The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At 508 million years old, it is one of the earliest fossil beds containing soft-part imprints.
The Cambrian Period was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago (mya) to the beginning of the Ordovician Period 485.4 mya. Its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name of Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian biology surpasses that of some later periods.
A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants. The totality of fossils is known as the fossil record.
Paleontology, also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene Epoch. It includes the study of fossils to classify organisms and study interactions with each other and their environments. Paleontological observations have been documented as far back as the 5th century BCE. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term itself originates from Greek παλαιός, palaios, "old, ancient", ὄν, on, "being, creature", and λόγος, logos, "speech, thought, study".
The cloudinids, an early metazoan family containing the genera Acuticocloudina, Cloudina and Conotubus, lived in the late Ediacaran period about 550 million years ago. and became extinct at the base of the Cambrian. They formed millimetre-scale conical fossils consisting of calcareous cones nested within one another; the appearance of the organism itself remains unknown. The name Cloudina honors the 20th-century geologist and paleontologist Preston Cloud.
The Proterozoic is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life on the Earth. The name Proterozoic combines the two forms of ultimately Greek origin: protero- meaning "former, earlier", and -zoic, a suffix related to zoe "life". The Proterozoic Eon extended from 2500 mya to 541 mya, and is the most recent part of the Precambrian "supereon." The Proterozoic is the longest eon of the Earth's geologic time scale and it is subdivided into three geologic eras : the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic.
The Archean Eon is one of the four geologic eons of Earth's history, occurring 4,000 to 2,500 million years ago. During the Archean, the Earth's crust had cooled enough to allow the formation of continents and the beginning of life on Earth.
Stromatolites or stromatoliths are layered mounds, columns, and sheet-like sedimentary rocks that were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe. Fossilized stromatolites provide records of ancient life on Earth. Lichen stromatolites are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by endolithic lichens.
Chert is a hard, fine-grained sedimentary rock composed of microcrystalline (or cryptocrystalline) crystals of quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.
The Mesoproterozoic Era is a geologic era that occurred from 1,600 to 1,000 million years ago. The Mesoproterozoic was the first period of Earth's history of which a fairly definitive geological record survives. Continents existed during the preceding era, but little is known about them. The continental masses of the Mesoproterozoic were more or less the same ones that exist today.
The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland. The belt is aged between 3.7 and 3.8 billion years. The belt contains variably metamorphosed mafic volcanic and sedimentary rocks. The occurrence of boninitic geochemical signatures, characterized by extreme depletion in trace elements that are not fluid mobile, offers evidence that plate tectonic processes in which lithic crust is melted may have been responsible for the creation of the belt. Another theory posits that the belt formed via a process known as vertical plate tectonics.
Vaalbara was an Archean supercontinent consisting of the Kaapvaal Craton and the Pilbara Craton. E. S. Cheney derived the name from the last four letters of each craton's name. The two cratons consist of crust dating from 2.7 to 3.6 Gya, which would make Vaalbara one of Earth's earliest supercontinents.
The Kaapvaal Craton, along with the Pilbara Craton of Western Australia, are the only remaining areas of pristine 3.6–2.5 Ga crust on Earth. Similarities of rock records from both these cratons, especially of the overlying late Archean sequences, suggest that they were once part of the Vaalbara supercontinent.
The Ediacaranbiota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period. These were composed of enigmatic tubular and frond-shaped, mostly sessile, organisms. Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms.
The evolutionary history of life on Earth traces the processes by which living and fossil organisms evolved, from the earliest emergence of life to the present. Earth formed about 4.5 billion years (Ga) ago and evidence suggests life emerged prior to 3.7 Ga. The similarities among all known present-day species indicate that they have diverged through the process of evolution from a common ancestor. Approximately 1 trillion species currently live on Earth of which only 1.75–1.8 million have been named and 1.6 million documented in a central database. These currently living species represent less than one percent of all species that have ever lived on earth.
This article attempts to place key plant innovations in a geological context. It concerns itself only with novel adaptations and events that had a major ecological significance, not those that are of solely anthropological interest. The timeline displays a graphical representation of the adaptations; the text attempts to explain the nature and robustness of the evidence.
The Cambrian explosion or Cambrian radiation was an event approximately 541 million years ago in the Cambrian period when practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification of other organisms.
The Warrawoona Group is a geological unit in Western Australia containing putative fossils of cyanobacteria cells. Dated 3.465 Ga, these microstructures, found in Archean chert, are considered to be the oldest known geological record of life on Earth.
The Barberton Greenstone Belt of eastern South Africa contains some of the most widely accepted fossil evidence for Archean life. These cell-sized prokaryote fossils are seen in the Barberton fossil record in rocks as old as 3.5 billion years. The Barberton Greenstone Belt is an excellent place to study the Archean Earth due to exposed sedimentary and metasedimentary rocks.
The Barberton greenstone belt (BGB) is located in the Kapvaal craton of southeastern Africa. It characterizes one of the most well-preserved and oldest pieces of continental crust today by containing rocks in the Barberton Granite Greenstone Terrain (3.55–3.22 Ga). The BGB is a small, cusp-shaped succession of volcanic and sedimentary rocks, surrounded on all sides by granitoid plutons which range in age from >3547 to <3225 Ma. It is commonly known as the type locality of the ultramafic, extrusive volcanic rock, the komatiite. Greenstone belts are geologic regions generally composed of mafic to ultramafic volcanic sequences that have undergone metamorphism. These belts are associated with sedimentary rocks that occur within Archean and Proterozoic cratons between granitic bodies. Their name is derived from the green hue that comes from the metamorphic minerals associated with the mafic rocks. These regions are theorized to have formed at ancient oceanic spreading centers and island arcs. In simple terms, greenstone belts are described as metamorphosed volcanic belts. Being one of the few most well-preserved Archean portions of the crust, with Archean felsic volcanic rocks, the BGB is well studied. It provides present geologic evidence of Earth during the Archean (pre-3.0 Ga). Despite the BGB being a well studied area, its tectonic evolution has been the cause of much debate.
