Late Paleozoic History Chapter 13 Late Paleozoic History 13.1 Tectonics A. Cratonic Disturbances: the North American craton suffered more severe deformation in the late Carboniferous time than ever before. The most intense disturbances occurred in the southern part of the Craton, represented by Colorado and the Oklahoma Mountains. Its believed that these mountains were internal cratonic by-products of the collision of Gondwanaland with southern North America. B. Appalachian Orogeny: sometimes also called Alleghanian orogeny, occurred between late Pennsylvanian and late Triassic times. Fig 13.28 summarizes the Paleozoic history of the Appalachian belt in plate tectonics terms.

Fig. 13.28 Cambrian rifting formed proto-Atlantic Ocean (PA) and Piedmont microcontinent (P). Ordovician subduction and closing of marginal ocean resulted in collision of microcontinent with North America (NA) by beginning of Silurian (Taconian orogeny). Subduction of proto-Atlantic plate. Continued subduction resulted in Permian collision of Gondwanaland (G) with North America, which in turn caused 5. large-scale overthrust faulting (Appalachian orogeny). Early Mesozoic rifting initiated present Atlantic Ocean (AO).

13.2 Late Paleozoic Mountain Building in Eurasia The end of Paleozoic Era was a time of unusually widespread mountain building, the result largely of several continental collisions. These produced a gigantic, interconnected supper continent called Pangea. Hercynian orogenic belt was in Central Europe, which caused by the collision of North Africa with Europe. Similar-aged deformation around the southern perimeter of the Siberian craton may have resulted from the collisions of several small Chinese cratons. Upheaval of the Ural belt at this time resulted from collision between lithosphere plates carrying Siberia and Europe.

The name Gondwana is derived from an ancient tribe in India. 13.3 Gondwanaland The name Gondwana is derived from an ancient tribe in India. Gondwana consists of South America, Antarctica, South Africa, Australia and India. In Late Paleozoic time, Gondwanaland collided with North America and Europe, which caused the Permo-Triassic Gondwana Orogeny. Gondwanaland have some similar features based on which the geologists can reconstruct the Paleo-continent Gondwana, some of these are: - Because much land area lay at high latitudes in late Paleozoic time, large ice sheets formed on up-land areas. - On the five southern continents, the Gondwana succession has prominent glacial tillites in its lower part. fig. 13.34. - Gondwana strata containing coal seams and Glossopteris flora. - Gondwana rock succession is capped everywhere either by thick basalt flow rocks or by dikes and sills, fig. 13.39.

Fig.13.34 Distribution of Gondwana rocks showing their remarkable similarity on all five southern continents.

Fig.13.35 Lower Gondwana tillite. This is the most famous ancient glacial deposit in the world, formed in in South Africa craton .

Fig.13.36 Striated glaciated surface beneath the Carboniferous Tillite, South Africa.

Fig. 13.37 Giant “dropstone” released by a melting iceberg as it floated away from the Gondwana ice sheet during Permian. Notice how the layered marine sediments were bent downward by the impact and then smoothly buried the dropstone once normal, quiet marine deposition had resumed.

Fig.13.38 Tongue-shaped leaves of the characteristic Gondwana seed ferns Glossopteris (whose name means ‘tongue fern”. Found on all the southern continents (including India, Madagascar, and Antarctica) during the Permian, Its seeds were too large to have been blown across the modern southern oceans, and apparently they did not float.

Fig.13. 39: Drakensburg Mountain in Royal Natal National Park, South Africa. The escarpment is capped by resistant basalts, which overlie wind-deposited white sandstone cliffs, both of which are Jurassic and constitute the upper Gondwana rock succession here.

13.4 Late Paleozoic Life In the Devonian period, animals and plants developed complex communities on the land as well as in the ocean. Late Paleozoic time was marked by a continued expansion of terrestrial forests, as well as further evolution of the marine communities. By the Carboniferous, the seas were beginning to withdraw, expanding the available habitat for terrestrial life. In the Permian, shallow-marine seas became very restricted and terrestrial deposits made up the bulk of the strata, (Umm Irna Formation in Jordan). In late Paleozoic, a new environments such coal swamps was originated as a result of sea regression. On late Paleozoic life we will shed the light on the following points:-

13.4.1 Marine Life Although the Late Devonian extinctions affected the reef community and caused widespread extinction in brachiopods and ammonoids, the major phyla of invertebrates soon recovered and remained dominant for the rest of the Paleozoic. During the early Carboniferous the shallow, warm, tropical waters was dominated by carbonate-producing organisms, such as Crinoids, Fig 13.50 A.

2. Blastoids which are another type of crinoids. Pentremites is a classic index Crinoids fossil of the late Carboniferous Period. Fig. 13.50B. Fig.13.50B Flower bud-shaped heads of the blastoid Pentremites. In life, these heads (about 1-2 cm in width) would have attached to long stems, like those of crinoids, and these animals would have had a similar filter-feeding mode of life, with tentacles extending from the five petal-like grooves on the top. 13.50B

3. Unlike the branching bryozoans of the Ordovician, the early Carboniferous bryozoan are fenestrate Fig. 13.51A, and Archimedes. Fig 13.51B 13.51A Fig. 13.51 A In addition to crinoids, the early Carboniferous witnessed a great abundance of other attached filter feeders, such as the bryozoans. Most were delicate, lacy forms called fenestellids, which had hundreds of tiny, filter-feeding animals along the lattice work of their skeleton.

Fig. 13.51B The most charateristic early Carboniferous bryozoan was Archimedes , a fenestellid whose lacy skeleton was arranged around a central spiral ‘corkscrew’ stem Fig. 13.51B

4.The sea floor was still dominated by brachiopods, but the spirifers had begun to decline, and they were replaced by a group of that dominated the rest of Paleozoic, this group known as Productids, (Fig. 13.52 text book). These brachiopods consists of to shells one concave and the other is flat used as cover for the concave one.

5. Most of the Devonian fish groups were extinct, but ray-finned fish like shark continued to thrive and were the dominant vertebrate predator. 6. The goniatitic ammonoids recovered in the early carboniferous and remained the dominant invertebrate predators. 7. Some typical early Paleozoic animals were no longer important:- - Graptolite were practically gone. - Trilobite were extremely scar. 2. Land life In the late Devonian, the first forests were emerging from the swamp, and diverse arthropods and the first amphibians were living in these forests. During the late Paleozoic, terrestrial life diversified into a much more complex range of communities, with a wide variety of new plants and animals.

In the Carboniferous time the coal swamps covering large areas of every continent for the first time in earth history. Coal never again accumulated to this extent. The coal were produced by a great variety of plants such as:- 1. Spore –bearing plants, the lycopsids produced trees reaching 30 meters in height, e.g. Lepidodendron and Sigillaria, and Calamites . 2. Seed-plants, e. g. Conifers and Ginkgoes, and Cordaites, and Glossopteris. Animal life in Land Arthropods from Silurian time still inhabit the land. The first land Snails and fresh water clams were inhabited the land to the first time in the Carboniferous. during the Carboniferous Amphibians were the largest animals in the great coal swamps, by the Permian time it reach 2 meters long and weighed about 130 Kg. Fig. 13.61.

Eryops Diplocaulus Seymouria Fig.13.61 Family tree of late Paleozoic amphibians. All from the early Permian of Texas. Eryops Diplocaulus Seymouria

Fig. 13.62 Top: Skeleton and reconstruction of one of the earliest known reptiles, Hylonomus, from the Carboniferous of Nova Scotia. Middle: The preservation of fossils, animals were trapped in Sigillaria stems. Bottom: The Amniotic egg of the reptile.

13.5 The Late Permian Catastrophe The Permian catastrophe marked the end of an era and rearranged the landscape of life. The phyla dominant since the late Cambrian , were decimated, and many groups went extinct altogether, 90-95 percent of all marine species on earth died out. When life recovered millions of years later in the Triassic, a completely new cast of characters recolonized the sea floor. Terrestrial extinctions were also severe. Permian floras show a gradual shift from Cordaites and ferns to conifers, cycads, ginkgoes and other gymnosperms. Terrestrial vertebrates show several waves of extinction as more primitive reptile were replaced by successive waves of more advanced vertebrates. The causes of the catastrophe: Global cooling. the reduction of shallow- marine habitat. the basaltic lave eruptions which injected sulfates into the atmosphere. The high CO2 ratio in marine water. meteoric impact activity.

Fig. 13.67

Fig. 13.60a The primitive conifer Walchia from the late Pennsylvanian of Kansas

Fig. 13.60b Permian conifer with slightly broader leaves.