Geometry and Mechanical Development of Heart Mountain Thrust Stack, Exshaw, Alberta: ABSTRACT

Abstract

Heart Mountain is located near Exshaw, Alberta, and forms a peculiar localized thrust stack along the otherwise relatively linear Exshaw thrust trace in the Canadian front ranges. Data from stratigraphic and structural mapping on a scale of 1:5,000 were used in the construction of balanced cross sections, longitudinal sections, and stratigraphic separation diagrams to reveal the true three-dimensional geometry of the mountain. The structure (the heart) is composed of a gently south-plunging canoe-shaped body of rock. Near its southern termination, however, the heart plunges steeply northward. Several previously unrecognized features of the Heart Mountain structure were discovered during mapping. The heart is a faulted syncline with its east limb thrust up relative to its west limb. The heart's collar is composed of the Loomis Member of the Mississippian Mount Head Formation, not the Mississippian Livingstone Formation as previously mapped. The panel of Livingstone rocks west of the heart is stratigraphically up to the east. Based on both stratigraphic and structural considerations, the thrust stack formed in an east-to-west sequential development from rock panels of relatively local origin. Mechanical considerations of the mountain's east-to-west sequential development require the location of the Exshaw thrust to be along the eastern margin of the structure. The Heart Mountain thrust stack, therefore, formed in the hanging wall of the Exshaw thrust. Hydrocarbons have been found in structural traps similar to Heart Mountain. Understanding the geometry and order of mechanical development of these traps is essential to profitable exploration ventures. End_of_Article - Last_Page 947------------