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The AAPG/Datapages Combined Publications Database
Montana Geological Society
Abstract
MTGS-AAPG
MONTANA GEOLOGICAL SOCIETY FIELD CONFERENCE & SYMPOSIUM GUIDEBOOK TO SOUTHWEST MONTANA
August,
GEOLOGIC HISTORY OF LEWIS AND CLARK CAVERNS, MONTANA
ABSTRACT
The growth of a limestone cave requires more than soluble rock and acidic water. In addition, the permeability of the limestone must be concentrated along joints, faults, or bedding planes. Also, sufficient topographic relief must be present from surface stream entrenchment that water will flow quickly through the subsurface.
Lewis and Clark Caverns formed at the base of the Mississippian Mission Canyon Limestone, where groundwater flow was perched above the less-soluble Lodgepole Limestone. A small Laramide anticline provided fractures in the rock, opening up bedding plane faults and axial plane joints. Excavation of the cave began within the past four million years, when the Jefferson River cut a 1500 foot deep canyon adjacent to the anticline.
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