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A preliminary history of Holocene colluvial (debris‐flow) activity, Leirdalen, Jotunheimen, Norway
Author(s) -
MATTHEWS JOHN A.,
DAHL SVEINOLAF,
BERRISFORD MARK S.,
NESJE ATLE,
DRESSER P. QUENTIN,
DUMAYNEPEATY LISA
Publication year - 1997
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/(sici)1099-1417(199703/04)12:2<117::aid-jqs296>3.0.co;2-1
Subject(s) - colluvium , geology , debris flow , holocene , debris , radiocarbon dating , peat , fluvial , geomorphology , physical geography , paleontology , oceanography , archaeology , geography , alluvium , structural basin
A stratigraphic succession of alternating peat and minerogenic sediments at the foot of a steep mountain slope provides the basis for the reconstruction of a preliminary colluvial history from the alpine zone of Jotunheimen, southern Norway. Layers of silty sand and sandy silt, typically 5–10 cm thick and interpreted as distal debris‐flow facies, are separated by layers of peat that have been radiocarbon dated. Deposition from at least 7500 to about 3800 14 C yr BP of predominantly minerogenic material suggests relatively infrequent but large‐magnitude debris‐flow events in an environment warmer and/or drier than today. Particularly low colluvial activity between about 6500 and 3900 14 C yr BP was terminated by a succession of major debris‐flow events between about 3800 and 3400 14 C yr BP. Unhumified peats indicative of higher water tables, separate six debris‐flows that occurred between about 3300 and 2300 14 C yr BP and signify a continuing high frequency of colluvial activity. Uninterrupted peat accumulation between about 2400 and 1600 14 C yr BP indicates reduced debris‐flow activity; subsequent renewed activity appears to have culuminated in the ‘Little Ice Age’ after about 600 14 C yr BP. This pattern of colluvial deposition demonstrates a long history of natural Holocene low‐alpine landscape instability, suggests an increase first in the magnitude and then in the frequency of debris‐flow activity coincident with late Holocene climatic deterioration, and points to the potential of debris‐flow records as a unique source of palaeoclimatic information related to extreme rainfall events. © 1997 John Wiley & Sons, Ltd.