Abstract
Radiocarbon-dated sediment cores from six lakes in the Ahklun Mountains, south-western Alaska, were used to interpolate the ages of late Quaternary tephra beds ranging in age from 25.4 to 0.4ka. The lakes are located downwind of the Aleutian Arc and Alaska Peninsula volcanoes in the northern Bristol Bay area between 159° and 161°W at around 60°N. Sedimentation-rate age models for each lake were based on a published spline-fit procedure that uses Monte Carlo simulation to determine age model uncertainty. In all, 62 14C ages were used to construct the six age models, including 23 ages presented here for the first time. The age model from Lone Spruce Pond is based on 18 ages, and is currently the best-resolved Holocene age model available from the region, with an average 2σ age uncertainty of about±109 years over the past 14.5ka. The sedimentary sequence from Lone Spruce Pond contains seven tephra beds, more than previously found in any other lake in the area. Of the 26 radiocarbon-dated tephra beds at the six lakes and from a soil pit, seven are correlated between two or more sites based on their ages. The major-element geochemistry of glass shards from most of these tephra beds supports the age-based correlations. The remaining tephra beds appear to be present at only one site based on their unique geochemistry or age. The 5.8ka tephra is similar to the widespread Aniakchak tephra [3.7±0.2 (1σ) ka], but can be distinguished conclusively based on its trace-element geochemistry. The 3.1 and 0.4ka tephras have glass major- and trace-element geochemical compositions indistinguishable from prominent Aniakchak tephra, and might represent redeposited beds. Only two tephra beds are found in all lakes: the Aniakchak tephra (3.7±0.2ka) and Tephra B (6.1±0.3ka). The tephra beds can be used as chronostratigraphic markers for other sedimentary sequences in the region, including cores from Cascade and Sunday lakes, which were previously undated and were analyzed in this study to correlate with the new regional tephrostratigraphy.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 344-359 |
| Number of pages | 16 |
| Journal | Journal of Quaternary Science |
| Volume | 27 |
| Issue number | 4 |
| DOIs | |
| State | Published - May 30 2012 |
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Keywords
- Alaska Peninsula
- Aleutian arc
- Quaternary stratigraphy
- Tephra
- Tephrochronology
ASJC Scopus subject areas
- Earth and Planetary Sciences (miscellaneous)
- Palaeontology
- Arts and Humanities (miscellaneous)
Cite this
Late Quaternary tephrostratigraphy, Ahklun Mountains, SW Alaska. / Kaufman, Darrell S; Jensen, Britta J L; Reyes, Alberto V.; Schiff, Caleb J.; Froese, Duane G.; Pearce, Nicholas J G.
In: Journal of Quaternary Science, Vol. 27, No. 4, 30.05.2012, p. 344-359.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Late Quaternary tephrostratigraphy, Ahklun Mountains, SW Alaska
AU - Kaufman, Darrell S
AU - Jensen, Britta J L
AU - Reyes, Alberto V.
AU - Schiff, Caleb J.
AU - Froese, Duane G.
AU - Pearce, Nicholas J G
PY - 2012/5/30
Y1 - 2012/5/30
N2 - Radiocarbon-dated sediment cores from six lakes in the Ahklun Mountains, south-western Alaska, were used to interpolate the ages of late Quaternary tephra beds ranging in age from 25.4 to 0.4ka. The lakes are located downwind of the Aleutian Arc and Alaska Peninsula volcanoes in the northern Bristol Bay area between 159° and 161°W at around 60°N. Sedimentation-rate age models for each lake were based on a published spline-fit procedure that uses Monte Carlo simulation to determine age model uncertainty. In all, 62 14C ages were used to construct the six age models, including 23 ages presented here for the first time. The age model from Lone Spruce Pond is based on 18 ages, and is currently the best-resolved Holocene age model available from the region, with an average 2σ age uncertainty of about±109 years over the past 14.5ka. The sedimentary sequence from Lone Spruce Pond contains seven tephra beds, more than previously found in any other lake in the area. Of the 26 radiocarbon-dated tephra beds at the six lakes and from a soil pit, seven are correlated between two or more sites based on their ages. The major-element geochemistry of glass shards from most of these tephra beds supports the age-based correlations. The remaining tephra beds appear to be present at only one site based on their unique geochemistry or age. The 5.8ka tephra is similar to the widespread Aniakchak tephra [3.7±0.2 (1σ) ka], but can be distinguished conclusively based on its trace-element geochemistry. The 3.1 and 0.4ka tephras have glass major- and trace-element geochemical compositions indistinguishable from prominent Aniakchak tephra, and might represent redeposited beds. Only two tephra beds are found in all lakes: the Aniakchak tephra (3.7±0.2ka) and Tephra B (6.1±0.3ka). The tephra beds can be used as chronostratigraphic markers for other sedimentary sequences in the region, including cores from Cascade and Sunday lakes, which were previously undated and were analyzed in this study to correlate with the new regional tephrostratigraphy.
AB - Radiocarbon-dated sediment cores from six lakes in the Ahklun Mountains, south-western Alaska, were used to interpolate the ages of late Quaternary tephra beds ranging in age from 25.4 to 0.4ka. The lakes are located downwind of the Aleutian Arc and Alaska Peninsula volcanoes in the northern Bristol Bay area between 159° and 161°W at around 60°N. Sedimentation-rate age models for each lake were based on a published spline-fit procedure that uses Monte Carlo simulation to determine age model uncertainty. In all, 62 14C ages were used to construct the six age models, including 23 ages presented here for the first time. The age model from Lone Spruce Pond is based on 18 ages, and is currently the best-resolved Holocene age model available from the region, with an average 2σ age uncertainty of about±109 years over the past 14.5ka. The sedimentary sequence from Lone Spruce Pond contains seven tephra beds, more than previously found in any other lake in the area. Of the 26 radiocarbon-dated tephra beds at the six lakes and from a soil pit, seven are correlated between two or more sites based on their ages. The major-element geochemistry of glass shards from most of these tephra beds supports the age-based correlations. The remaining tephra beds appear to be present at only one site based on their unique geochemistry or age. The 5.8ka tephra is similar to the widespread Aniakchak tephra [3.7±0.2 (1σ) ka], but can be distinguished conclusively based on its trace-element geochemistry. The 3.1 and 0.4ka tephras have glass major- and trace-element geochemical compositions indistinguishable from prominent Aniakchak tephra, and might represent redeposited beds. Only two tephra beds are found in all lakes: the Aniakchak tephra (3.7±0.2ka) and Tephra B (6.1±0.3ka). The tephra beds can be used as chronostratigraphic markers for other sedimentary sequences in the region, including cores from Cascade and Sunday lakes, which were previously undated and were analyzed in this study to correlate with the new regional tephrostratigraphy.
KW - Alaska Peninsula
KW - Aleutian arc
KW - Quaternary stratigraphy
KW - Tephra
KW - Tephrochronology
UR - http://www.scopus.com/inward/record.url?scp=84859604317&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84859604317&partnerID=8YFLogxK
U2 - 10.1002/jqs.1552
DO - 10.1002/jqs.1552
M3 - Article
AN - SCOPUS:84859604317
VL - 27
SP - 344
EP - 359
JO - Journal of Quaternary Science
JF - Journal of Quaternary Science
SN - 0267-8179
IS - 4
ER -