Middle and early Late Cambrian stratigraphic sections from southeastern California, across eastern Nevada, to northern Utah are characterized by the rhythmic repetition of dolomitic algal biostromes and dolomitized pelletiferous calcisiltite. Stratigraphic and petrographic criteria indicate deposition on a very wide, shallow, low-gradient shelf on which extensive calcareous algal mats formed. Penesaline conditions, resulting in part from the combination of the width and shallowness of the shelf, led to production of brines and syndiagenetic dolomitization of the algal mats.

Syndiagenesis is suggested by associated intraformational breccias composed chiefly of dolomitized algal debris in a matrix of calcisiltite and by a few erosion pits cut to depths of several inches. Subaqueously formed cracks across wrinkled mats, probably caused by the drag of passing waves, appear to represent an incipient stage in the formation of the breccias.

The pelletiferous calcisiltite is a more seaward deposit and is believed to be composed largely of detritus washed from the algal-mat environment. Seaward refluxion of the brines led to the dolomitization of these rocks.

Rhythmic repetition of these environmentally controlled lithic types reflects a set of conditions which alternately inhibit and enhance algal growth.

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