Facies architecture of a continental, below-wave-base volcaniclastic basin: The Ohanapecosh Formation, Ancestral Cascades arc (Washington, USA)

Abstract

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Grain-size distribution of volcaniclastic rocks 2: Characterizing grain size and hydraulic sorting

“…Typical examples comprise graded beds 57 and 61 in the Chinook Pass section, beds 40 and 42 in the Cayuse Pass section (Chinook Pass Member), and bed B-3 at Cougar Lake (Jutzeler et al, 2014b). These five beds in the Ohanapecosh Formation were interpreted as deposits from eruption-fed and resedimented subaqueous volcaniclastic density currents, and most likely to be related to subaerial, pumice-rich pyroclastic flows that entered water.…”

“…The matrix-rich, very thick, graded facies (MR-thick) includes examples from the Ohanapecosh Formation, the Dogashima Formation, and the Manukau Subgroup (Jutzeler, 2012;Jutzeler et al, 2014a;Jutzeler et al, 2014b). Typical examples comprise graded beds 57 and 61 in the Chinook Pass section, beds 40 and 42 in the Cayuse Pass section (Chinook Pass Member), and bed B-3 at Cougar Lake (Jutzeler et al, 2014b).…”

“…Most samples belong to the Pliocene Dogashima (Izu Peninsula, Japan) and Oligocene Ohanapecosh (Ancestral Cascades, USA) formations (Fiske, 1963;Cashman and Fiske, 1991;Jutzeler, 2012;Jutzeler et al, 2014a;Jutzeler et al, 2014b). Additional samples were collected in the Miocene Manukau Subgroup (Northland, New Zealand; Allen et al, 2007;Jutzeler, 2012) and in the Quaternary Sierra la Primavera caldera (Jalisco State, Mexico; Clough et al, 1981).…”

“…Results of facies analysis (Jutzeler, 2012;Jutzeler et al, 2014a;Jutzeler et al, 2014b) are used to test whether proportional volume and grain size distribution of coarse (>2 mm) clasts in graded volcaniclastic beds indicate specific types of transport and depositional processes in a context of submarine volcanism. In particular, we analyze the most likely subaqueous transport mechanisms using the hydraulic equivalence signature in context of deposition from vertical settling, collision-induced rolling and shear rolling, through stratigraphy of thick, graded deposits.…”

Field-trip guide to subaqueous volcaniclastic facies in the Ancestral Cascades arc in southern Washington State—The Ohanapecosh Formation and Wildcat Creek beds

“…The formation covers an extremely wide area between the Snoqualmie area (north), the Columbia Gorge (south to Mount St. Helens and Mount Adams), Mount Rainier and Lake Tapps (west), and the Little Naches River area (east) (Jutzeler, 2012;Jutzeler and 2014, and references therein). Tabor and others (1984) and Johnson (1985) interpreted this formation to mark the end of the Eocene strike-slip faulting and magmatism of the Cascades arc in southern Washington.…”