TWO EXCEPTIONAL EDUCATIONAL FIELD SITES IN NORTHERN NEW JERSEY

Finding field trip sites that are accessible, informative, unique, and safe is often a challenge in New Jersey. Two such sites in the Hamburg Quadrangle of Sussex County provide an exceptional teaching opportunity for all grade levels, as they exhibit a variety of characteristics that are both easy to see and are representative of their paleoenvironment. The first site, previously described by Monteverde (2004) and by Freile et al. (2007), is a glacially-smoothed exposure of the Allentown Dolomite Formation containing well-preserved stromatolites. This outcrop is located at lat: 41.142693^o, long: -74.577880^o, near Hamburg, NJ. The exposure is noted for the numerous stromatolite “heads,” both large and small, along with mudcracks, ooids, styolites, ripples, rip-up clasts, and cross-bedding. These features provide consistent support for a wave-dominated, shallow-water environment, with periodic subaerial drying events. Because of glacial erosion and polish, the surface is unusually smooth and clear of chemical weathering effects that would otherwise hide or degrade such surface features. Glacial erosion also is evident by the numerous striations on the bedding planes and the larger glacial grooves (N30^oE) found at the top of the outcrop.

The second outcrop is located at lat: 41.140930^o, long: -74.590360^o, and shows a relatively fresh cut through the Precambrian–Cambrian boundary. The Precambrian rock is a metamorphic amphibolite unit unconformably overlain by Paleozoic meta-sedimentary units. This unconformity zone is heavily weathered and likely sheared, producing a fine fissile texture, and represents a loss of some 700 million years of geologic history. The Cambrian Hardyston Quartzite overlies the unconformity with thick quartzite beds dipping to the northwest. Stratigraphically above the Hardyston is the Cambrian Leithsville Fm., consisting of finely-layered (varves in places) dolomitic limestone interbedded with sand and shale layers. One favorable aspect of this site is a fairly continuous stratigraphic section that can easily be examined by simply walking along the road. A comparison of the geology can also be made along strike, as the rocks are exposed on both sides of the road.