scholarly journals Refined magnetostratigraphic position of the Shyrokyne unit in loess sequences from Central Ukraine

2019 ◽  
Vol 28 (2) ◽  
pp. 301-312
Author(s):  
D. V. Hlavatskyi
Keyword(s):  
Transition Zone ◽  
Careful Analysis ◽  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Preliminary Results ◽  
Soil Complex ◽  
Lowermost Part ◽  
Geomagnetic Polarity

The youngest geomagnetic polarity reversal, the Matuyama–Brunhes boundary (MBB), which occurred 780 kyr ago, is a “golden spike” in the age calibration of sediment sequences. The use of palaeomagnetic method as a stratigraphic tool in the study of loess sequences from Ukraine originated some 50 years ago. One major problem in using the available data is the contradictory position of the MBB in different stratigraphic units, which affected historic evolution of thechronostratigraphic models of the Quaternary in Ukraine. The most important units in this regard are the Shyrokyne and Martonosha units, in which the MBB had been defined most often. This paper provides the careful analysis of the previous magnetostratigraphic data and new preliminary results from key loess-palaeosol sections in Central Ukraine. Shyrokyne palaeosol complex in four loesspalaeosol sections located in the Middle Dnieper and Podolia regions has been palaeomagnetically studied. It is shown that the transition zone of the Matuyama–Brunhes palaeomagnetic reversal is most likely located at the base of the soil complex. In the Vyazivok section the MBB has been found in the lowermost part of Shyrokyne palaeosol sh1. Preliminary palaeomagnetic studies of theStari Kaydaky section reveal that the MBB cannot be defined at least above sh1 subunit. Medzhybizh and Holovchyntsi sections were deposited after the Matuyama–Brunhes reversal; however, the palaeomagnetic informativeness of the part of studied strata is doubtful. Magnetostratigraphic position of the Shyrokyne unit below the MBB in some previous studies is explained by methodological reasons and inconsistent chronostratigraphic models. The paper substantiates that normal magnetic polarity zone in the Pryazovya loess and upper part of the Shyrokyne soil is not associated with the influence of secondary processes on the palaeomagnetic record.

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.

scholarly journals Reversals in the large-scale αΩ-dynamo with memory

2015 ◽  
Vol 22 (4) ◽  
pp. 361-369 ◽  
Author(s):  
L. K. Feschenko ◽  
G. M. Vodinchar
Keyword(s):  
Magnetic Field ◽  
Power Law ◽  
Geomagnetic Field ◽  
Large Scale ◽  
Magnetic Polarity ◽  
Power Law Model ◽  
The Real ◽  
Geomagnetic Polarity ◽  
With Memory ◽  
The Magnetic Field

Abstract. Inversion of the magnetic field in a model of large-scale αΩ-dynamo with α-effect with stochastic memory is under 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 timescale is fractal. Its dimension is consistent with the dimension of the real geomagnetic polarity timescale.

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.

New advances on the magnetic chronostratigraphy of cave sediments in Atapuerca Gran Dolina, Spain

2021 ◽  
Author(s):  
Josep M Pares ◽  
Mathieu Duval ◽  
Isidoro Campaña ◽  
José M. Bermúdez de Castro ◽  
Eudald Carbonell
Keyword(s):  
Magnetic Polarity ◽  
Age Dating ◽  
Middle Pleistocene ◽  
Geologic History ◽  
Cave Sediments ◽  
Normal Polarity ◽  
Gran Dolina ◽  
Geomagnetic Polarity ◽  
Quartz Grains ◽  
Numerical Dating

&lt;p&gt;Magnetostratigraphy has proven to be a powerful and versatile method as well the first line of defence for dating sediments. When properly anchored to the Geomagnetic Polarity Time Scale (GPTS), chron boundaries provide a basis for numerical dating by correlating the local magnetostratigraphy to the GPTS. A caveat and intrinsic limitation when anchoring magnetic stratigraphy to the GPTS is that we deal with essentially a binary code, a sequence of normal and reverse polarity zones. To overcome such limitation biostratigraphy or (ideally) numerical (absolute) age dating is required. Unfortunately, numerical dating of sediments is typically hampered by the lack of amenable minerals for the application of standard methods such as Ar-Ar, requiring thus the use of less conventional methods. Burial dating is possible using methods such as Electron Spin Resonance (ESR) on optically bleached quartz grains. Similar to luminescence, ESR is a paleodosimetric method that provides the time elapsed since the last exposure of quartz grains to natural sun light. Cave sediments are particularly amenable for paleodosimetric methods, as sediments are preserved in the dark and the ESR signal should survive over the geologic history of the deposits. On the down side, we date the moment when the quartz grain enters the karst system, not its deposition. If the transit time is too long, this might be an issue and we would be significantly overestimating the true burial age. Caves at Atapuerca (N Spain) hold the richest Quaternary paleontological record in Eurasia, including fossils and lithic tools. Sediments in these caves have been traditionally dated via magnetostratigraphy by identifying the Matuyama-Brunhes reversal (0.78 Ma) thus providing the Lower to Middle Pleistocene boundary. Nevertheless, the appearance of older sediments in the caves required the combination of paleomagnetism with methods such as ESR to interpret older intra-Matuyama Subchrons. In the deepest levels of the Gran Dolina cave, close to the floor of the cavity, a number of short intervals of normal polarity have been identified in the fluviatile sediments belonging to TD1 unit, which we interpret in terms of Subchrons using ESR ages of quartz grains. We will discuss both paleomagnetic data and interpret the magnetic polarity stratigraphy in the view of the ESR ages obtained from the Multiple Centre (MC) approach.&amp;#160;&lt;/p&gt;

Davis Creek silt, an Early Pleistocene or Late Pliocene deposit in the Cypress Hills of Saskatchewan

1989 ◽  
Vol 26 (1) ◽  
pp. 192-198 ◽  
Author(s):  
W. J. Vreeken ◽  
R. W. Klassen ◽  
R. W. Barendregt
Keyword(s):  
Volcanic Ash ◽  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Early Pleistocene ◽  
The South ◽  
Glacial Deposits ◽  
Late Pliocene ◽  
Late Wisconsinan ◽  
Weathering Zone ◽  
Magnetic Polarity Reversal

Davis Creek silt is the informal name for a previously unreported loess and its reworked detritus encountered at several locations to the south of the east and centre blocks of the Cypress Hills. This unit intervenes between a pediment with an estimated age of 10 Ma and Late Wisconsinan glacial deposits. Because the unit has reversed magnetization, it is older than 788 ka, the astronomical age of the Matuyama–Brunhes magnetic polarity reversal. The unit also contains an undated volcanic ash from the Pearlette ash family that could represent the Mesa Falls (1.27 Ma) or the Huckleberry Ridge (2.02 Ma) ash bed. Davis Creek silt overlies an oxidized weathering zone and contains large secondary carbonate nodules near its truncated top that were, in places, reworked into a lag deposit or stone line before accumulation of the glacial overburden. At one location Davis Creek silt is separated from this overburden by a unit of cryoturbated gravelly loam with remnants of a reddish-yellow paleosolic B horizon.

Preliminary results from the Orbiting Solar Observatory 8 - Transition-zone dynamics over a sunspot

1976 ◽  
Vol 210 ◽  
pp. L97 ◽  
Author(s):  
E. C., Jr. Bruner ◽  
E. G. Chipman ◽  
B. W. Lites ◽  
G. J. Rottman ◽  
R. A. Shine ◽  
...  
Keyword(s):  
Transition Zone ◽  
Solar Observatory ◽  
Preliminary Results

scholarly journals Magnetic cycles of the planet-hosting star τ Bootis - II. A second magnetic polarity reversal

2009 ◽  
Vol 398 (3) ◽  
pp. 1383-1391 ◽  
Author(s):  
R. Fares ◽  
J.-F. Donati ◽  
C. Moutou ◽  
D. Bohlender ◽  
C. Catala ◽  
...  
Keyword(s):  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Magnetic Cycles ◽  
Magnetic Polarity Reversal
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