The Swarbrick Formation was defined at Tybo in the Hot Creek Range (Ferguson, 1933).

The Swarbrick is considered Middle to early Late Cambrian (pre-latest Dresbachian) in age (Quinlivan and Rogers, 1974; Kleinhampl and Ziony, 1985).

The Swarbrick Formation is composed of interbedded red to reddish-brown weathering or gray chert, and thin-bedded and laminated, flaggy to slabby, medium-gray to brown-weathering, very fine-grained and locally silty limestone with olive gray fissile shale (Quinlivan and Rogers, 1974). The chert is commonly more abundant in the upper portion of the unit, and is composed of 80 to 90 percent microcrystalline quartz and about 10 percent sponge spicules and dolomite rhombs (Kleinhampl and Ziony, 1985). The upper 200 to 300 feet of the Swarbrick in the Hot Creek Range are shale-rich with less chert and limestone which are both siltier and more platy than similar lithologies below. Although the unit is overall thinly and evenly bedded, it is strongly crumpled and sheared in the Hot Creek Range, where it is thrown into a series of small overturned folds (Quinlivan and Rogers, 1974).

The Swarbrick is about 1,700 feet thick at Tybo in the Hot Creek Range (Quinlivan and Rogers, 1974).

The Swarbrick Formation is exposed in the Hot Creek Range where it forms the base of the Paleozoic section.

The depositional setting of the Swarbrick is poorly understood. The presence of laminated sponge-spicule chert, laminated shale and silty, laminated limestone suggests an outer shelf to upper slope environment.