| Summary: | Complex post‐sedimentary deformation structures, extending to depths of 3–4 m below the surface, are present in the near‐surface gravel of the Pine Barrens of southern New Jersey. The deformations include: (i) amorphous (involuted) bedding, (ii) downward‐penetrating tongues of finer‐grained sediment, and (iii) sediment‐filled ‘pots’ or kettle‐like depressions. The structures are thought to have formed when Late‐Pleistocene permafrost degraded. The involuted bedding was caused by loading and loss of intergranular contact as icy layers within the permafrost thawed. The downward‐penetrating sediment tongues represent the thaw‐modified remnants of ancient frost fissures. The sediment‐filled pots are interpreted as ‘thaw sinks’ that formed either at wedge intersections or along wedge furrows. Optically stimulated luminescence (OSL) dates suggest that the majority of thermokarst activity was associated with the degradation of permafrost that had formed in either Early Wisconsinan, or older (Oxygen Isotope Stage 6), time. The thaw of frozen ground in the Late Wisconsinan appears not to have been accompanied by significant thermokarst activity. Copyright © 2005 John Wiley & Sons, Ltd.
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