Evidence for late‐Pleistocene permafrost in the New Jersey Pine Barrens (latitude 39°N), eastern USA

摘要: Relict sand wedges, up to 2.5 m deep and 0.4 m wide, are present in the Pine Barrens of southern New Jersey. They indicate previous existence permafrost. The wedges composed predominantly that shows evidence wind transport abrasion. Optically-stimulated-luminescence dating infill material indicates thermal-contraction-cracking emplacement must have occurred during two separate periods Late Pleistocene. most recent was Wisconsinan times,∼15–18 ka. An earlier period permafrost conditions is indicated by dates >55–65 ka. On both occasions, Late-Pleistocene ice sheets would advanced as far south northern Jersey strong winds lower mid-latitudes. sandy soils allowed ice-marginal periglacial zone extend southwards into sparse tundra vegetation on substrate, with its relatively high thermal conductivity, permitted frost penetration because ‘thermal offset’ been minimized. A mean annual air temperature between −3.0°C −4.0°C inferred. Permafrost probably discontinuous less than 10–15 m thickness. Episodes thaw widespread occurrence deformed sediments (‘thermokarst involutions’) various small-scale non-diastrophic structures associated bog ironstone beds. presence soil (ground) adjacent Delaware also suggest seasonal frost, when degraded. Copyright © 2003 John Wiley & Sons, Ltd.