Tuff breccia (tuff breccia)

Japanese: 凝灰角レキ岩(凝灰角礫岩) - ぎょうかいかくれきがん（英語表記）tuff breccia

A rock consisting mainly of medium-grained volcanic rock fragments, with volcanic ash filling the gaps. In RV Fisher's (1966) definition of pyroclastic rock, fragments over 64 mm in diameter make up 1/3 to 2/3 of the total, with the remainder being finer volcanic ejecta fragments. Pyroclastic rocks in which fragments over 64 mm in diameter make up 1/3 or less, fragments between 2 and 64 mm in diameter and fragments under 2 mm in diameter make up 2/3 or less are called volcanic pebble tuff. This classification definition does not include the origin of tuff breccia.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

中粒の火山岩の破片が主体で，間に火山灰がつまっている岩石。フィッシャーR.V.Fisherの火山砕屑（さいせつ）岩の定義(1966)では直径64mm以上の破片が全体の1/3～2/3を占め，残りはより細粒な火山噴出物片からできている場合をさす。直径64mm以上の岩片が1/3以下で直径2～64mmと2mm以下の破片がそれぞれ2/3以下の火山砕屑岩は火山レキ凝灰岩という。この分類定義には凝灰角レキ岩の成因は含まれていない。

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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