[1] The flat summit of the Corvan Plateau is capped by a layer of ooidal limestone — a rock composed of tiny concentric carbonate spheres that, in the modern world, form almost exclusively in warm, shallow, wave-agitated seawater. [2] The same limestone preserves occasional ripple marks of the kind produced by gently moving currents. [3] The geologist R. Almeida concludes that the plateau's summit must once have lain beneath a shallow tropical sea and was later uplifted to its present elevation. [4] She observes that no other environment today produces ooids in comparable abundance, and infers that the ancient setting can only have been marine.
Which of the following, if true, most seriously undermines Almeida's conclusion that the plateau's summit once lay beneath a shallow sea?
