Earth History GEOL 2110 The Paleozoic Era Silurian and Devonian Periods – Part II Stratigraphy and Tectonics

Major Concepts The proliferation of coral reefs caused restricted basins wherein great thickness of limestone and evaporites were deposited. Along the eastern margin of North America the collision with the European craton and Avalonian micro- continents and volcanic arcs created a new orogenic belt in the Devonian This orogenic event caused intense warping of the craton that accentuated the arches and basins that had begun to form in the Ordovician. It also generated a new clastic wedge of redbed mollasse sediments in eastern NA and northern Europe Devonian tectonism also affected arctic regions and the western margin of North America

Silurian – Devonian Major Events

Proliferation of Organic Reefs in the Silurian and Devonian

Carbonate Reefs and Evaporites

Carbonate Reefs Inorganic Precipitation of Calcite Ca HCO - 3 CaCO 3 + H 2 O + CO 2 Increased temperature reduces the solubility of Ca in seawater and drives the reaction to the right

Dolomitization Calcite  Dolomite 2CaCO 3 + Mg +2  CaMg(CO 3 ) 2 + Ca +2 River Water | Sea Water Ca 73% 3% Mg 11% 11% Na 9% 84% K 7% 3% Relative solubility Na>> K > Mg >> Ca Sabhkas

Evaporites Density of Brines Salts in Normal Seawater NaCl – 2.72% Halite(Salt) MgCl 2 – 0.38% MgSO 4 – 0.16% CaSO 4 – 0.12% Anhydrite K 2 SO 4 – 0.08% CaCO 2 – 0.01% Calcite

Evaporite Basins of the Silurian Salt Mine under Detroit

Early Devonian Regression Break between Tippecanoe and Kaskasia Sequences

Early Devonian Regression Much of the Silurian Removed on Arches Silurian Missing from MN

Kaskasia Sequence of the Devonian Mountain-building and Craton-warping affects Sedimentation

Craton Warping Creates Multiple Unconformities Unconformities draping the Ozark Dome, Missouri Mississippian LS thin Silurian LS Ordovician LS Devonian Missing

Acadian Orogeny A New Clastic Wedge Forms Coarse Immature Sandstone and Conglomerate (Molasse) Redeformation of Late Ordovician Taconian Deformation Organic Black Shale (Flysch)

The Devonian Marcellus Shale

Acadian Orogeny Overprints Precusor Orogens Late Ordovician Middle Silurian Late Devonian K-Ar ages

Remember the Grenville Collision of Laurentia with Amazonia (SA) at 1 Ga

Caledonian Orogeny Europe Docks to the North in Early Devonian

Caledonian Orogeny A Continent-Continent Collision

Devonian Old Red Sandstone Clastic Wedge on European Side of the Caledonian Orogen

Minor Devonian Orogenies Ellesmerian (Arctic) Antler (Western NA)

More to Come Making Pangea

Feedback of the Organic and Physical World

Next Lecture The Paleozoic Era The Carboniferous and Permian Periods The Making of Pangea QUIZ on Chapter 13