Portal:Cambrian

Topics Culture Geography Health History Mathematics Nature People Philosophy Religion Society Technology The Cambrian Portal The Cambrian is the first geological period of the Paleozoic Era, lasting from 541.0 ± 1.0 to 485.4 ± 1.9 million years ago (mya) and is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinname for Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of lagerstätten. These are sites of exceptional preservation, where 'soft' parts of organisms are preserved as well as their more resistant shells. This means that our understanding of the Cambrian biology surpasses that of some later periods. The Cambrian Period marked a profound change in life on Earth; prior to the Cambrian, living organisms on the whole were small, unicellular and simple. Complex, multicellular organisms gradually became more common in the millions of years immediately preceding the Cambrian, but it was not until this period that mineralized – hence readily fossilized – organisms became common. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, produced the first representatives of many modern phyla, representing the evolutionary stems of modern groups of species, such as the arthropods. While diverse life forms prospered in the oceans, the land was comparatively barren – with nothing more complex than a microbial soil crust and a few forms that apparently emerged to browse on the microbial materials. Most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia. The seas were relatively warm, and polar ice was absent for much of the period. (See more…) Template:/box-footer Death Valley viewed from space. The exposed geology of the Death Valley area presents a diverse and complex set of at least 23 formations of sedimentary units, two major gaps in the geologic record called unconformities, and at least one distinct set of related formations geologists call a group. The oldest rocks in the area are extensively metamorphosed by intense heat and pressure and are at least 1700 million years old. These rocks were intruded by a mass of granite 1400 Ma (million years ago) and later uplifted and exposed to nearly 500 million years of erosion. Marine deposition occurred 1200 to 800 Ma, creating thick sequences of conglomerate, mudstone, and carbonate rock topped by stromatolites, and possibly glacial deposits from the hypothesized Snowball Earth event. Rifting thinned huge roughly linear parts of the supercontinent Rodinia enough to allow sea water to invade and divide its landmass into component continents separated by narrow straits. A passive margin developed on the edges of these new seas in the Death Valley region. Carbonate banks formed on this part of the two margins only to be subsided as the continental crust thinned until it broke, giving birth to a new ocean basin. An accretion wedge of clastic sediment then started to accumulate at the base of the submerged precipice, entombing the region's first known fossils of complex life. These sandy mudflats gave way about 550 Ma to a carbonate platform which lasted for the next 300 million years of Paleozoic time. (see more...) Charles Darwin (12 February 1809 – 19 April 1882) was an English naturalist and geologist, best known for his contributions to evolutionary theory. He established that all species of life have descended over time from common ancestors, and in a joint publication with Alfred Russel Wallace introduced his scientific theorythat this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding. His five-year voyage onHMS Beagle established him as an eminent geologist whose observations and theories supported Charles Lyell'suniformitarian ideas. Darwin later published his theory of evolution with compelling evidence in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species. By the 1870s the scientific community and much of the general public had accepted evolution as a fact. However, many favoured competing explanations and it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 1950s that a broad consensus developed in which natural selection was the basic mechanism of evolution. In modified form, Darwin's scientific discovery is the unifying theory of the life sciences, explaining the diversity of life. In recognition of Darwin's pre-eminence as a scientist, he was honoured with a major ceremonial funeral and buried in Westminster Abbey, close to John Herschel and Isaac Newton. Darwin has been described as one of the most influential figures in human history. (see more...) Various species of Cambrian sponge-like animals, known as Archaeocyathans. Counterclockwise, from the upper left corner, Coscinoptycta zunyiensis, Kotuyicyathus debilis, Tumuliolynthus musatovi, Beltanacyathus digitus, Fransuasaecyathus novus, Orbicyathus mongolicus, Center, Paranacyathus subartus. Photo credit: Stanton F. Fink Restoration of two Hurdia victoria ... that the 500-million-year-old Cambrian predator Hurdia was thought to be a number of separate organisms for 100 years, until the complete animal was reconstructed in March 2009? ... that the shrimp-like 510-million-year-old arthropod Waptia was named after two mountains? ... that Orsten, fossil-bearing lagerstätten in Sweden and elsewhere, are called "stinking stones" from organic content that has been preserved since the Cambrian Period? ... that the fordilloid Camya asy is one of four accepted Cambrian bivalves? ...that despite being known from many specimens, the fossil Fuxianhuia (pictured) remains one of the most controversial Cambrian arthropods? Template:/box-header Epochs - Terreneuvian - Cambrian Series 2 - Cambrian Series 3 - Furongian Ages - Fortunian - Cambrian Stage 2 - Cambrian Stage 3 - Cambrian Stage 4 - Cambrian Stage 5 - Drumian - Guzhangian -Paibian - Jiangshanian - Cambrian Stage 10 Events - Cambrian Explosion - Cambrian substrate revolution - End-Botomian mass extinction - Cambrian–Ordovician extinction event Geography - Pannotia - Baltica - Gondwanaland - Laurentia - Siberia Animals - Archaeocyathans - Trilobites Trace fossils - Climactichnites - Protichnites Plants - Dalyia - Margaretia Fossil sites - Walcott Quarry Stratigraphic units - Burgess Shale - Maotianshan Shales Researchers - Stephen Jay Gould - Simon Conway Morris - Charles Doolittle Walcott Culture - Wonderful Life (book) Template:/box-footer Template:/box-header Featured Cambrian articles - None Good Cambrian articles - Fossils of the Burgess Shale - Opabinia - Small shelly fauna - Stephen Jay Gould - Waptia Template:/box-footer ▼ Cambrian ► Cambrian life Here are some tasks awaiting attention: Stubs : Cambrian stubs Current Cambrian FACs - none currently Template:/box-footer Time Earth sciences Paleontology Extinct and Endangered Species Paleozoic Cambrian Ordovician Silurian Error creating thumbnail: File missing Devonian Carboniferous Permian What are portals? 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