Subaqueous Pyroclastic Flow Deposits in the Upper Donzurubo Formation, Nijo-San District, Osaka, Japan

Kato, Iwao; Muroi, Isao; Yamazaki, T.; Abe, Masahiro

doi:10.5575/geosoc.77.193

Cited by 26 publications

(8 citation statements)

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“…Where bottom contacts are plane and sharp, missing underlying strata m a y indicate erosion (Yamada 1973). The lower division of a subaqueous pyroclastic flow unit is a single, coarse grained bed commonly lacking internal structures or laminations (Fiske & Matsuda 1964;Bond 1973), although some beds have incipient crosslaminations outlined by a crude orientation of coarse fragments (Kato et al 1971;Yamazaki et al 1973). Larger and more dense fragments generally occur near the base of the massive divisions, with crystals, glass shards and pumice becoming more abundant toward the top.…”

Section: Non-welded Depositsmentioning

confidence: 98%

“…9), as are glassy fragments produced by sudden quenching. Fine perlitic cracks are characteristic of essential, non-vesicular, vitric clasts (Kato et al 1971). Non-welded subaqueous pyroclastic flow deposits characteristically are massive to poorly bedded and poorly sorted in their lower part (lower division), and are thinly bedded in their upper part (upper division) (Fig.…”

Section: Non-welded Depositsmentioning

confidence: 98%

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Submarine volcaniclastic rocks

Fisher

1984

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The type, relative abundance and stratigraphical relationships of volcanic rocks that comprise island volcanoes are a function of (i) depth of extrusion beneath water, (ii) magma composition, and (iii) lava-water interactions. The water depth at which explosions can occur is called the pressure compensation level (PCL) and is variable. Explosive eruptions that occur above the PCL and below sealevel can give rise to abundant hydroclastic and pyroclastic debris. Below the PCL, clastic material cannot form explosively; it forms from lava by thermal shock. The volcaniclastic products are widely dispersed in basins adjacent to extrusion sources by three principal kinds of marine transport processes. These are slides, sediment gravity flows and suspension fallout. Volcaniclastic debris can be derived in subaqueous and subaerial-to-subaqueous environments (i) directly from eruptions, (ii) from remobilization of juvenile volcaniclastics, or (iii) from epiclastic material which initially develops above sealevel.Sediment gravity flows (fluids driven by sediment motion) exhibit the phenomenon of flow transformation. This term is used here for the process by which (i) sediment gravity flow behaviour changes from turbulent to laminar, or vice versa, within the body of a flow, (ii) flows separate into laminar and turbulent parts by gravity, and (iii) flows separate by turbulent mixing with ambient fluid into turbulent and laminar parts.

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Section: Non-welded Depositsmentioning

confidence: 98%

Section: Non-welded Depositsmentioning

confidence: 98%

Submarine volcaniclastic rocks

Fisher

1984

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“…Accretionary lapilli may also occur. In pyroclastic flow deposits of the Upper Donzurubo Formation (Kato et al 1971), slightly vesiculated perlite fragments are also considered as essential particles. Pumice is usually white, with abundant capillary-tubed vesicles, but grey, denser pumice (scoria) and grey and white banded pumice also occur.…”

Section: Constituents Of Subaqueous Pyroclastic Flow Depositsmentioning

confidence: 99%

Subaqueous pyroclastic flows: their development and their deposits

Yamada

1984

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Subaqueous pyroclastic flows are generated by eruptions in shallow water or close to a shore. Their flow mechanism is similar to that of their subaerial counterparts, except that they incorporate steam and not air. Near the source area, their deposits are non-sorted and resemble subaerial flow deposits. In some cases evidence of high temperature is recognized. Within a short distance (less than a few km) they are sorted and five subdivisions can be determined. In upward succession these are: (i) massive graded pumice tuff; (ii) parallel-laminated pumice tuff; (iii) parallel-laminated sandy tuff; (iv) parallel-laminated fine tuff; and (v) massive very fine tuff. With ificreasing distance from the source, and laterally from the main direction of the flow, the lower divisions gradually die out. Deposition of the upper three divisions is greatly influenced by sedimentary processes. The thickness and constitution of each division vary according to the volume and nature of the associated eruption.

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“…Some deposits are, however, welded (e.g. Francis and Howells 1973;Howells et al 1985;Kokelaar and Busby 1992;Schneider et al 1992), or show magnetic evidence (Kato et al 1971;Yamazaki et al 1973;Tamura et al 1991) or textural evidence (Kano 1990;Cole and DeCelles 1991;Kano et al 1994) for high-temperature emplacement. Others show lateral and vertical facies changes from debrisflow deposits to turbidites (Tasse et al 1978;Lajoie 1979) or from high-density turbidites to low-density turbidites (Yamada 1973(Yamada , 1984Cole and Stanley 1994) with little evidence of high-temperature emplacement.…”

Section: Introductionmentioning

confidence: 98%

A Miocene coarse volcaniclastic mass-flow deposit in the Shimane Peninsula, SW Japan: product of a deep submarine eruption?

Kano

1996

Bull Volcanol

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A subaqueous volcaniclastic mass-flow deposit in the Miocene Josoji Formation, Shimane Peninsula, is 15-16 m thick, and comprises mainly blocks and lapilli of rhyolite and andesite pumices and non-to poorly vesiculated rhyolite. It can be divided into four layers in ascending order. Layer 1 is an inversely to normally graded and poorly sorted lithic breccia 0.3-6 m thick. Layer 2 is an inversely to normally graded tuff breccia to lapilli tuff 6-11 m thick. This layer bifurcates laterally into minor depositional units individually composed of a massive, lithic-rich lower part and a diffusely stratified, pumice-rich upper part with inverse to normal grading of both lithic and pumice clasts. Layer 3 is 2.5-3 m thick, and consists of interbedded fines-depleted pumice-rich and pumice-poor layers a few centimeters thick. Layer 4 is a well-stratified and well-sorted coarse ash bed 1.5-2 m thick. The volcaniclastic deposit shows internal features of high-density turbidites and contains no evidence for emplacement at a high temperature. The mass-flow deposit is extremely coarsegrained, dominated by traction structures, and is interpreted as the product of a deep submarine, explosive eruption of vesicular magma or explosive collapse of lava.

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Subaqueous Pyroclastic Flow Deposits in the Upper Donzurubo Formation, Nijo-San District, Osaka, Japan

Cited by 26 publications

References 0 publications

Submarine volcaniclastic rocks

Submarine volcaniclastic rocks

Subaqueous pyroclastic flows: their development and their deposits

A Miocene coarse volcaniclastic mass-flow deposit in the Shimane Peninsula, SW Japan: product of a deep submarine eruption?

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