Picture Page 4: Silica Filled Cysts in the Chattanooga Shale
Silica filled cysts in the Chattanooga Shale (Late Devonian) are a potential source of "in situ" silt to sand-sized quartz grains (Schieber, J., 1996. Early diagenetic silica deposition in algal cysts and spores: A source of sand in black shales? Journal of Sedimentary Research, v. 66, p. 175-183). The following four pictures illustrate these grains. If you have seen shales with features resembling those shown below, send me a message ( schieber@uta.edu ). Photos are low resolution for faster loading. Click on the image to get a larger, high resolution picture.
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Figure 4/1: Photomicrograph of Chattanooga black shale with abundant silica filled cysts (bright spots). Most cysts have been partially compressed. Scale bar is 0.1 mm long. |
| Figure 4/2: Photomicrograph (close-up) of partially compressed silica filled cyst. The quartz grain in the center is a single crystal, and is surrounded by the organic cyst wall (brownish membrane). The scale bar is 0.1 mm long. |
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Figure 4/3: Photomicrograph of spherical cyst in dolomitic shale bed. Shows the radial fibrous texture of chalcedony (crossed polarizers) that infills the cyst. The scale bar is 0.1 mm long. |
| Figure 4/4: Photomicrograph of a cyst quartz grain in a sandstone bed. The organic cyst wall has been removed during reworking, but the grain still shows an outer rim of fibrous chalcedony (marked R), and a central portion that is filled with megaquartz (marked M). The scale bar is 0.05 mm long. |
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Back to Pictures on Pyrite Ooids: Enigmatic Particles of Uncertain Origin
Back to Pictures on Microbial Mat Features in Proterozoic Shales
Back toPictures on Miscellaneous Sedimentary Features
More Pictures on Sculpting of Muddy Bottoms, Erosion Surfaces and Ripples
More Pictures on Bioturbation in the Chattanooga Shale
© Jürgen Schieber, UTA Department of Geology
Last updated: March 12, 2001.