A 3-D GEOLOGICAL MODEL OF THE RATTLESNAKE RIDGE LARAMIDE FOLD, WYOMING

We constructed a 3-D geological model of the Rattlesnake Ridge anticline at Shoshone Canyon near Cody, Wyoming, using Earthvision software. The purposes of the model were to explore the subsurface shape of the fold and to develop methods to create a model of a high-relief structure solely from surficial data (the geologic map). The fold is a classic Laramide structure cored by a thrust fault and dissected by the Shoshone River, which provides spectacular exposures of the fold. The folded strata include units from the Archaean crystalline rocks and the Great Unconformity to the Permian Dinwoody formation. To create the fold, we began with a reference horizon, the contact beween the Madison and Tensleep formations, which has the best outcrop distribution across the model area. We then calculated thicknesses to other contacts up and down from the reference horizon using the map contacts, then projected contacts into the air or into the subsurface to extrapolate the surfaces away from map control. Our model shows that the fold has a relatively complex shape in three dimensions, plunging and changing trend toward the southeast. Modeling also shows wrinkles in the fold that are not apparent from the ground or on the geologic map.