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White Sea Assemblage
The White Sea assemblage was the second of the three Late Ediacaran biotic assemblages, following the Avalon assemblage and preceding the Nama assemblage. It spanned from 560 Ma to 550 Ma. Showing an increase in genus diversity from the Avalon assemblage, it concluded with a faunal turnover often characterized as the first pulse of the end-Ediacaran extinction, with only 20% of White Sea taxa found in the later Nama assemblage despite similar taphonomic Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov ... processes. References Ediacaran {{Ediacaran-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kimberella
''Kimberella'' is an extinct genus of marine bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity with this group is contentious. Specimens were first found in Australia's Ediacara Hills, but recent research has concentrated on the numerous finds near the White Sea in Russia, which cover an interval of time from . As with many Ediacara biota, fossils from this time, its evolutionary relationships to other organisms are hotly debated. Paleontologists initially classified ''Kimberella'' as a type of Cubozoan, but, since 1997, features of its anatomy and its association with scratch marks resembling those made by a radula have been interpreted as signs that it may have been a mollusc. Although some paleontologists dispute its classification as a mollusc, it is generally accepted as being at least a bilaterian. The classification of ''Ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ustʹ Pinega Formation
The Ust Pinega Formation is an Upper Ediacaran geological formation exposed along the banks of the Syuzma and Onega Rivers in Arkhangelsk Oblast, northwestern Russia, and spans from around 580 Ma to 550 Ma, with fossilferous stones restricted to between 565 and 555 Ma. It also preserves a wealth of rare Ediacaran fossils, like ''Zolotytsia'', ''Ventogyrus'' and ''Bomakellia''. Dating The Ustʹ Pinega Formation is relatively large, and using Uranium-lead dating, zircon U-Pb dating, a date of had been recovered for the top of the formtion, whilst the known base of the formation is restricted to . As for the lower and upper dates of the fossiliferous units within the formtaion, using the Rubidium–strontium dating, Rb–Sr dating method, the lowest fossiliferous unit of the Ustʹ Pinega Formation has been dated to , whilst the upper-most fossiliferous unit was dated using zircon U-Pb dating, which had recovered a date of . Paleobiota The Ustʹ Pinega Formation is home to man ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Sea
The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the northeast. The whole of the White Sea is under Russian sovereignty and considered to be part of the internal waters of Russia.A. D. Dobrovolskyi and B. S. Zalogi"Seas of USSR. White Sea" Moscow University (1982) (in Russian) Administratively, it is divided between the Arkhangelsk Oblast, Arkhangelsk and Murmansk Oblast, Murmansk oblasts and the Republic of Karelia. The Port of Arkhangelsk, major port of Arkhangelsk is located on the White Sea. For much of Russia's history this was Russia's main centre of international maritime trade, conducted by the Pomors ("seaside settlers") from Kholmogory, Arkhangelsk Oblast, Kholmogory. In the modern era it became an important Soviet Union, Soviet naval and submarine base. The White Sea–Baltic Canal co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders of Russia, land borders with fourteen countries. Russia is the List of European countries by population, most populous country in Europe and the List of countries and dependencies by population, ninth-most populous country in the world. It is a Urbanization by sovereign state, highly urbanised country, with sixteen of its urban areas having more than 1 million inhabitants. Moscow, the List of metropolitan areas in Europe, most populous metropolitan area in Europe, is the capital and List of cities and towns in Russia by population, largest city of Russia, while Saint Petersburg is its second-largest city and Society and culture in Saint Petersburg, cultural centre. Human settlement on the territory of modern Russia dates back to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avalon Assemblage
The Avalon assemblage was the first of the three Late Ediacaran biotic assemblages, spanning from 575 Ma to 560 Ma. It was followed by the White Sea assemblage, although temporal overlaps have been noted between the biotic assemblages. While earlier macroscopic fossils, mostly of algal origin, are known from the Lantian Formation, Avalon-type localities provide some of the first evidence of putative metazoan ancestors, as part of the Ediacaran biota. Research history The division of the Ediacaran biota in three separate assemblages was first postulated by Ben Waggoner in 2003. Geography Most Avalonian fossil sites are known from the central United Kingdom and eastern Newfoundland, historically connected as part of the Avalonia microcontinent. Outside of Avalonia proper, other sites have been identified as part of the Avalon assemblage, such as the Olenek Uplift in Siberia, and Sekwi Brooke in the Northwest Territories of Canada. Biota Deep-water rangeomorphs, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nama Assemblage
The Nama assemblage was the last of the Ediacaran biotic Faunal assemblage, assemblages. Following the Avalon assemblage, Avalon and White Sea assemblages, it spanned from 550 megaannum, Ma to 539 Ma, coinciding with the Terminal Ediacaran biozone. The assemblage was characterized by a faunal turnover, with the decline of the preexisting White Sea biota. The drop of diversity has been compared to the mass extinctions of the Phanerozoic. A second drop of diversity occurred at the Ediacaran–Cambrian boundary, concluding the Nama assemblages with the end-Ediacaran extinction. Etymology and definitions The Nama assemblage is named after the Nama Group from the Tsaus Mountains of Namibia, which preserves a Late Ediacaran record of soft-bodied fossils. The Biota (ecology), biota of the Namibian sites clusters with similar biotas found in the Southwestern United States, South China and British Columbia, leading to a Nama assemblage being first defined by Gehling in 2001. This def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megaannum
A year is a unit of time based on how long it takes the Earth to orbit the Sun. In scientific use, the tropical year (approximately 365 solar days, 5 hours, 48 minutes, 45 seconds) and the sidereal year (about 20 minutes longer) are more exact. The modern calendar year, as reckoned according to the Gregorian calendar, approximates the tropical year by using a system of leap years. The term 'year' is also used to indicate other periods of roughly similar duration, such as the lunar year (a roughly 354-day cycle of twelve of the Moon's phasessee lunar calendar), as well as periods loosely associated with the calendar or astronomical year, such as the seasonal year, the fiscal year, the academic year, etc. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the planet, four seasons are gener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
End-Ediacaran Extinction
The end-Ediacaran extinction is a mass extinction believed to have occurred near the end of the Ediacaran period, the final period of the Proterozoic eon. Evidence suggesting that such a mass extinction occurred includes a massive reduction in diversity of acritarchs, the sudden disappearance of the Ediacara biota and calcifying organisms, and the time gap before Cambrian organisms "replaced" them. Some lines of evidence suggests that there may have been two distinct pulses of the extinction event, one occurring and the other . Evidence Biotic evidence Ediacaran organisms During the Ediacaran period, two main groups of organisms are found in the fossil record: the "Ediacaran biota" of soft-bodied organisms, preserved by microbial mats; and calcifying organisms such as ''Cloudina'' and ''Namacalathus'', which had a carbonate skeleton. Because ''both ''these groups disappear abruptly at the end of the Ediacaran period, , their disappearance cannot simply represent the closure of a p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taphonomy
Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek language, Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Yefremov, Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms from the biosphere to the lithosphere. The term taphomorph is used to describe fossil structures that represent poorly-preserved, deteriorated remains of a mixture of Taxon, taxonomic groups, rather than of a single one. Description Taphonomic phenomena are grouped into two phases: biostratinomy, events that occur between death of the organism and the burial; and diagenesis, events that occur after the burial. Since Efremov's definition, taphonomy has expanded to include the fossilization of organic and inorganic materials through both cultural and environmental influences. Taphonomy is now most widely defined as the study of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
