James S. Aber
|Goemmer Butte is the low, brown knob to left with West Spanish Peak visible in the background. The butte peak, at 8043 feet, stands more than 1600 feet (500 m) above the surrounding terrace surface (foreground). Image date 3/99; © J.S. Aber.|
|View of the south side of Goemmer Butte. The main body of the butte is made up of intrusive rock, and the lower south side contains breccia (broken/crushed rock). Image date 6/99; © J.S. Aber.|
Goemmer Butte is considered by some to be a "volcanic plug" in which magma vented to the surface (Penn and Lindsey 1996). The evidence for this volcanic interpretation is the breccia pipe that partly surrounds the butte's core. Breccia is associated with explosive volcanic eruptions in which pre-existing rocks are broken, mixed, and violently ejected by high-pressure gas/steam explosions. In this case, rocks derived from the surrounding Cuchara Formation and the trachyte plug make up the breccia. This implies that the breccia pipe must be younger than the trachyte plug. Goemmer Butte is considered to be Miocene, although its exact age and relationship to other intrusions of the region are uncertain (Lindsey 1995).
|Breccia zone on the south side of Goemmer Butte. Note the unusual weathering pattern of vertical pillars. Image date 6/99; © J.S. Aber.|
|Closeup view of breccia from the south side of Goemmer Butte. Note the broken rock fragments within the boulder as well as covering by brightly colored lichens (orange, yellow, green). Image date 6/99; © J.S. Aber.|
Sulfur Springs takes its name from springs that emit hydrogen-sulfide gas, where Indian Creek crosses the main frontal thrust. Many other springs are situated along the mountain front to the north and south.
|Dakota hogback at Sulfur Springs, west of Goemmer Butte. The hogback is formed by resistant strata of the Purgatoire Formation and Dakota Sandstone. The strata have been tilted up and overturned (to the right) along the main frontal thrust of the Culebra Range, Sangre de Cristo Mountains. Image date 3/99; © J.S. Aber.|
|W-E cross section of the Culebra Range foothills in vicinity of Sulfur Springs, CO. Note
overturning of strata at the mountain front. Green dot marks the hogback of the Purgatoire
Formation and Dakota Sandstone (Kdp); red lines are dikes; east to right. Adapted from Lindsey
GO 547/ES 747 © J.S. Aber (2002).