oligomictic orthoconglomerate

geology

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July 1, 2026

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An oligomictic orthoconglomerate is a type of sedimentary rock composed of rounded fragments larger than 2 millimeters in diameter. It is characterized by having less than 15% matrix (finer material) and a framework where the coarse clasts touch each other. These conglomerates can be made of a single rock or mineral type, in which case they are called oligomictic orthoconglomerates. They are typically deposited by turbulent water currents, such as those found on beaches, and are known for their high porosity and permeability, making them excellent sources of groundwater.12

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sedimentary rock
Clast-supported conglomerates
…contain lenses and bands of oligomictic orthoconglomerate, composed mainly (95 percent or more) of stable, resistant, coarse clasts of vein quartz, quartzite, quartz sandstone, and chert. Such deposits are typically generated in the upper reaches of winter storm beaches where strong surf can sift, winnow, and abrade coarse pebbles and…
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…contain lenses and bands of oligomictic orthoconglomerate, composed mainly (95 percent or more) of stable, resistant, coarse clasts of vein quartz, quartzite, quartz sandstone, and chert. Such deposits are typically generated in the upper reaches of winter storm beaches where strong surf can sift, winnow, and abrade coarse pebbles and…
Read More