Cold-climate slope deposits and landscape modifications of the Mid-Atlantic Coastal Plain, Eastern USA

Abstract

The effects of Pleistocene cold-climate geomorphology are distributed across the weathered and eroded Mid-Atlantic Coastal Plain uplands from the Wisconsinan terminal moraine south to Tidewater Virginia. Cold-climate deposits and landscape modifications are superimposed on antecedent landscapes of old, weathered Neogene upland gravels and Pleistocene marine terraces that had been built during warm periods and sea-level highstands. In New Jersey, sequences of surficial deposits define a long history of repeating climate change events. To the south across the Delmarva Peninsula and southern Maryland, most antecedent topography has been obscured by Late Pleistocene surficial deposits. These are spatially variable and are collectively described as a cold-climate alloformation. The cold-climate alloformation includes time-transgressive details of climate deterioration from at least marine isotope stage (MIS) 4 through the end of MIS 2. Some deposits and landforms within the alloformation may be as young as the Younger Dryas. Southwards along the trend of the Potomac River, these deposits and their climatic affinities become diffused. In Virginia, a continuum of erosion and surficial deposits appears to be the product of ‘normal’ temperate, climate-forced processes. The cold-climate alloformation and more temperate deposits in Virginia are being partly covered by Holocene alluvium and bay mud.

Relict Thermal-contraction-crack Polygons and Past Permafrost South of the Late Wisconsinan Glacial Limit in the Mid-Atlantic Coastal Plain, USA

“…This interpretation is consistent with the subdivision of large polygons by smaller ones (Figures B, S143, S152), a characteristic feature of polygons in permafrost (Black, ). In view of the relict sand wedges reported in this region (Andres and Howard, ; Lemcke and Nelson, ; French et al , , ; Losco et al ., ; Newell and DeJong, ), many of the polygons identified in the present study may have a similar origin. But without ground truthing of the stratigraphy, distinctions between relict sand wedges, ice‐wedge pseudomorphs and composite‐wedge pseudomorphs cannot be made.…”

“…The mid‐Atlantic Coastal Plain has been considered permafrost‐free during the Last Glacial Maximum (LGM) (Black, ; Péwé, ). Recently, however, a few reports of sediment‐filled wedge structures interpreted as relict sand wedges have provided evidence of extensive permafrost in this area during the Late Pleistocene (Figure ) (Lemcke and Nelson, ; French et al ., ; Newell and DeJong, ). Thus, further study of relict periglacial features in this area is needed to elucidate the nature and extent of past permafrost.…”

“…Note the permafrost boundary from this work is for continuous permafrost, whereas those from Péwé () and French and Millar () are for undifferentiated continuous and discontinuous permafrost. Capital letters indicate the source of information on wedge structures: F: French et al (, ); L: Lemcke and Nelson (); LS: Losco et al (); N: Newell and DeJong (); W: Walters (). Stippled areas are urban centres.…”

Pleistocene relative sea levels in the Chesapeake Bay region and their implications for the next century

“…The basins and channel are likely relict from periglacial processes that dominated this landscape beginning ca. 30 ka and continued through the LGM (Denny et al, 1979;Newell and Clark, 2008;French et al, 2009;Markewich et al, 2009;Newell and DeJong, 2011;Gao, 2014).…”

Nitrate fate and transport through current and former depressional wetlands in an agricultural landscape, Choptank Watershed, Maryland, United States

“…Tracts of forested wetlands are interspersed with agricultural fields. Depressional wetlands are relatively abundant and are often characterized as Delmarva Bays (figure 2), which are believed to have formed from freezing and thawing related to the cold climate during the last glacial period (Newell and Dejong 2011;Owens and Minard 1979). Soils range from very poorly drained mucks with high organic matter content in depressions to well-drained sandy loams beneath farm fields.…”