Refinements of the European Mammal Biochronology from the Magnetic Polarity Record of the Plio–Pleistocene Zújar Section, Guadix-Baza Basin, SE Spain

1999 ◽  
Vol 51 (1) ◽  
pp. 94-103 ◽  
Author(s):  
Oriol Oms ◽  
Jaume Dinarès-Turell ◽  
Jordi Agustı́ ◽  
Josep M. Parés
Keyword(s):  
Time Scale ◽  
Magnetic Polarity ◽  
Time Constraints ◽  
Se Spain ◽  
Lowermost Part ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale ◽  
Early Late ◽  
New Time

AbstractThe magnetobiostratigraphy study of the 130-m-thick Zújar section (Negratı́n clays unit, Guadix-Baza Basin, Spain) provides a remarkable opportunity to improve the correlation of European mammal biostratigraphy to the Geomagnetic Polarity Time Scale. The occurrence of 12 well-defined magnetozones and four paleontological sites with diagnostic faunas ranging from the MN 15 biozone (Ruscinian) to the MN 17 biozone (Villanyian), leads to an unambiguous correlation to chrons spanning from the Gilbert to the Matuyama epochs. This provides two new time constraints: (1) the boundary between MN 15 (Ruscinian) and MN 16 (Villanyian) biozones is recorded between chron C2An.3n and the base of chron C2An.2n and (2) the boundary between the upper and lower MN 16 subzones (Villanyian) is located between chron C2An.2n and the base of chron C2An.1n. The correlation between the Ruscinian–Villanyian boundary and the 3.3-myr-B.P. cooling event seems to be confirmed, while the early/late Villanyian boundary could be tentatively correlated to the glacial event at 2.6 myr B.P. Furthermore, MN 15 faunas are found in the lowermost part of chron C2Ar, which is in agreement with and reinforces the emplacement of the MN 14–MN 15 Ruscinian zones boundary at the reversal from chron 3n.1n to chron C2Ar.

Accuracy and precision of the late Eocene–early Oligocene geomagnetic polarity time scale

2019 ◽  
Vol 132 (1-2) ◽  
pp. 373-388 ◽  
Author(s):  
Diana Sahy ◽  
Joe Hiess ◽  
Anne U. Fischer ◽  
Daniel J. Condon ◽  
Dennis O. Terry ◽  
...  
Keyword(s):  
Time Scale ◽  
Late Eocene ◽  
Magnetic Polarity ◽  
White River ◽  
Early Oligocene ◽  
White River Group ◽  
Astronomical Tuning ◽  
Normal Polarity ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale

AbstractAn accurate and precise geomagnetic polarity time scale is crucial to the development of a chronologic framework in which to test paleoclimatic and paleoenvironmental interpretations of marine and terrestrial records of the Eocene–Oligocene transition (EOT). The magnetic polarity patterns of relatively continuous marine and terrestrial records of the EOT have been dated using both radio-isotopic techniques and astronomical tuning, both of which can achieve a precision approaching ±30 k.y. for much of the Paleogene. However, the age of magnetic reversals between chrons C12n and C16n.2n has proved difficult to calibrate, with discrepancies of up to 250 k.y. between radio-isotopically dated and astronomically tuned marine successions, rising to 600 k.y. for comparisons with the 206Pb/238U-dated terrestrial record of the White River Group in North America. In this study, we reevaluate the magnetic polarity pattern of the Flagstaff Rim and Toadstool Geologic Park records of the White River Group (C12n–C16n.2n). Our interpretation of the Flagstaff Rim polarity record differs significantly from earlier studies, identifying a previously unreported normal polarity zone correlated to C15n, which eliminates discrepancies between the WRG and the 206Pb/238U-dated marine record of the Rupelian Global Stratotype Section and Point in the Italian Umbria-Marche basin. However, residual discrepancies persist between U-Pb–dated and astronomically tuned records of the EOT even when stratigraphic and systematic uncertainties associated with each locality and dating method are taken into account, which suggests that the uncertainties associated with astronomically tuned records of the EOT may have been underestimated.

scholarly journals Reversal in the nonlocal large-scale αΩ-dynamo

2014 ◽  
Vol 1 (2) ◽  
pp. 1715-1734
Author(s):  
L. K. Feschenko ◽  
G. M. Vodinchar
Keyword(s):  
Time Scale ◽  
Geomagnetic Field ◽  
Large Scale ◽  
Magnetic Polarity ◽  
Scale Model ◽  
Power Law Model ◽  
Large Scale Model ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale ◽  
The Magnetic Field

Abstract. Inversion of the magnetic field in a large-scale model of αΩ-dynamo with nonlocal α-effect is under the investigation. The model allows us to reproduce the main features of the geomagnetic field reversals. It was established that the polarity intervals in the model are distributed according to the power law. Model magnetic polarity time scale is fractal. Its dimension is consistent with the dimension of the real geomagnetic polarity time scale.

scholarly journals Orbitally tuned time scale and astronomical forcing in the middle Eocene to early Oligocene

2013 ◽  
Vol 9 (6) ◽  
pp. 6635-6682 ◽  
Author(s):  
T. Westerhold ◽  
U. Röhl ◽  
H. Pälike ◽  
R. Wilkens ◽  
P. A. Wilson ◽  
...  
Keyword(s):  
High Resolution ◽  
Time Scale ◽  
Middle Eocene ◽  
Late Eocene ◽  
Magnetic Polarity ◽  
Driving Mechanisms ◽  
Early Oligocene ◽  
Age Model ◽  
Geomagnetic Polarity ◽  
New Time

Abstract. Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, we construct a robust astronomically calibrated age model for the middle Eocene to early Oligocene interval (31–43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the Middle Eocene Climate Optimum and the Eocene/Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new time scale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and -U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently we applied orbital tuning of the records to the La2011 orbital solution. The resulting new time scale revises and refines the existing orbitally tuned age model and the Geomagnetic Polarity Time Scale from 31 to 43 Ma. Our newly defined absolute age for the Eocene/Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano (Italy) global stratotype section and point. Our compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during very long eccentricity cycle minima around 35.5, 38.3 and 40.1 Ma.

The quest for chron E23r at Partridge Island, Bay of Fundy, Canada: CAMP emplacement postdates the end-Triassic extinction event at the North American craton

2011 ◽  
Vol 48 (8) ◽  
pp. 1282-1291 ◽  
Author(s):  
M.H.L. Deenen ◽  
W. Krijgsman ◽  
M. Ruhl
Keyword(s):  
Magnetic Polarity ◽  
Bay Of Fundy ◽  
Long Distance ◽  
The North ◽  
Extinction Event ◽  
Maritime Canada ◽  
North American Craton ◽  
Geomagnetic Polarity ◽  
Central Atlantic ◽  
Geomagnetic Polarity Time Scale

The Partridge Island stratigraphic section at the Bay of Fundy, Maritime Canada, reveals a continental sedimentary succession with the end-Triassic mass extinction level closely followed by basalts of the Central Atlantic Magmatic Province (CAMP). New Paleomagnetic data show that a short reverse magnetic polarity chron, correlative to E23r of the Newark Geomagnetic Polarity Time Scale (GPTS), is present below the extinction event. Organic carbon isotope data and basalt geochemistry further indicate that the onset of CAMP emplacement in the Bay of Fundy was roughly synchronous with emplacement in the Newark basin, but slightly postdates the oldest CAMP volcanism in Morocco by ∼20 ka. These results confirm the potential for long-distance CAMP correlations based on geochemical trace elements, indicate substantiate provincialism of latest Triassic palynoflora, and suggest a very concise period (<<100 ka) of CAMP emplacement in the northern Atlantic region.

Devonian magnetostratigraphy: new data and old problems

2021 ◽  
Author(s):  
Annique van der Boon ◽  
Andy Biggin ◽  
Daniele Thallner ◽  
Mark Hounslow ◽  
Jerzy Nawrocki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Scale ◽  
Age Determination ◽  
Paleomagnetic Data ◽  
Show Evidence ◽  
Reversal Frequency ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale

&lt;p&gt;The global polarity time scale (GPTS) is relatively unconstrained for the Paleozoic, particularly the Devonian. Constraining the GPTS and reversal frequency for the Devonian is crucial for the understanding of the behaviour of Earth&amp;#8217;s magnetic field. Furthermore, construction of a GPTS for the Paleozoic could provide a valuable tool for age determination in other studies. However, most paleomagnetic data from the Devonian is problematic. The data are difficult to interpret and don&amp;#8217;t have a single easy to resolve (partial or full) overprint. Paleointensity studies suggest that the field was much weaker than the field of today, which could have been accompanied by many reversals (a hyperreversing field). In order to improve the geomagnetic polarity time scale in the Devonian, and quantify the number of reversals in this time, we sampled three Devonian sections in Germany, Poland and Canada. These sections show evidence that the rocks were not significantly heated, and they show little evidence for remineralisation. This minimises the chance the rocks were remagnetised after the Devonian. Our data show that even when rocks are well qualified to have reliably recorded the Devonian field, the interpretation is not straightforward. We also discuss problems with the Devonian GPTS as presented in the geologic timescale.&lt;/p&gt;

A new, early Puercan (earliest Paleocene) species ofPurgatorius(Plesiadapiformes, Primates) from Saskatchewan, Canada

2011 ◽  
Vol 85 (3) ◽  
pp. 537-548 ◽  
Author(s):  
Richard C. Fox ◽  
Craig S. Scott
Keyword(s):  
North America ◽  
North Dakota ◽  
Time Scale ◽  
Taxonomic Composition ◽  
Williston Basin ◽  
Evolutionary Diversification ◽  
Early Paleocene ◽  
Brick And Tile ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale

The early PaleocenePurgatoriusVan Valen and Sloan is the most primitive plesiadapiform primate yet discovered, mostly known from middle to late Puercan strata in Montana, deposited during the interval C29N of the geomagnetic polarity time scale. Here we describePurgatorius coracisn. sp. from the Ravenscrag Formation, at the Rav W-1 horizon, Medicine Hat Brick and Tile Quarry, southwestern Saskatchewan. This horizon occurs within C29R, makingP. coracisthe earliest known primate, while strengthening the evidence that plesiadapiforms, and hence primates, originated and underwent their initial evolutionary diversification in North America. Most North American mammalian local faunas correlating with C29R have been assigned to the Pul (earliest Puercan) interval zone, but the taxonomic composition of the mammals accompanyingP. coracisat Rav W-1 more resembles local faunas of Pu2 age. The occurrence at Rav W-1 of Pu2 aspect mammals within C29R agrees with similar occurrences at the Hiatt and PITA Flats localities in Montana and North Dakota, also possibly correlated with C29R. The evidence from these three sites, all in the Williston Basin, suggests that in some areas of the Western Interior Pu2 aspect local faunas were coeval with those of latest Pu1 age, having evolved earlier than has commonly been assumed.

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