (249.5 m) below the first shell bed separating glauconite clay above from clayey glauconite sand, both with abundant quartz sand. The sequence from 810.3 to 818.5 ft (247.0 to 249.5 m) is assigned to Zones NP6–NP7, whereas the sequence below (818.5–822.95 ft; 249.6–250.8 m) is assigned to Zone P3. The high abundance of quartz sand is unusual for the Hornerstown Formation.
A thick shell bed at 820 ft (249.9 m) is likely the Gryphaea dissimilis bed observed throughout the coastal plain. Samples at 820 and 821 ft (249.9 and 250.2 m) are assigned to Zone P3 (820 ft; 249.9 m) based on the presence of Morozovella angulata. The unit becomes slightly silty glauconitic quartz sand from 820 to 822.1 ft (249.9–250.6 m), where there is a contact at 822.95 ft (250.8 m) interpreted as a sequence boundary. Below this sequence boundary (Fig. F6) is a clayey quartzose, glauconitic clay (822.9–828 ft; 250.8–252.37 m) that coarsens downsection from 828 to 831 ft (252.37 to 253.29 m). Clayey silty glauconite sands from 831 to 834.65 ft (253.29 to 254.4 m) contain disseminated shell debris and pyrite concretions, along with rare mica. A sample at 830 ft (253.0 m) contains Parasubbotina bulloides, Subbotina triloculinoides, and Globoconusa daubjergensis and is assigned to the Danian (Zone P1c). A zone containing clay rip-up clasts (832.25–832.65 ft; 253.7–253.8 m) marks a sequence boundary separating the Zone P1c sequence above from the lowermost Danian. Below the sequence boundary at 832.65 ft (253.8 m; Fig. F6) is a glauconite sand, with quartzose (10%–15%) glauconite sandy burrowed zones (836.25–836.4 and 837.3–837.9 ft; 254.89–254.93 and 255.2–255.4 m). There is a shell concentration at 837.3–837.4 ft (255.2–255.25 m). The Cretaceous/Paleogene boundary occurs at 838.35–838.65 ft (255.5–255.6 m), with possible spherules observed. There are two white chalky clasts at 838.9 and 839.1 ft (255.7 and 255.8 m) that may be carbonate accretionary lapilli. Below this are clayey glauconite sands of the Navesink Formation.
A very dark greenish gray clayey glauconite sand (~50%–60% glauconite) to glauconitic clay occurs from 838.85 to 852.6 ft (255.7 to 259.9 m). The section is heavily burrowed and is very slightly quartzose (~1% very fine sand). The sand has pyritized or sulfur-rich burrows that are common from 840.35 to 851.1 ft (256.1 to 259.4 m). The section becomes very slightly micaceous from 848 to 851 ft (258.5 to 259.4 m). There are brown carbonate clay clasts that are likely altered shells (840.7, 844.8, 844.5, 853.2, and 854.0 ft; 256.2, 257.5, 257.4, 260.1, and 260.3 m). There is a contact at 852.6 ft (259.9 m; adjusted core depth), with very dark gray glauconite clay below. The clay is heavily burrowed with glauconite-filled burrows. The main upsection change in the Navesink Formation is a decrease in clay content (Fig. F6). We interpret the Navesink to basal Hornerstown Formation (to 832.65 ft; 253.8 m) as one shallowing upward sequence across the K/Pg boundary, with increasing glauconite and quartz sand above 852.6 ft (259.9 m). We tentatively place an MFS at 854.0–854.2 ft (260.3–260.4 m) at a concentration of clay clasts that was likely a shell layer. This unit is uppermost Cretaceous, with Sr ages of ~65 Ma.