Conduit Flow in the Cambrian Lone Rock Formation, Southeast Minnesota, U.S.A.

Abstract

dominated units generally have bedding-parallel and vertically oriented apertures less than a few centimeters. The process by which the bedding-parallel secondary pore networks form remains obscure; some appear to be mechanically developed. However, interstitial carbonate cement within these units leads to the possibility of dissolution being a minor factor in the formation's groundwater flow characteristics. These dye traces were conducted at three different sites across a twenty-three kilometer distance and are evidence that the siliciclastic Lone Rock Formation has a conduit-flow component similar to that found in carbonate karst aquifers.

Creation of a Map of Paleozoic Bedrock Springsheds in Southeast Minnesota

“…The Lone Rock is mostly composed of a fine-grained sandstone and siltstone with interbedded shale and dolostone (Mossler, 2008). Dye traces from St. Lawrence stream sinks at three sites in southeast Minnesota have been detected at Lone Rock springs (Barry et al, 2015). These traces have demonstrated that the Lone Rock also has a karstlike conduit flow component.…”

“…These traces have demonstrated that the Lone Rock also has a karstlike conduit flow component. Observed breakthrough travel velocities were between 21-214 meters/day using passive charcoal detectors and 314 meters/day using automatic water samplers; dye was still being detected over one year later at springs monitored from one of the tracing sites (Barry et al, 2015).…”

Origin of Fracture-Controlled Conduits in Calcite-Rich Highly Productive Aquifers Impregnated with Diagenetic Silica

“…The results of tracer tests in the Březová nad Svitavou spring area clearly showed that the fracture-controlled conduits did not form only short, isolated segments, but an extensive interconnected network through which 1100 L/s flows at a velocity of 400-650 m/day over a distance of several kilometers to the largest springs in the BCB, which now supply the second largest city in the Czech Republic with groundwater [21]. Comparable flow velocities have been found in open fractures in siliciclastic-carbonate rocks in Minnesota and Wisconsin, USA (35-750 m/day [8,9]), in conduits in Sherwood sandstone with intergranular carbonate cement in the UK [34], and in fissures in sandstone with carbonate beds in Luxembourg (2-8400 m/day [35]).…”

“…Hydrogeological characteristics and karst evolution have been described in numerous publications in both fractured and/or folded telogenetic and young eogenetic highpercentage carbonates [3]. Less information is available on karst in evaporites [4], quartzites [5], and especially for lithologies at the transition between carbonates and siliciclastics [6][7][8][9][10]. Ghost-rock karst is a specific type of karstification.…”

“…The origin of large-aperture fractures is poorly understood. Some authors consider them to be of karstic origin [8], others of mechanical origin [9]. New insights into the origin of conduits in calcareous sandstones and sandy limestones in the western part of the BCB were provided by K ůrková et al [10], but these rocks are lithologically different from those in the eastern part of the BCB.…”