Depositional features of March 1982 Mount St Helens sediment flows

Harrison, Sylvia; Fritz, William J.

doi:10.1038/299720a0

Cited by 32 publications

(10 citation statements)

References 2 publications

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“…Several instances were noted where trees which had been buried by earlier mudflows were exhumed by recent eruptions, demonstrating a cyclical nature of sediment deposition (Figs. 4 and 5) that has been reported also by workers in other areas (Harrison and Fritz, 1982). Our evidence from both localities supports climatic change during the time intervals represented between deposition of different stratigraphic units as a better explanation for the diversity of upright trees preserved in Yellowstone National Park than transport from higher to lower elevations.…”

Section: Our Observations At Mount St Helens and Atsupporting

confidence: 90%

Burial of trees by eruptions of Mount St Helens, Washington:implications for the interpretation of fossil forests

Karowe

Jefferson

1987

Geol. Mag.

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Lahars and fluvial sediments which buried trees following the 18 May 1980 eruption of Mount St Helens were investigated during August of 1982. Trees buried in older mudflows, dated at a.d. 1885, a.d. 1450–1550, and 36000 years b.p., also were examined. Although many logs clearly were transported, large numbers of trees were buried in growth position. Burial by lahars generally resulted in the death of trees, whereas some trees survived burial by fluvial sediments. Scanning electron microscope studies show that trees buried in lahars are well preserved. Pre-1885 buried woods show incipient silicification, and woods buried 36000 years b.p. show silica impregnation of cell walls.Features of in situ and allochthonous burial very similar to those seen in southern Washington are found also in Eocene silicified forests in Yellowstone National Park, Wyoming, U.S.A., and in Cretaceous fossil forests in southeastern Alexander Island, Antarctica. Observations of Recent wood from volcaniclastic deposits of Mount St Helens provide valuable insights into processes of burial and silicification of fossil forests of various ages around the world.

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Section: Our Observations At Mount St Helens and Atsupporting

confidence: 90%

Burial of trees by eruptions of Mount St Helens, Washington:implications for the interpretation of fossil forests

Karowe

Jefferson

1987

Geol. Mag.

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“…(1980) have shown that dense pyroclastic flows can move underwater but no ignimbrites have yet been recognized in the Cretaceous marine succession of the northern Antarctic Peninsula. However, the graded, feldspathic conglomerates (particularly types i and iii) are remarkably similar to the deposits of subaerial sediment flows associated with the 19 March 1982 eruption of Mount St Helens (Harrison & Fritz 1982). These deposits result from single catastrophic events and are restricted to certain river valleys.…”

Section: Graded Feldspathic Conglomeratesmentioning

confidence: 65%

Proximal volcaniclastic sedimentation in a Cretaceous back-arc basin, northern Antarctic Peninsula

Farquharson

Hamer

Ineson

1984

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During Cretaceous times, the northern Antarctic Peninsula was the site of an active ensialic magmatic arc. Volcanism was dominated by pyroclastic eruptions with rare lava flows. Marine conglomerates and sandstones formed a volcaniclastic apron along the eastern margin of the arc and represent the proximal deposits of an extensive back-arc basin. Volcanogenic material, redeposited by turbidity currents and other sediment gravity flows, forms an important part of the proximal basin fill. Air-fall tufts and eruption-induced sediment flows form a small but significant part of the succession and large exotic slideblocks of Jurassic sediment are a distinctive feature of the Lower Cretaceous strata on James Ross Island. Aeromagnetic data and regional geology indicate that the arc-back-arc basin boundarv was fault-controlled. Sedimentation within the basin was strongly influenced by both the steep, unstable nature of the faulted arc flanks and the coeval volcanism.

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“…The overall character of the thinly stratified sandstone resembles sheet flood deposits formed by shallow supercritical flow during periods of considerable discharge over broad areas (Bull, 1972;Ruegg, 1977;Gloppen and Steel, 1981;Houmark-Nielsen, 1983;Ballance, 1984;Wells, 1984;Brodzikowski and Van Loon, 1987;Blair, 2000). Laterally persistent parallel stratification conforming to the depositional surface without any internal truncation surface has also been reported from a number of catastrophic flood flow deposits and has been attributed to rapid accumulation from heavily sediment-laden unconfined turbulent flow (Harrison and Fritz, 1982;Blair, 1987;Smith and Lowe, 1991). This type of sheet floods often results from rapid but infrequent drainage of a high volume of water due to heavy rainfall, quick snowmelt or released stored water (Hogg, 1982;Blair, 1987).…”

Section: Discussionmentioning

confidence: 94%

Facies characteristics of Talchir Formation, Jharia Basin, India: Implications for initiation of Gondwana sedimentation

Dasgupta

2006

Sedimentary Geology

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Depositional features of March 1982 Mount St Helens sediment flows

Cited by 32 publications

References 2 publications

Burial of trees by eruptions of Mount St Helens, Washington:implications for the interpretation of fossil forests

Burial of trees by eruptions of Mount St Helens, Washington:implications for the interpretation of fossil forests

Proximal volcaniclastic sedimentation in a Cretaceous back-arc basin, northern Antarctic Peninsula

Facies characteristics of Talchir Formation, Jharia Basin, India: Implications for initiation of Gondwana sedimentation

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