The Poleta Formation is mainly composed of
limestone rocks within its lower and upper sections, with its middle section containing
siltstone,
quartzite, and some
limestone. It is overlain by the
Harkless Formation, whilst it is underlain by the
Campito Formation.
Members The formation contains three members, which are as follows, in ascending
stratigraphic order (lowest to highest): •
Lower Member: This member is the thickest of the three, getting up to thick. It is primarily composed of medium to light-gray
oolitic limestone, containing an abundance of
archeocyathid reefs. The limestone is mostly well-bedded, although it is occasionally thin to very thin-bedded. There is also a single inter-stratified layer of greenish-gray or olive-gray siltstone, getting up to thick. •
Middle Member: This member in some areas gets up to thick. It is dominated by siltstones, limestones, and
sandstones or quartzites. The siltstone layers are made up of grayish-olive, pale-olive, and locally pale-yellowish-brown or light-brown siltstone,
shale, and
phylitic silstone, which are composed of subangular silt-sized grains of
quartz, embedded in a fine-textured matrix of
muscovite or mica
clay, and
chlorite. The limestone layers are composed of medium-gray to grayish-orange or mottled-gray to light-brown aphanitic to medium crystalline limestone, which is inter-stratified with occasional siltstone. The sandstone or quartzite layers are primarily pale-brown, light-brown and very-pale-orange, very fine to fine grained and commonly evenly laminated. In some areas, these layers can grade into a coarse siltstone. They also contain quartz and
feldspars. •
Upper Member: This member is the thinnest, only getting up to thick. It is mostly composed of medium-gray limestone, which is very thin to thin-bedded. It also contains a few archaeocyathid fossils. == Depositional setting ==