Part 3: Cambrian and Ordovician History of Minnesota and Wisconsin Earth History GEOL 2110 The Paleozoic Era Part 3: Cambrian and Ordovician History of Minnesota and Wisconsin

Major Concepts When sea-level rose in the Cambrian and Ordovician (Sauk and Tippecanoe Trangressions), the mid-continent of Laurentia was low lying, but with some broad topographic highs (Wisc. Dome, Transcontinental Arch, Sioux Highland, Taylors Falls Volcanic Islands) and lows (Hollandale Embayment). Four major transgressive cycles are represented by stratigraphic sequences of sandstoneshalelimestone in Minnesota and Wisconsin. Regressions are marked by regressive sands capped by unconformities. The purity and coarseness of the Cambrian and Ordovian quartz sandstone formations have made them important sources for glass –making and other industrial uses over the decades. However, they are currently highly sought after as sources of natural proppants for use in hydrofracing extraction of oil and gas.

Geologic Timescale in Minnesota Today’s Lecture

Evolution of the Penokean Mountains JAY COOKE St. CLOUD HIBBING

1,000,000,000 Years Ago 500,000,000 Years Ago Minnesota becomes the stable interior of the North American Continent 500,000,000 Years Ago Shallow seas begin to periodically flood Minnesota

Laurentia Set Adrift from Rodinia

Early Paleozoic Epicontinental Seas

Distribution of Cambrian Sediments over Laurentia Warping of the Craton Broad horizontal tectonic stresses related to plate motion Sediment loading Isostatic adjustments due to different densities within the crust MCR

Paleogeography of Middle Laurentia in the Early Paleozoic

Depositional Environments in Cambrian Epiric Seas From A. Runkel (MGS)

Transgression of Depositional Environments

Regression  No Deposition/Erosion The Jordan Unconformity

Transgressive - Regressive Cycles of the Hollandale Embayment

The Actual Picture Storms, Trans-Regress Mini-cycles From A. Runkel (MGS)

Ordovician Rocks of the Mississippi River Bluffs P-Platteville Limestone G-Glenwood Shale S-St. Peter Sandstone P G-- S Indian Mounds Park P Minnehaha Falls G-- S P G-- S Ford Dam and Lock

Fossil Hunting in the Twin Cities Lilydale Park (the Brickyards)

Silica Sand Resources in SE Minnesota and SW Wisconsin Mined since the late 1800’s silica-rich sandstone current and proposed sand mines In 2012, 70% of US silica sand goes to  30% to Hydro-fracing for Oil and Gas Currently 36 in WI, 7 in MN, 178 in US

Use Silica Sand in Hydrofracing for Oil and Gas Drilling Ideal Proppant Characteristics Strong - crush resistant Med-crs sand size (16-70 mesh) Rounded and well sorted Homogeneous physical properties Low specific gravity Low cost and accessible

High Purity Quartz Sandstone Formations >95% Qtz ~5mm

18 =1mm 60=.25mm 100=.15 mm

OPPOSITION TO EXPANSION OF SILICA SAND MINING Concerns: - Transportation (truck traffic, road degradation, noise, safety, dust) high road use taxes, noise and dust abatement Air quality, silicosis? wetting, minimal crushing Water quality and quantity issues recycling Landscape alterations reclamation plans up front - Opposition to end use-hydrofrac drilling for oil and gas Most operations are currently regulated to varying degrees by State and County level ordinances. Key questions How does SS mining differ from aggregate mining that has been practiced and regulated for decades? What is the magnitude and duration of the expansion?

Part 4: The Silurian and Devonian Periods Next Lecture The Paleozoic Era Part 4: The Silurian and Devonian Periods