Harkless Formation

Geology

Members

• Weepah Member: Near the Andrews Mountain, at the type area of the formation, the member is dominated by greenish-gray and light-olive-gray siltstone, alongside a few layers of yellowish-gray fine to medium grained quartzite. The quartzite layers are identical to the layers found in the Zabriskie Quartzite. The siltstone ranges from grayish-olive, pale-olive, and dark-greenish-gray, and is composed of silt-size grains within a matrix of muscovite and chlorite, and is thinly laminated. They have also slightly metamorphosed, resulting in phyllite or hornfels. The hornfels are primarily composed of muscovite, chlorite, biotite, and quartz. Trace fossils are relatively common within the type area. Within the Esmeralda County, Nevada, the lower sections of the member is still dominated by siltstone, although this differs greatly from the siltstones higher up in the formation. This is due to the layers being quartzitic, coarser and more resistant to natural erosion. The sizes of the grains within these layers hovers around the boundary between coarse silt and very fine sand.
• Alkali Member: The upper Alkali member is composed of limestone layers, up to thick, inter-stratified with siltstone, and contain an abundance of archeocyathid sponges. Further still there are light-brown limestone layers, only up to thick, that contain Salterella, and are also inter-stratified with the siltstone layers in the middle of the formation. More limestone can be found at the top of the member, being gray or locally yellowish-brown, and up to thick. In some areas of the member, there are also tongues from the Zabriskie Quartzite, composed primarily of medium-grained quartzite, and can get up to thick in some places, and inter-stratify with the siltstones. The colour of the quartzite is commonly yellowish-gray or greenish-gray. It is also laminated to thin-bedded. Trace fossils are also common within these quartzite tongues, also appearing on the underlying siltstone layers.

Paleobiota

Arthropoda

Lophotrochozoa

Chancelloriidae

Cnidaria

Echinodermata

Porifera (Sponges)

''incertae sedis''

Flora

Ichnogenera