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| Sipapu Bridge is carved into the Cedar Mesa Sandstone. The Cedar Mesa Sandstone consists most of a light colored, fine-grained, quartz sandstone. It is tightly cemented by calcium carbonate (calcite) cement. Although fossils are extremely rare, tiny sand-sized fragments of shell can be seen in microscopic examination of rock samples. The fossil shell material and other regional evidence indicate that the original sediments were deposited in nearshore waters and coastal sand dune environments associated with a shallow seaway that covered the region during the Late Permian Period, about 260 million years ago. The seaway persisted in the region for many millions of years, long enough for nearly 1,200 feet (360 meters) of sandy sediments to accumulate. Sedimentary structures preserved in the rock, particularly the thick layers of cross-bedded sandstone, are some of the obvious evidence that the sand was deposited in shallow water, on beaches, and dunes, because we can see similar sedimentary features forming in modern coastal environments today. |
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