Brown clay

Japanese: 褐色粘土 - かっしょくねんど

Brown clay is a pelagic clay containing less than 30% by weight of biological remains (average of 9% foraminifera and 0.7% radiolaria), with particles of 4 μm or less in diameter making up about 80% of the total. It accounts for 28% of the total ocean surface area, and is distributed on the ocean floor at depths of 4,500 to 7,000 m, gradually changing to calcareous mud at shallower depths. Its color is reddish brown or chocolate brown, and it was previously called red clay, but recently the official name brown clay has been changed to brown clay. Its color is due to hydroxides of iron and manganese, as it is formed on the ocean floor in an oxidizing environment.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

褐色粘土は生物遺骸を重量で30％以下(平均で有孔虫9％，放散虫0.7％)を含む遠洋性粘土で，直径4μm以下の粒子が約80％を占める。それは全海洋面積の28％を占め，水深4500～7000mの大洋底に分布し，それより浅くなると石灰質軟泥に漸移する。その色は赤色がかった褐色ないしチョコレート色を帯びた褐色で，赤粘土red clayと呼ばれたが，最近は褐色粘土brown clayが正式に使用されている。その色は鉄とマンガンの水酸化物によるもので，酸化環境の海底で生じたためである。

出典　株式会社平凡社世界大百科事典第２版について　情報

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