The continental situation of the late Precambrian was a super continent called Rhodinia. This continent did not fragment until the boundary of the late Precambrian and the early Cambrian. This fragmentation resulted in smaller plates now known as Gondwana (now present-day South America, Africa, Southern Europe, Saudi Arabia, Australia, and Antarctica), Laurentia (now present-day North America and Greenland), Baltica (now present-day Russia and Northern Europe), and Siberia. The divergence of these plates continues through Ordovician. Bretagne belonged to the northern margin of Gondwana throughout the Paleozoic. The later reconvergence of these plates forms Pangea.

The last orogeny of the Precambrian Era is the Cadomian Orogeny, which formed the Amorican Massif bedrock. This is represented in Bretagne by the Brioverian Formation, found in present-day Northern and Central Armorican Domain. This formation is composed of sandstones and shales which were deposited and intruded by Cadomian granites that mark the end of the Cadomian Orogeny.


During the Cambrian, the fragmentation of the super continent, Rhodinia, began. The Laurentia plate starts migrating north, creating the Iapetus Ocean between itself and Baltica. Between the late Cambrian and the early Ordovician, Baltica begins it northern migration, opening an ocean between itself and Gondwana. Avalonia, a microplate, follows Baltica in its northern migration and begins the opening of the Rheic Ocean. The convergence of Baltica, along with Avalonia, and Laurentia begins in the Ordovician and continues through the Devonian, resulting in the closure of the Iapetus Ocean. This collision is known as the Caledonian Orogeny and formed another land mass called Euramerica. The erosion of the orogeny belt resulted in the Old Red Sandstones. Throughout this time, Gondwana is also migrating northward. This consequently results in the progressive closure of the Rheic Ocean. In the late Ordovician, a glacial period affected the globe. The center of the ice sheet was located in the Gulf of Guinea. The Carboniferous collision of Gondwana and Euramerica results in the closure of the Rheic Ocean, also known as the Hercynian Orogeny. This orogenic belt extends from Florida, extends through Northern Morocco, Spain, and the Armorican Massif and ends in Ardennes. In the late Paleozoic, more specifically the Permian Period, Siberia and Euramerica collide, resulting in the Ural Mountain Range. By the end of the Paleozoic’s convergence phase a new land mass has formed, known as Pangea. The formation of Pangea marks the end of the Paleozoic Era and caused the Permian Extinction. This extinction arose from the north-to-south continental barrier in the Panthalassic Ocean, stopping the circulation of the oceans.

In Bretagne, the first Paleozoic deposits occur during the Ordovician. And are known as the Red Ordovician Formation. The bottom of this formation is composed of detritic conglomerates and is topped with shales and sandstones. This formation appears mostly in the Central Armorican Domain with outcrops in Cap de la Chèvre and Southern Rennes. Other outcrops appear in the North Armorican Domain in the Bay of St-Brieux. The Red Formation is interpreted to be a filled basin by the erosion of the surrounding relief. The Ordovician transgression deposited the Armorican Sandstone on top of the Red Ordovician Formation or directly on the Precambrian bedrock. This Armorican Sandstone also appears in Spain and on the Iberian Peninsula. This Sandstone can be found many places in the Central Armorican Domain, Point of Pen-Hir for example. In the Central Armorican Domain, there are middle Ordivician shale deposits, due to the high water levels, and late Ordovician fine-grained sandstones. Ice rafted debris from the Ordovician glacial period (during the Ashgill Epoch) can be found in the shales.

The early Silurian deposits are composed of fine-grained sandstones in continuity with the Ordovician sandstones. Deposited on top of the sandstone is a discontinuous layer of graptolitic shale, present in the Central Armorican Domain such as the Crozon Peninsula (Veryarc’h outcrop). Covering the shale is a formation of sandstone which can be found throughout the Armorican Domain. Because there was not a lack of deposition between the Silurien and the Devonian in Bretagne, the region was not affected by the Cadomian Orogeny.

The early Devonian deposits are composed of detritic sandstones followed by limestone. These Armorique limestone can be found in the Crozon Peninsula (Veryarc’h outcrop). A formation of fine-grained sandstones with mica covers the limestone. During the Famennien Epoch there was a lack of deposition during the uplift of the Armorican Massif, known as the Phase Bretonne.

The Carboniferous deposits are inconsistent with the Devonian deposits. During the early Carboniferous, or Dinancian, there was a deposition of conglomerates followed by sandstones and then shales. Volcanic rock levels can be found throughout the formation which is evidence of tectonic activity during this period. During the late Carboniferous, or Stephanian, there are small lacustrian deposits with thin layers of coal in pull-apart basins. These basins can be found in the Baie des Trépassés as well as north of Quimper.

The Permian deposits in Bretagne are only in small basins and are composed of red sandstones and shales. These deposits are found on top of Stephanian deposits, if any, or on top of early Paleozoic deposits. After the Paleozoic, all of present-day Bretagne was above sea level and therefore did not acquire any more marine deposits.

Throughout the Paleozoic Era, Bretagne has followed the migration of northern Gondwana, from the southern hemisphere to the northern hemisphere. There is a lack of deposits during the Cambrian Period; however, there is continuous deposition of marine sediments from the Ordovician through the Famennien Epoch. In the late Paleozoic the only deposition is the infilling of small basins. The end of the Paleozoic is marked by the end of marine sedimentation due to the uplift of the Armorican Massif in the Hercynian Orogeny.

Maps and animations are available on the C. Scotese's Website

Late Carboniferous