Summerville Formation, Geological formation in San Rafael Swell, Utah, United States.
The Summerville Formation is a sequence of rock layers found across Utah, Colorado, and New Mexico with alternating bands of red mudstone and green sandstone. Gypsum deposits are scattered throughout this layered structure.
Geologists Gilluly and Reeside first documented this formation in 1928, establishing its reference section at Summerville Point in Emery County, Utah. Their work laid the foundation for later geological studies of these rock layers.
The formation contains preserved theropod and pterosaur tracks, providing evidence of ancient reptilian life in the southwestern United States during the Late Jurassic period.
This rock sequence is accessible at several locations including the San Rafael Reef, Waterpocket Fold, and Henry Mountains where researchers collect samples. Visitors should wear sturdy shoes and sun protection since the exposure points are in open, arid areas.
The lower layers show desiccation cracks and salt structures that reveal an ancient sabkha environment along the margin of the Sundance Sea. These features tell the story of the region's former marine history and shifting climate conditions.
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