From the principle of superposition, we know that the Tecate Arkose was deposited first. The Berry Breccia through the Coal layers were deposited in succession after The Tecate Arkose. Then thesee layers were folded. We know this by the principle of original horizontality. Folding is usually caused by tectonic compression and often accompanied by uplift above sea level. Uplift is, in turn, followed by erosion.
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Surface
of erosion = unconformity |