[7] Much of the Mountain Lake Member comprises meter-scale, deep ramp cycles that overlie a lowstand systems tract of sandstones and sandy crinoidal grainstones.

The Bromide Formation was deposited in a shallow, storm-dominated epeiric sea that extended over part of the Laurentia continent, in what is today Southern Oklahoma.

Eventually, sea level rise caused by subsidence drowned the borderlands cutting off the supply of sand, and now the shales and limestones of the Middle Bromide (upper Mountain Lake Member) accumulated on a broad ramp.

Further eustatic sea level rise (transgression) cut off the supply of virtually all sediments from land, and remains of carbonate-producing organisms began filling the basin.

[8] Fossils have been found in the Bromide Formation of green algae, sponges, corals, graptolites, lampshells, moss animals, trilobites, clam shrimps, molluscs, several groups of echinoderms, and teeth of jawless fish.