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Permian Period
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What was the Permian Period?
The Permian Period, the last period of the Paleozoic Era, began 298.9 million years ago and ended 252.2 million years ago.
The assembly of the supercontinent Pangea led to global warming and dry climates. Terrestrial plants broadly diversified, and insects rapidly evolved. Several reptile lineages appeared, including those that eventually gave rise to mammals.
The largest mass extinction in Earth’s history occurred during the latter part of the Permian Period, where only 10% or less of the species survived. This extinction may have resulted from high ocean temperatures or volcanic eruptions that emitted ash, blocking sunlight and disrupting food chains.
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When did the Permian Period occur in Earth's history?
The Permian Period, the last period of the Paleozoic Era, began 298.9 million years ago and ended 252.2 million years ago. It spanned from the end of the Carboniferous Period to the beginning of the Triassic Period. The Permian Period is named after the region of Perm in Russia, where rocks from this period are well-developed.
The assembly of the supercontinent Pangea led to global warming and dry climates. Glaciation persisted from the Carboniferous Period into the Early Permian Epoch across areas of present-day India, Australia, Antarctica, and Siberia. The Permian-Triassic extinction event, also known as the "Great Dying," occurred about 252 million years ago and eliminated a significant percentage of marine invertebrate and terrestrial vertebrate species.
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How do scientists use geochronology to learn about the Permian Period?
Geochronology helps scientists study the Permian Period by determining the age and history of the period's rocks and rock assemblages. This is achieved through studying rock strata distribution, succession, and fossil organisms.
By using radiometric dating, which measures the decay of radioactive atoms in geologic materials, scientists can numerically quantify the age of rocks from the Permian. This method provides a tool for dating rocks even before life-forms emerged. The Permian Period began 298.9 million years ago and ended 252.2 million years ago.
Isotope geology complements geochronology by tracing isotopes produced by radioactive decay through geologic processes, offering insights into these processes.
The isochron method also helps determine precise ages, utilizing the abundance of parent and daughter isotopes relative to the initial background.
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What are some important subdivisions or stages of the Permian Period?
The Permian Period is divided into three epochs: Early (Cisuralian), Middle (Guadalupian), and Late (Lopingian). These epochs correspond to the Cisuralian, Guadalupian, and Lopingian rock series.
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Cisuralian Epoch Named after its location in the Ural Mountains, this epoch is further divided into four ages: Asselian, Sakmarian, Artinskian, and Kungurian. The base of these stages are marked by the appearance of specific conodont species such as Streptognathodus isolatus, Sweetognathus merrilli, Sweetognathus whitei, and Mesogondolella bisselli.
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Guadalupian Epoch Named after the Guadalupe Mountains in the West Texas region, this epoch includes three ages: Roadian, Wordian, and Capitanian. The first appearance of Jinogondolella nankingensis, Jinogondolella aserrata, and Jinogondolella postserrata specify the base of the Roadian, Wordian, and Capitanian Stages, respectively.
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Lopingian Epoch Named after its type area in China, this epoch contains two ages: Wuchiapingian and Changhsingian. The emergence of Clarkina postbitteri marks the base of the Wuchiapingian Stage, and the first appearance of Clarkina wangi characterizes the base of the Changhsingian.
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How do fossils help date rocks from the Permian Period?
Fossils are critical for dating rocks from the Permian Period. Index fossils, which are easily recognizable, widespread, and existed for a short time, help define geologic time scale boundaries and correlate strata.
During the Permian Period, the diversification and evolution of marine and terrestrial life, such as plants and insects, provide a basis for relative dating. The principle of faunal succession, where fossil assemblages follow a specific order, allows geologists to determine the relative age of rocks based on their fossil content. The presence of similar fossils in separated rocks indicates contemporary formation.
Different conodont species help classify subdivisions within the Permian Period. Although many marine invertebrate faunas are endemic and hard to correlate between paleobiotic provinces, the succession of conodont faunas in type regions helps define regional patterns and assist in correlating rock series.
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Why was the end of the Permian Period significant in Earth's geological timeline?
The end of the Permian Period is a major turning point in Earth's history because of a mass extinction event that occurred approximately 252 million years ago, marking the boundary between the Paleozoic and Mesozoic eras. This event, sometimes called the "Great Dying," was the most severe in Earth's history, wiping out a large percentage of marine invertebrate species (80%) and terrestrial vertebrate species (70%). It profoundly affected life during the Triassic Period.
The Permian-Triassic extinction had many proposed causes, including intense volcanic activity, changes in sea levels, and fluctuations in oxygen and carbon dioxide levels. The assembly of Pangea also led to global warming and dry climates.
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Permian Period, in geologic time, the last period of the Paleozoic Era. The Permian Period began 298.9 million years ago and ended 252.2 million years ago, extending from the close of the Carboniferous Period to the outset of the Triassic Period.
At the beginning of the period, glaciation was widespread, and latitudinal climatic belts were strongly developed. Climate warmed throughout the Permian times, and, by the end of the period, hot and dry conditions were so extensive that they caused a crisis in Permian marine and terrestrial life. This dramatic climatic shift may have been partially triggered by the assembly of smaller continents into the supercontinent of Pangea. Most of Earth’s land area was incorporated into Pangea, which was surrounded by an immense world ocean called Panthalassa.
Terrestrial plants broadly diversified during the Permian Period, and insects evolved rapidly as they followed the plants into new habitats. In addition, several important reptile lineages first appeared during this period, including those that eventually gave rise to mammals in the Mesozoic Era. The largest mass extinction in the Earth’s history occurred during the latter part of the Permian Period. This mass extinction was so severe that only 10 percent or less of the species present during the time of maximum biodiversity in the Permian survived to the end of the period.
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Permian rocks are found on all present-day continents; however, some have been displaced considerable distances from their original latitudes of deposition by tectonic transport occurring during the Mesozoic and Cenozoic eras. Some beds dated from the latest Permian ages are renowned for their fossils; strata (rock layers) in the Russian Platform contain a remarkable vertebrate faunal assemblage as well as fossil insects and plants.
The Permian Period derives its name from the Russian region of Perm, where rocks deposited during this time are particularly well developed.
The Permian environment
The Permian Period constitutes an important crossroads both in the history of the Earth’s continents and in the evolution of life. The principal geographic features of the Permian world were a supercontinent, Pangea, and a huge ocean basin, Panthalassa, with its branch, the Tethys Sea (a large indentation in the tropical eastern side of Pangea).
Paleogeography
Distribution of land
During the Early Permian (Cisuralian) Epoch, northwestern Gondwana collided with and joined southern Laurussia (a craton also known as Euramerica), resulting in the Alleghenian orogeny, occurring in the region that would become North America, and the continuance of the Hercynian orogeny, its northwestern European counterpart. The assembly of Pangea was complete by the middle of the Early Permian Epoch following its fusion to Angara (part of the Siberian craton) during the Uralian orogeny.
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On the periphery of Pangea was Cathaysia, a region extending beyond the eastern edge of Angara and comprising the landmasses of both North and South China. Cathaysia lay within the western Panthalassic Ocean and at the eastern end of Tethys (sometimes called Paleo-Tethys) Sea. The Panthalassa and Tethys also contained scattered fragments of continental crust (microcontinents), basaltic volcanic island arcs, oceanic plateaus, and trenches. The island arcs featured extensive fringing limestone reefs and platforms that were subsequently displaced by seafloor spreading. These isolated landmasses were later welded onto the margins of Pangea, forming accreted terranes.
Sea level
Evidence of sea-level rise and fall is well displayed in Permian strata. Fluctuations in sea level are often associated with changes in climate. Some fluctuations with large magnitudes and short durations, such as near the base of the Permian Period, are likely the result of glaciation. For others, the possibility that Milankovitch cycles (adjustments in Earth’s axis and the long-term orbital patterns of Earth about the Sun) directly affect sea level is still being investigated, though their periodic occurrence has been linked to episodes of glaciation. Global sea-level events are marked by four long lowstands (times when sea level falls below the level of the continental shelf) within the Early Permian Epoch, a major lowstand near the base of the Middle Permian (Guadalupian) Epoch, and four long lowstands within and at the top of the Middle Permian Epoch. Lowstands are also recorded at various times within the Late Permian (Lopingian) Epoch and at the terminus of the Permian Period. Extended global withdrawal of seas from continental shelves and platforms led to significant unconformities (gaps in the geologic record) and to extensive evolutionary turnovers (events of species diversification and extinction) in shallow marine faunas at the family and superfamily levels.