Drilling began 16 March 1994 at the Coast Guard Training Center, Cape May, New Jersey (38°56´52"N, 74°53´00"W; elevation 5 ft [1.5 m]; Cape May 7.5-min quadrangle), located approximately 350 m west-southwest of Cape May Inlet. Drilling operations were superintended by Don Queen, U.S. Geological Survey; drillers were Gene Cobbs, Todd Heibel, and Gene Cobbs III. Water and electricity for core description were provided by the base commander, Captain Donald Anderson. A temporary field lab was set up in a Hecht trailer.
The first core was obtained on 16 March 1994. All cores were measured in feet (all depths are given in feet below land surface) and all operations are described in feet only. Coring proceeded to 25 ft using a Christensen 94-mm (HQ) system, 4.25- to 4.50-in. hole diameter, and 2.5-in. core diameter. Three types of extended shoe were used to contact the formation in front of the bit in unconsolidated sands: short (1 in.), medium (1.5 in.), and long (2 in.). Five-inch PVC casing was set and grouted at 23 ft, to be extracted later. A total of 55 ft was penetrated on 16 March and 35 ft was recovered (63.6%). Recovery was poor to moderate in the sandy top 33 ft (51%), but it was much improved in sandy clays between 33 and 55 ft (82.7%). Biostratigraphic sampling started at 40 ft, and one sample was taken from each 5-ft core. Drilling was suspended on 17 March because of frozen drilling mud and high winds.
Drilling resumed on 18 March with smooth coring to 85 ft through clay and medium sand with 81.5% recovery. The cores from 75 to 80 ft recovered 2.35 ft; subsequent cores from 80 to 83 ft and from 83 to 85 ft recovered 3.7 and 2.8 ft, respectively (130% recovery). The extra material from these cores came from the 75 to 80 ft interval, and this section should be bottom justified at 85 ft. The water swivel failed at the end of the day and was replaced. All hoses were drained in case of overnight freezing.
On 19 March, 14 core runs were made from 85 to 155 ft with a recovery of 60 ft (86%). Smooth coring continued on 20 March to 225 ft (75% recovery), flushing the hole between runs. Coring was slow but generally smooth on 21 March (82% recovery) and 22 March (67% recovery) to 285 and 320 ft, respectively. The final core on 21 April was lost with no recovery, and a 1-ft core run was attempted with the long shoe to improve recovery. The long shoe could not push through the unconsolidated medium sands, and we switched back to the short shoe. Otherwise, recovery in these coarse-grained unconsolidated sediments was very good (Fig. 2) as a result of slow drilling and adjustment of feed pressures.
On 23 March, the first core recovered 4.8 ft between 320 and 322.5 ft; the coarse sands at the top of the core were less consolidated and apparently were caved. Smooth coring continued to 330 ft. The core from 330 to 335 ft recovered only a 0.2-ft plug of peat and clay; sands were washed away as evidenced by sands in the fluids. A confining clay layer was penetrated between 335 and 355 ft. The core from 342 to 345 ft recovered 4 ft, including 1 ft left in the hole as evidenced by recoring; depths need to be adjusted between 335 and 345 to reflect 7.7 ft of recovery. We decided to set casing in these tight clays at 335 ft, concerned that the caving of the sands might compromise the hole.
On 23 March, John Curran of the New Jersey Geological Survey (NJGS) obtained an analog gamma-ray log through the rods of the hole from 352 ft to surface. Log quality was good. On 24 March, the 5-in. diameter PVC surface casing was removed and 6-in. PVC casing installed to ~4 ft. The hole was reamed to ~200 ft using HQ rod, a 5-7/8-in. diameter tricone roller bit, and heavier drilling mud to flush sand out of the hole. On 25 March, the drillers returned to Reston, Virginia, for more equipment. Drilling operations were suspended 26 and 27 March.
On 28 March, the drillers returned from Reston with 1500 ft of NQ rod, shoes, catcher, and inner and outer core barrels. Four additional drillers (William Mahoney, USGS, Water Resources; and John Longman, Lenny Washburn, and Brad Winters, all from the Bureau of Reclamation) joined the crew to prepare for 24-hr operations. On 29 March, reaming continued from 200 to 340 ft using a 5-7/8 in. tricone bit and by subbing NQ to HQ rod. Drilling mud began to seep out of the ground, and the drilling mud thickness was increased. We pulled all rods at the end of the day.
On 30 March, 4-in. PVC casing was set to 315 ft to be removed at completion. Unconsolidated pebbly coarse sand above 322.5 ft was caving into the hole and the PVC casing could not be inserted to the clay at 335 ft. These caving sands caused circulation problems. We faced either pulling casing, reaming the hole, and recasing (with no guarantee that casing would penetrate further) or continued pumping of sands out of the hole. We decided to continue drilling using heavy mud and considered recasing after penetrating the base of the "Atlantic City 800-ft sands."
On 31 March, we installed a "T" to the top of the 4-in. casing, installed a 3-5/8-in. diameter tricone roller bit, and began to lower NQ rods. At 110 ft, the casing was blocked and we pulled the rods. We installed a 3-1/8-in. wafer coring bit, reamed from 110 to 340 ft, and flushed the hole while adding additional NQ rods without an inner barrel. The inner core barrel was lowered at 355 ft in preparation of taking a core. The end of the rods became blocked by very coarse sand, and the inner barrel became stuck in the rods. All rods were pulled. The gravel and coarse sands between 315 and 322.5 ft were apparently caving and lodging between the inner and outer barrels, causing circulation problems.
On 1 April, the rods were reinstalled and the core barrel reached 355 ft. We tried to add 7 ft of additional PVC casing below the base of the gravels and coarse sands (322.5 ft). Only 6 in. of additional casing penetrated. Heavier drilling mud was used to overcome the circulation problem caused by the caving of sand.
Coring resumed on 1 April at 355 ft with a Christensen CNWL (NQ) system, 3.162-in. hole diameter, and 1.875-in. (1-7/8 in.) core diameter with rock shoe, and 1.67-in. core diameter with extended shoes. The first three cores (355-370 ft) recovered 12.8 ft (85%). A lithologic change from laminated firm clay to sand was encountered at 356.9-360 ft. The medium quartz sand below 360 ft caused drilling problems caused by caving. We ran the interval from 360 to 365 ft again and recovered 2.1 ft of caved sands.
We started 10-ft core runs on 2 April. The first core (370-380 ft) recovered only 0.9 ft of pebbly sand with broken thin shells. The second core (380-390 ft) recovered 9.6 ft with shelly fine-medium quartz sand and a few shell hashes. When coring from 380 to 390 ft, caving sand again blocked the inner barrel. The rods were pulled and run back after clearing the blockage. A total of three runs (23.5 ft) were made and 13.6 ft was recovered (58%). Approximately 100 ft of rods were pulled out, and drilling was suspended on 3 April for Easter Sunday.
We began 24-hr operations on 4 April. Three shifts were run to minimize overtime costs: 0700-1500 hr (Brad Winters [driller], John Longman, and Todd Heibel), 1500-2300 hr (Gene Cobbs [driller], Gene Cobbs III, and Lenny Washburn), and 2300-0700 hr (Don Queen [driller] and William Mahoney). A heavy mud was used to prevent uncased sands from caving. Circulation was lost several times, and coring runs were delayed while the drillers flushed the hole. We began using the open (rock) shoe below 462 ft because the extended shoe would not penetrate. Coring was generally slow and recovery good on 4 April (58.6 ft recovery between 393.5 and 469.5 ft; 77%).
On 5 April, recovery was moderate between 469.5 and 600 ft (88 ft recovered; 68%), with the exception of the medium sands between 550 and 570 ft and shelly, clayey sands between 580 and 590 ft where recovery dropped below 50%. We began to experience trouble at the end of the day, losing all of the interval from 590 to 600 ft.
On the next core (6 April), we switched from the rock shoe to the medium shoe; however, we recovered only 0.3 ft from 600 to 610 ft. We switched back to the rock shoe at 613.5 ft. Only 1 ft was recovered from the next two cores to 617.5 ft, at which point the rods were pulled and the hole was flushed; the hole may have been caving between 590 and 617.5 ft and we only recovered 0.8 ft from this 27.5 ft interval. A run was then made between 617.5 and 618.5 ft without drilling, recovering 1 ft that was protruding from the bottom of the hole. Smooth coring and excellent recovery (97%) returned from 618.5 to 659 ft in interbedded sands and clays. Some chattering occurred while drilling the clays, and down pressure was adjusted to avoid washing away the sands. Smooth coring continued through laminated clays and sands until 680 ft, at which point we hit a lithified layer. We made a 1-ft run through this, recovering 0.5 ft. The remainder of this layer was found at the top of the next core (top 0.4 ft), below which we cored smoothly through clay and sand to 706.2 ft (recovered on 7 April). Despite the recovery problems noted with these lithologies, recovery for 6 April was 73% for the 100 ft drilled.
Alternating hard and soft layers hindered recovery on 7 April. Recovery was moderate (58%) from 710 to 720 ft despite penetration of a very hard unit and problems with the release latch. Recovery was poor from 720 to 730 ft (1 ft); a section apparently broke off and we re-ran the interval with no recovery. Relatively quick drilling from 730 to 740 ft may have blown away unconsolidated sands; only 0.6 ft of pebbly sand was recovered. A hard interval in this 0.6-ft section indicates that we penetrated alternations of hard and unconsolidated layers. We continued to use the rock shoe, washing caving sands for ~15 min between each run. Recovery improved in fairly consolidated sands and gravely sands from 740 to about 790 ft. A 1-ft run (790-791 ft) was attempted with the extended shoe, but we switched to a rock shoe when the shoe would not penetrate. The following 9-ft core recovered only 1.4 ft of coarse sands, indicating that sands were being blown away or the core had slipped out of the barrel. The bottom of hole (BOH) collapsed and the hole was flushed while rotating. We switched to a short extended shoe and recovered 7.3 ft on the next run (800-810 ft). Because of problems with hard/soft alternations, drilling on 7 April ended at 810 ft (110 ft drilled) with a recovery rate of 45%.
On the first core run on 8 April, the hole collapsed and we spent 1 hr regaining circulation. A run to 816 ft was attempted, but the rods became lodged while retrieving the core. Rods were pulled to a depth of 770 ft and progressively lowered while the hole was flushed. The next two runs (810-820 and 820-830 ft) saw poor recovery (25% and 32%, respectively). A lithologic change occurred at 830 ft, and we enjoyed an average recovery of 82% in very firm clayey sands and sandstones down to 882.8 ft. Midway through the 890-900 ft run, we switched to a rock catcher and cored an 8-ft-thick, very hard sandstone. We averaged 78% recovery over the next four cores through muddy sands, gravels, sandy silts, and silty clays. Recovery for 8 April averaged 67% on 130 ft drilled (86.6 ft recovered).
On 9 April, the first core (940-950 ft) recovered 10 ft. The bottom 40 ft of hole collapsed and was then flushed through the night and the hole cleared. From 950 to 960 ft, coring was slow and high pressure was applied, although recovery remained good (74%). At 960 ft, we ran into circulation problems again and we pulled 100 ft of rods. Smooth coring resumed and, over the next five cores, recoveries ranged from 77% to 97% in mainly silty clays. Only 2.1 ft were recovered from the next run (1000-1005 ft). 9 April ended with 52 ft of recovery from 65 ft drilled (81%).
At 0100 hr on 10 April, very high pressure occurred while drilling silty clay. All rods were pulled out to the surface. We found that the bit had cracked at the base of a tooth and a small piece of core was lodged between the inner barrel and bit. This may have caused misalignment of the outer and inner core barrels from 1000 to 1005 ft (42% recovery), which blocked mud flow. The 0700-1500 shift replaced the worn wafer bit with a carbide bit and sent the rods back down the hole. For the remainder of the day, we continued with recovery generally exceeding 90% in hard clay.
On 11 April, we passed into coarse-grained glauconite sands with a clay matrix, and recovery levels continued to improve. By 1800 hr, drilling was very slow and mud pressures were consistently high over the course of the afternoon and evening. The day ended with 82% recovery from 1050 to 1138 ft.
On 12 April, drilling problems developed with no recovery from 1138 to 1140 ft. All rods were pulled to the surface. The carbide bit was destroyed, proving to be unsuitable for these sediments. We had spare carbide bits but only the old wafer bit (pulled on 10 April). We considered sending Department of Reclamation drillers back early (they were scheduled to depart on 15 April) and having them return with a new wafer bit. We decided to use the old wafer bit and ran the rods back in the hole. Coring was resumed at 1730 hr. A 7-ft core was pulled out from a 10-ft (1140-1150 ft) run and the rods became blocked. Nine rods (180 ft) were pulled out and the obstruction broke loose. We increased mud weight and continued to rotate and flush. In the process, pressure dropped to <100 lb and the hole seemed to clear.
Coring resumed early on 13 April with very good recovery from the first run (1150-1160 ft; 100%), pumping 40 min between runs (20 min each at BOH and 10 ft from BOH). We capped the hole while retrieving the sand line and this seemed to prevent sands from being sucked into the hole. The next run from 1160 to 1168 ft recovered 60%. No core was recovered from 1168 to 1170 ft; from 1170 to 1180 ft we recovered only 1 ft of core. A clay plug at the base may have blocked the barrel. The next three cores (1180-1184, 1184-1190, and 1190-1200 ft) recovered 100%, 83%, and 74% of clayey glauconite sands, respectively. The clays made it easier to capture the sands and we returned to 100% recovery at 1200-1220 ft. Coring ended on 13 April, with recovery of 53 ft out of 70 ft drilled (76%).
As we were nearing the end of the contract for the extra drilling crews, scheduled from 28 March to 15 April, we discussed either suspending operations from 15 to 17 April to rest the USGS crew or to extend the Department of Reclamation drilling crew and to finish the hole by 17 April. Because drilling conditions were good, Don Queen decided to continue through the weekend and finish the hole.
On 13 April to early on 14 April, thunderstorms slowed drilling and made footing treacherous. Recovery was moderate to good from 1220 to 1248 ft (39%-93%) in consolidated/unconsolidated sands. Recovery improved in clays below 1248.5 ft. Excellent recovery and smooth drilling continued through the clays and fine-grained clayey sands (1300-1330 ft) and 1330 ft was reached by the end of 14 April (110 ft drilled, 89% recovery).
On 15 April, drilling began with a loss of most of the first run (1330-1340 ft). Good to excellent recovery soon resumed with the exception of the 1350-1360-ft interval, where a lithologic contact (1350.8 ft) separated firm glauconitic silty clay beneath from the very dark glauconitic fine sand/sandy clay above. The core from the shell bed in 1352.5-1354.5 ft was twisted and recovery was moderate (4.5 ft out of a 10-ft run). Recovery was excellent in the firm clay below 1360 ft, and most cores had full recovery. We cut short a 10-ft run after refusal occurred at 1419 ft. The following core was run 11 ft to 1430 ft. The next core (1440-1450.5 ft) slipped out of the inner barrel but was retrieved intact. At day's end, we had recovered 103.75 ft over a cored interval of 120.5 ft (86%).
On 16 April, we began coring smoothly in firm clay at 1450.5 ft with full recovery for all cores to 1480 ft. We had problems with catching the inner barrel when we attempted to pull the core from the 1480- to 1490-ft interval. The inner core barrel became lodged and efforts to free it were unsuccessful. All the rods were pulled and a full core was retrieved. We averaged 99.9% recovery over 39.5 ft of coring on 16 April.
The rods were sent back down the hole for the last core on 17 April. The final run to 1500 ft recovered 5.85 ft of core. Dennis Talbot from BPB Instruments arrived at 0930 hr to log the hole. A gamma log and neutron density log was first run through the rods down to 1500 ft. The drillers pulled the entire drill string between 1241 and 1530 hr and the hole remained open. Unfortunately, none of the slim logging tools would fit in the hole below casing. The logger was released. The gamma and neutron logging data can be matched with breaks between lithologic units identified in the subsurface, although log depths are approximately 2.5 ft shallower than corresponding core depths.
At Cape May, we recovered 1129.41 ft of core from a 1500-ft hole (mean recovery = 75%, median recovery = 85%; Table 1). Cores were photographed onsite in color using Tungsten lighting and 160T film. Lithologies were described on site and subsequently in Summer 1994 at the Rutgers core facility; these form the basis of the preliminary lithologic descriptions (Table 1). Samples were obtained at ~2- to 5-ft intervals for planktonic foraminifer, nannofossil, and diatom biostratigraphy. Cores were cut into 2-ft sections, labeled at the top and bottom of each section, placed into split PVC pipes, wrapped in plastic sheeting, and stored in 2-ft wax boxes. One hundred seventy-nine core boxes were moved to interim storage at the Rutgers core library for further lithologic description and sampling for paleomagnetic and other studies. The cores will ultimately be stored and archived as ODP cores and transferred to the East Coast Repository.