Marine placer deposits and sea-level changes
Kudrass, H.R. (2000). Marine placer deposits and sea-level changes, in: Cronan, D.S. (Ed.) Handbook of marine mineral deposits. CRC Marine Science Series, 17: pp. 3-12
In: Cronan, D.S. (Ed.) (2000). Handbook of marine mineral deposits. CRC Marine Science Series, 17. CRC Press: Boca Raton. ISBN 0-8493-8429-X. 406 pp., more
In: Kennish, M.J.; Lutz, P.L. (Ed.) CRC Marine Science Series., more
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| Abstract |
The origin of placer deposits is closely related to Pleistocene glacio-eustatic changes of sea level. Fluviatile placer deposits of gold and cassiterite (tin oxide) on the inner shelf originated during glacial periods of falling sea level, when rejuvenated fluviatile erosion concentrated these heavy minerals in lag sediments. Other economically important placer minerals such as rutile, ilmenite (titanium), magnetite (iron), and monazite (rare earth elements) are predominantly concentrated by the panning system of the surf zone. Beach placer deposits containing these minerals were formed on the middle shelf during glacial periods of low sea level. Most of these deposits were destroyed by the transgressing sea. Parts of them were moved onshore, and the wealth of placer deposits along many present shorelines is predominantly a result of transgressive beach-barrier migration. Only a few shelf deposits were large enough to survive the transgression as disseminated shelf deposits. Eluvial placer deposits of gold, cassiterite, and phosphorite may also be concentrated by submarine erosion. |
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