scispace - formally typeset
Search or ask a question
Journal ArticleDOI

High-precision U–Pb zircon age from the Anfiteatro de Ticó Formation: Implications for the timing of the early angiosperm diversification in Patagonia

TL;DR: The Baquero Group is one of the most relevant units regarding the study of the early diversification of angiosperms in South America and has been recently dated at 118.23 ± 0.09 ǫ for a tuff interlayered with fossiliferous rocks of the Anfiteatro de Tico Formation as mentioned in this paper.
About: This article is published in Journal of South American Earth Sciences.The article was published on 2013-12-01. It has received 42 citations till now. The article focuses on the topics: Aptian.
Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, structural, 2D and 3D seismic data at the San Bernardo FTB and the adjacent Rio Mayo Basin were analyzed to unravel the different evolutionary stages of the Chubut Group Basin.

86 citations

Journal ArticleDOI
TL;DR: Gonzalez et al. as mentioned in this paper presented a study of the relationship between geology and ecology, and proposed a method for the extraction of geologic features from the ground truth, using the Facultad de Ciencias Exactas y Naturales.

86 citations

Journal ArticleDOI
TL;DR: This article studied the detrital and volcanic zircon U-Pb geochronology from coarse-grained deposits represented by the Rio Belgrano and Rio Tarde formations at the northern end of the Austral or Magallanes basin.

64 citations

Journal ArticleDOI
TL;DR: In this paper, the authors synthesize the tectonomagmatic evolution of the Andes between 35°30′S to 48°S with the aim to spotlight early contractional phases on Andean orogenic building and to analyze their potential driving processes.

57 citations

Journal ArticleDOI
TL;DR: The Andes in northern Patagonia are mainly formed by Mesozoic magmatic units: the mostly Jurassic and Cretaceous North Patagonian Batholith and volcanism of the Jurassic Lago La Plata (Ibanez) Formation as well as the mid-Cretaceous Divisadero Group.
Abstract: The Andes in northern Patagonia are mainly formed by Mesozoic magmatic units: the mostly Jurassic–Cretaceous North Patagonian Batholith and volcanism of the Jurassic Lago La Plata (Ibanez) Formation as well as the mid-Cretaceous Divisadero Group. These rocks represent the development of a magmatic belt through Jurassic–mid-Cretaceous time, during a switch of the tectonic regime from extension to compression. To study arc evolution during this transition, we carried out fieldwork and geochemical sampling at c. 43°S, clarifying structural relationships and characterizing the magmatic sources. Multi-element diagrams for both volcanic units suggest a slab-derived signature, whereas isotopic ratios (Sr–Nd–Pb) indicate parental melts sourced from the subduction-modified asthenospheric mantle interacting with crustal sources during their emplacement. An angular unconformity is identified between the synextensional Jurassic volcanic rocks and Lower Cretaceous sedimentary rocks beneath the mid-Cretaceous sequences. Although this deformational event was simultaneous with generalized overriding plate compression, geochemical ratios indicate an immature Aptian–Albian arc with no associated crustal thickening. Late Jurassic to mid-Cretaceous arc settlement after a trenchward retraction of magmatism from the foreland between c. 41 and 45°S, with an associated increase in slab dip angle, may have provoked crustal softening facilitating the subsequent initial fold–thrust belt growth. Supplementary material: Petrographic descriptions and geochemical–isotopic data are available at https://doi.org/10.6084/m9.figshare.c.3677974

50 citations

References
More filters
Journal ArticleDOI
TL;DR: In this paper, a two-stage model for terrestrial lead isotope evolution is proposed, which permits the age of the earth to be that of the meteorite system and also yields good model ages for samples of all ages.

8,218 citations

Journal ArticleDOI
TL;DR: New determinations of the half-lives of half-life values of $ −235 and −238 have been made improved techniques have allowed the halflife values to be measured with greater accuracy than has been heretofore achieved as discussed by the authors.
Abstract: New determinations of the half-lives of $^{235}\mathrm{U}$ and $^{238}\mathrm{U}$ have been made Improved techniques have allowed the half-life values to be measured with greater accuracy than has been heretofore achieved Samples were prepared by molecular plating and counted in a intermediate-geometry $\ensuremath{\alpha}$-proportional counter with an extremely flat pulse-height plateau The small amount of residual nonplated uranium was counted in a $2\ensuremath{\pi}$ counter Energy analysis with a silicon-junction detector was used to measure the presence of "foreign" activities For $^{235}\mathrm{U}$, the measured specific activity was (47981\ifmmode\pm\else\textpm\fi{}33) (dis/min)/(mg $^{235}\mathrm{U}$), corresponding to a half-life of (70381\ifmmode\pm\else\textpm\fi{}00048) \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ yr For $^{238}\mathrm{U}$, the specific activity was measured as (74619\ifmmode\pm\else\textpm\fi{}041) (dis/min)/(mg $^{238}\mathrm{U}$), corresponding to a half-life of (44683\ifmmode\pm\else\textpm\fi{}00024) \ifmmode\times\else\texttimes\fi{} ${10}^{9}$ yr Errors quoted are statistical (standard error of the mean), based upon the observed scatter of the data This scatter exceeds that expected from counting statistics alone We believe that systematic errors, if present, will no more than double the quoted errors

2,543 citations

Journal ArticleDOI
TL;DR: CA-TIMS as discussed by the authors uses high-temperature treatment to anneal zircon lattice radiation damage from natural alpha, alpha recoil, and spontaneous fission processes; this annealing eliminates elemental and isotopic leaching effects that have limited earlier efforts at chemical leaching or multi-step step-wise dissolution or partial dissolution analysis (PDA)

1,200 citations

Journal ArticleDOI
17 Sep 2004-Science
TL;DR: Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss.
Abstract: The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss. The U/Pb age of the main pulse of the extinction is 252.6 ± 0.2 million years, synchronous with the Siberian flood volcanism, and it occurred within the quoted uncertainty.

562 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive treatment of the derivation of U-Pb isotope ratios and their corresponding uncertainties from isotope dilution thermal ionization mass spectrometric measurements is presented.
Abstract: A comprehensive treatment of the derivation of U-Pb isotope ratios and their corresponding uncertainties from isotope dilution thermal ionization mass spectrometric measurements is presented. Standard parametric statistical methods of error propagation are utilized to convolve uncertainties associated with instrumental mass fractionation, tracer subtraction, blank Pb and U subtraction, and initial common Pb correction. Derivations include errors and error correlations for total sample U/Pb and Pb isotope ratios (including radiogenic and initial common Pb) for two- and three-dimensional isochron calculations, radiogenic U/Pb and Pb isotope ratios for concordia and radiogenic model age calculations, and the propagation of model age errors from radiogenic isotope ratios.

420 citations