Geologic Publications for Mount Rainier

A Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon, USA

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Author(s): Michael A. O'Neal, Katherine R. Schoenenberger

Category: PUBLICATION
Document Type:
Publisher: Quaternary Research
Published Year: 2003
Volume: 60
Number:
Pages: 233 to 241
DOI Identifier:
ISBN Identifier:
Keywords: lichen lichenometry lichenometric dating Rhicozarpon Mount Baker Mount Rainier Mount Hood

Abstract:
Lichen thallus measurements from 22 surfaces of known age on Mount Baker, Mount Hood, and Mount Rainier are used to construct a regional Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon. Growth rates determined by measuring the largest thallus diameters on the same surfaces at Mount Rainier in 1976 and 2002 are used for comparison with lichenometric data from Mount Baker and Mount Hood. Similar lichen thallus diameter vs age relationships identified in the data from the three mountains suggest the presence of uniform growth rates over the 400-km range. A regional growth curve developed during our study shows three growth phases of successively slower growth: a rapid phase from 8 to 20 yr, a linear phase from 20 to 145 yr, and a slow phase of unknown duration beyond ca. 145 yr. Uncertainty in lichen growth rates beyond 145 yr limits projection of the curve beyond that age; however, the age range of the constrained growth curve covers an important period of recent climate variability. When applied in appropriate settings, our growth curve can be used to determine numeric ages to ±
10 yr for surfaces between 20 and 145 years old in areas where other techniques are not applicable or do not provide unique or well-constrained ages.

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In Text Citation:
O'Neal and Schoenenberger (2003) or (O'Neal and Schoenenberger, 2003)

References Citation:
O'Neal, M.A. and K.R. Schoenenberger, 2003, A Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon, USA: Quaternary Research, Vol. 60, pp. 233-241.