Plate 8

Sample Depth: 8914.3 ft

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A.	Textural overview of bioclastic, calcareous wackestone, one of two distinct carbonate textures in this sample. Skeletal assemblage is relatively diverse, comprising pelmatozoans, gastropods, brachiopods, bryozoans, ostracodes, algal fragments, and other unidentified fossil debris. Tan or white patches, such as at upper right, are zones where silica (chert) has replaced both grains and matrix. Replacive pyrite (arrow) and dolomite (d) are also visible. Plane-polarized light. (20x)
B.	High-magnification view of the dolomitic portion of the sample, which is texturally similar to sample 8908 above. Here, finely crystalline euhedral-to-subhedral dolomite replaces calcareous grains and matrix (pink), leaving remnants of limestone texture shown in view A. Replacive dolomite is darker, with more inclusion material, whereas pore-filling dolomite is euhedral, inclusion-poor, and exhibits ferroan rims (arrow) in places. Later, pore-filling anhydrite (a) is also shown. Note paucity of intercrystalline porosity. Plane-polarized light. (100x)
C.	General view of dolomite texture shows well-packed, finely crystalline dolomite in matrix, with coarser, euhedral dolomite filling porosity at center. This dark area is a patch of partially dissolved and replaced, microporous chert (note remnant chert at bottom right), that was likely similar in texture to silica patch shown in A. Textures shown here suggest that pore-filling dolomite precipitated after silica. Crossed nicols. (40x)
D.	Same view as above highlights microporosity associated with microporous chert cement and several open microfractures. Overall, porosity development is much poorer here than in sample 8908 as a result of tighter dolomite texture, remnant calcite, and pore filling cements. Outside of this microporous patch, little if any matrix porosity exists in this view; poor permeability is, therefore, expected at this depth. Reflected ultraviolet light with blue-violet filter. (40X)