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| Chinaman's Arch is located along the East Grade Auto Tour route. The bedrock throughout the national monument consists dominantly of Middle- to Late-Cambrian-age dolomite and limestone (deposited as limey sediments in a relatively warm, shallow seaway or shelf environment roughly 530 to 500 million years old). The sequence of Cambrian-age sedimentary rocks is estimated to be about 10,000 feet thick, and these rocks have been heavily altered over time, in some locations converted to marble, and is heavily fractured, folded, and faulted by tectonic forces over time. Chinaman Arch probably formed in-part by wave erosion along the shore of ancient Lake Bonnieville, a great freshwater lake that extensively flooded the eastern Great Basin region throughout Utah and Nevada. The last high-standing water level in the lake was about 15,000 years ago. The Great Salt Lake is but a tiny remnant of the great lakes that episodically filled the internally drained basin through the Quaternary Period over the last few million years. |
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