| * Particle sizes are defined in the graph on page 6 ----------> |
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Boulders: Larger than 25.6 cm Cobbles: 6.4 to 25.6 cm Pebbles: 0.2 to 6.4 cm Sand: 0.006 to 0.2 cm Silt: 0.0004 to 0.006 cm Clay: Less than 0.0004 cm |
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Breccia
Breccia is formed by the cementation of angular particles including pebbles and possibly cobbles and boulders* in a mix of sand, silt and/or clay. The finer particles serve as a kind of glue or cement binding all of the larger particles together.
The larger particles in breccia are sharp and angular which means they were subjected to little or no 'stream abrasion' (rolling around at the bottom of a river or stream). Instead these particles were probably deposited directly onto the land often in a desert environment where streams dry up before reaching the sea.
| * Particle sizes are defined in the graph on page 6 ----------> |
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Boulders: Larger than 25.6 cm Cobbles: 6.4 to 25.6 cm Pebbles: 0.2 to 6.4 cm Sand: 0.006 to 0.2 cm Silt: 0.0004 to 0.006 cm Clay: Less than 0.0004 cm |
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