M-B boundary age constrained by high-precision U-Pb zircon dating of a widespread tephra in a sedimentary sequence
Yûsuke SuganumaMakoto OkadaKenji HorieH. KaidenMami TakeharaRyoko SendaJun‐Ichi KimuraKenji KawamuraYuuki HanedaOsamu KazaokaMartin J. Head
0
Citation
0
Reference
20
Related Paper
Keywords:
Sequence (biology)
Cite
Cite
Citations (0)
Tephrochronology
Geochronology
Cite
Citations (19)
Caldera
Cite
Citations (0)
Tephrochronology
Pumice
Silicic
Volcanic hazards
Cite
Citations (235)
A mid-Holocene tephra, LBA-2 has been found in a peat bog in central Sweden. Geochemical analyses suggest an origin in an evolved volcanic centre, most likely the Snæfellsnes volcanic centre in western Iceland. The geochemistry of the LBA-2 tephra is similar to the youngest of three silicic tephra layers from Snæfellsjökull, Sn-1 dated to 1780 cal yr BP. However, wiggle-match dating indicates an age of 3550–3650 cal yr BP, close in age to the Hekla-S/Kebister tephra (3720 cal yr BP), previously found in several sites in Scandinavia. Detailed geochemical analyses and dating is lacking for the mid-Holocene Sn-2 tephra in Iceland but it is likely that the geochemical composition is similar as the Sn-1 tephra. The LBA-2 tephra is tentatively correlated with the Sn-2 tephra and we also suggest that the ‘x’ tephra layer (ca 3500 BP) found in the Dyngjufjöll area, central Iceland (Sigvaldason et al. 1992) can be correlated with the Sn-2 tephra.
Silicic
Tephrochronology
Cite
Citations (8)
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 0.4 ka. 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 14 C 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 14.5 ka. 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 5.8 ka 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 0.4 ka 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 ± 0.2 ka) and Tephra B (6.1 ± 0.3 ka). 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. Copyright © 2012 John Wiley & Sons, Ltd.
Tephrochronology
Cite
Citations (54)
Caldera
Cite
Citations (8)
Peninsula
Cite
Citations (0)
Abstract. Two Quaternary tephras derived from the Jemez Mountains, New Mexico – the Guaje and Tsankawi tephras – are difficult to distinguish due to their similar glass-shard chemical composition. Differences in bulk chemical composition are small as well. Here we examine the feasibility to assign an age to a distal tephra layer in the La Sal Mountains, Utah, by U–Pb dating of zircons and to correlate it with one of the two Jemez eruptions. We also dated original Jemez tephras for comparison. Even though the tephras are very young, we obtained reasonable age determinations using the youngest cluster of zircon grains overlapping in age at 2σ. Thereafter, the Guaje tephra is 1.513 ± 0.021 Myr old. The La Sal Mountains tephra is correlated with the Tsankawi tephra. Three samples yielded a common age range of 1.31–1.40 Myr. All ages are in slight disagreement with published age determinations obtained by 40Ar ∕ 39Ar dating. These findings indicate that distal Jemez tephras can be distinguished by U–Pb dating. Furthermore, we encourage giving this method a try for age assignments even of Quaternary volcanic material.
Cite
Citations (4)
Beringia
Tephrochronology
Radiometric dating
Cite
Citations (7)