siliciclastic rock

geology

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July 13, 2026

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Siliciclastic rocks are a type of sedimentary rock composed primarily of detrital fragments of pre-existing rocks and minerals, which are rich in silica. These rocks are also known as terrigenous clastic sedimentary rocks.1

The main types of siliciclastic rocks are classified by the size of their constituent grains:
* Conglomerate and breccia: Composed of coarse clasts (pebbles, cobbles, boulders). Conglomerates have rounded clasts, while breccias have angular clasts.1
* Sandstone: Formed from sand-sized grains.1
* Siltstone and mudrock: Made of finer grains, including silt and clay.1

Siliceous rocks, such as chert, are chemically precipitated and consist almost entirely of silicon dioxide, distinguishing them from siliciclastic rocks which are of detrital origin. Silcrete is a silica-rich layer formed in soils, typically in arid climates.23

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sedimentary rock
Classification systems
…are also referred to as siliciclastic sedimentary rocks. Siliciclastics are further subdivided on the basis of clast diameter into conglomerate and breccia, sandstone, siltstone, and finer-than-silt-sized mudrock (shale, claystone, and mudstone). The carbonates, limestones and dolomites, consist of the minerals aragonite, calcite, and dolomite. They are chemical sedimentary rocks in…
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…are also referred to as siliciclastic sedimentary rocks. Siliciclastics are further subdivided on the basis of clast diameter into conglomerate and breccia, sandstone, siltstone, and finer-than-silt-sized mudrock (shale, claystone, and mudstone). The carbonates, limestones and dolomites, consist of the minerals aragonite, calcite, and dolomite. They are chemical sedimentary rocks in…
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Ordovician Period
Significant geologic events
Ordovician siliciclastic (made from broken parts of silica rocks) rocks can be divided into coarse-grained and fine-grained types. Relatively coarse-grained siliciclastic rocks such as sandstones and conglomerates tended to accumulate in high latitudes where significant carbonate accumulation was precluded and in low latitudes where orogenic uplift…
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Ordovician siliciclastic (made from broken parts of silica rocks) rocks can be divided into coarse-grained and fine-grained types. Relatively coarse-grained siliciclastic rocks such as sandstones and conglomerates tended to accumulate in high latitudes where significant carbonate accumulation was precluded and in low latitudes where orogenic uplift…
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