scholarly journals Geologic context, age constraints, and sedimentology of a Pleistocene volcaniclastic succession near Mount Spurr volcano, south-central Alaska

2014 ◽  
Author(s):  
T. M. Herriott ◽  
C. J. Nye ◽  
R. D. Reger ◽  
M. A. Wartes ◽  
D. L. LePain ◽  
...  
Keyword(s):  
South Central ◽  
Mount Spurr ◽  
Age Constraints ◽  
Volcaniclastic Succession

scholarly journals Direct dating of lithic surface artifacts using luminescence

2021 ◽  
Vol 7 (23) ◽  
pp. eabb3424
Author(s):  
Luke Andrew Gliganic ◽  
Michael Christian Meyer ◽  
Jan-Hendrik May ◽  
Mark Steven Aldenderfer ◽  
Peter Tropper
Keyword(s):  
Optically Stimulated Luminescence ◽  
Rock Surface ◽  
Earth Surface ◽  
Surface Dynamics ◽  
Dynamic Nature ◽  
South Central ◽  
Central Tibetan Plateau ◽  
Human Use ◽  
Surface Scatter ◽  
Age Constraints

Archaeological surface assemblages composed of lithic scatters comprise a large proportion of the archaeological record. Dating such surface artifacts has remained inherently difficult owing to the dynamic nature of Earth-surface processes affecting these assemblages and because no satisfactory chronometric dating technique exists that can be directly applied to constrain the timing of artifact manufacture, discard, and thus human use of the landscape. Here, we present a dating approach based on optically stimulated luminescence (OSL)—OSL rock-surface burial dating—and apply it to a lithic surface scatter in Tibet. We generate OSL burial ages (age-depth profiles) for each artifact, outline the methodological complexities, and consider the artifact burial ages in the context of local-scale Earth-surface dynamics. The oldest age cluster between 5.2 and 5.5 thousand years is likely related to quarrying activities at the site and thus represents the oldest chronometric age constraints for human presence on the south-central Tibetan plateau.

U – Pb age constraints for the lithotectonic evolution of the Grenville Province along the Mauricie transect, Quebec

1997 ◽  
Vol 34 (3) ◽  
pp. 299-316 ◽  
Author(s):  
David Corrigan ◽  
Otto van Breemen
Keyword(s):  
Shear Zone ◽  
Tectonic Evolution ◽  
High Grade ◽  
Isotopic Age ◽  
Grenville Province ◽  
Zircon Age ◽  
South Central ◽  
Continental Arc ◽  
Structural Levels ◽  
Age Constraints

New U–Pb zircon and monazite ages on 12 samples from the Mauricie transect in Quebec provide constraints on the lithologic and tectonic evolution of the south-central Grenville Province. From lowest to highest structural levels, the Mékinac, Shawinigan, and Portneuf – St. Maurice domains are identified on the basis of protolith age, tectonic overprint, and plutonism. The structurally highest Portneuf – St. Maurice domain consists of remnants of an island arc (Montauban Group) that was deformed and metamorphosed before and during the intrusion of continental arc plutons (La Bostonnais complex). A tonalitic orthogneiss yielding a [Formula: see text] zircon age suggests that most of the structurally underlying Mékinac and Shawinigan domains consist of orthogneisses that may be high-grade equivalents of the La Bostonnais complex. A voluminous metasedimentary unit occurring in the Shawinigan domain (St. Boniface unit) was deposited between ca. 1.18 and 1.09 Ga, precluding any correlation with the ca. 1.45 Ga Montauban Group. Two suites of anorthosite–mangerite–charnockite–granite (AMCG) plutonic rocks are identified on the basis of field relationships and isotopic age. A megacrystic granite belonging to the "older" AMCG suite yielded a [Formula: see text] zircon age. Three plutons from the "younger" suite yielded ages of [Formula: see text], 1059 ± 2, and 1056 ± 2 Ma. The Mékinac and Shawinigan domains, excluding the younger AMCG plutons, were penetratively deformed at granulite to uppermost amphibolite facies during west-northwest-directed thrusting between 1.15 and 1.09 Ga. At ca. 1.09 Ga, a transition from contraction to oblique extension resulted in the juxtaposition of the "cold" Portneuf – St. Maurice domain with the "hot" Shawinigan domain, along the Tawachiche shear zone. Oblique extension may have been active from ca. 1.09 to 1.04 Ga and was contemporaneous with emplacement of the younger AMCG suite.

Seismicity and stress in the vicinity of Mount Spurr volcano, south central Alaska

1994 ◽  
Vol 99 (B8) ◽  
pp. 15305 ◽  
Author(s):  
Arthur D. Jolly ◽  
Robert A. Page ◽  
John A. Power
Keyword(s):  
South Central ◽  
Mount Spurr

U-Pb CA-IDTIMS geochronology of the Late Paleozoic glacial and post-glacial deposits in southern Paraná Basin

2020 ◽  
Author(s):  
Joice Cagliari ◽  
Mark D. Schmitz ◽  
Ernesto L. C. Lavina ◽  
Renata G. Netto
Keyword(s):  
Ice Age ◽  
Late Paleozoic ◽  
South American ◽  
Glacial Deposits ◽  
Glacial Sediments ◽  
South Central ◽  
Late Paleozoic Ice Age ◽  
Age Model ◽  
Eastern Border ◽  
Age Constraints

<p>The Late Paleozoic Ice Age (LPIA), one of the best known and prolonged glaciation events in Earth's history, resulted in the deposition of glacial sediments over Gondwana. The terminal deglaciation, a diachronic event starting earlier at the western and later in the eastern part of the continent, caused sea level rise and the widespread deposition of transgressive sedimentary successions. The Paraná Basin is one of these basins recording both glacial influenced (Itararé Group) and post-glacial (Guatá Group) deposits. However, the absence of Carboniferous and Permian guide fossils has motivated a chronostratigraphic approach based on plants and palynomorphs, which associated with sparse radioisotopic ages have suggested that transition between the glacial-influenced and the post-glacial succession would have occurred in the Sakmarian, early Permian (Holz et al., 2010).  These results are in conflict with recent studies that indicate LPIA glacial deposits are constrained to the Carboniferous (Cagliari et al., 2016; Griffis et al., 2019). Therefore, in this study we present new high-precision single-crystal CA-ID-TIMS U-Pb radioisotopic ages for the glacial influenced (one samples) and post-glacial (six samples) deposits in the southern Paraná Basin. Along with these new radioisotopic ages, a Bayesian age-depth model was applied to constrain the age of the LPIA demise in the southern Paraná Basin, which also represents the icehouse-greenhouse transition. The resulting age for the Rio do Sul Formation, topmost unit of the Itararé Group, is Ghzelian (Carboniferous). For the Rio Bonito Formation, basal Guatá Group, all samples are Asselian (Permian). The results reinforce that glacial-influenced deposits in the southern Paraná Basin are constrained to the Carboniferous. Based upon the depth-age model, the icehouse to greenhouse transition likely occurred in the Late Carboníferous. The integration between our results and recent published high-resolution U-Pb ages allowed us to detail the Carboniferous-Permian chronostratigraphic framework of the southern Paraná Basin.</p><p> </p><p>References:</p><p>Holz, M., França, A.B., Souza, P.A., Iannuzzi, R., Rohn, R. (2010). A stratigraphic chart of the Late Carboniferous/Permian succession of the eastern border of the Paraná Basin, Brazil, South America. Journal of South American Earth Sciences 29, 381–399.</p><p>Cagliari, J., Philipp, R.P., Buso, V.V., Netto, R.G., Hillebrand, P.K., Lopes, R.C.L., Basei, M.A.S., Faccini, U.F. (2016). Age constraints of the glaciation in the Paraná basin: Evidence from new U–Pb dates. Journal of the Geological Society 173, 871–874.</p><p>Griffis, N.P., Montañez, I.P., Mundil, R., Richey, J., Isbell, J., Fedorchuk, N., Linol, B., Iannuzzi, R., Vesely, F., Mottin, T., Rosa, E., Keller, B., Yin, Q. (2019). Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana. Geology 47, 1146–1150.</p>

Radiocarbon Age of Soil Organic Matter Fractions Buried by Tephra in Alaska

Radiocarbon ◽  
2016 ◽  
Vol 59 (2) ◽  
pp. 465-472 ◽  
Author(s):  
Alexander Cherkinsky ◽  
Kristi Wallace
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Bulk Soil ◽  
Radiocarbon Age ◽  
South Central ◽  
Eruption Frequency ◽  
Contamination Of Soils ◽  
The Difference ◽  
Organic Matter Fractions ◽  
Mount Spurr

AbstractRadiocarbon ages were determined on different fractions extracted from buried paleosols in south-central Alaska as an experiment to establish best practices for analysis of low-organic-matter paleosols. Seven samples were collected from directly beneath tephra deposits to determine the eruption frequency of Mount Spurr Volcano, Alaska. Soil development near the volcano is poor due to the high-latitude climate and frequent burial of soil surfaces by tephra. Contamination of soils by local wind-blown material is a concern. The humic acid 14C ages are consistently younger than both the bulk soil and residue after extraction ages. The difference in ages between the humic acid extract and bulk soil range from 60–1130 14C yr BP and 180–4110 14C yr BP, respectively, for residue. Previous observations from dating different soil fractions show that residue ages are typically younger than humic acid extracts presumably because they contain a fraction of younger plant material including roots. We attribute the older ages to contamination by old carbon from eolian charcoal particles. This study supports the use of accelerator mass spectrometry (AMS) 14C dating of the humic acid fraction in order to estimate the age of soil that presumably marks the age of burial and avoids suspected contamination by old carbon.

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