Abstract
Karst features pose significant risks to infrastructure and land use, from reducing tillable acreage to causing catastrophic failures in wastewater lagoons. This study analyzes the stratigraphic and spatial distribution of karst features in southeastern Minnesota to better understand their geologic controls. By seamlessly merging raster surfaces of Paleozoic bedrock units and intersecting them with regional karst datasets in a GIS framework, we found that over 95 percent of mapped sinkholes occur where unconsolidated sediment overlying bedrock is 15 meters or less. Furthermore, 81 percent of sinkholes are concentrated in just six of the 21 mappable bedrock units, each of which is carbonate-dominated. Sinkhole densities calculated independent of stratigraphic context vary spatially, locally exceeding 40 features per square kilometer. In contrast, springs show a broader stratigraphic range with 51 percent occurring within four specific units. Increased spring frequency correlates with zones where gravity-driven vertical groundwater flow through fractured carbonate encounters low-vertical but high-horizontal hydraulic conductivity intervals—underscoring a highly anisotropic flow system. In deeply incised valleys characterized by artesian conditions, spring frequencies increase in units subcropping along aquitard edges. This comprehensive stratigraphic analysis enhances our understanding of geologic controls on karstification, providing a tool for better land and water resource management decisions in southeast Minnesota.
DOI
https://doi.org/10.5038/9781967518012.1008
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A Comprehensive Analysis of Stratigraphic Influence on Karst Feature Distribution and Density Across Southeast Minnesota, USA
Karst features pose significant risks to infrastructure and land use, from reducing tillable acreage to causing catastrophic failures in wastewater lagoons. This study analyzes the stratigraphic and spatial distribution of karst features in southeastern Minnesota to better understand their geologic controls. By seamlessly merging raster surfaces of Paleozoic bedrock units and intersecting them with regional karst datasets in a GIS framework, we found that over 95 percent of mapped sinkholes occur where unconsolidated sediment overlying bedrock is 15 meters or less. Furthermore, 81 percent of sinkholes are concentrated in just six of the 21 mappable bedrock units, each of which is carbonate-dominated. Sinkhole densities calculated independent of stratigraphic context vary spatially, locally exceeding 40 features per square kilometer. In contrast, springs show a broader stratigraphic range with 51 percent occurring within four specific units. Increased spring frequency correlates with zones where gravity-driven vertical groundwater flow through fractured carbonate encounters low-vertical but high-horizontal hydraulic conductivity intervals—underscoring a highly anisotropic flow system. In deeply incised valleys characterized by artesian conditions, spring frequencies increase in units subcropping along aquitard edges. This comprehensive stratigraphic analysis enhances our understanding of geologic controls on karstification, providing a tool for better land and water resource management decisions in southeast Minnesota.