The contact breccia is associated with the West edge of the main volcanic edifice.
The contact breccia is very well exposed only in the West Quarry section, with a maximum thickness of 17.1 m that progressively decreases toward the eastern parts of the phreatomagmatic ring.
This is deduced from: a) the tectonic structure of the Sierra de las Cabras, b) the highest values of dipping of the phreatomagmatic breccia at the southwest edge, c) the highest content of contact breccia on the West edge (Fig.
b.--The crystalline lamproitic dome of the volcano is surrounded by a ring constituted by the phreatomagmatic-effusive complex, composed by contact breccia, phreatomagmatic breccia (with pyroclast ash, lapilli and bombs, and white carbonate clasts from the host rock) and lava interlayers (massive clastogenics and banded vesiculars).
In this sector, contact breccia and host rock xenoliths are more common.