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Publication Date

January 2002

Keywords

Anthropology, Geology

Description

MS Thesis of Beverly Lynn Shade, University of Minnesota, 2002. The landscape of central Pine County, in east-central Minnesota, contains a series of sinkholes, streamsinks, springs and short caves. These landforms occur in and over Precambrian Hinckley Sandstone, and the overlying unconsolidated glacial deposits. These features serve the same function as in carbonate karst terrains: sinkholes and caves focus recharge, feeding a heterogeneous subterranean flow system. This drainage system exploits high permeability zones in the sandstone, and discharges into springs. In north-central Pine County, 262 sinkholes, 25 streamsinks and 32 springs have been mapped. The Hinckley Sandstone is a quartz arenite. No carbonate grains or cements have been found in sandstone samples from the sinkhole area. No evidence has been found that calcite solution controls bedrock permeability. This is a sandstone karst . Three parameters appear to control the occurrence of karst sinkholes: the depth to bedrock, the type of underlying bedrock, and meter-scale heterogeneity in surface sediments. The subsurface heterogeneity implied by the presence of active karst sinkholes is supported by the analysis of groundwater chemistry in the area . Based on a preliminary groundwater investigation, water in the Hinckley and Fond du Lac sandstones can come from a variety of sources: modern precipitation, old sandstone brines, connate brines in basalt, and mixtures of all three. The heterogeneous permeability structure of the Hinckley Sandstone appears to be controlled by outcrop and hand sample scale fractures and sedimentary features appear to control the occurrence of karst sinkholes: the depth to bedrock, the type of underlying bedrock, and meter-scale heterogeneity in surface sediments. The subsurface heterogeneity implied by the presence of active karst sinkholes is supported by the analysis of groundwater chemistry in the area. Based on a preliminary groundwater investigation, water in the Hinckley and Fond du Lac sandstones can come from a variety of sources: modern precipitation, old sandstone brines, connate brines in basalt, and mixtures of all three. The heterogeneous permeability structure of the Hinckley Sandstone appears to be controlled by outcrop and hand sample scale fractures and sedimentary features. Open Access Northup Database Collection See Extended description for more information.

Subject: topical

Anthropology; Geology

Type

Article

Genre

Thesis / Dissertation; serial

Identifier

K26-04350

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