Upper Pleistocene to Holocene stratigraphy in the Higashi-Niigata gas field, central Japan-The characteristics and sources of maker pumice beds-

Urabe, Atushi; Yasui, Satoshi; Inaba, Mitsuru; Kataoka, Kyoko; Takahama, Nobuyuki; Mitsuda, Shinichi

doi:10.3720/japt.71.337

Cited by 4 publications

(1 citation statement)

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“…50 ka, 220 ka, and 290 ka, based on evidence from boreholes in the Niigata coastal plain. These deposits are associated with earlier eruptions from the nested Numazawa and Sunagohara calderas (Urabe et al, 2006) and may have been generated by similar breakout fl oods. Also, recent geothermal activity at these volcanic centers suggests that volcanic eruptions may recur.…”

Section: Large-scale Floods and Distal Flood Hazardsmentioning

confidence: 83%

Breakout flood from an ignimbrite-dammed valley after the 5 ka Numazawako eruption, northeast Japan

Kataoka

Urabe

Manville

et al. 2008

Geological Society of America Bulletin

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Numazawa volcano in northeast Japan erupted most recently at ca. 5 ka, forming a 2-km-diameter caldera and emplacing at least 4 km 3 of valley-confi ned ignimbrite. The ignimbrite dammed the Tadami River to a depth of >100 m, temporarily impounding >1.6 km 3 of water. Overtopping of the barrier triggered breaching and catastrophic release of the dam lake. Pyroclastic material redeposited by the ensuing fl ood is widely distributed along the Tadami and Agano Rivers in deposits tens of meters thick as far as the coastal Niigata Plain >150 km downstream of the volcano. Evidence for damming and fl ooding found along the rivers includes (1) fi ne-grained, thinly laminated lacustrine deposits upstream of the pyroclastic blockage; (2) 30-m-thick, pumiceous debris-fl ow and hyperconcentrated-fl ow deposits that show continuous sedimentation with no major hiatus downstream of the volcano; (3) fi ne-grained slackwater deposits at tributary river mouths; and (4) large fl ood boulders that form lags on stripped ignimbrite surfaces and younger terrace surfaces, or cropping out within hyperconcentrated-fl ow deposits. Paleohydraulic estimation techniques indicate a peak discharge of 30,000-50,000 m 3 /s at the breach point. Burial of Neolithic Jomon settlements by fl ood and volcaniclastic aggradational deposits at distal locations indicates that such indirect volcanogenic hazards are signifi cant, even where direct primary consequences of volcanic eruptions are minor or absent.

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Section: Large-scale Floods and Distal Flood Hazardsmentioning

confidence: 83%