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Devonian

About: Devonian is a research topic. Over the lifetime, 13014 publications have been published within this topic receiving 254772 citations. The topic is also known as: Devonian period.


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Journal ArticleDOI
19 Mar 1982-Science
TL;DR: A new compilation of fossil data on invertebrate and vertebrate families indicates that four mass extinctions in the marine realm are statistically distinct from background extinction levels.
Abstract: A new compilation of fossil data on invertebrate and vertebrate families indicates that four mass extinctions in the marine realm are statistically distinct from background extinction levels. These four occurred late in the Ordovician, Permian, Triassic, and Cretaceous periods. A fifth extinction event in the Devonian stands out from the background but is not statistically significant in these data. Background extinction rates appear to have declined since Cambrian time, which is consistent with the prediction that optimization of fitness should increase through evolutionary time.

1,412 citations

Journal ArticleDOI
03 Oct 2008-Science
TL;DR: A history of sea-level fluctuations for the entire Paleozoic by using stratigraphic sections from pericratonic and cratonic basins is reconstructed, revealing a gradual rise through the Cambrian and a short-lived but prominent withdrawal in response to Hirnantian glaciation.
Abstract: Sea levels have been determined for most of the Paleozoic Era (542 to 251 million years ago), but an integrated history of sea levels has remained unrealized. We reconstructed a history of sea-level fluctuations for the entire Paleozoic by using stratigraphic sections from pericratonic and cratonic basins. Evaluation of the timing and amplitude of individual sea-level events reveals that the magnitude of change is the most problematic to estimate accurately. The long-term sea level shows a gradual rise through the Cambrian, reaching a zenith in the Late Ordovician, then a short-lived but prominent withdrawal in response to Hirnantian glaciation. Subsequent but decreasingly substantial eustatic highs occurred in the mid-Silurian, near the Middle/Late Devonian boundary, and in the latest Carboniferous. Eustatic lows are recorded in the early Devonian, near the Mississippian/Pennsylvanian boundary, and in the Late Permian. One hundred and seventy-two eustatic events are documented for the Paleozoic, varying in magnitude from a few tens of meters to ∼125 meters.

1,227 citations

Journal ArticleDOI
TL;DR: The concept of major rock-stratigraphic units of interregional scope was introduced in 1948 by Longwell, 1949 as discussed by the authors, and the sedimentary record of the North American craton from late Precambrian to present is characterized by six major unconformities.
Abstract: The concept of major rock-stratigraphic units of interregional scope was introduced in 1948 (Longwell, 1949). It is now possible to restate the concept and to define more explicitly the sequences delimited by interregional unconformities in the continental interior of North America. The sedimentary record of the North American craton from late Precambrian to present is characterized by six major unconformities. These interregional unconformities subdivide the cratonic stratigraphic column into six sequences—major rock-stratigraphic units (of higher than group, megagroup, or supergroup rank) which can be identified, where preserved, in all cratonic interior areas. At the cratonic margins the bounding unconformities tend to disappear in continuous successions, and the cratonic sequences are replaced by others controlled by events in the marginal basins and eugeosynclinal borders. Although the time values of the unconformities vary widely because of differences in degree of nondeposition and amount of erosion, the approximate dates of the regressional maxima represented are: (1) very late Precambrian, (2) early Middle Ordovician, (3) early Middle Devonian, (4) “post-Elvira” Mississippian, (5) early Middle Jurassic, and (6) late Paleocene. A seventh major regression is now in progress.

1,172 citations

Journal ArticleDOI
TL;DR: The latest Neoproterozoic through Phanerozoic stratigraphy of the Zagros fold-thrust belt of Iran has been revised in the light of recent investigations.
Abstract: The latest Neoproterozoic through Phanerozoic stratigraphy of the Zagros fold-thrust belt of Iran has been revised in the light of recent investigations. The revised stratigraphy consists of four groups of rocks, each composed of a number of unconformity-bounded megasequences representing various tectonosedimentary settings. In the lowest group, ranging in age from latest Precambrian to Devonian(?), the uppermost Neoproterozoic to middle Cambrian rocks constitute a megasequence of evaporites, siliciclastic deposits, and interlayered carbonates, which were deposited in pull-apart basins that developed by the Najd strike-slip fault system. This megasequence is overlain by a second one, Middle to Late Cambrian in age, which consists of shallow, marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform. The overlying shales, siltstones, and partly volcanogenic sandstones of Ordovician, Silurian, and Devonian(?) age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities. The second group consists of two megasequences, one Permian and the other Triassic, composed of widespread, transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial, epi-Pangean, very shallow platformal sea. The third group is composed of four megasequences formed of shallow- and deep-water carbonates with some siliciclastic and evaporite deposits, which accumulated on a Neo-Tethyan continental shelf during earliest Jurassic through late Turonian time. The fourth group comprises siliciclastic and carbonate deposits of a largely underfilled, NW- to SE-trending, forward and backward migrating, late Cretaceous to Recent proforeland basin, which has evolved as an integral part of the Zagros orogen. This last group consists of three megasequences (IX, X, and XI) with distinctive lateral and vertical facies variations, which reflect specific tectonic events. Megasequence IX comprises uppermost Turonian to middle Maastrichtian prograding and retrograding siliciclastic and carbonate deposits, whose accumulations reflect emplacement (“obduction”) of ophiolite slivers and subsequent collisional events in the Zagros orogen. Megasequence X consists of uppermost Maastrichtian to upper Eocene siliciclastic and carbonate rocks, which deposited first progradationally in front of the Zagros orogenic wedge with reduced contractional tectonic activity, and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen. Megasequence XI consists of Oligocene and lower Miocene carbonate strata deposited retrogradationally shortly after a period of intensified late Eocene thrust faulting in the deformational wedge, and an overlying succession of upward-coarsening, northeasterly-derived siliciclastic deposits of lower Miocene to Recent age which are composed of erosional byproducts of the southwest-vergent Zagros thrust sheets.

1,168 citations

Book
01 Sep 2008
TL;DR: For a detailed discussion of the international divisions of geologic time, see as discussed by the authors, where the authors present the standard colors for the international division of geology time scales in detail.
Abstract: Introduction Planetary time scale Precambrian period Cambrian period Ordovician period Silurian period Devonian period Carboniferous period Permian period Triassic period Jurassic period Cretaceous period Paleogene period Neogene period Quaternary period Appendix Standard colors of the international divisions of geologic time References Index

1,155 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023255
2022617
2021302
2020270
2019260
2018295