ABSTRACT

A laminated, fine-grained, pure limestone bed two to three feet thick with wave to dome-like structures superimposed on the laminae crops out in an area of 600 square miles in central Utah. The bed occurs near the middle of the Mississippian Gardner dolomite. Individual laminae of the bed range from .06 to 5 mm and average about .25 mm in thickness, while length may be several feet. Texture of the limestone is extremely fine-grained and only locally are microscopic structures, other than minute calcite crystals and light- and dark-gray laminae, visible. Domelike structures superimposed on the laminae range to 10 cm in diameter and may be composed entirely of domed laminae or a hemispherical mass of rod to leaf-like crenulated gray bodies resting on horizontal laminae and covered by la inae. Epigenetic dolomitization has affected local areas of the bed, but distinctive structures are retained. Though both subaqueous slumping and organic origins have been suggested for the bed, the latter origin is strongly supported by megascopic and microscopic features related to organisms.