A test for systematic errors in 40Ar/39Ar geochronology through comparison with U/Pb analysis of a 1.1-Ga rhyolite

Min, Kyoungwon; Mundil, Roland; Renne, Paul R.; Ludwig, K. R.

doi:10.1016/s0016-7037(99)00204-5

Cited by 811 publications

(566 citation statements)

References 61 publications

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“…Rogers et al (1993) reported a 40 Ar/ 39 Ar radioisotopic age of 227.8 ± .3 Ma from the lower portion of the formation. This age was recently revised to 231.4 Ma by Furin et al (2006) to account for re-calibration of the age standard used in the original analysis as well as the bias in the Ar/ Ar system that systematically yields ages ∼1% too young (e.g., Min et al, 2000;Mundil et al, 2006;Kuiper et al, 2008). Unpublished 40 Ar/ 39 Ar ages indicate the top of the Ischigualasto Formation is between 223 and 220 Ma (Shipman, 2004).…”

Section: Dating the Origin Of Dinosaursmentioning

confidence: 99%

The origin and early radiation of dinosaurs

Brusatte

Nesbitt

Irmis

et al. 2010

Earth-Science Reviews

240

214

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Dinosaurs were remarkably successful during the Mesozoic and one subgroup, birds, remain an important component of modern ecosystems. Although the extinction of non-avian dinosaurs at the end of the Cretaceous has been the subject of intense debate, comparatively little attention has been given to the origin and early evolution of dinosaurs during the Late Triassic and Early Jurassic, one of the most important evolutionary radiations in earth history. Our understanding of this keystone event has dramatically changed over the past 25 years, thanks to an influx of new fossil discoveries, reinterpretations of long-ignored specimens, and quantitative macroevolutionary analyses that synthesize anatomical and geological data. Here we provide an overview of the first 50 million years of dinosaur history, with a focus on the large-scale patterns that characterize the ascent of dinosaurs from a small, almost marginal group of reptiles in the Late Triassic to the preeminent terrestrial vertebrates of the Jurassic and Cretaceous. We provide both a biological and geological background for early dinosaur history. Dinosaurs are deeply nested among the archosaurian reptiles, diagnosed by only a small number of characters, and are subdivided into a number of major lineages. The first unequivocal dinosaurs are known from the late Carnian of South America, but the presence of their sister group in the Middle Triassic implies that dinosaurs possibly originated much earlier. The three major dinosaur lineages, theropods, sauropodomorphs, and ornithischians, are all known from the Triassic, when continents were joined into the supercontinent Pangaea and global climates were hot and arid. Although many researchers have long suggested that dinosaurs outcompeted other reptile groups during the Triassic, we argue that the ascent of dinosaurs was more of a matter of contingency and opportunism. Dinosaurs were overshadowed in most Late Triassic ecosystems by crocodile-line archosaurs and showed no signs of outcompeting their rivals. Instead, the rise of dinosaurs was a two-stage process, as dinosaurs expanded in taxonomic diversity, morphological disparity, and absolute faunal abundance only after the extinction of most crocodile-line reptiles and other groups.

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Section: Dating the Origin Of Dinosaursmentioning

confidence: 99%

The origin and early radiation of dinosaurs

Brusatte

Nesbitt

Irmis

et al. 2010

Earth-Science Reviews

240

214

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“…The young ages of the Coso rhyolites make their 40 Ar/ 39 Ar analysis insensitive to the interpreted age bias due to 40 K decay constant errors (i.e., Min et al 2000). The exception is the 623 ± 6 ka Devils Kitchen rhyolite that after correction is *10 ka older than measured (i.e., 613 ka).…”

Section: Discussionmentioning

confidence: 94%

“…When comparing U-Th-Pb crystal ages and 40 Ar/ 39 Ar eruption ages, it is important to consider the intercalibration bias between the two systems. This bias, mainly a product of error in the electron capture decay constant for 40 K (Min et al 2000), is small (ca. 1%) compared with the differences considered in this paper.…”

Section: Methodsmentioning

confidence: 99%

Accessory mineral U–Th–Pb ages and 40Ar/39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California

Simon

Renne

Schmitt

et al. 2009

Contrib Mineral Petrol

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We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a longlived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In B230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the *85 ka rhyolites yielded ages between *100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an *200 ka granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (B10's to 100's ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies.

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“…Our principal area of interest, within the Kula Volcanic Province, is situated in the southern half of the Neogene Selendi Basin (Figures 2,3), where the evolution of the Gediz river system reflects progressive incision into thick Miocene Basin fill sediments. Understanding the lithostratigraphy of the Basin fill and its principal structures is therefore an essential context for understanding the Quaternary river behaviour and the resulting fluvial archive.…”

Section: Pre-quaternary Stratigraphy and Neotectonics In The Selendi mentioning

confidence: 99%

“…The oldest basement rocks (Figure 2,3) underlying the basin fill are the pre-Neogene metamorphics of the Menderes Massif (predominantly gneiss, schist, quartzite and marble).…”

Section: Pre-quaternary Stratigraphy and Neotectonics In The Selendi mentioning

confidence: 99%

The Gediz River fluvial archive: A benchmark for Quaternary research in Western Anatolia

Maddy

Veldkamp

Demi̇r

et al. 2017

Quaternary Science Reviews

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Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTThe Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River Project (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) and present new data which leads to a revised stratigraphical model for the Early Pleistocene development of this fluvial system.In previous work we confirmed the preservation of eleven buried Early Pleistocene fluvial terraces of the Gediz River (designated GT11, the oldest and highest, to GT1, the youngest and lowest) which lie beneath the basalt-covered plateaux of the Kula Volcanic Province. Deciphering the information locked in this fluvial archive requires the construction of a robust geochronology. Fortunately, the Gediz archive provides ample opportunity for ageconstraint based upon age estimates derived from basaltic lava flows that repeatedly entered the palaeo-Gediz valley floors. In this paper we present, for the first time, our complete dataset of 40 Ar/ 39 Ar age estimates and associated palaeomagnetic measurements. These data, which can be directly related to the underlying fluvial deposits, provide age constraints critical to our understanding of this sequence.The new chronology establishes the onset of Quaternary volcanism at ~1320ka (MIS42). This volcanism, which is associated with GT6, confirms a pre-MIS42 age for terraces GT11-GT7. Evidence from the colluvial sequences directly overlying these early terraces suggests that they formed in response to hydrological and sediment budget changes forced by climatedriven vegetation change. The cyclic formation of terraces and their timing suggests they represent the obliquity-driven climate changes of the Early Pleistocene. By way of contrast the GT5-GT1 terrace sequence, constrained by a lava flow with an age estimate of ~1247ka, span the time-interval MIS42 -MIS38 and therefore do not match the frequency of climate change as previously suggested. The onset of volcanism breaks the simple linkage of terracing to climate-driven change. These younger terraces more likely reflect a localized terracing process triggered by base level changes forced by volcanic eruption and associated reactivation of pre-existing faults, lava dam construction, landsliding and subsequent lavadammed lake drainage.Establishing a firm stratigraphy a...

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A test for systematic errors in 40Ar/39Ar geochronology through comparison with U/Pb analysis of a 1.1-Ga rhyolite

Cited by 811 publications

References 61 publications

The origin and early radiation of dinosaurs

The origin and early radiation of dinosaurs

Accessory mineral U–Th–Pb ages and 40Ar/39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California

The Gediz River fluvial archive: A benchmark for Quaternary research in Western Anatolia

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