Oldwick Quarry (Stavola Quarry), Tewksbury Township, Hunterdon County, New Jersey, USAi

Regional Level Types
Oldwick Quarry (Stavola Quarry)	Quarry
Tewksbury Township	Township
Hunterdon County	County
New Jersey	State
USA	Country

Oldwick quarry was purchased by New Jersey quarry operator Stavola in 2001.

The Oldwick Quarry is located approximately 3500 feet southwest of the center of the village of Oldwick, NJ. For many years this quarry was operated by Houdaille Construction Materials, the dominant player in the northern New Jersey aggregate and concrete business from the 1950’s to the mid 1970’s. In the 1980’s and ‘90’s it was operated by Manzo Contracting who, in turn, sold the property to Stavola.

The Oldwick quarry is excavated in an outlier of the Orange Mountain (First Watchung) basalt contained in a structure known as the Oldwick (New Germantown) syncline. This structure is one of many synclines formed in the hanging walls of, and perpendicular to, the Newark Basin’s major faults. For a discussion of the structural development the reader is referred to: Schlische, R.W., 2002. Progress in understanding the structural geology, basin evolution, and tectonic history of the eastern North American rift system, in The Great Rift Valleys of Pangea in Eastern North America, Volume 1, edited by Peter M. LeTourneau and Paul E. Olsen: New York, Columbia University Press and the references therein.

To the northwest of the quarry, approximately 5500 feet, is a dome-like hill, now covered by houses, that is capped by a remnant of the Preakness (Second Watchung) basalt. Another 2500 feet beyond this hill and a fault slice of border facies conglomerate, is the border fault marking the northwestern margin of the Newark Basin and a ridge underlain by Protorozoic metamorphic rocks. In this area, 7 miles west of the southwestern end of the Watchung syncline, the main outcrop region of the Watchung basalts, the western edge of the basin has stepped back, westward, from the Ramapo fault to the Flemington fault.

The quarry is comprised of 2 separate pits in the axial part of the fold. The entrance of the lower pit is immediately inside the entrance to the operation off Rockaway Road. Little quarrying has been done here since the 1980’s. Near the entrance of this pit, on the right, is exposed a sequence of sedimentary rocks that appeared to be both overlain and underlain by basalt. These rocks appeared to be thermally metamorphosed to an extent not usually seen associated with basalt flows. There were no significant fractures or breccias and, therefore, no mineral specimens. Nor were there any fossils in this material. A very small intrusion of diabase has been mapped a very short distance west of this outcrop. The “basalt” underlying the sediments may be the fine grained, chilled margin of an intrusive rock. This would account for the thermal effects seen in the sediments.


Near the far end of the lower pit was a faulted block of Passaic Formation mudrock. Calcite veins in this mudrock occasionally contained some small, unremarkable stilbite crystal groups.

The upper pit is somewhat wider and longer than the lower one. The basalt throughout most of this pit is extensively sheared, altered and slickensided but mineral-bearing veins are rare. Amygdaloidal rock, much of which has irregular, angular cavities and looks more like a breccia, outcrops along the pit’s western side. Alteration of the amygdaloidal/brecciated rock is often intense with widespread reddening. The mineral assemblage here is similar to most of the other basalt quarries in the region but is much less extensive. Prehnite, occasionally with anhydrite casts, and calcite are the dominant species. Heulandite, usually as tiny crystals, is fairly common locally. Stilbite is uncommon. In this author’s 30 years of experience with this quarry specimen quality was consistently quite poor, given the standards of the region, and a piece worth working out and taking home was rare.

The reason for Oldwick’s stunted secondary mineral development may be its proximity to the border fault and the more shallow dip of this section of the fault. The Watchung basalts were probably altered and mineralized to clays and zeolites during an extended period of burial metamorphism. However, late in the basin’s history there was an inversion of the tectonic regime from one of tension to compression. This was accompanied by extensive fracturing and the initiation of large scale heat (fluid) flow. Mineral distribution patterns in many basalt quarries in the Watchung syncline, northeast of Oldwick, consistently indicate that fluid movement was upward out of the Passaic Formation and through the basalt flows. In the main Watchung region fluid flux was also sufficient to introduce substantial amounts of sediment derived chemical components, most obviously sulphate, boron and copper, into the basalts where they became major components of the secondary mineral assemblages. This is not the case at Oldwick.

There are several possible mechanisms for driving fluid migration including compaction and episodic dewatering. Steckler, et al (1993) proposed a variation on artesian driven migration, a system extensively evaluated in connection with Mississippi Valley Type lead-zinc deposits. In this model Oldwick was to near the basin margin recharge area to receive the full compliment of formation brine and heat driven upward through fractures from the depths of the basin that pushed temperatures to slightly above 200 deg's C in the quarries to the east from Chimney Rock to Paterson. More shallow circulation and basin margin facies rocks beneath the basalt at Oldwick may have produced mineralizing fluids that were not only cooler but less saline.

The Oldwick quarry presents an abbreviated version of Schaller’s (1932) paragenetic sequence that can be observed at nearly all basalt quarries in the region and in many cases in vein occurrences in diabase. That Schaller’s paragenesis applies at Oldwick and in such a variety of other situations, suggests that only within broad limits are temperature and chemical parameters of the fluids determinative of the final mineral assemblage. The biggest difference at Oldwick is that the mineralizing system seems to be more rock dominated, i.e. less material added from outside the basalt. The resulting mineral assemblage is calcium-rich, reflecting the Ca-rich nature of the basalt. Schaller's paragenetic sequence is reduced to its bare essentials: Ca sulphate -> prehnite -> Ca zeolite -> calcite. There's neither the higher temperature required for minerals like epidote and pumpellyite nor the sodium, boron and copper that diversifies the mineral assemblage elsewhere. In short this is a geologist's quarry not a collector's quarry.

Other Regions, Features and Areas containing this locality

References