Figure 24. Outcrop of Collings Ranch Conglomerate.
Site 5. Collings Ranch Conglomerate.
Conglomerate is a sedimentary rock
consisting of cemented rounded pebbles, cobbles and boulders. The Collings Ranch
Conglomerate is distributed around the margins of the Arbuckle Mountains and
probably formed as the mountains were uplifted and rapidly eroded. The photo
below shows a typical outcrop - the red/brown cement holding the cobbles and
boulders together is probably precipitated minerals such as iron oxide.
Figure 24. Outcrop of Collings Ranch Conglomerate.
The close up below shows some of the rounded clasts (rocks) and
the finer cement matrix (quarter for scale).
Figure 25. Close up of Collings Ranch Conglomerate showing rounded clasts in a
finer matrix.
The rock does exhibit some layering - much of the material was
probably deposited by rapidly flowing mountain streams or by debris flows.
Figure 26. Layering in Collings Ranch Conglomerate.
The rock is relatively hard, although weathering of the cement
does result in some erosion, such as the gullying shown below.
Figure 27. Gullying (recent erosion).
Figure 28. Evidence of recent weathering and erosion.