Slide 1

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

Slide 2

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.

Slide 3

Geologic Timescale in MinnesotaTodaysLecture

Slide 4

Slide 5

Evolution of the Penokean Mountains St. CLOUD JAY COOKE HIBBING

Slide 6

Slide 7

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

Slide 8

Laurentia Set Adrift from Rodinia

Slide 9

Early Paleozoic Epicontinental Seas

Slide 10

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

Slide 11

Paleogeography of Middle Laurentia in the Early Paleozoic

Slide 12

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

Slide 13

Slide 14

Transgression of Depositional Environments

Slide 15

Regression No Deposition/Erosion The Jordan Unconformity

Slide 16

Transgressive - Regressive Cycles of the Hollandale Embayment

Slide 17

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

Slide 18

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

Slide 19

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

Slide 20

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

Slide 21

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

Slide 22

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

Slide 23

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

Slide 24

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?

Slide 25

Next Lecture The Paleozoic Era The Silurian and Devonian Periods Part 1 Quiz on Chapter 12 and MaG-Pz