Paleozoic 2: Laurentian Orogenies - University of South Alabama

Quiz Nine (9:30-9:35 AM)

GY 112: Earth History

Lecture 25: Paleozoic 2: More Laurentia!

Instructor: Dr. Douglas W. Haywick

UNIVERSITY OF SOUTH ALABAMA

Last Time

The Paleozoic of North America

1) Laurentian passive continental margin sedimentation

2) Central North America 3) The Grand Canyon (geology)

(web notes 24)

Laurentia (Paleozoic North America)

Consider: 1) passive continental margin 2) shallow marine water (shelf) 3) tropical climate All the way from Labrador to Alabama 1+2+3= Fossil. Limestone, oolite, quartz arenite etc.

Equator:


The Humber zone is a region of undeformed, passive continental margin rocks

http://iz.carnegiemnh.org/crayfish/country_pages/newfoundland.htm


Classic Paleozoic reef rocks (stromatolites, rugose and tabulate corals), quartz arenite sandstone, shallow marine dolostone, even some evaporites


A sudden (localized) deepening occurred (transgression) and above that….


Thrust faulting…

A

B

A

B

Thrust Faulting

Cratonic Sequences

Middle Ordovician Early Devonian

Ignoring tectonics for a moment and you’ll see that sea water covers much of the craton in these 2 paleogeographic images, but not always to the same extent…

Cratonic Sequences

When continents flood during transgressions, sediment is deposited. When regressions occur, erosion takes place producing unconformities (disconformities) Thick sedimentary packages between disconformities are called cratonic (depositional) sequences.

Cratonic Sequences

When continents flood during transgressions, sediment is deposited. When regressions occur, erosion takes place producing unconformities (disconformities) Thick sedimentary packages between disconformities are called cratonic (depositional sequences). •Basins have thick sequences (shorter disconformities)

•Arches/domes have thin sequences (longer disconformities)

Cratonic Sequences

Today’s Agenda

The Paleozoic Part 2

1) Back to Newfoundland 2) Eastern Laurentian Orogenies (Appalachians) 3) Other Laurentian Orogenies (Antler, Ouachita)

(web notes 25)


The Humber zone is a region of undeformed, passive continental margin rocks

http://iz.carnegiemnh.org/crayfish/country_pages/newfoundland.htm


Thrust faulting…


Even though this coastline of Laurentia was a passive continental margin, a plate tectonic boundary was rapidly approaching…

A

B

A

B


Middle Ordovician

Laurentia

Baltica

Island arc A

B

A

B

The resulting Taconic Orogeny first depressed the seafloor (localized transgression) and then pushed previously deposited passive continental margin sediments up into thrust fault mountains. There was only minimal metamorphism and igneous intrusions.


Laurentia

Baltica

Middle Ordovician


Late Ordovician

Laurentia

Baltica

A

B

A

B

The next tectonic event (the Acadian Orogeny) was caused by the approach of Baltica

Baltica

Baltica


Early Devonian

A

B

The Acadian Orogeny was more extensive and more intense (metamorphism and lots of igneous intrusions)

A

B


Early Devonian

The Acadian Orogeny was more extensive and more intense (metamorphism and lots of igneous intrusions)


Mississippian

B

Lastly, along comes Gondwanna and…. …well you get the idea. A

B A

B


Pennsylvannian

B

Lastly, along comes Gondwanna and…. …well you get the idea. A

B A

B

Suture zone


Pennsylvanian

B

Lastly, along comes Gondwanna and…. …well you get the idea.

Other Laurentian Orogenies

Period North America

Permian Alleghenian Orogeny* (SE)

Pensylvannian

Mississippian Ouachita Orogeny (S)

Devonian Acadian Orogeny* (E) Antler Orogeny (W)

Silurian

Ordovician Taconic Orogeny* (NE)

Cambrian


Antler Orogeny



Pensylvannian



Silurian


Cambrian




Pensylvannian



Silurian


Cambrian


Ouachita Orogeny



Pensylvannian



Silurian


Cambrian

Today’s Homework 1. Catch up on your sleep!

Next Time 1. Paleozoic Geology of Alabama

Paleozoic 2: Laurentian Orogenies - University of South Alabama

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