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230 results on '"Ramezani, Jahandar"'

1. Recommendations for the reporting and interpretation of isotope dilution U-Pb geochronological information

Author

Condon, Dan, primary, Schoene, Blair, additional, Schmitz, Mark, additional, Schaltegger, Urs, additional, Ickert, Ryan B., additional, Amelin, Yuri, additional, Augland, Lars E., additional, Chamberlain, Kevin R., additional, Coleman, Drew S., additional, Connelly, James N., additional, Corfu, Fernando, additional, Crowley, James L., additional, Davies, Joshua H.F.L., additional, Denyszyn, Steven W., additional, Eddy, Michael P., additional, Gaynor, Sean P., additional, Heaman, Larry M., additional, Huyskens, Magdalena H., additional, Kamo, Sandra, additional, Kasbohm, Jennifer, additional, Keller, C. Brenhin, additional, MacLennan, Scott A., additional, McLean, Noah M., additional, Noble, Stephen, additional, Ovtcharova, Maria, additional, Paul, André, additional, Ramezani, Jahandar, additional, Rioux, Matt, additional, Sahy, Diana, additional, Scoates, James S., additional, Szymanowski, Dawid, additional, Tapster, Simon, additional, Tichomirowa, Marion, additional, Wall, Corey J., additional, Wotzlaw, Jörn-Frederik, additional, Yang, Chuan, additional, and Yin, Qing-Zhu, additional

Published
2024
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5. Redefinition of the Global Stratotype Section and Point (GSSP) and new Standard Auxiliary Boundary Stratotype (SABS) for the base of Wuchiapingian Stage (Lopingian Series, Permian) in South China

Author

Shen, Shu-zhong, primary, Yuan, Dong-xun, additional, Zhang, Yi-chun, additional, Henderson, Charles, M., additional, Zheng, Quan-feng, additional, Zhang, Hua, additional, Zhang, Min, additional, Dai, Yu, additional, Xu, Hai-peng, additional, Wang, Wen-qian, additional, Li, Qian, additional, Wang, Yue, additional, Wang, Xiang-dong, additional, Mu, Lin, additional, Ramezani, Jahandar, additional, Erwin, Douglas H., additional, Angiolini, Lucia, additional, Zhang, Fei-fei, additional, Hou, Zhang-shuai, additional, Chen, Jun, additional, Zhang, Xi-yang, additional, Zhang, Shu-han, additional, Wu, Qiong, additional, Pan, Yong-xin, additional, Stephenson, Michael, additional, and Mei, Shi-long, additional

Published
2023
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6. U–Pb age constraints on the Carboniferous–Permian transition in continental basins of eastern equatorial Pangaea (France): implications for the depositional history and correlations across the late Variscan Belt

Author

Mercuzot, Mathilde, primary, Rossignol, Camille, additional, Bourquin, Sylvie, additional, Ramezani, Jahandar, additional, Ducassou, Céline, additional, Poujol, Marc, additional, Beccaletto, Laurent, additional, and Pellenard, Pierre, additional

Published
2023
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7. Reconnaissance basement geology and tectonics of North Zealandia

Author

Mortimer, Nick, primary, Williams, Simon, additional, Seton, Maria, additional, Calvert, Andy, additional, Waight, Tod, additional, Turnbull, Rose, additional, Nelson, Demian, additional, Palin, Mike, additional, Ramezani, Jahandar, additional, Sagar, Matthew W., additional, Tulloch, Andy, additional, Stratford, Wanda, additional, Collot, Julien, additional, and Etienne, Samuel, additional

Published
2023
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13. The Global Stratotype Section and Point (GSSP) for the base of the Capitanian Stage (Guadalupian, Middle Permian)

Author

Shen, Shu-zhong, primary, Yuan, Dong-xun, additional, Henderson, Charles M., additional, Lambert, Lance L., additional, Zhang, Yi-chun, additional, Erwin, Douglas H., additional, Ramezani, Jahandar, additional, Wang, Xiang-dong, additional, Zhang, Hua, additional, Wu, Qiong, additional, Wang, Wen-qian, additional, Hearst, Jonena M., additional, Chen, Jun, additional, Wang, Yue, additional, Qie, Wen-kun, additional, Qi, Yu-ping, additional, and Wardlaw, Bruce R., additional

Published
2022
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17. Failed rifting and fast drifting: Midcontinent Rift development, Laurentia’s rapid motion and the driver of Grenvillian orogenesis

Author

Swanson-Hysell, Nicholas L, Ramezani, Jahandar, Fairchild, Luke M, and Rose, Ian R

Subjects
Geochemistry, Geology, Geophysics
Abstract

The late Mesoproterozoic was a time of large-scale tectonic activity both in the interior and on the margins of Laurentia-most notably the development of the Midcontinent Rift and the Grenvillian orogeny. Volcanism within the North American Midcontinent Rift between ca. 1109 and 1083 Ma, as well as other contemporaneous volcanism within Laurentia, has provided an opportunity to develop extensive paleomagnetic data sets spanning this time period. These data result in an apparent polar wander path (APWP) for Laurentia that goes from a high-latitude apex known as the Logan Loop into a swath known as the Keweenawan Track. A longstanding challenge of these data was the appearance of asymmetry between relatively steep reversed polarity directions from older rift rocks and relatively shallow normal polarity directions from younger rift rocks. This asymmetry was used to support an interpretation that there were large non-dipolar components to the geomagnetic field at the time. Recent data sets support the interpretation that this directional change was progressive and therefore a result of very rapid motion of Laurentia from high to low latitudes rather than a stepwise change across non-dipolar reversals. We present high-precision U-Pb dates from Midcontinent Rift volcanics that result in an improved chronostratigraphic framework for rift volcanics and unconformities that improves correlations as well as constraints on rift development. We use these dates in volcanostratigraphic context to temporally constrain a new compilation of Midcontinent Rift paleomagnetic poles. These paleomagnetic poles include new data from the North Shore Volcanic Group, Minnesota, USA and the Osler Volcanic Group, Ontario, Canada. The U-Pb dates constrain the rate of implied plate motion more precisely than has previously been possible. We apply a novel Bayesian approach to assess the rate of implied plate motion through inverting for paleomagnetic Euler poles. If the path is to be explained by a single Euler pole these inversions reveal that motion of the continent exceeded 27 cm/yr. The path is particularly well-explained by a model wherein there is continuous true polar wander in addition to rapid plate motion that changes direction and slows ca. 1096 Ma. Laurentia's movement from high to low latitudes resulted in collisional tectonics on its leading margin which could be associated with such a change in plate motion. We propose that upwelling of the Keweenawan mantle plume was associated with an avalanche of subducted slab material and associated downwelling that drove fast plate motion. This fast plate motion was followed by the Grenvillian orogeny from ca. 1090 to 980 Ma. Prolonged collisional orogenesis could have been sustained due to this strong convective cell that therefore played an integral role in the assembly of the supercontinent Rodinia.

Published
2019

23. The end of Midcontinent Rift magmatism and the paleogeography of Laurentia

Author

Fairchild, Luke M, Swanson-Hysell, Nicholas L, Ramezani, Jahandar, Sprain, Courtney J, and Bowring, Samuel A

Subjects
Geochemistry, Geology, Geophysics
Abstract

Paleomagnetism of the North American Midcontinent Rift provides a robust paleogeographic record of Laurentia (cratonic North America) from ca. 1110 to 1070 Ma, revealing rapid equatorward motion of the continent throughout rift magmatism. Existing age and paleomagnetic constraints on the youngest rift volcanic and sedimentary rocks have been interpreted to record a slowdown of this motion as rifting waned. We present new paleomagnetic and geochronologic data from the ca. 1090-1083 Ma "late-stage" rift volcanic rocks exposed as the Lake Shore Traps (Michigan), the Schroeder-Lutsen basalts (Minnesota), and the Michipicoten Island Formation (Ontario). The paleomagnetic data allow for the development of paleomagnetic poles for the Schroeder-Lutsen basalts (187.8°E, 27.1°N; A95 = 3.0°, N = 50) and the Michipicoten Island Formation (174.7°E, 17.0°N; A95 = 4.4°, N = 23). Temporal constraints on late-stage paleomagnetic poles are provided by high-precision, 206Pb-238U zircon dates from a Lake Shore Traps andesite (1085.57 ± 0.25 Ma; 2σ internal errors), a Michipicoten Island Formation tuff (1084.35 ± 0.20 Ma) and rhyolite (1083.52 ± 0.23 Ma), and a Silver Bay aplitic dike from the Beaver Bay Complex (1091.61 ± 0.14 Ma), which is overlain by the Schroeder-Lutsen basalt flows. These Michipicoten Island Formation dates are the youngest yet obtained from Midcontinent Rift volcanic rocks and indicate that rift magmatism was active for at least 25 m.y. The addition of these late-stage paleomagnetic poles to the Laurentian apparent polar wander path suggests that rapid motion of Laurentia continued throughout the entirety of rift volcanism.

Published
2017

25. Calibrating geologic strata, dinosaurs, and other fossils at Dinosaur Provincial Park (Alberta, Canada) using a new CA-ID-TIMS U–Pb geochronology.

Author

Eberth, David A., Evans, David C., Ramezani, Jahandar, Kamo, Sandra L., Brown, Caleb M., Currie, Philip J., and Braman, Dennis R.

Subjects
PARKS, BENTONITE, GEOLOGICAL time scales, DINOSAURS, FOSSILS, CHRONOSTRATIGRAPHY
Abstract

The 100 m thick stratigraphic section exposed at Dinosaur Provincial Park (DPP; southern Alberta) contains bentonites that have been used for more than 30 years to date DPP's rocks and fossils using the K–Ar decay scheme. Limited reproducibility among different vintages of K–Ar and 40Ar/39Ar ages inhibited the development of a high-resolution chronostratigraphy. Here, we employ and further test a recently completed U–Pb geochronology and associated age-stratigraphy model to update temporal constraints on the Park's bentonites, formational contacts, and other markers. In turn, we document rock accumulation rates and calibrate ages and durations of informal megaherbivore dinosaur assemblage zones and other biozones. Weighted mean 206 Pb/238 U ages from five bentonites range from 76.718 ± 0.020 to 74.289 ± 0.014 Ma (2σ internal uncertainties) through an interval of 88.75 m, indicating a duration of ∼2.43 Myr and an overall rock accumulation rate of 3.65 ± 0.04 cm/ka. An increase in rate above the Oldman–Dinosaur Park formational contact conforms to a regionally expressed pattern of increased accommodation at ∼76.3 Ma across Alberta and Montana. Palynological biozone data suggest a condensed section/hiatus in the uppermost portion of the Oldman Formation. Dinosaur assemblage zones exhibit durations of ∼700–600 kyr and are significantly shorter than those in the overlying Horseshoe Canyon Formation. A decreased rate in dinosaur assemblage turnovers in the last eight million years of the Mesozoic in western Canada may be explained by withdrawal of the Western Interior Seaway and the expansion of ecologically homogenous lowlands in its wake. [ABSTRACT FROM AUTHOR]

Published
2023
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26. When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin, South Africa

Author

Day, Michael O, Ramezani, Jahandar, Bowring, Samuel A, Sadler, Peter M, Erwin, Douglas H, Abdala, Fernando, and Rubidge, Bruce S

Subjects
Life Below Water, Animals, Biodiversity, Extinction, Biological, Fossils, Reptiles, South Africa, biostratigraphy, Permian, Karoo, tetrapod extinction, U-Pb geochronology, Guadalupian, U–Pb geochronology, Biological Sciences, Agricultural and Veterinary Sciences, Medical and Health Sciences
Abstract

A mid-Permian (Guadalupian epoch) extinction event at approximately 260 Ma has been mooted for two decades. This is based primarily on invertebrate biostratigraphy of Guadalupian-Lopingian marine carbonate platforms in southern China, which are temporally constrained by correlation to the associated Emeishan Large Igneous Province (LIP). Despite attempts to identify a similar biodiversity crisis in the terrestrial realm, the low resolution of mid-Permian tetrapod biostratigraphy and a lack of robust geochronological constraints have until now hampered both the correlation and quantification of terrestrial extinctions. Here we present an extensive compilation of tetrapod-stratigraphic data analysed by the constrained optimization (CONOP) algorithm that reveals a significant extinction event among tetrapods within the lower Beaufort Group of the Karoo Basin, South Africa, in the latest Capitanian. Our fossil dataset reveals a 74-80% loss of generic richness between the upper Tapinocephalus Assemblage Zone (AZ) and the mid-Pristerognathus AZ that is temporally constrained by a U-Pb zircon date (CA-TIMS method) of 260.259 ± 0.081 Ma from a tuff near the top of the Tapinocephalus AZ. This strengthens the biochronology of the Permian Beaufort Group and supports the existence of a mid-Permian mass extinction event on land near the end of the Guadalupian. Our results permit a temporal association between the extinction of dinocephalian therapsids and the LIP volcanism at Emeishan, as well as the marine end-Guadalupian extinctions.

Published
2015

28. High-precision U-Pb age constraints on the Permian floral turnovers, paleoclimate change, and tectonics of the North China block

Author

Wu, Qiong, primary, Ramezani, Jahandar, additional, Zhang, Hua, additional, Wang, Jun, additional, Zeng, Fangui, additional, Zhang, Yichun, additional, Liu, Feng, additional, Chen, Jun, additional, Cai, Yaofeng, additional, Hou, Zhangshuai, additional, Liu, Chao, additional, Yang, Wan, additional, Henderson, Charles M., additional, and Shen, Shu-zhong, additional

Published
2021
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30. Progress, problems and prospects: An overview of the Guadalupian Series of South China and North America

Author

Shen, Shu-zhong, primary, Yuan, Dong-xun, additional, Henderson, Charles M., additional, Wu, Qiong, additional, Zhang, Yi-chun, additional, Zhang, Hua, additional, Mu, Lin, additional, Ramezani, Jahandar, additional, Wang, Xiang-dong, additional, Lambert, Lance L., additional, Erwin, Douglas H., additional, Hearst, Jonena M., additional, Xiang, Lei, additional, Chen, Bo, additional, Fan, Jun-xuan, additional, Wang, Yue, additional, Wang, Wen-qian, additional, Qi, Yu-ping, additional, Chen, Jun, additional, Qie, Wen-kun, additional, and Wang, Tian-tian, additional

Published
2020
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33. Crustal eduction and slab-failure magmatism in an Orosirian (2.05–1.80 Ga) postcollisional cratonic foredeep: geochronology of Seton volcanics and Compton laccoliths, Tu Cho (Great Slave Lake), NWT, Canada.

Author

Hoffman, Paul F., Macdonald, Francis A., Bowring, Samuel A., Ramezani, Jahandar, Buchwaldt, Robert, Hildebrand, Robert S., and Whalen, Joseph B.

Subjects
VOLCANOLOGY, GEOLOGICAL time scales, THRUST belts (Geology), MAGMATISM, OROGENIC belts, VOLCANISM, LAKES
Abstract

Three Orosirian basins and associated foreland thrust-fold belts are preserved on the margins of the Slave craton. All three are related to orogenic belts where oceans opened and later closed, uniting new crustal partners. The Great Slave basin differs from the Kilhigok and Coronation basins in ways that have defied explanation. It lacks a passive margin sequence and hosts two discrete igneous suites, separated by large-scale thrusting, that occurred well after the adjacent paleocean had closed. Here we report U–Pb zircon geochronology by chemical abrasion isotope dilution thermal ionization mass spectrometry for a member of each suite to constrain the age and origin of postcollisional thrusting. A widespread pulse of mainly phreatic alkaline volcanism, coeval with renewed foredeep flexure, occurred at 1889.0 ± 0.7 Ma (2σ internal error). A quartz-monzodiorite body, one of a belt-parallel chain of laccoliths that postdate thrusting, was emplaced at 1866.9 ± 0.9 Ma. These ages bracket renewed foredeep sedimentation and thrusting that telescoped major facies zones and was rooted within the basin. The older age is 70 and 30−60 Myr younger than collision in the Thelon and Taltson orogens, respectively. We attribute postcollisional thrusting and foredeep subsidence to "eduction"—the upward and outward ejection of partly subducted crust—and postulate that the top of the ejected wedge was a normal-sense detachment fault projecting beneath the Nonacho basin. We infer that eduction was triggered by slab failure, producing alkaline volcanism, and ended with delamination and laccolith emplacement. Eduction was facilitated by tradewind-driven erosion. Delamination was enabled by crustal transfer to the educted wedge, reducing footwall buoyancy. Slab failure and/or delamination removed the passive margin. [ABSTRACT FROM AUTHOR]

Published
2023
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34. The Late Triassic Ischigualasto Formation at Cerro Las Lajas (La Rioja, Argentina): fossil tetrapods, high-resolution chronostratigraphy, and faunal correlations

Author

Desojo, Julia B., primary, Fiorelli, Lucas E., additional, Ezcurra, Martín D., additional, Martinelli, Agustín G., additional, Ramezani, Jahandar, additional, Da Rosa, Átila. A. S., additional, von Baczko, M. Belén, additional, Trotteyn, M. Jimena, additional, Montefeltro, Felipe C., additional, Ezpeleta, Miguel, additional, and Langer, Max C., additional

Published
2020
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36. Paleoenvironments, taphonomy, and stable isotopic content of the terrestrial, fossil-vertebrate–bearing sequence of the El Disecado Member, El Gallo Formation, Upper Cretaceous, Baja California, México

Author

Fastovsky, David E., primary, Montellano-Ballesteros, Marisol, additional, Fricke, Henry C., additional, Ramezani, Jahandar, additional, Tsukui, Kaori, additional, Wilson, Gregory P., additional, Hall, Paul, additional, Hernandez-Rivera, Rene, additional, and Alvarez, Geraldo, additional

Published
2020
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39. Reevaluating the evidence for a Hadean-Eoarchean dynamo

Author

Borlina, Cauê S., primary, Weiss, Benjamin P., additional, Lima, Eduardo A., additional, Tang, Fengzai, additional, Taylor, Richard J. M., additional, Einsle, Joshua F., additional, Harrison, Richard J., additional, Fu, Roger R., additional, Bell, Elizabeth A., additional, Alexander, Ellen W., additional, Kirkpatrick, Heather M., additional, Wielicki, Matthew M., additional, Harrison, T. Mark, additional, Ramezani, Jahandar, additional, and Maloof, Adam C., additional

Published
2020
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42. SA01 – A Proposed Zircon Reference Material for Microbeam U‐Pb Age and Hf‐O Isotopic Determination

Author

Huang, Chao, primary, Wang, Hao, additional, Yang, Jin‐Hui, additional, Ramezani, Jahandar, additional, Yang, Chuan, additional, Zhang, Shao‐Bing, additional, Yang, Yue‐Heng, additional, Xia, Xiao‐Ping, additional, Feng, Lian‐Jun, additional, Lin, Jie, additional, Wang, Tian‐Tian, additional, Ma, Qian, additional, He, Huai‐Yu, additional, Xie, Lie‐Wen, additional, and Wu, Shi‐Tou, additional

Published
2019
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50. Multiple Proxy Estimates of Atmospheric CO2 From an Early Paleocene Rainforest

Author

Kowalczyk, Jennifer B., primary, Royer, Dana L., additional, Miller, Ian M., additional, Anderson, Clive W., additional, Beerling, David J., additional, Franks, Peter J., additional, Grein, Michaela, additional, Konrad, Wilfried, additional, Roth‐Nebelsick, Anita, additional, Bowring, Samuel A., additional, Johnson, Kirk R., additional, and Ramezani, Jahandar, additional

Published
2018
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