4.1 Sample 1 DH Dove Holes
This sample is a fine-grained limestone that consists predominantly of calcite, with a high volume of allochems in the form of various types of bioclasts. Minor coarser-grained calcite and narrow quartz veinlets also traverse this sample.
4.1.1 Macroscopic Features
This sample is a fine-grained, pale grey sedimentary rock that is competent (flexed during formation) in nature, and exhibits an abundance of fossil fragments (Figure 4.11.1 part D). Narrow calcite veinlets can be seen traversing the sample.
4.1.2 Mineralogy and Petrography
The bulk of this sample consists of a fine-grained calcite matrix together with abundant medium to coarse-grained allochems. The fine-grained matrix that hosts the variety of allochems (Figure 4.11.1 part A+B+C) consists of calcite grains, that are typically <5µm in size and may be referred to as a micrite or carbonate mud.
The allochemical components of this sample consist largely of different types of bioclasts, including brachiopods and various foraminifers, namely endothyracids (Figure 4.11.1 part A+B). Several narrow cross cutting calcite veins were also observed (Figure 4.11.1 part C). Examination of this rock using qualitative energy dispersive analysis revealed the presence of narrow quartz veinlets (Figure 4.11.1 part D) that possibly formed during compaction.
(a and b) Colour, transmitted light photomicrographs that illustrate the nature of the fine-grained calcite matrix (greenish grey) with abundant fossil fragments, mainly different types of bioclasts. (c) Narrow cross cutting calcite (grey-white) veinlets are present. (d) A false coloured backscattered electron image illustrating the presence of a narrow quartz veinlet (mauve) in the fine-grained calcite (orange) matrix.