Late Quaternary cryptotephra detection and correlation in loess in northeastern Japan using cummingtonite geochemistry     

Tabito Matsu'ura  Isoji Miyagi  Akira Furusawa 《Quaternary Research》2011,75(3):624-635

We detected late Pleistocene cummingtonite-bearing cryptotephras in loess deposits in NE Japan and correlated them with known tephras elsewhere by using major-element compositions of the cummingtonite. This is the first time cryptotephras have been identified by analysis of a crystal phase rather than glass shards. In central NE Japan, four cummingtonite-bearing tephras, the Ichihasama pumice, the Dokusawa tephra, the Naruko–Nisaka tephra, and the Adachi–Medeshima tephra, are present in late Pleistocene loess deposits. Because the cummingtonite chemistry of each tephra is different and characteristic, it is potentially a powerful tool for detecting and identifying cryptotephras. An unidentified cummingtonite-bearing cryptotephra previously reported to be present in the late Pleistocene loess deposits at Kesennuma (Pacific coast) did not correlate with any of the known cummingtonite-bearing tephras in central NE Japan, but instead with the Numazawa–Kanayama tephra (erupted from the Numazawa caldera, southern NE Japan), although Kesennuma is well beyond the previously reported area of the distribution of the Numazawa–Kanayama tephra. Three new cummingtonite-bearing cryptotephras in the mid and late Pleistocene loess deposits (estimated to be less than 82 ka, 100–200 ka, and ca. 250 ka) on the Isawa upland were also detected.  相似文献   

Late Quaternary uplift rate of the northeastern Japan arc inferred from fluvial terraces   总被引：1，自引：0，他引：1  

Tabito Matsu''ura  Akira Furusawa  Hidetaka Saomoto 《Geomorphology》2008,95(3-4):384-397

Glacial Lake Wisconsin was a large proglacial lake that formed along the southern margin of the Laurentide Ice Sheet during the Wisconsin glaciation. It was formed when ice of the Green Bay Lobe came into contact with the Baraboo Hills in southwestern Wisconsin and blocked the south-flowing Wisconsin River. During early glacial recession, the ice dam failed catastrophically and the lake drained in about a week. Despite early recognition of the former lake and the likelihood that it failed catastrophically, outflow rates during the failure have not been previously evaluated. Estimates based on step-backwater modeling indicate that peak discharge was between 3.6 and 5.3 × 10⁴ m³/s in the lower Wisconsin River. As an alternate method, we used a previously derived empirical relationship between lake volume and peak discharge for dam-break events. From a digital elevation model altered to incorporate isostatic depression, we estimated the lake volume to be 87 km³ just prior to dam breach, suggesting that the flooding magnitude was as high as 1.5 × 10⁵ m³/s at the outlet. Adjusting these results for downstream flood wave attenuation gives a discharge of around 4.4 × 10⁴ m³/s in the lower reach, which closely matches the results of the step-backwater modeling. These estimates of discharge from the catastrophic failure of ice-marginal lakes improve our understanding of the processes that have produced the morphology and behavior of present-day upper Midwest river systems.  相似文献   

Long-term and short-term vertical velocity profiles across the forearc in the NE Japan subduction zone     

Tabito Matsu'ura  Akira Furusawa 《Quaternary Research》2009,71(2):227-377

We estimated the long-term vertical velocity profile across the northeastern Japan forearc by using the height distribution of late Quaternary marine and fluvial terraces, and we correlated the ages of the two marine terraces with marine isotope stages (MIS) 5.5 and 5.3 or 5.1 by cryptotephra stratigraphy. The uplift rate, estimated as 0.11-0.19 m ka^− 1 from the relative heights between the terrace surfaces and eustatic sea levels, was nearly equal to, or slightly slower than, the uplift rate farther inland (0.15-0.19 m ka^− 1), as determined from the relative heights of fill terrace surfaces. In contrast, the short-term vertical velocity profile, obtained from GPS observations, showed that the forearc is currently subsiding at a maximum rate of 5.4 ± 0.4 mm yr^− 1. Thus, the current short-term (geodetic) subsidence does not reflect long-term (geological) tectonic movement. Short-term vertical deformation is probably driven by subduction erosion or elastic deformation caused by interplate coupling, or both. However, long-term uplift is probably due not to moment release on the mega-thrust but to crustal thickening.  相似文献