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Sediments and Sedimentary Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Figure 8.15 shows a 2-meter-tall outcrop in Point Lobos State Reserve, near Carmel, California. In this outcrop, clasts of different sizes have been sorted (fine at the bottom and coarse at the top), and many sizes are present. This outcrop is a good example of immature sediment: it is poorly sorted and contains angular clasts. The clasts are of several different compositions and contain a variety of minerals. In contrast with immature sediments, the most mature sediments are well sorted and contain well-rounded grains because they have had a long history, involving transportation that included many opportunities for sorting and abrasion. Mature sediments also are composed only of very stable Earth surface minerals, such as quartz, because other minerals have had ample time to decompose.
Morphogenetic landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Hamada surfaces, characterized by cobbles and boulders, are established by the nature of the underlying rock, or rock derived from a nearby escarpment and they are residual. Hence the hamada is a mantle protecting the underlying sediments or rock. The reg, on the other hand, is usually deposited by streamflow or sheetfloods and the coarser component is concentrated to form a desert pavement. The concentration process can be by deflation, as the finer sediments are blown away. This sorting process leaves the coarser fraction of the sediment on the surface with unsorted sediments beneath the armour, and is effected by rainbeat and surface runoff that carries away the finer sediments.
Index, Compressibility, and Strength of Marine Sediments
Published in Ronald C. Chaney, Marine Geology and Geotechnology of the South China Sea and Taiwan Strait, 2020
If you are a geologist a sediment consisting of single-sized particles is considered well sorted. A well sorted sediment is one that has a limited size range of particles. The other sized particles in the sediment have been removed, usually by currents or waves. If you are an engineer it is just the reverse (i.e., poorly sorted). A poorly sorted sediment contains different sized particles. This usually indicates that little mechanical energy has acted to sort the particles.
Sedimentological analysis of marine deposits off the Bagnoli-Coroglio Site of National Interest (SNI), Pozzuoli (Napoli) Bay
Published in Chemistry and Ecology, 2020
Flavia Molisso, Mauro Caccavale, Monica Capodanno, Costantino Di Gregorio, Mauro Gilardi, Antimo Guarino, Elvira Oliveri, Stella Tamburrino, Marco Sacchi
The area is located between Nisida Island and Trentaremi, from −5 to −60 m depth and includes 6 samples collected with Van Veen grab. The sediment mainly consists of moderately sorted, coarse and very coarse sand with lithoclasts and bioclasts. Station 123 is characterised by gravelly sand, where gravel represents 18%. The bioclastic fraction is generally abundant and in stations 120 and 123 it also includes fragments of rhodoliths. Mean size ranges from 0 to 1.21 phi. The sediment texture can be described as coarse-skewed to fine-skewed and mesokurtic.