History of the Redwall Limestone of Northern Arizona


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Publication Date

January 1969


Throughout most of northern Arizona the Redwall Limestone of Mississippian age is readily divisible into four lithologic units, designated in ascending order as the Whitmore Wash, Thunder Springs, Mooney Falls, and Horseshoe Mesa Members. The first and third members are thick-bedded to massive carbonate rock. The Horseshoe Mesa Member is relatively thin-bedded limestone, and the Thunder Springs Member is distinctive because it consists of chert beds alternating with thin beds of carbonate rock.Trends in thickness of the various members indicate that the sediment that formed the Redwall was deposited on an even, gently sloping shelf that extended westward from the Defiance positive element, a low landmass located near the present eastern border of northern Arizona. The Peach Springs and Payson ridges projected west and southwest, respectively, from the positive element. These ridges, which were partly submerged and partly above sea level during Mississippian time, are indicated by the patterns of isopach lines and, in part, by the distribution of faunas. The ridges divided the Arizona section of the shelf into three segments: the northern-most, which slopes northwest toward the Cordilleran geosyncline, and the other two, which slope toward the south and southwest.Two transgressions and two regressions of the western and southern seaways are believed to be represented by the Redwall. The first transgression, which is recorded by thick beds of clastic sediment of the Whitmore Wash Member, was less extensive than the second, which is recorded by massive beds of the Mooney Falls Member, for on the western margins of the Defiance positive element the Mooney Falls Member overlaps the two lower members. Furthermore, south of Grand Canyon the Whitmore Wash and Thunder Springs Members lap against the Payson ridge without covering it, whereas the Mooney Falls Member, although relatively thin, extends across it. Regression is believed to be represented by thin beds of the Thunder Springs and Horseshoe Mesa Members, which are


Arizona, Usa, Redwall Limestone

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