How do angular clasts form

Sorting - a breccia comprising a mixture of clast sizes is poorly sorted, while one comprising mostly clasts of the same size is well sorted;. Lithology - a breccia where the clasts represent more than one rock type is termed polymictic or petromictic , while one where the clasts are of a single rock type are monomictic or oligomictic. Other specimens - Click the thumbnails to enlarge.

Introduction Features Igneous rocks Sedimentary rocks Metamorphic rocks. Introduction Features Igneous rocks Sedimentary rocks Metamorphic rocks Breccia Breccia is a rock formed from angular gravel and boulder-sized clasts cemented together in a matrix. The degree of sorting of clasts can be an important indicator of depositional environment.

In water, larger clasts are generally not transported great distances, and they settle faster. For example, in a mixture of mud and sand being transported in a river to the sea, the sand larger clast size, heavier would begin to deposit as soon as the river's energy dissipated, while the mud fine, light-weight would be transported far off shore.

Therefore, a well sorted clasts of approximately the same size , coarse sandstone indicates deposition in a reasonably high energy environment near-shore probably close to the source of the sand. Conversely, a mudstone generally indicates deep water deposition low energy environment, far off shore. Structures produced during deposition, e. Fabric strength and the interpretation of sedimentary fabric data. Journal of Sedimentary Research A64 , Evans, D.

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