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| Perm II | |
|---|---|
| Name | Perm II |
| Type | Stratigraphic unit |
| Period | Permian |
| Location | Perm region |
| Thickness | variable |
| Lithology | mixed clastic and carbonate |
| Namedfor | Perm (city) |
| Namedby | stratigraphers |
Perm II Perm II is a stratigraphic interval within the Permian succession of the Perm region that has been recognized by regional stratigraphers and petrographers. The unit is documented in lithostratigraphic columns studied by researchers from institutions such as the Russian Academy of Sciences, the Geological Survey of Russia, and universities including Saint Petersburg State University and Ural State Mining University. It has significance for interpretations by paleontologists working at museums like the Zoological Museum of Moscow State University and for resource assessments by companies such as Gazprom and Rosneft.
Perm II is defined in stratigraphic frameworks issued by commissions such as the International Commission on Stratigraphy and national stratigraphic committees represented by the Russian Academy of Sciences. The name derives from the type area near the city of Perm, Russia and follows conventions used by geologists at institutions like the Academy of Sciences of the USSR historically. The unit is distinguished from adjacent intervals (e.g., lower and upper Permian units described by geologists at Moscow State University and by field teams from the Ural State University) by lithologic markers and fossil assemblages curated by staff at the Paleontological Institute, Russian Academy of Sciences.
Perm II occupies a stratigraphic position within the middle part of the Permian succession in the European Russia and Ural Mountains region as mapped by the All-Russian Geological Research Institute. Regional cross-sections prepared by researchers at Krasnoyarsk State University correlate Perm II with flanking units identified near structural features such as the Kama River basin and the Ural orogen. Stratigraphic practice by the International Commission on Stratigraphy and regional stratigraphic charts from the Russian Geological Map place Perm II between lower Permian formations described by teams from Saint Petersburg State University and higher Permian units investigated by paleontologists at the Paleontological Institute. Key marker horizons used in correlation include ash layers sampled by geochemists at the Institute of Geology and Geophysics and unconformities mapped by field parties from the Institute of Earth Sciences.
Lithologic descriptions produced by petrographers at Ural Federal University indicate that Perm II comprises interbedded sandstones, siltstones, shales, dolomites, and limestones; mineralogists at the Moscow State University have documented feldspar, quartz, and carbonate content. Sedimentological analyses by researchers from the Institute of Geology of Ore Deposits interpret depositional settings ranging from fluvial-deltaic systems near the Volga River catchment to shallow marine shelves adjacent to the Ural seaway. Paleocurrent studies led by scientists at Tomsk State University and facies models from the Geological Institute of the Russian Academy of Sciences suggest shifts between siliciclastic influx sourced from the Ural orogen and carbonate production associated with faunal communities studied by curators at the Zoological Museum of Moscow State University.
Fossils recovered from Perm II have been described by specialists at the Paleontological Institute, Russian Academy of Sciences, with collections housed in museums such as the State Darwin Museum and the Russian Museum of Paleontology. The assemblage includes brachiopods, bivalves, ammonoids, and foraminifera examined by micropaleontologists at Saint Petersburg State University, as well as vertebrate remains—tetrapod and fish elements—studied by paleozoologists from the Institute of Evolutionary Morphology and Ecology. Plant fossils and palynological data analyzed at the Institute of Botany provide evidence for terrestrial floras comparable to collections curated at the Komarov Botanical Institute. Ichnological work on trace fossils has been published by researchers affiliated with the Paleontological Society of Russia and compared to assemblages from the Permian Basin described by geologists at Bureau of Economic Geology.
Perm II hosts reservoirs and source rocks evaluated by petroleum geologists at Rosneft, Gazprom Neft, and consulting firms that collaborate with the All-Russian Geological Research Institute. Reservoir-quality sandstones and carbonate intervals have been targeted in exploration campaigns documented by engineers from the Institute of Oil and Gas Problems. Mineralization, including stratabound sulfide and carbonate-hosted deposits, has been investigated by economic geologists at the Ural Geological Survey and mapped in reports from the Ministry of Natural Resources and Environment of the Russian Federation. Stratigraphic traps and seal analyses have been the subject of studies by researchers at Saint Petersburg Mining University.
The unit was recognized in early stratigraphic syntheses compiled by geologists affiliated with the Academy of Sciences of the USSR in the 20th century and was refined by successive generations of stratigraphers at institutions such as Moscow State University and the Geological Institute of the Russian Academy of Sciences. Key publications by field parties from the Ural Branch of the Russian Academy of Sciences and monographs from the Paleontological Institute established biostratigraphic frameworks and lithologic descriptions. Nomenclatural debates have involved committees at the International Commission on Stratigraphy and national panels convened by the Russian Academy of Sciences.
Regional correlation exercises led by stratigraphers at Saint Petersburg State University and the Geological Survey of Russia link Perm II to equivalent intervals in the Siberian Platform, the Kazakhstan basins, and the Timan-Pechora Province, and compare faunal assemblages with those from the Permian Basin of Texas and New Mexico studied by researchers at University of Texas at Austin and New Mexico Museum of Natural History and Science. Global correlation uses biostratigraphic markers evaluated by the International Commission on Stratigraphy and chemostratigraphic signals compared with datasets from the National Museum of Natural History (Smithsonian Institution).
Category:Geologic formations of Russia