Cold‐climate origin of the enclosed depressions and wetlands (‘spungs’) of the Pine Barrens, southern New Jersey, USA

The ‘frost‐thaw’ or thermokarst‐lake‐basin hypothesis, first invoked by P. E. Wolfe in 1953 to explain the enclosed depressions and shallow basins (‘spungs’) of southern New Jersey, is re‐examined. The most probable explanation is that they formed in late Wisconsinan times as deflation hollows, or ‘blowouts’, when strong katabatic winds flowed southwards from the continental ice margin across the sparsely vegetated, tundra terrain of the Pine Barrens. Wedge structures and cryoturbation phenomena suggest the existence of either permafrost or deep seasonal frost, and imply mean annual air temperatures of between −0.5 °C and −6 °C. When the groundwater table rose in late‐glacial times, the hollows became ponds or wetlands. These were utilized as early as 12,000 years ago by palaeoindian and early archaic cultures as hunting camp sites. Today, many of these wetlands are drying up as the regional water table falls in response to increased water usage from agriculture and urbanization.