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Geotechnical soils mapping for construction purposes in Central Saudi Arabia
Published in P.G. Fookes, R.H.G. Parry, Engineering Characteristics of Arid Soils, 2020
J.S. Griffiths, P.G. Fookes, A.D. Hardingham, R.D. Barsby
Rockhead was close to the surface through the centre of the site and along the northern and western boundaries. The central tableland (Figure 1) was composed of Neogene arenaceous siltstones and argillaceous sandstones (although not proven to depth). Because this was a relatively young sedimentary rock it was deemed unlikely to possess the qualities necessary to make a good construction material. It would be suitable, however, as a rock fill (possibly select fill and sub-base). The northern part of the site was underlain by Cretaceous siltstones and sandstones. These older rocks displayed a weathering profile over three metres deep and had limited potential for use as construction materials. The Lower Cretaceous formation that formed an outcrop in the western margin of the project area was composed of moderately strong calcilutite and calcisiltite interbedded with anhydrite/gypsum rich residual soils. Particular beds within the sequence may have been be suitable as a source of crushed aggregate but processing the material to remove the salts would have been necessary. Jurassic rocks were found in the south west corner of the site and appeared to be mainly strong crystalline limestones. These were likely to be impregnated with anhydrite or gypsum close to rock head, but at depth may have provided a good supply of concrete aggregate, sub-base and also a good supply of large and small rock armour.
Sedimentary Petrology
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
Mudstone consists of extremely fine-grained carbonate, comparable to the calcilutite of Grabau (1904) or the micrite of Folk (1959). The fine-grained, perfectly homogeneous variety of ‘mudstone’ used for lithographic purposes is called a lithographic stone. Mudstones may be produced by attrition, or may be chemically or biochemically precipitated. The choice of the term ‘mudstone’ to designate a particular type of limestone is not a happy one because argillaceous rocks of terrigenous origin and composed of silt-clay are also called mudstones (see Table 4.5).
Geoheritage values of consanguineous wetland suites on the Swan Coastal Plain, Western Australia
Published in Australian Journal of Earth Sciences, 2019
Asymmetry in telluric water supply and the position of wetlands in their geomorphic setting, may result in asymmetry in stratigraphic sequences. Ca-enriched influx water derived from carbonate terrains results in calcilutite-dominated sediment. Si-enriched influx water deriving from carbonate terrains results in diatomite-dominated sediment. Vegetation-dominated sedimentation results in peat-dominated sediment. A complex history of wetlands may also result in a layered or asymmetric stratigraphy (Figure 8). Where wetland basins are sited on relatively soluble basement (e.g. carbonate sand, or limestone), long-term solution of the basement can result in subsidence and deepening of the basin (cf. C. A. Semeniuk, 2007).