Paleoenvironment and "Pocket Fen" Development on the Western Great Plains

Datos Bibliográficos

ID4487332
AutoresKevin P Gilmore (Archaeologist and principal investigator for ero Resources Corporation, Denver, Colorado 80218.), Donald G Sullivan (Associate professor of geography at the University of Denver, Denver, Colorado 80208.)
Año2010
Volumen100
Número3
Páginas413-429
Fecha de publicación2010-07-01
Peer ReviewedSí
Open AccessSí
TipoARTICLE
RevistaGeographical Review (JOURNAL)
Identificadores de la revistaISSN: 0016-7428 • E-ISSN: 1931-0846
EditorialInforma UK Limited (PUBLISHER • GB)
DOI10.1111/j.1931-0846.2010.00044.x
OpenAlexW2006626429
IdiomaEN
Referencias citadas34

The western Great Plains of eastern Colorado are characterized by low precipitation and a negative water balance (Topper and others 2003). Unlike the mountains to the west and the Central Plains to the east, many observers perceived the High Plains as a semiarid area devoid of perennial sources of water outside the few rivers that arise in the Rocky Mountains and flow through the region. However, recent investigations of small wetlands in eastern Colorado indicate that, though not common, perennial sources of water occur with greater frequency on the western Great Plains of eastern Colorado than past perceptions of this semiarid region would suggest. In a response to regional classifications of that are overly narrow and sometimes inaccurate in their terminology, James Amon and his coauthors proposed a simplified classification of Temperate-Zone of the Midwest based on descriptive and functional criteria (2002). We aim to extend this classification to the western Great Plains of Colorado, focusing on the origin and evolution of fens and the paleoenvironmental records they preserve. fens a name we propose here to replace the less specific and inaccurate terms used to describe these features, are so called because they are minerotrophic (groundwater-fed) peatlands that form in small basins situated on slopes above the channel of stream-cut valleys. In the classification of midwestern fens, most researchers categorize what we refer to as fens as a subtype of slope fen. However, because they form in a more arid environment than do those that Amon and his coauthors documented (2002), we believe that a basin is essential to initiate and maintain the saturated environment necessary for peat accumulation. Although pocket have a wide spatial distribution throughout eastern Colorado, in this research note we focus on those found at the Chico Basin Ranch and the Pueblo Chemical Depot in the valley of Chico Creek, a tributary of the Arkansas River northeast of the city of Pueblo (Figure 1). [FIGURE 1 OMITTED] Following Dan Charman (2002), the Chico Valley wetlands roughly fall into two categories: and marshes. A is a graminoid (grass and sedge)-covered wetland with a peat (partially decomposed plant material) substrate; is a more general term for wetlands with a mineral sediment substrate. Fens and marshes are also developmental stages, for most pass through a stage before the onset of peat formation. The formation of peat requires a low-oxygen, waterlogged environment. Previous investigators have identified what we refer to as fens by a variety of names, including marshes, side-hill seeps, mound springs, wet prairies, sedge meadows, and sloughs (Bryan 1993). Some investigators mistakenly call these features hanging bogs, or hillside bogs. However, Georgia Bryan (1993), as well as John Pearson and Mark Leoschke (1992), noted that calling these features which are ombrotrophic (precipitation-fed) peatlands composed mostly of Sphagnum spp., is a misnomer and rightfully identified these features as fens. To clarify the taxonomy, we propose the terms fen and marsh for groundwater-supported wetlands that occupy small basins situated at any position on a valley side slope. Pocket are small--30-3,000 square meters--inconspicuous features on the landscape (Figure 2). Partly because of their small size, they are subject to high rates of sedimentation--0.04-0.5 centimeters per year--which potentially provides decadal- to subdecadal-resolution paleoenvironmental records. The pocket investigated to date have contained 135-400 centimeters of peat and organic sediment, which have provided continuous records of effective moisture and relative temperature extending to the middle Holocene (approximately 8000 B.P.). Our present work concerns the past 3,000 years. [FIGURE 2 OMITTED] The discovery of pocket as sources of paleoenvironmental information overcomes several obstacles to examining long-term climate change on the western Great Plains, such as the general lack of paleoenvironmental data sources specific to this area and the inherent limitations of available data sources

Archaeology · Arid · Geography · Hydrology (agriculture · Peat · Perennial stream · Physical geography · STREAMS · Structural basin · Temperate climate · Wetland · Ecology · Geology · Geology and Paleoclimatology Research · Paleontology · Peatlands and Wetlands Ecology · Tree-ring climate responses