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A marine terrace represents the former shoreline of a sea or ocean. It can be formed by marine abrasion or erosion of materials comprising the shoreline (marine-cut terraces or wave-cut platforms); the accumulations of sediments in the shallow-water to slightly emerged coastal environments (marine-built terraces or raised beach); or the bioconstruction by coral reefs and accumulation of reef ...
A series of terraces along a river. The oldest terraces (T1) are higher standing than the younger terraces (T3). The present floodplain (T4) will soon become the youngest terrace surface as the river incises. Terraces can be formed in many ways and in several geologic and environmental settings. By studying the size, shape, and age of terraces ...
At the same time, the term "alluvium" came to mean all sediment deposits due to running water on plains. The definition gradually expanded to include deposits in estuaries, coasts, and young rock of marine and fluvial origin. [8] Alluvium and diluvium were grouped as colluvium in the late 19th century. "Colluvium" is now generally understood as ...
The Terrace 5 paleochannel is the western most of the alluvial diamond prospects at Ellendale and was discovered by the Kimberley Diamond Company NL in 1994. The Terrace 5 paleochannel is an ancient buried river system, possibly of Miocene age, which extends more than 35 kms.
These diamonds are then weathered from the source and swept away by alluvial processes (transported by water) to a source that becomes a diamond deposit. Alluvial diamond deposits are mined after removing overburden from the top of the rich, diamond-gravel layer. Roughly 10 percent of diamonds are mined from alluvial diamond placer mines. [8]
The Jones Diamond, also known as the Punch Jones Diamond, The Grover Jones Diamond, or The Horseshoe Diamond, was a 34.48 carat (6.896 g) alluvial diamond found in Peterstown, West Virginia by members of the Jones family. It remains the largest alluvial diamond ever discovered in North America.
The lamproite diamond source is unusual, as almost all diamonds are mined from kimberlite formations and from alluvial deposits of diamonds weathered from that "hardrock" source. The most prominent lamproite diamond source is the Argyle diamond mine in Australia. It is notable that the physical characteristics of Australian lamproite and the ...
Deeper workings encountered less altered rock, serpentinized kimberlite, which miners call "blue ground". Yellow ground kimberlite is easy to break apart and was the first source of diamonds to be mined. Blue ground kimberlite needs to be run through rock crushers to extract the diamonds. [27] Mir mine