[1] In these areas the Organ Rock typically outcrops as a dark-red/brown siltstone to mudstone gently dipping towards the southeast.

In locations where the De Chelly and White Rim are absent, the Organ Rock is unconformably overlain by the Triassic Moenkopi or Chinle Formations by an erosional contact.

[5] The anteceding De Chelly and White Rim Sandstones are dated to the Leonardian (ICS stage: Kungurian).

This is during the early to mid-Permian, a time where synapsids and temnospondyl amphibians are the dominant players in terrestrial ecosystems.

[1] These rocks occur in two primary facies: floodplain and channel, as well as eolian dunes and sand sheets.

In these deposits, mixed reddish-brown sands and silts dominate with minor mudstones and conglomerates interspersed.

[1] Interpreted channel deposits grade from laterally accreting coarse sands – into conglomerates of pebble-sized carbonate clasts.

Fossil vertebrates represent the majority of the faunal assemblage present in the Organ Rock Formation.

Taxa recovered include: freshwater actinopterygian fishes, temnospondyl amphibians, diadectomorphs, seymouriamorphs, and early synapsids.

Remains of this animal are very common in other formations of the Cutler Group and in general during the Early Permian of southwestern North America.

Originally described by Vaughn,[8] this animal was first assigned to the group Seymouriamorpha, however, upon reassessment of the holotype it was demonstrated to have a closer affinity to Diadectomorpha.

These animals have a generalized early amphibian body plan with a large “u”-shaped head and a sprawling lizard-like posture.

[14] Some early synapsids adapted an herbivorous diet, however, the Organ Rock Formation only preserves carnivorous animals; these were likely the apex predators of this ecosystem.

The three sphenacodontids were terrestrial predators consuming other tetrapods, while Ophiacodon likely hunted fishes and other aquatic animals.

The vertebrate faunal assemblage found in the Organ Rock Formation is diverse with respect to taxonomic groups, body plans, and diets.

[12] As one moves younger in time through the Organ Rock Formation, temnospondyls become less abundant with respect to other major groups such as diadectomorphs and early synapsids.

This trend is globally recognized during the Early Permian, supported by many lines of geologic evidence including significant deposits of calcretes, eolianites, and evaporites.