Early Paleozoic Geology

Basic Rules of Geology Transgression – rise in sea level Regression – lower in sea level Convergence leads to orogeny Orogeny leads to erosion

Continental Architecture Craton Mobile Belt Epeiric Seas – Stable, immobile part of a continent – Located along continental margins, receive sediments, and deform during collision – Widespread shallow seas that transgress and regress over the continent – i.e., Franklin, Corilleran, Quachita, Appalachian

Phanerozoic Eon Phanerozoic – comprises 12% of all geologic time – Paleozoic Era – 6.5% of all geologic time

Paleozoic Eon Introduction 6 major continents were present – as well as several microcontinents and island arcs – Deposition due to transgressions and regressions – Mountain building (orogeny) due to collision of continents

Early Paleozoic Cordilleran Appalachian Craton Late Paleozoic Early Paleozoic Major Events of North America –Sauk Sequence –Tippecanoe Sequence –Taconic Orogeny

Paleozoic Paleogeography Global History Late Cambrian Late Ordovician – H 2 O circulated freely Late Silurian – Polar regions ice free – Epeiric seas – Major highlands – Gondwana moved southward and across the South Pole  Laurentia, Baltica, Siberia, Kazakhstania, China  Gondwana, Siberia  Tillites in Sahara Desert – Laurentia developed active convergent boundary in eastern margin – Baltica moved NW and collided with Laurentia

Paleozoic – Late Cambrian Sauk Sequence First major transgression – Most of N.A. covered by epeiric seas Evidence of shallow-water deposition – well-sorted, clean sands (ancient shoreline) – Carbonates (stromatolites & ooids) – N.A. along equator

Grand Canyon Paleozoic – Late Cambrian Sauk Sequence – Good example of Sauk Sequence  Tapeats Sandstone  Bright Angel Shale  Mauv Limestone – Transgression – “fining upwards” – Time transgressive

Paleozoic – Late Ordovician Tippecanoe Sequence Sauk Sea regressed – Produced unconformity N.A. in tropical environment – Limestone and dolostone experienced rapid erosion  Boundary between Sauk and Tippecanoe Sequences Major transgression – St. Peter SS at base of sequence – Followed by widespread reefs and evaporites – Carbonates Carbonate--corals, bryzoans, dolostone-- reefs/evaporites

Tippecanoe famous for basin rimmed by reefs and evaporites (?) Paleozoic – Late Ordovician Tippecanoe Sequence Modern reef structure – 30º N&S of equator – Warm, shallow H 2 O – No sedimentation input – Normal salinity – Michigan Basin Evaporites – Evaporation > precipitation – High salinity

Paleozoic – Late Ordovician Michigan Basin Contradiction – Pinnacle reef – Evaporites Possible Explanation – Rimmed coral basin – Periodically flooded – evaporation  Pinnacle reef grew upwards in response to rising sea level  Evaporite formation

During L. Cambrian & L. Ordovician (Sauk and Tippecanoe Sequences) Paleozoic – Late Silurian Appalachian Mobile Belt Broad, passive margin along eastern edge of Laurentia Deposition of carbonates overlying shallow-marine seds.

Paleozoic – Late Silurian Appalachian Mobile Belt Taconic Orogeny – Baltica collided with Laurentia – Widening of Iapetus Ocean along divergent boundary – Iapetus plate subducted beneath Laurentia – Results in arc volcanism (mountain-building)  Passive  active margin Birth of Appalachian Mts

Late Silurian

Passive margin, L. Proterozoic-L.Ordovician Mid Ordovician Orogeny

Silurian