Society for Sedimentary Geology Takes Trip to Mason Area
Wednesday, April 16, 2014 • Posted April 16, 2014
All smiles after a challenging paddle trip, a happy, but tired kayaker, one of 18 visiting geologists with SEPM, comes in above the James River Crossing Bridge. SEPM members later enjoyed Cooper’s BBQ at Honey Creek Ranch. The following day the group explored the geology of a local ranch, and took in a fine evening meal at Mi Pueblos and some fine Texas wine at Sandstone Cellars Winery before retiring to their B&Bs. On Sunday the group concluded their Mason weekend with a visit to the Hwy 87 San Saba Bridge Park to view Stromatlites from a slightly younger formation. These fossils are easily visible in the river bed and banks below the bridge. Breakfast and lunch were provided by Willow Creek Café and kept the group fully fortified while on the river.
The cliffs between White’s and James River Crossing make an excellent geologic “classroom”. This Stromatolitic Bioherm, is one in a series that make up an ancient, fossilized reef system and is a world-renowned example that draws geologists from across the globe. In a warm, shallow sea, microbial organisms (blue-green algae) colonized and built upon their ancestors for generations creating tall columns and also oxygenating the atmosphere. These columns infilled with sedimentation as the columns grew and the weight pushed the reef structures deep into the less dense silt below as can be witnessed by the compressed layers at the base of the bioherm. This particular example is located directly across from Honey Creek Ranch where geologists often stay while visiting.
Two SEPM members from Nigeria pause for a classic geology photo in front of a collapsed section of a fossilized bioherm. This massive boulder, lying on its side, clearly displays the tops of the Stromatolitic columns that made up ancient reefs that once ringed the edge of a warm, shallow, Cambrian sea at a time when the landmass that Mason now sits on was just below the Equator approximately 500 million years ago before Earth’s plate movements brought it north.
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