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Despite recent work, a comprehensive understanding of pre-Devonian terrestrial ecosystems remains elusive, resulting in frequent speculation about their composition. Terrestrial microbial mats are known from the Precambrian paleosol record, and bryophytes are known from the Middle Ordovician palynological record. The intervening time, however, remains enigmatic, although recent studies indicate a progressive “greening” of the Precambrian prior to the first unambiguous fossil evidence for land plants. In this study, an older than 503 Ma, heavily weathered, clay-rich soil was identified and provides a window to a probable Cambrian terrestrial landscape. The paleosol developed on the ancient continent of Laurentia in a dry, subtropical climate. Mobilization of Si, Al, and P indicate the influence of organic acids. Apatite, a recalcitrant mineral present throughout the majority of the weathered section, is notably …