Holocene development of parabolic dunes in the central St. Lawrence Lowland, Québec

Abstract

Stabilized parabolic dunes in the central St. Lawrence Lowland are oriented NE-SW, in the postulated direction of dune-building winds coming from anticyclonic air circulation induced by the retreating Laurentide Ice Sheet about 10,000 yr ago. The eolian chronology reconstructed from several sections in mixed dune-peatland environments indicates that postglacial plant colonization, characterized by a fortuitous assemblage of arctic-subarctic and boreal elements, preceded dune formation during Champlain Sea regression around 10,000 yr B.P. Confined peatlands and small forests were buried by eolian sands between 10,000 and 7500 yr B.P. under dry and temperate conditions. This eolian episode lasted about 2500 14C yr and ended when cyclonic air circulation similar to the present humid climatic regime was established following the breakup and disappearance of the Laurentide Ice Sheet over Hudson Bay and peripheral areas. Dune stabilization, through paludification of well-drained eolian sands about 7500 yr B.P., suggests a major shift in climate toward wetter conditions that have been characteristic during most of the Holocene in eastern North America. Minor eolian erosion induced by wildfire was recorded during late Holocene time (about 1250 yr B.P.). Anthropogenic perturbation (logging and agriculture practice) was also responsible for recent very local eolian activity.