Page 453 - Carbonate Facies in Geologic History

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Plate XVI. Types of Intraformational Pebble Conglomerates

(A) Lithoclastic packstone, standard microfacies 24. Calcisilt laminated pebbles a
em or so long, incorporated in a fine calcisilt matrix with little or no micrite. The
tiny grains in the matrix include a few bioclasts. The lithoclasts are locally derived
intraclasts; such sediment occurs typically in tidal channels. Sample AGH is from
EI Paso Limestone (Lower Ordovician) at Skyline Drive, Franklin Mountains, EI
Paso, Texas. Thin section, x 15

(B) Lithoclastic grainstone, standard microfacies 24. Rounded aggregates and
locally eroded lithoclasts (intraclasts of Folk) are of bioclastic peloidal wacke-
stone. Some are peripherally micritized and all are thoroughly bored by blue-
green filamentous algae (Girvanella structure) although this is too fine to be seen
in the photograph. The cement is blocky calcite mosaic. Infiltered silt-size grains
caught against larger clasts show that the top is to the right side of illustration.
This sample AGE is also from a tidal channel in the EI Paso limestone (Lower
Ordovician) at Skyline Drive, Franklin Mountains, EI Paso, Texas. Thin section,
x 15