Journal article. Access the full text Link. Lookup at Google Scholar. Magnetostratigraphic dating of the Shanshenmiaozui mammalian fauna in the Nihewan Basin, North China. Timing of the mammalian faunas in the Nihewan Basin, North China has provided insights into our understanding of Quaternary biochronology and biostratigraphy in East Asia. Here we contribute to this topic with detailed magnetostratigraphic investigation, coupled with mineral magnetic measurements on a fluvio-lacustrine sequence in this basin, which contains the Shanshenmiaozui mammalian fauna. Magnetite and hematite were identified as the main carriers for the characteristic remanent magnetizations. Magnetostratigraphic results show that the Shanshenmiaozui sedimentary sequence recorded the Brunhes chron, the Jaramillo subchron, and the late Matuyama chron.

Canadian Journal of Earth Sciences

Shipboard paleomagnetism was investigated mainly to determine directions of remanence components. Routine measurements were conducted on archive section halves with stepwise alternating field AF demagnetization. Discrete cube and minicore samples were taken from selected working-half sections and measured with stepwise AF and thermal demagnetization. These data were used for core orientation and magnetostratigraphic dating.

Ocean drilling cores generally carry secondary overprint remanence components. Common overprints for ocean drilling cores include natural viscous remanence and a steep downward-pointing component attributed to the drill string.

Once a calibrated “standard” or a so- called “geomagnetic polarity timescale” (​GPTS) is constructed, dated by radiometric methods and/or by orbital tuning, one.

Deep-sea basins are one of the least-known sedimentary environments although they cover almost one-quarter of the Earth’s surface McKenzie, Abyssal plains within the deep-ocean basins are important because they may provide records of major tectonic events in the erosional and depositional history of a continental margin. The use of deep-sea drilling techniques to investigate the geological evolution of the ocean basins and their margins depends critically on an accurate knowledge of the geological ages of the sediments found.

Without such knowledge, comparisons of contemporaneous paleoenvironment in different regions cannot be made and the recognition of important geological and tectonic events, represented by such features as sedimentary hiatuses, angular unconformities, and changes in sedimentation rates, becomes impossible. Biostratigraphy, isotope stratigraphy, and magnetostratigraphy are the three principal techniques for chronostratigraphic analysis of long, continuous sedimentary sequences.

Among them, biostratigraphy is the most widely used technique for determining the relative age of deep-sea sediments, and its contribution to our current understanding of the geological evolution of ocean basins cannot be overemphasized. However, this technique does suffer certain fundamental limitations. In particular, it requires the presence of suitable conditions for the existence and preservation of ancient marine organisms, and time resolution depends upon the identification of particular assemblages of rapidly evolving species.

Biostratigraphic zonations generally use the first and last appearance datums for subdividing geologic time and correlating the sedimentary section, but the relative abundances of the datums are often complicated by geographic and environmental factors, or masked in the sedimentary record by dissolution effects. This can lead to local difficulties in identifying boundaries in biostratigraphic zones and in ascribing a precise synchroneity as chronostratigraphic horizons. Geomagnetic polarity transitions, on the other hand, are the most frequent, best-dated, and globally synchronous geophysical phenomena.

Recent advances in magnetostratigraphy, especially for the Late Cretaceous and Cenozoic which have resulted from the first decade of the ODP, have been important for the refinement of chronostratigraphic framework and have enhanced the importance of magnetostratigraphy as a correlation tool in paleogeographic studies. Although the magnetostratigraphic dating technique offers certain important advantages over the micropaleontological dating method, it is itself subject to limitations.

For example, it is first necessary to demonstrate that the remanent magnetization of the sediment is stable primary magnetization acquired at, or close to, the time of deposition.

The shutdown of an anoxic giant: Magnetostratigraphic dating of the end of the Maikop Sea

Paleomagnetic studies of lake bottom sediments in Japan have been reviewed to establish a method of magnetostratigraphic dating using geomagnetic secular variations and excursions. For the last For the last 60ka, the inclination record from the top 60m of the m-core from Lake Biwa may be used for dating with magnetostratigraphic correlation. Tephrochronological data recently published revise the ages of the geomagnetic excursions in the Lake Biwa m-core.

The excursion at 54m, formally known as the Blake event, is a new one from about 56ka.

End Page: Publisher: Elsevier Ltd. All titles: “Magnetostratigraphic dating of the Shanshenmiaozui mammalian fauna in the Nihewan Basin, North China”.

A molasse sequence comprising 1. The magnetic fabric comprises primary sedimentary-compactional and secondary tectonic components. Remanence ratios derived from demagnetization data allowed the first-order estimation of remanence contributions from magnetic minerals goethite, maghemite, magnetite and hematite , and discrimination of rockmagnetic zones correlatable with distinct lithofacies, which will facilitate objective mapping. We correlated a magnetic polarity sequence, constructed from normal and reverse polarity directions from 77 levels that passed the reversal test and represented primary remanences, with the standard geomagnetic polarity timescale to constrain the depositional age between ca.

We calculated the sediment accumulation rate for polarity zones from the chronologically better constrained part below Chron C5n. The notable increase in accumulation rate after Constraining the base of the Tinau Khola north section to This group represents an important sediment archive of the chronology and mechanisms of past palaeoclimatic e. Flynn et al. The Nepalese FBSs lack fossils for reasonably accurate dating e. Thermochronometry based on detrital zircon and apatite grains has increasingly been used to determine source-area exhumation dates and thence to constrain the maximum possible depositional ages of these sediments in the foredeep that constitutes the present-day sub-Himalaya West et al.

Magnetostratigraphic Dating

Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their characteristic remanent magnetization ChRM , that is, the polarity of Earth’s magnetic field at the time a stratum was deposited. This is possible because volcanic flows acquire a thermoremanent magnetization and sediments acquire a depositional remanent magnetization , both of which reflect the direction of the Earth’s field at the time of formation.

This technique is typically used to date sequences that generally lack fossils or interbedded igneous rock. When measurable magnetic properties of rocks vary stratigraphically they may be the basis for related but different kinds of stratigraphic units known collectively as magnetostratigraphic units magnetozones.

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The Neogene succession of the Aktau Mountains in the Ili Basin, southeast Kazakhstan, is a terrestrial archive well suited for researching the role of Central Asia in Miocene climate evolution. We present an integrated approach for dating the well-exposed Bastau Formation, based on magnetostratigraphy and constraints from cyclostratigraphy and biostratigraphy.

Stepwise demagnetization yielded characteristic remanence directions that are consistent with those expected for the Miocene in Central Asia. The reddish-colored alluvial floodplain deposits and gray lacustrine deposits show partly complex magnetic behavior with magnetite and hematite as the main magnetic carriers, with variable demagnetization behavior and non-dipolar normal and reverse polarity directions.

The observed magnetic properties are best explained by depositional variability and magneto-mineralogical alteration effects of both dissolution and neo-formation of magnetite, including significant secondary magnetization. The mean of reverse polarity directions is flatter than the expected Middle Miocene Earth magnetic field, which is an indicator for the existence of inclination shallowing that supports a primary origin.

Magnetostratigraphy

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Based on recent 40Ar/39Ar geochronological dating of the site, faunal constraints and a magnetostratigraphic pattern, the sequence is.

The recovery and subsequent prolific radiation of mammals in the northern Western Interior of North America following the Cretaceous—Paleogene K—P boundary is well documented in rocks attributed to the Puercan Land Mammal Age. The most complete Puercan record is that of the Tullock Formation, which crops out widely in Garfield and McCone counties, eastern Montana.

The Tullock Formation overlies the dinosaur-bearing Hell Creek Formation and consists of a stratigraphic series of channel and overbank deposits from which well-preserved Puercan faunas have been collected. These channel deposits are typically bracketed by widespread coal beds. The IrZ- and Z-coals mark the base of the Puercan at the K—P boundary as defined by the highest appearing local occurrences of in situ dinosaur fossils, the highest stratigraphic occurrence of Cretaceous pollen, and an anomalously high concentration of the element iridium Ir.

Earliest Torrejonian To1? The Y through W coals, as well as the fossil vertebrate-bearing sandstones of the Garbani Channel and Purgatory Hill, are contained in an overlying zone of normal polarity, correlated with chron C29n. Rocks immediately above the W-Coal through the U-Coal, which include the Farrand Channel, are in a zone of reversed polarity, correlated here with chron C28r.

The top of the section, just above the U-Coal, is in the uppermost zone of normal polarity, tentatively correlated here with the base of chron C28n. Replicate analyses of single crystals of sanidine yield weighted mean ages for bentonites in the following coals: IrZ, To1 land mammal ages and provide crucial calibration for the nonmarine K—P boundary and the Early Paleogene portion of the geomagnetic polarity time scale.

Xiao-Chun Wu , Donald B. Advanced Search.

Magnetostratigraphic dating of early humans in China

The sequence also contains numerous in situ stone artifacts and fossils of other vertebrate taxa. Therefore, multiple dating techniques are crucial to secure the age of the fossil and artifact-bearing layers, especially the one with the hominin remains. Palaeomagnetic sampling was conducted in four sections along a west to east transect.

Four magnetozones can be recognized, consisting of two reverse and two normal polarity zones. Ao, H.

We present an integrated approach for dating the well-exposed Bastau Formation, based on magnetostratigraphy and constraints from.

Popov, L. Golovina, K. Kuiper , S. Liu, W. Paratethys, the lost sea of central Eurasia, was an anoxic giant during Oligocene — early Miocene Maikop Series times. With a size matching the modern-day Mediterranean Sea and a history of anoxic conditions that lasted for over 20 Myrs, the eastern part of this realm Black Sea-Caspian Sea domain holds key records for understanding the build-up, maintenance and collapse of anoxia in marginal seas.

Here, we show that the collapse of anoxic Maikop conditions was caused by middle Miocene paleogeographic changes in the Paratethys gateway configuration, when a mid-Langhian Badenian-Tarkhanian transgression flooded and oxygenated the Eastern Paratethys. We present an integrated magneto-biostratigraphic framework for the early Middle Miocene Tarkhanian-Chokrakian-Karaganian regional stages of the Eastern Paratethys and date the lithological transition from anoxic black shales of the Maikop Series to fossiliferous marine marls and limestones of the regional Tarkhanian stage.

For this purpose, we selected two long and time-equivalent sedimentary successions, exposed along the Belaya and the Pshekha rivers, in the Maikop type area in Ciscaucasia southern Russia.

Paleomagnetism

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