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Random Formation
The Random Formation is a rock unit in Newfoundland dating to the early Cambrian period, dominated by tidal quartz arenites deposited in a near-shore environment, but also incorporating intertidal and open-shelf deposits, including glauconitic and mud-cracked mudstones (now shales), and red channel sandstones. It was deposited quickly and is approximately 175 m thick. The Blue Pinion Formation was originally recognized as a separate formation, but is now interpreted as an expression of the Random Formation. Sedimentology Its white arenitic sandstones are very distinctive, recognizable from their herringbone cross-stratification that denotes the influence of storm systems. Interbedded green-grey sands and silts represent an intertidal setting. Spatial distribution It is widespread throughout Newfoundland unlike its underlying units. It was deposited in intertidal mud flats to subtidal setting, then (later) near the bottom of an open marine shelf. The top of the unit intergr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formation (stratigraphy)
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Formation Megaripples
In common usage, randomness is the apparent or actual lack of pattern or predictability in events. A random sequence of events, symbols or steps often has no order and does not follow an intelligible pattern or combination. Individual random events are, by definition, unpredictable, but if the probability distribution is known, the frequency of different outcomes over repeated events (or "trials") is predictable.Strictly speaking, the frequency of an outcome will converge almost surely to a predictable value as the number of trials becomes arbitrarily large. Non-convergence or convergence to a different value is possible, but has probability zero. For example, when throwing two dice, the outcome of any particular roll is unpredictable, but a sum of 7 will tend to occur twice as often as 4. In this view, randomness is not haphazardness; it is a measure of uncertainty of an outcome. Randomness applies to concepts of chance, probability, and information entropy. The fields o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cruziana
''Cruziana'' is a trace fossil consisting of elongate, bilobed, approximately bilaterally symmetrical burrows, usually preserved along bedding planes, with a sculpture of repeated striations that are mostly oblique to the long dimension. It is found in marine and freshwater sediments. It first appears in upper Fortunian rocks of northern Iran and northern Norway. ''Cruziana'' has been extensively studied because it has uses in biostratigraphy (specific scratch patterns are unique to specific time intervals), and because the traces can reveal many aspects of their makers' behavior. ''Cruziana'' is typically associated with trilobites but can also made by other arthropods. ''Cruziana'' appears in non-marine formations such as the Beacon Supergroup that would have been unsuitable environments for trilobites, and in Triassic sediments that were deposited after trilobites became extinct at the end of the Permian Period. ''Cruziana'' traces can reach 15 mm across and 15 cm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rusophycus
''Rusophycus'' is a trace fossil ichnogenus allied to '' Cruziana''. ''Rusophycus'' is the resting trace, recording the outline of the tracemaker; ''Cruziana'' is made when the organism moved. The sculpture of ''Rusophycus'' may reveal the approximate number of legs that the tracemaker had, although striations (scratchmarks) from a single leg may overlap or be repeated. Both ''Rusophycus'' and ''Cruziana'' are typically associated with trilobites but can also be made by other arthropods. ''Rusophycus'' is known from sediments dating to the earliest Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ... Period (somewhat before the first appearance trilobite fossils), and from the Triassic Period (after the Permian extinction of trilobites), indicating that other producers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobite
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period () and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described. By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, they left an extensive fossil record. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smith Point Formation
The Smith Point Formation is an Early Cambrian (c. Tommotian), fossil-rich, pink to brick red limestone formation cropping out in Newfoundland. Palaeontology Its fossil assemblage includes trilobites, hyoliths, and microbialites (stromatolites/ oncolite Oncolites are sedimentary structures composed of oncoids, which are layered structures formed by cyanobacterial growth. Oncolites are very similar to stromatolites, but, instead of forming columns, they form approximately spherical structures. ...s). References {{Reflist Geologic formations of Newfoundland and Labrador Cambrian Newfoundland and Labrador Limestone formations of Canada ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atdabanian
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about million years ago, though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera '' Olenellus'' or ''Redlichia'' around million years ago. Naming The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. The stage approximately corresponds to the "Atdabanian", which is used by geologists working in Siberia. Biostratigraphy The oldest trilobite known is '' Lemdadella'' which appears at the beginning of the ''Fallotaspis'' zone. The Cambrian rad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tommotian
Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian Series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia. Neither the upper nor lower boundary has yet been defined by the International Commission on Stratigraphy. The preferred definitions for the lower boundary are the first appearance of the molluscs ''Watsonella crosbyi'' or '' Aldanella attleborensis'' around million years ago. The proposed upper boundary might be the first appearance of trilobites around million years ago. Possible candidates for a GSSP include the first appearance of ''Watsonella crosbyi'' in the Zhujiaqing Formation (朱家庆组) in Yunnan, China or the Pestrotsvet Formation near the Aldan River on the Siberian Platform Siberia, also known as Angaraland (or simply Angara) and Angarida, is an ancient craton in the heart of Siberia. Today forming the Central Siberian Plateau, it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diachronous
In geology, a diachronism (Greek ''dia'', "through" + ''chronos'', "time" + ''-ism''), or diachronous deposit, is a sedimentary rock formation in which the material, although of a similar nature, varies in age with the place where it was deposited.Whitten F.G.A & Brooks J.R.V., (1972),''A Dictionary of Geology'', Penguin, Typically this occurs as a result of a marine transgression or regression, or the progressive development of a delta. As the shoreline advances or retreats, a succession of continuous deposits representing different environments (for example beach, shallow water, deeper water) may be left behind. Although each type of deposit (facies) may be continuous over a wide area, its age varies according to the position of the shoreline through time. An example is the sandy beds near the end of the lower Carboniferous of the west of England (the ''Drybrook sandstone'' of the Forest of Dean). Deposition of this began much later in the Bristol area than further north. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brachiopod
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically-oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chapel Island Formation
The Chapel Island Formation is a sedimentary formation from the Burin Peninsula, Newfoundland, Canada. It is a succession of siliciclastic deposits, over thick, that were deposited during the latest Ediacaran and earliest Cambrian. Stratigraphy The formation's sequence stratigraphy is detailed in a journal article by Myrow and Hiscott. The formation starts in an intertidal zone, then, as the Cambrian progresses, becomes deeper water (outer shelf) as a general trend. The Chapel Island Formation lies on top of the Rencontre Formation and below the Random Formation. It is thick in Fortune Bay as a fault-bounded basin, consisting of grey-green siltstones and sandstones, with minor limestone beds near its top. Small shelly fossils have been recovered – primitive taxa only. The setting is nearshore or open shelf. Subdivisions The formation is divided into six members, numbered 1 to 5, with Member 2 split into 2A and 2B. The Proterozoic–Cambrian boundary occurs above the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ediacaran
The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and the beginning of the Phanerozoic Eon. It is named after the Ediacara Hills of South Australia. The Ediacaran Period's status as an official geological period was ratified in 2004 by the International Union of Geological Sciences (IUGS), making it the first new geological period declared in 120 years. Although the period takes its name from the Ediacara Hills where geologist Reg Sprigg first discovered fossils of the eponymous Ediacaran biota in 1946, the type section is located in the bed of the Enorama Creek within Brachina Gorge in the Flinders Ranges of South Australia, at . The Ediacaran marks the first appearance of widespread multicellular fauna following the end of Snowball Earth glaciation events, the so-called Ediacaran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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