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Oncolite
Oncolites are sedimentary structures composed of oncoids, which are layered structures formed by cyanobacterial growth. Oncolites are very similar to stromatolites, but, instead of forming columns, they form approximately spherical structures. The oncoids often form around a central nucleus, such as a shell fragment,〔 〕 and a calcium carbonate structure is deposited by encrusting microbes. Oncolites are indicators of warm waters in the photic zone, but are also known in contemporary freshwater environments.〔Riding, Robert. 1991. ''Calcareous Algae and Stromatolites'', pp. 32. Springer-Verlag Press.〕 These structures rarely exceed 10 cm in diameter. The appearance of recent/subrecent freshwater onciods has been documented in two rivers in Bavaria: the Alz, whose source is the Chiemsee, and the Moosach, near Freising. ==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Oncolite」の詳細全文を読む
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