Flowers and Rock, Catalina State Park and Alamo Canyon – 5/7/2016

Saguaro Flower in Catalina State Park. May 2016.
Saguaro Flower in Catalina State Park. May 2016.
More Saguaro Flowers in Catalina State Park. May 2016.
More Saguaro Flowers in Catalina State Park. May 2016.

The pictures above are from Catalina State Park but Doug Kreutz’s recent article Saguaros on a blooming binge in Sabino Canyon still seems relevant – and on the subject of Saguaros perhaps some photographic inspiration from Jack Dykinga

Leviathan Dome from Alamo Canyon. May 2016.
Leviathan Dome from Alamo Canyon. May 2016.

I was recently reminded of John V. Bezy’s A Guide to the Geology of Catalina State Park and the Western Santa Catalina Mountains (available as a free PDF file) – the guide is accessible to readers without any formal training in geology and has been interesting to read again because it contains information on so many familiar sights.  From a section titled Granite Pinnacles (p.15):

Catalina State Park is best known for the dramatic granite pinnacles that have developed in the upper, cliff-forming unit of the Wilderness Suite granite in this part of the Santa Catalina Mountains. These towering spires are the products of surface weathering and erosion by running water guided by deep joints in the rock.

The Wilderness Suite granite differs from the Oracle and Catalina granites that make up the western face of the range in that it is dominated by widely spaced, vertical joints. These fractures serve as avenues along which chemical and physical weathering and erosion penetrate the granite. Rock shattering, caused by ice expansion, wedging by plant roots, and chemical decomposition, enlarges the joints. Water from rain and snowmelt is channeled into the joints, cutting them into ravines and canyons. Joints actually control the location of most streams crossing bedrock. This concentrated action of weathering and erosion eventually widens and deepens the ravines and canyons, leaving the massive granite in between standing as towering pinnacles.

Table Tooth from Catalina State Park - Table Mountain is just to the right. May 2016.
Table Tooth from Catalina State Park – Table Mountain is just to the right. May 2016.

A Guide to the Geology of Catalina State Park and the Western Santa Catalina Mountains – p.10:

The bedrock of this part of the Santa Catalina Mountains is mainly the Oracle, Catalina, and Wilderness Suite granites. These granites were injected deep within the Earth’s crust as great molten masses. They were emplaced at different times: the Oracle Granite 1.45 billion years ago, and the Wilderness Suite Granite 45-50 million years ago, and the Catalina Granite 26 million years ago. The molten rock, which cooled and solidified over millions of years and miles below the Earth’s surface, has since been exposed by erosion.

Near the Mouth of Romero Canyon, Below Breccia Hill – 5/8/2016

Looking up Romero Canyon. May 2016.
Looking up Romero Canyon. May 2016.

With the Bighorn Sheep Closure over for the year we took advantage of a not-too-hot day to wander out of Catalina State Park and into Romero Canyon, just inside the Pusch Ridge Wilderness. Romero Canyon was completely dry in some places while other spots had trickling flow and pools of water.

Romero Canyon wall not far from the mouth of the canyon. May 2016.
Romero Canyon wall not far from the mouth of the canyon. May 2016.
In Romero Canyon below Bressia Rock. May 2016.
In Romero Canyon below Breccia Hill. May 2016.

Near the mouth of Romero Canyon there is an brief, but fascinating, section of canyon where canyon walls of an unusual rock close in tightly. This section of canyon is just below the prominent green colored Breccia Hill and the rock is mentioned in A Guide to the Geology of Catalina State Park and the Western Santa Catalina Mountains (p. 29):

Tremendous friction is generated as fault surfaces slide together. This grinding action produced a zone of powdered rock (fault gouge) and highly broken rock (fault breccia) that can be observed here at Breccia Hill and at other locations where the Cañada del Oro has exposed the fault surface … Movement on the Pirate Fault is thought to have occurred six to twelve million years ago. This demonstrates how an ancient geologic structure, in this case a fault, can control modern landscapes.