Mioclines in Space and Time: ABSTRACT

Abstract

Many continental margins are capped by wedge-shaped prisms of Cretaceous to Recent shallow-water marine strata. These prisms were deposited on down-flexing continental margins, presumably subsiding because of regional isostatic compensation caused by the growth of adjacent continental-rise prisms. The writers equate these continental-terrace wedges with miogeosynclines of the past, which are wedge-shaped as now preserved and which probably were never synclinal in form--hence the shortened term miocline. Modern mioclines thicken toward the ocean and terminate by thickening-out against water at the continental slope; it is presumed that ancient ones did also. Ancient mioclines thicken toward, and abut, a deformed eugeosynclinal lithofacies. These are interpreted to be c llapsed continental rises deposited synchronously with the adjacent miocline and later accreted to the continent. Mioclines probably have been formed by marginal sedimentation throughout geologic history, the outer limits being former continental boundaries before the accretion of new fold belts. The Appalachian miocline may be one Paleozoic example and the Millard miocline of the western United States may be another. More speculatively, Precambrian examples of mioclines may be the Huronian metasedimentary sequence abutting the Grenville fold belt in Canada and the Witwatersrand Series in South Africa. End_of_Article - Last_Page 646------------