Holocene Climatic Change and the Distribution of Peatlands in Western Interior Canada

Abstract Dates of basal fen peat at 52 locations across west-central Canada indicate that peat deposition began 6000 yr B.P. basal fen peat parallels the foothills of the Rocky Mountains, and extends eastward along 54°30′ north latitude. The absence of >6000 yr B.P. peat within this zone is attributed to a warmdry early to middle Holocene climate that caused severe seasonal droughts and prevented the establishment of peat-forming fen vegetation. Wetlands west (and probably north) of this line experienced lower water tables, but supported fen vegetation. As the climate became cooler and moister, stable water tables allowed the development of fens and rapid peat accumulation ensued, reaching the modern distribution of fens between 2000 and 3500 yr B.P. Projections of climatic parameters indicate that the mean annual growing degree days were 6 to 21% higher during the early and middle Holocene, and that precipitation was reduced through most of the area, resulting in much higher (by 17 to 29%) aridity than at present.

[1]  J. Lowdon,et al.  Geological Survey of Canada radiocarbon dates XIX , 1979 .

[2]  H. Bostock.  Physiographic subdivisions of Canada , 1970 .

[3]  J. Lowdon,et al.  Geological Survey of Canada radiocarbon dates VII. , 1968 .

[4]  R. Vance.  Pollen stratigraphy of Eaglenest Lake, northeastern Alberta , 1986 .

[5]  G. MacDonald,et al.  Postglacial development of the subalpine-boreal transition forest of western Canada , 1987 .

[6]  H. Nichols.  The Late Quaternary History of Vegetation and Climate at Porcupine Mountain and Clearwater Bog, Manitoba , 1969 .

[7]  Kerstin O. Griffin.  Paleoecological aspects of the Red Lake Peatland, northern Minnesota , 1977 .

[8]  J. C. Ritchie.  The late-Quaternary vegetational history of the Western Interior of Canada , 1976 .

[9]  R. Vance,et al.  A mid-Holocene record of vegetative change in central Alberta , 1983 .

[10]  L. Cwynar,et al.  Evidence from north-west Canada for an early Holocene Milankovitch thermal maximum , 1983, Nature.

[11]  R. Forester,et al.  Mid-Holocene Climate in Northern Minnesota , 1987, Quaternary Research.

[12]  E. Deevey,et al.  Postglacial Hypsithermal Interval. , 1957, Science.

[13]  J. Kutzbach,et al.  Milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr BP , 1985, Nature.

[14]  M. Hickman,et al.  The developmental history of peatlands at Muskiki and Marguerite lakes, Alberta , 1989 .

[15]  S. Zoltai.  Late Quaternary volcanic ash in the peatlands of central Alberta , 1989 .

[16]  G. MacDonald.  Late Quaternary paleoenvironments of the Morley Flats and Kananaskis Valley of southwestern Alberta , 1982 .

[17]  N. Malmer.  Vegetational gradients in relation to environmental conditions in northwestern European mires , 1986 .

[18]  C. Schweger,et al.  Holocene paleohydrology of central Alberta: testing the general-circulation-model climate simulations , 1989 .

[19]  Cohmap Members.  Climatic changes of the last 18,000 years: observations and model simulations. , 1988, Science.

[20]  Sakari Tuhkanen,et al.  Climatic parameters and indices in plant geography , 1980 .

[21]  D. Vitt,et al.  The paleoecology of a peatland complex in continental western Canada. , 1990 .