Rapid rainfall shift as seen in rocks
This photo shows an outcrop in Northeastern Spain, where 2 sedimentary units come together. The lower unit consists of fairly fine-grained sedimentary deposits, including some soils, deposited in channels flowing out of the Pyrenees Mountains. All of a sudden, about 55 million years ago, the type of sediment depositing across a wide area of northern Spain changed. It switched from fine-grained, like you see in the lower layers, to coarse-grained conglomerates like you see in the upper layer.
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