Description
The most noticeable feature on a large scale is the brick-red color, caused by oxidation of iron minerals in the rock. This color is periodically interrupted by streaks and spots of reduced iron, a light bluish-gray shade. Near the top of the formation is a thick layer of gypsum of very high quality. The whole rock is interrupted by gypsum veins as well as having a disrupted texture because of the precipitation of gypsum crystals after deposition of the rock.
The Chugwater consists mainly of siltstone or very fine-grained durable sandstone; it is quite hard and does not break easily. Though most sedimentary structures are not visible due to the gypsum interruption, there are a few examples of ripple marks and occasional crossbedding. Examples of infilled mudcracks of irregular shape, are common.
The main constituent of the Chugwater is quartz, which helps to account for its unusual hardness. Feldspars are also present, though in lesser amounts, as are hematite and gypsum. Small flecks of a dark, opaque mineral have been tentatively identified as biotite. The minerals are cemented by a non-carbonate matrix, probably siliceous.
The Chugwater is a prime example of red beds, commonly deposited during the Permian and Triassic periods.
Read more about this topic: Chugwater Formation
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