Sizes and shapes of quartzite boulders in Cambrian strata surrounding ancient islands at Baraboo, Wisconsin, allow estimation of the magnitude of Cambrian ocean waves using results from wave tank and flume experiments, as well as observations of very coarse stream gravel. Breakers at least 7 to 8 m high were required to tumble and move the largest well-rounded boulders (1.5 m diam) interstratified with Cambrian sandstone. Storm generation of waves of such magnitude is consistent with independent paleomagnetic evidence that suggests that Wisconsin lay near the equator 500 m.y. ago, at which latitude intense tropical storms would be expected.

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