The Experts below are selected from a list of 75 Experts worldwide ranked by ideXlab platform
Charles L Angevine - One of the best experts on this subject based on the ideXlab platform.
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is the middle cretaceous pulse of rapid Sea Floor Spreading real or necessary
Geology, 1996Co-Authors: Paul L Heller, Don L Anderson, Charles L AngevineAbstract:It is commonly accepted that the major control on long-term eustasy is variation in Sea-Floor Spreading rate. The middle Cretaceous Sea-level highstand, in particular, has been correlated with a postulated pulse of rapid Spreading in the Pacific basin. This inferred event took place during the Cretaceous normal superchron (CNS) and has also been used as evidence for the existence of superplumes from the deep mantle, giving a causative link between core-mantle interactions and the record of Sea-level change. There are reasons, however, to question the foundation upon which this linkage is based. Recent studies of marine geochemistry show no evidence for large hydrothermal fluxes during middle Cretaceous time that require major increases in oceanic Spreading rates. Plate reorganizations in the Pacific during the CNS show evidence of ridge jumps, indicating that more of the Sea Floor of this age may be preserved than has been presumed. Improvements in the Mesozoic time scale indicate that the CNS was longer than previously assumed, reducing the need for rapid Spreading rates in the Pacific basin. Middle Cretaceous rapid plate generation rates are not needed to explain the history of Sea-level change. Long-term eustasy can easily be accounted for by supercontinent breakup, variations in the distribution of crust consumed at subduction zones, and other effects. Because the inferred pulse of Spreading was, in part, used to argue for the existence of a superplume, the basis for this hypothesis is diminished. The phenomena attributed to deep mantle plumes can be accounted for by plate tectonic forces and plate reorganization. Hence, we question the basis and need for the Cretaceous pulse of rapid Sea-Floor Spreading.
Trond H Torsvik - One of the best experts on this subject based on the ideXlab platform.
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north atlantic Sea Floor Spreading rates implications for the tertiary development of inversion structures of the norwegian greenland Sea
Journal of the Geological Society, 2002Co-Authors: Jon Mosar, Gavin Lewis, Trond H TorsvikAbstract:The Tertiary development of the Norwegian continental margin was dominated by the opening of the Arctic–North Atlantic Ocean. The correct identification of magnetic anomalies and their ages and the analysis of Spreading rates during the formation of this ocean are important in understanding the development of the region and specifically the history of its passive margins. Three ocean domains, the AEgir, Reykjanes and Mohns regions, were investigated in an effort to understand the lateral changes in structural development of the passive margin after continental break-up. Spreading rates generally slowed down from 2 cm a −1 after Early Eocene initiation of Sea-Floor Spreading, to values around 0.5 cm a −1 in Oligocene time. An increase in Spreading rates to around 1 cm a −1 coincided with the positioning of the Iceland hotspot under the North Atlantic mid-ocean ridge. At the same time, the European plate changed its absolute plate motion from a north-directed drift to a motion more towards the east. The location of inversion structures in the Voring and Faeroes Basin rather than in the More Basin is related to differences in Spreading rates. The Mohns and the Reykjanes Ridges produced more ocean Floor than the AEgir–Kolbeinsey Ridges. Asymmetric ocean-Floor formation in the AEgir Ridge led to differential stress at the base of the lithosphere, which probably explains the absence of inversion features in the More Basin (less mantle drag). Furthermore, upper plate margins such as the Voring Basin and possibly the Faeroe Basin have a lower compressional strength than lower plate margins such as the More Basin, and therefore preferentially developed inversion structures. Along the transform boundaries separating the domains, additional stress probably built up along extension of the transform zones into the extended continental crust. This additional stress probably also assisted initiation of the inversion structures in the Voring Basin and the Faeroes area. The amplification of the inversion structures in the Voring Basin and the Faeroes Basin was subsequently caused by a variety of processes related to sedimentation and uplift–erosion.
Paul L Heller - One of the best experts on this subject based on the ideXlab platform.
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is the middle cretaceous pulse of rapid Sea Floor Spreading real or necessary
Geology, 1996Co-Authors: Paul L Heller, Don L Anderson, Charles L AngevineAbstract:It is commonly accepted that the major control on long-term eustasy is variation in Sea-Floor Spreading rate. The middle Cretaceous Sea-level highstand, in particular, has been correlated with a postulated pulse of rapid Spreading in the Pacific basin. This inferred event took place during the Cretaceous normal superchron (CNS) and has also been used as evidence for the existence of superplumes from the deep mantle, giving a causative link between core-mantle interactions and the record of Sea-level change. There are reasons, however, to question the foundation upon which this linkage is based. Recent studies of marine geochemistry show no evidence for large hydrothermal fluxes during middle Cretaceous time that require major increases in oceanic Spreading rates. Plate reorganizations in the Pacific during the CNS show evidence of ridge jumps, indicating that more of the Sea Floor of this age may be preserved than has been presumed. Improvements in the Mesozoic time scale indicate that the CNS was longer than previously assumed, reducing the need for rapid Spreading rates in the Pacific basin. Middle Cretaceous rapid plate generation rates are not needed to explain the history of Sea-level change. Long-term eustasy can easily be accounted for by supercontinent breakup, variations in the distribution of crust consumed at subduction zones, and other effects. Because the inferred pulse of Spreading was, in part, used to argue for the existence of a superplume, the basis for this hypothesis is diminished. The phenomena attributed to deep mantle plumes can be accounted for by plate tectonic forces and plate reorganization. Hence, we question the basis and need for the Cretaceous pulse of rapid Sea-Floor Spreading.
W R Roest - One of the best experts on this subject based on the ideXlab platform.
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earliest Sea Floor Spreading magnetic anomalies in the north arabian Sea and the ocean continent transition
Geophysical Journal International, 1993Co-Authors: Peter R Miles, W R RoestAbstract:SUMMARY Magnetic and gravity data collected during a GLORIA survey of the Indus Fan provide new information on the earliest Sea-Floor Spreading history of the Arabian Sea. A negative gravity anomaly correlates with the buried Laxmi Ridge. This ridge is interpreted here to be a sliver of continental crust adjacent to the oceancontinent transition which bounds thinned, probably intruded, transitional crust to the NE. The oldest Sea-Floor Spreading anomaly is anomaly 28 (65-66 Ma), breakup occurring at the time of the Deccan Traps volcanic event. The earliest oceanic crust formed from two phases of rift propagation which accommodates the angular disparity between the E-W trending anomalies in the western Arabian Sea and the NE-SW trending western part of the Laxmi Ridge. Flow-line projection shows that the Laxmi ridge forms the conjugate structure to the northern Mascarene Plateau margin.
Daniel Bernoulli - One of the best experts on this subject based on the ideXlab platform.
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the transition from rifting to Sea Floor Spreading within a magma poor rifted margin field and isotopic constraints
Terra Nova, 2002Co-Authors: Urs Schaltegger, Laurent Desmurs, Gianreto Manatschal, Othmar Muntener, Martin Meier, Martin Frank, Daniel BernoulliAbstract:We provide new geological and isotope geochemical constraints on the evolution from continental rifting to Sea-Floor Spreading along a segment of the Jurassic Tethyan margin exposed in the Platta and Err nappes (eastern Central Alps). Field observations show that the ocean–continent transition zone is characterized by oceanward-dipping detachment faults leading to the exhumation of subcontinental mantle rocks subsequently intruded by gabbro bodies and dolerite dikes, and covered by pillow basalts and radiolarites. Zircons extracted from gabbros and albitite yield concordant U–Pb ages of 161 ± 1 Ma; their initial ɛHf (+ 14.4 to + 14.9) as well as bulk rock ɛNd values of from gabbros and basalts (+ 7.3 to + 9.5) point to a MORB-type depleted mantle source. These data suggest that the onset of magmatic activity coincides with the latest phase of mantle exhumation along low-angle detachment faults and may be controlled by upwelling asthenosphere beneath a zone of exhumed continental mantle.