extraformational breccia

rock

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July 21, 2026

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Extraformational breccia is a type of sedimentary rock composed of angular fragments of pre-existing rocks. These fragments, or clasts, are larger than 2 millimeters and are held together by a cementing material or a finer-grained matrix. Unlike conglomerates, which have rounded clasts, breccias are characterized by their angular fragments.123

Extraformational breccias are derived from source rocks located outside the area where the deposit occurs. They are one of four genetic categories of breccias, alongside pyroclastic, cataclastic, and meteoritic types. While sedimentary breccias are the only true sedimentary rocks among these categories, breccias can also form through volcanic activity, earth movements, or meteorite impacts.13

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sedimentary rock
Epiclastic conglomerates and breccias
…the depositional basin itself; and extraformational, derived from source rocks that lie outside the area in which the deposit occurs. Epiclastic conglomerates and breccias together probably make up no more than 1 or 2 percent of the conventional sedimentary rock record.
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…the depositional basin itself; and extraformational, derived from source rocks that lie outside the area in which the deposit occurs. Epiclastic conglomerates and breccias together probably make up no more than 1 or 2 percent of the conventional sedimentary rock record.
Read More