Organ Mountains (New Mexico) - Geology

Geology

The Organ Mountains are made up of three major sections:

• On the north end is a narrow ridge of vertically-jointed Tertiary granite (more specifically, quartz monzonite) called The Needles. This is the most picturesque section and includes the highest point in the range, Organ Needle at an elevation of 8,990 feet (2,740 m).
• On the south side of The Needles is a much wider section of extrusive igneous rock, mostly a purplish-gray rhyolite. This section forms the bulk of the mountain range and reaches heights nearly as great as The Needles. This section is cut in half by Soledad Canyon, which extends west from the east side of the range, separated by a low ridge and Soledad Pass from Bar Canyon on the west side.
• The third portion of the Organ Mountains consists of the Bishop's Cap Hills on the southwest side of the range and Rattlesnake Ridge on the southeast side of the range. This third section is much smaller and lower in elevation than the other sections of the range, and consists of fault-block limestone similar to that of the San Andres and Franklin Mountains.