Earth history geol 2110
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Earth History GEOL 2110. The Paleozoic Era Cambrian and Ordovician History of Minnesota and Wisconsin. Major Concepts.

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Earth History GEOL 2110

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Earth history geol 2110

Earth History GEOL 2110

The Paleozoic Era

Cambrian and Ordovician History of Minnesota and Wisconsin


Major concepts

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.


Earth history geol 2110

Geologic Timescale in Minnesota

Today’s

Lecture


Earth history geol 2110

Evolution of the Penokean Mountains

JAY COOKE

St. CLOUD

HIBBING


Earth history geol 2110

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


Laurentia set adrift from rodinia

Laurentia Set Adrift from Rodinia


Earth history geol 2110

Early Paleozoic Epicontinental Seas


Distribution of cambrian sediments over laurentia

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


Earth history geol 2110

Paleogeographyof Middle Laurentia in the Early Paleozoic


Earth history geol 2110

Depositional Environments in Cambrian Epiric Seas

From A. Runkel (MGS)


Transgression of depositional environments

Transgression of Depositional Environments


Earth history geol 2110

Regression  No Deposition/Erosion

The Jordan Unconformity


Earth history geol 2110

Transgressive - Regressive Cycles of the Hollandale Embayment


The actual picture storms trans regress mini cycles

The Actual PictureStorms, Trans-Regress Mini-cycles

From A. Runkel (MGS)


Earth history geol 2110

Ordovician Rocks of the Mississippi River Bluffs

P-Platteville Limestone G-Glenwood Shale S-St. Peter Sandstone

P

G--

S

Indian Mounds Park

Minnehaha Falls

P

G--

P

S

G--

S

Ford Dam and Lock


Fossil hunting in the twin cities lilydale park the brickyards

Fossil Hunting in the Twin CitiesLilydale Park (the Brickyards)


Earth history geol 2110

Silica Sand Resources in SE Minnesota and SW Wisconsin

Mined since the late 1800’s

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

silica-rich sandstone

current and proposed sand mines


Earth history geol 2110

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

High Purity Quartz Sandstone Formations

>95% Qtz

~5mm


Earth history geol 2110

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


Earth history geol 2110

  • 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?


No class on friday have a great spring break

NO CLASS on FRIDAY!!!HAVE A GREAT SPRING BREAK

  • Next Lecture

  • The Paleozoic Era

  • The Silurian and Devonian Periods – Part 1

  • Quiz on Chapter 12


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