China
Africa
Explore chapters and articles related to this topic
Sedimentary rocks
Published in W.S. MacKenzie, A.E. Adams, K.H. Brodie, Rocks and Minerals in Thin Section, 2017
W.S. MacKenzie, A.E. Adams, K.H. Brodie
The sedimentary rock in Figure 155 is a bioclastic limestone with a variety of shell fragments of different sizes. Two principal types of fragment are present; those with a regular, layered structure such as the two large fragments in the lower part of the photograph are shells which have been preserved with their original calcite mineralogy. The smaller fragments such as those in the upper right hand part of the figure are pieces of originally aragonite shell, in which the metastable aragonite has been replaced by calcite sparite. The limestone is grain-supported and contains sparite cement, but carbonate mud matrix is also present and it would thus classify as a packstone.
Stromatolite framework builders: ecosystems in a Cryogenian interglacial reef
Published in Australian Journal of Earth Sciences, 2020
Facies 1 Interbedded micritic mudstone and intraclastic packstone comprises thin to medium, laterally discontinuous, interbeds of micritic mudstone and intraclastic packstone. Laminae show low-angle cross-stratification, poorly developed hummocky cross-stratification, convolutions, overturned beds, scour and infill, edgewise breccia, ripples and draping fabric (Figure 5a, b). Locally, packstone is dedolomitised to sparry limestone, which weathers recessively compared with dolomitic mudstone interbeds. Packstone comprises coarse sand-to-gravel-sized micrite intraclasts, ooids and aggregates in a micritic matrix with cement-filled vughs. The lime mudstone is homogenous with very subtle layer-parallel lamination. Discontinuous amorphous dark wrinkly stringers encrust and bind small angular intraclasts and minor quartz silt (Figure 5c).
The effects of heterogeneity on pressure derived porosity changes in carbonate reservoirs, Mishrif formation in SE Iraq
Published in Petroleum Science and Technology, 2023
Mustafa Mohsin, Vahid Tavakoli, Adeleh Jamalian
The facies of the selected samples are mainly grain-dominated. From 73 core plug samples, 55 samples are rudist rudstone. Dominant allochems are rudist debris and benthic foraminifera. Semi-rounded shapes of bioclasts indicate reworking and re-deposition. Ooids and intraclasts are rarely seen. The remaining samples mainly contain bioclast debris (rudist, coral, and algae) and small peloids with packstone to floatstone textures. Dissolution is dominant diagenetic process which resulted in vuggy pore spaces. Syntaxial rim cement is frequently seen in grain-dominated facies. Most of the grains have been micritized in packstone textures. Mechanical and chemical compaction are the most abundant diagenetic processes in all facies.
Geology, geochemistry and depositional history of the Port Campbell Limestone on the eastern flank of the Otway Basin, southeastern Australia
Published in Australian Journal of Earth Sciences, 2022
B. Radke, D. C. Champion, S. J. Gallagher, L. Wang, D. De Vleeschouwer, A. Kalinowski, E. Tenthorey, M. Urosevic, A. Feitz
The generally unconsolidated fine-grained carbonate sediment has uniform mid-grey appearance but is ‘lumpy’ and texturally variable (Figure 16) from bioturbation, as well as from subsequent cementation and later dissolution effects. Grainstone and packstone textures predominate. The matrix of variably indurated lumpy limestones is packstone. Wackestone and mudstone textures are rare.