Specimen: 2014-017

This specimen is a limestone with a low fossil content. The limestone is not grain supported and has a predominantly micrite cement matrix. These criteria define the limestone as a mudstone. Allochems comprise about 5 to 10 percent of the slide area. This classifies this limestone as a bioclast fossiliferous micrite. Bioclasts are composed of shell fragments likely from both bivalve and brachiopod species, based on variable preservation of internal shell structure. These fragments have a maximum dimension of .4 mm and a modal range around .15 to .25 mm. Monocrystalline grains of calcite with sieve texture may, in some cases, represent echinoderm parts. There is no appreciable porosity but deformation of allochems is lacking, indicating low to moderate compaction prior to lithification. The most common inclusion is elongate collophane at 1 to 3 percent of slide area. These are likely indicative of bone and other organic fragments and have a maximum dimension of 1.7 mm and a modal range around .5 to .3 mm. They show a preferential orientation that is parallel to bands of iron hydroxide (limonite) staining. This staining is more prevalent near the rock surface and is perceptible for about 1 cm of rock depth. The slide’s orientation is perpendicular to these bands. There is visibly less compaction or alternatively more alteration near the rocks surface. The limonite staining imparts a yellow-orangish color to the rock. Extant voids are essentially absent, the degree of compaction is difficult to estimate.
MP 7/21/2015