Abstract

Stratigraphic and microfacies analyses of Mississippian-age Lodgepole Limestone, Monroe Canyon Formation, Great Blue Limestone and Aspen Range Formation in southeastern Idaho provide new insights into the behavior of the shelf during orogenic or post-orogenic time. The Lodgepole Limestone has variably developed thickness with the following lithofacies: 1) Massive grainstone, 2) laminated grainstone, 3) wacke-mudstone and 4) dolomite. Because of the placement of these lithologies, recognition of Paine and Woodhurst Members in southeastern Idaho is difficult. Depositional modeling of the lower Lodgepole suggests activation of the Bannock High during lowest Mississippian (Kinderhook) time. Grainstones deposited on the Bannock High give way to Waulsortian-mound build-ups and periplatform muds in a marginal basin to the east. Farther east contour current-modified grainstones and packstones suggest development of a ramp at the slope. Upper Lodgepole lithofacies suggest a less prominent Bannock High, grainstones prograding over an in-filled marginal basin with additional Waulsortian build-ups and a well developed ramp to the east. Storm-modified lithologies suggest proximity to wave base at many localities. Starved basin facies, not studied herein, suggest rapid subsidence. Monroe Canyon (and equivalent) lithofacies are primarily: 1) Mudstone, 2) wackestone, 3) packstone and 4) grainstone. Many lithologies have abundant pellets. A carbonate progradation developed over the starved basin lithologies with formation of a pellet-ooid barrier bank. Eastward were lagoonal muds with a near-shore shoal being developed yet farther east. Such a history suggests episodic tectonic modification to the shelf during Mississippian time with carbonate lithofacies responding accordingly.