rudite

Rudite is a clastic sedimentary rock that is composed of at least 30% gravel-sized clasts. Clasts are fragments of pre-existing rock or mineral grains that have been eroded, transported, and deposited. The remaining 70% of the rock consists of finer-grained matrix material, such as sand, silt, or clay, which fills the spaces between the larger clasts.

The gravel-sized clasts in rudites can vary widely in size, from pebbles to boulders. Their shape also depends on the distance and energy of transport. Rounded clasts suggest longer transport distances or high-energy environments like fast-flowing rivers or beaches. Angular clasts, on the other hand, indicate shorter transport distances or deposition in lower-energy environments. The composition of the clasts reflects the lithology of the source area from which they were derived.

Rudites are classified based on the rounding and sorting of their clasts, as well as the composition of the matrix. Conglomerate is a type of rudite where the gravel-sized clasts are rounded. Breccia is a rudite where the clasts are angular. If the matrix is primarily sand, the rock is called a sandy rudite. If the matrix is primarily silt or clay, it is termed a muddy rudite. These rocks are typically formed in high-energy depositional environments such as alluvial fans, braided rivers, deltas, and submarine fans, where significant erosional forces are present to break down and transport larger fragments.