The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Jeong Hwan Kim - One of the best experts on this subject based on the ideXlab platform.
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Structural characteristics of the central Ogcheon Belt, South Korea: orogen-parallel tectonic transport model
Journal of Asian Earth Sciences, 2003Co-Authors: You Hong Kihm, Jeong Hwan KimAbstract:Abstract The rocks in the central Ogcheon Belt, South Korea, underwent three deformational phases (D1, D2 and D3) during the Mesozoic Era. In the study area, NW- and NE-trending geological structures such as thrusts and folds are juxtaposed. The NW- and NE-trending folds deform isoclinal folds (F1) with axial planar slaty cleavage (S1), and have axial planar crenulation cleavage. All of these folds are overprinted by brittle faults (D3). It is inferred from field data that the NW- and NE-trending structures are products of a single deformational phase (D2). A very large-scale inclined NE-vergent isoclinal fold (F1) produced an irregular boundary of Precambrian basement and a basement promontory, which acted as a structural obstacle against subsequent deformational phases. During the E-vergent phase (D2), deformation partitioning occurred due to the irregular block boundary, and orogen-parallel and -orthogonal structures were produced. The D3 phase is recognized as large-scale E–W trending structures including folds and faults. Thus, the structural evolution of the central Ogcheon Belt is related to the clockwise rotation of the maximum compressive stress axis from NE–SW to N–S during the Mesozoic Era. This study shows that the shape of colliding boundary is a very important factor in controlling the structural pattern and evolution in the study area.
Daniel J. Field - One of the best experts on this subject based on the ideXlab platform.
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The changing face of birds from the age of the dinosaurs
Nature, 2020Co-Authors: Daniel J. FieldAbstract:A fossil from the Mesozoic Era illuminates the evolution of bird skulls. The fossil record traces the origin of the modern bird skull as birds evolved from their dinosaurian ancestors. Now the discovery of a bizarre fossil reveals a surprising diversion during this process of facial transformation.
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late cretaceous neornithine from europe illuminates the origins of crown birds
Nature, 2020Co-Authors: Daniel J. Field, Juan Benito, A A Chen, John Wm Jagt, Daniel T KsepkaAbstract:Our understanding of the earliest stages of crown bird evolution is hindered by an exceedingly sparse avian fossil record from the Mesozoic Era. The most ancient phylogenetic divergences among crown birds are known to have occurred in the Cretaceous period1–3, but stem-lineage representatives of the deepest subclades of crown birds—Palaeognathae (ostriches and kin), GalloansErae (landfowl and waterfowl) and Neoaves (all other extant birds)—are unknown from the Mesozoic Era. As a result, key questions related to the ecology4,5, biogeography3,6,7 and divergence times1,8–10 of ancestral crown birds remain unanswered. Here we report a new Mesozoic fossil that occupies a position close to the last common ancestor of GalloansErae and fills a key phylogenetic gap in the early evolutionary history of crown birds10,11. Asteriornis maastrichtensis, gen. et sp. nov., from the Maastrichtian age of Belgium (66.8–66.7 million years ago), is represented by a nearly complete, three-dimensionally preserved skull and associated postcranial elements. The fossil represents one of the only well-supported crown birds from the Mesozoic Era12, and is the first Mesozoic crown bird with well-represented cranial remains. Asteriornis maastrichtensis exhibits a previously undocumented combination of galliform (landfowl)-like and anseriform (waterfowl)-like features, and its presence alongside a previously reported Ichthyornis-like taxon from the same locality13 provides direct evidence of the co-occurrence of crown birds and avialan stem birds. Its occurrence in the Northern Hemisphere challenges biogeographical hypotheses of a Gondwanan origin of crown birds3, and its relatively small size and possible littoral ecology may corroborate proposed ecological filters4,5,9 that influenced the persistence of crown birds through the end-Cretaceous mass extinction. A newly discovered fossil from the Cretaceous of Belgium is the oldest modern bird ever found, showing a unique combination of features and suggesting attributes shared by avian survivors of the end-Cretaceous extinction.
You Hong Kihm - One of the best experts on this subject based on the ideXlab platform.
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Structural characteristics of the central Ogcheon Belt, South Korea: orogen-parallel tectonic transport model
Journal of Asian Earth Sciences, 2003Co-Authors: You Hong Kihm, Jeong Hwan KimAbstract:Abstract The rocks in the central Ogcheon Belt, South Korea, underwent three deformational phases (D1, D2 and D3) during the Mesozoic Era. In the study area, NW- and NE-trending geological structures such as thrusts and folds are juxtaposed. The NW- and NE-trending folds deform isoclinal folds (F1) with axial planar slaty cleavage (S1), and have axial planar crenulation cleavage. All of these folds are overprinted by brittle faults (D3). It is inferred from field data that the NW- and NE-trending structures are products of a single deformational phase (D2). A very large-scale inclined NE-vergent isoclinal fold (F1) produced an irregular boundary of Precambrian basement and a basement promontory, which acted as a structural obstacle against subsequent deformational phases. During the E-vergent phase (D2), deformation partitioning occurred due to the irregular block boundary, and orogen-parallel and -orthogonal structures were produced. The D3 phase is recognized as large-scale E–W trending structures including folds and faults. Thus, the structural evolution of the central Ogcheon Belt is related to the clockwise rotation of the maximum compressive stress axis from NE–SW to N–S during the Mesozoic Era. This study shows that the shape of colliding boundary is a very important factor in controlling the structural pattern and evolution in the study area.
Guo Hua - One of the best experts on this subject based on the ideXlab platform.
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Tectonic evolutionary characteristics of Yanshanian intraplate orogenic belt in Mesozoic Era
Uranium Geology, 2003Co-Authors: Guo HuaAbstract:Since Late Triassic the Yanshanian region has enter a development stage of intraplate orogeny,which is characterized by multi stage and episotic evolution and may be divided into 3 phases,i.e.the pre orogenic phase (T 3),the main orogenic phase (J 1～J 3),and the post orogenic phase (K 1).With respect to the tectonic deformation,the fundamental tectonic framework represents a huge tectonic wedge composed of a system of overthrust nappes extending in piggyback propogation leading to a crust shortening of about 44 1%.The dynamometamorphism was characterized by high pressure dynamometamorphic rocks (eclogite,high pressure granulite) were formed from the conversion of felsic rocks of middle upper crust at the hanging wall of overthrusts where tectonic stress was concentrated.Magmatic rocks in the region are of calc alkaline series and an intermediate acidic association.Rock types and their REE distribution pattern,as well as the related tectonic intensity are characteristic and typical.The formation of the orogenic belt was associated by three stages of synorogenic molasses,i.e.the Xingshikou molasses (T 3x),the Houcheng molasse (J 3h) and the Qingshila molasses (K 1q) reflecting the episodic evolution and the heterogeneity of tectonic intensity during different orogenies.
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Mesozoic OVERTHRUST-NAPPE TECTONIC SYSTEM IN THE DABIESHAN OROGENIC BELT
2002Co-Authors: Guo HuaAbstract:The Dabie shan orogen represents a contractional belt of intracontinent in Mesozoic Era and its fundamental tectonic system is characterized by a tectonic wedge towards south, which consists of a overthrust nappe structrue. The propagation style of the four main overthrust faults, which constitute overthrust system, is backward compared to the root zone from south to north. For the sake of the structural deformation of the rock system of the basement and sedimentary covers the large scale thin skinned structure formed, and the shortening of crust amounts to 48 6 percent. The overthrust nappe tectonic system in the Dabieshan orogenic belt accomplished from later Lower Jurassic to Early Cretaceous (J 3 1-K 1).
Yang Lei - One of the best experts on this subject based on the ideXlab platform.
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Long-term electromagnetic core–mantle coupling and the Earth’s rotation accelEration in the Mesozoic Era☆
Russian Geology and Geophysics, 2012Co-Authors: Weijia Zhang, Yuanlin Sun, Neil P. Kelley, Yang LeiAbstract:Abstract Growth lines in the minEralized tissues of living and fossil organisms often exhibit regular patterns that record daily, monthly, or annual cycles. Growth laminations in fossil corals and other marine invertebrates indicate long-term decelEration of the Earth’s rotation, probably largely due to tidal friction, resulting in a decline in the number of days per year over the Earth’s history. Fossils suggest the rate of decline has not been uniform, with the trend between the late Carboniferous and Cretaceous in particular departing from preceding and subsequent periods. However, insufficient data have obscured the nature and cause of the apparent halt in despinning within this time interval. Here we present new fossil geochronometer data that reveal a sustained accelEration in the Earth’s rotation in the early Mesozoic Era, lasting about 90 million years and producing a decrease in the length of day (LOD) at an avErage rate of about 3 ms/cy. The coincidence of this accelEration with certain geophysical events including the final assembly of Pangaea and a change in the intensity and stability of the geomagnetic field strongly suggests that its cause is rooted in the deep interior of the Earth. A similar explanation has been proposed for observed decadal variations in the Earth’s rotation. Our results suggest large-scale linkage of rotational variation, tectonics, and the geomagnetic field to core–mantle boundary (CMB) dynamics. Furthermore the newly identified accelEration in the Earth’s rotation which began at the end of the Paleozoic, and the geophysical factors that are associated with it, can ultimately bear on the causal mechanisms behind the Permo-Triassic mass extinction.
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long term electromagnetic core mantle coupling and the earth s rotation accelEration in the Mesozoic Era
Russian Geology and Geophysics, 2012Co-Authors: Weijia Zhang, Yuanlin Sun, Neil P. Kelley, Yang LeiAbstract:Abstract Growth lines in the minEralized tissues of living and fossil organisms often exhibit regular patterns that record daily, monthly, or annual cycles. Growth laminations in fossil corals and other marine invertebrates indicate long-term decelEration of the Earth’s rotation, probably largely due to tidal friction, resulting in a decline in the number of days per year over the Earth’s history. Fossils suggest the rate of decline has not been uniform, with the trend between the late Carboniferous and Cretaceous in particular departing from preceding and subsequent periods. However, insufficient data have obscured the nature and cause of the apparent halt in despinning within this time interval. Here we present new fossil geochronometer data that reveal a sustained accelEration in the Earth’s rotation in the early Mesozoic Era, lasting about 90 million years and producing a decrease in the length of day (LOD) at an avErage rate of about 3 ms/cy. The coincidence of this accelEration with certain geophysical events including the final assembly of Pangaea and a change in the intensity and stability of the geomagnetic field strongly suggests that its cause is rooted in the deep interior of the Earth. A similar explanation has been proposed for observed decadal variations in the Earth’s rotation. Our results suggest large-scale linkage of rotational variation, tectonics, and the geomagnetic field to core–mantle boundary (CMB) dynamics. Furthermore the newly identified accelEration in the Earth’s rotation which began at the end of the Paleozoic, and the geophysical factors that are associated with it, can ultimately bear on the causal mechanisms behind the Permo-Triassic mass extinction.