Start Date

11-4-2013

Abstract

With more than 267 m (166 miles) of mapped cave passages, Jewel Cave is the third longest cave in the world. The passages are beneath an area of 775 ha (3 mi2), located almost entirely within the Hell Canyon drainage basin. The canyon itself is situated in the bottom of a south-plunging syncline and most of the cave passages are located within the east limb. A down-dip cross section shows the cave passages assuming the shape of an elongate lens, located just below the Pahasapa/Minnelusa contact. The lower boundary is a maximum of 75 m (250 feet) below the contact, but thins at each end, where the permeable, basal Minnelusa sandstone is exposed.

Based on these observations, a conceptual model has been created to portray cave development as the result of local groundwater movement in geologically recent time. The apparent recharge was in the Pass Creek and Lithograph Canyon areas, and the discharge was in Hell Canyon. Groundwater initially moved through a shallow confined aquifer comprised of the basal Minnelusa sandstone, which was initially confined by the underlying Pahasapa Limestone and an overlying Minnelusa limestone. Although Laramide fractures provided secondary porosity, there is no evidence of sufficient connectivity to provide landscape-scale permeability. As water from the sandstone circulated into the discontinuous fractures of the Pahasapa, dissolutional enlargement integrated them to form the system of interconnected cave passages known today. The model precludes the need for direct recharge from rainfall, hydrothermal waters rising from below, or prior development of a Mississippian karst.

 
Nov 4th, 12:00 AM

Paleohydrology and the origin of Jewel Cave

With more than 267 m (166 miles) of mapped cave passages, Jewel Cave is the third longest cave in the world. The passages are beneath an area of 775 ha (3 mi2), located almost entirely within the Hell Canyon drainage basin. The canyon itself is situated in the bottom of a south-plunging syncline and most of the cave passages are located within the east limb. A down-dip cross section shows the cave passages assuming the shape of an elongate lens, located just below the Pahasapa/Minnelusa contact. The lower boundary is a maximum of 75 m (250 feet) below the contact, but thins at each end, where the permeable, basal Minnelusa sandstone is exposed.

Based on these observations, a conceptual model has been created to portray cave development as the result of local groundwater movement in geologically recent time. The apparent recharge was in the Pass Creek and Lithograph Canyon areas, and the discharge was in Hell Canyon. Groundwater initially moved through a shallow confined aquifer comprised of the basal Minnelusa sandstone, which was initially confined by the underlying Pahasapa Limestone and an overlying Minnelusa limestone. Although Laramide fractures provided secondary porosity, there is no evidence of sufficient connectivity to provide landscape-scale permeability. As water from the sandstone circulated into the discontinuous fractures of the Pahasapa, dissolutional enlargement integrated them to form the system of interconnected cave passages known today. The model precludes the need for direct recharge from rainfall, hydrothermal waters rising from below, or prior development of a Mississippian karst.