Day 1 : Stop 3

DAY 1 (9/26/2025) - STOP 3

"El Capitan Viewpoint"

COORDINATES: 31.85462° N, 104.84396° W

Fig. 5 Our class in front of the El Capitan Viewpoint 

    Our next stop was a roadside pull-off known as the El Capitan Viewpoint (fig. 5), which provided a clear view of the El Capitan summit. Unlike modern coral reefs, this one was dominated by sponges and other organisms. This limestone layer felt notably porous, with cavities now cemented by calcite and fine micritic material that filled in the spaces between the skeletal structures, creating a rigid and porous framework.       

To summarize, the Capitan Limestone preserves a reef built not by corals but by sponges and microbial communities, forming a porous, calcite-rich framework that later cemented into massive limestone cliffs. Compared to the dark, fine-grained basin limestones we saw earlier in the day, the Capitan is massive, bright, and full of former biological structure.

  Reaching this viewpoint required us to drive upward through the Brushy Canyon, Cherry Canyon, and Bell Canyon formations, each representing deeper-water deposits from the ancient reef and slope. Essentially, we drove through layers from the deep basin up toward the shallower, more energetic reef environment. This site is described as the former continental-shelf slope, a place where storms and heavy rains would have triggered turbidity currents powerful enough to transport sediment downslope. Today, the canyon formations we passed record those events, while the Capitan Limestone depicts the position of the reef wall that once stood above them.