Early Paleozoicum Ch. 10.


Each continent can be divided into two major part:


-Mobil belts

  Craton -- stable immobile part, Upon which Phanerozoic sediments can be found.

          shield(Precambrian met. and igneous rocks)

          platform  Outward part of craton, where metamorphic rocks are           covered by shallow water sediments

Epiric seas seawater covers some part of the craton

Mobile belts

Elongated areas of mountain building activity. They occur along       continent margins


The location of continents in the Earth history is not stable, everything is moving all the time.

It is a big buisness to reconstruct the paleogeography for a certain time.

What can we use?

1. Paleomagnetism (for younger ages than Paleozoic)

2. Climate sensitive rocks

3. Environmnet sensitive rocks

4. Fossils

5.Tectonic data

Paleozoic Paleogeography

In the beginning of Paleozoic, there were 6 continents:

1. Baltica (west of Ural Mountains)

2. China (China, indochina and the Malay Penninsula)

3. Gondwana (Africa, Antarctica, Australia, Florida, India, Madagaskar)

4. Kasakhstania (extension of Siberia)

5. Laurentia (North America, Greenlans, Ireland, Scotland, part of Russia)

6. Siberia (E of Ural, North of Kazahstan South of Mongolia)


North America

Mobil belts:






Sequence stratigraphy

Laurence Sloss in 1963 proposed that sedimentary rock record in North America could be divided into six cratonic sequences.

A cratonic sequence is a large scale (larger than supergroup) lithostratigraphic unit representing a major transgressive-regressive  cycle bounded by cratonwide unconformities. Transgressive phase is well preserved, regressive part is marked by unconformities.

For the Early Paleozoic their name are: Sauk and Tippeconoe

The global correlation of this super sequences is called sequence stratigraphy

Sauk Sequence (This is the first Phanerozoic transgression over the Precambrian american craton)

During the latest Proterozoic and earliest Cambrian the sea did not cover the craton, just along the border (Appalachian, and Cordilleran borders). These borders were passive margin during this time. Thick carbonate sequence formed, because the north american continents were located around the equator.

The other parts were emerged, and extensive weathering of Precambrian rocks took place.

North America was situated in the tropics at this time, and there is no evidence for any kind of vegetation, therefore erosion rate must have been really high.

During the Middle and late Cambrian a transgression started, and epiric sea covered much of the craton living just a few land area behind. Such a high area was the so called transcontinental arch (highland area) extended from Lake Superior to New Mexico, and some part of hte Canadian shield.

This time is characterized by wide spreaded shallow marine water sedimentation. Many of the shallow water carbonates contain bioclastics, organic fragments of fossils, and stromatolites (blue-green algae). They also frequently have oolitic textures.

Grand Canyon shows an excellent example for the Sauk marine transgression.         

Carbonate deposition dominated on the craton in the latest Cambriam, and even the Transconintal arch was covered by seawater.

As the Sauk sea regressed from the craton during the early Ordovician most of the craton become emerged. The rocks exposed, were predominantly limestone and dolostone, that experienced deep erosion (karst) (tropical climate). The result of this was a widespreaded unconformity giving the boundary between Sauk and Tippecanoe sequences.

The Tippecanoe sequence

Tippecanoe also started with a major transgression onto the craton

The first product of the transgression was a very clean quartz sandstone all over the craton.

          St. Peter Sandstone almost pure Q ----glass industry

          This sandstone is most likely recycled Proterozoic sandstone

The sandstone is overlied by limestone, as the second product of Tippecanoe transgression. This carbonate is mostly biochemical in origin containing  Corals, Brachiopods, Stromatoporoids, and Bryozoans. There were also many dolomites. (dol. formation!!!!!)

Seaward the carbonate deposition grades into shale, which is the deeper water facies.

Major features of the Tippecanoe sequences are reef facies and evaporites.

In the Middle Ordovician stromatoporoid-coral reefs become common in the low-latitudes.

During the Middle Silurian reef and evaporite facies are even more common.

A great example for this is the Michigan basin.

This basin at that time was surrounded by large barrier reefs. Within the fast subsiding basin Pinnacle reefs were formed. These are tall, spindly structures up to 100 m high. They had to grow pretty fast to be able to keep up with the subsidence rate.

On the shallow water part of the platform, evaporite and anhydrite formed indicating very arid climate.

During the Late Silurian, as the Tippekanoe sea was regressing, about 1500 m sediment deposited, and nearly half of it was salt and anhydrite.

At the end of the Silurian and the earliest Devonian the Tippecanoen sea regressed even further, and the whole craton became exposed, and experienced a large scale erosion again.

The Appalachian mobil belt, Taconic orogeny

During the Middle Ordovician in the Appalachian mobile belt the first Phanerozoic orogenic event started.

During Sauk time, this area was a passive margin, similarly to the present day situation. Sedimentation was balanced by subsidence, and thick shallow marine carbonate formed (the big outcrop on 81.) During this time the Iapetus ocean (preatlantic) was getting wider.

When the subduction between Laurentia and the Iapetus ocean started, the Appalachian area become similar to the Rockies.

The period of subduction and mountain forming is called orogenesis. This particular one is the so called Tacony orogeny.

In the Middle Ordovician, the carbonate deposition ceased, and the basin become deep, and started to be filled by graywacke, coarse sandstone  which marks the onset of mountain building.

Adjacent to the uplifted area a foreland basin formed, and filled up quickly by clastic sediments (Clastic wedge) coming from the Taconi highland (qeenston delta).

Mineral resources of the Paleozoic

q-sandstone, gravel, limestone   building stones

evaporites Michigan, Ohio, Virginia

Missisippi Valley type deposits