Characterization of Lower and Middle Pleistocene tephra beds in the southern plains of western Canada

Wellsch Valley tephra, near Swift Current, southwestern Saskatchewan, and Galt Island tephra, near Medicine Hat, southeastern Alberta, have been referenced in the literature since the 1970s, but little is available on their physical and chemical attributes – necessary information if they are to be recognized elsewhere. This study seeks to remedy this situation. Both have a calc-alkaline rhyolitic composition with hornblende, biotite, plagioclase, pyroxene, and Fe-Ti oxides being dominant. They have a similar composition but are not the same. Wellsch Valley tephra has a glass fission-track age of 0.75 ± 0.05 Ma, a reversed magnetic polarity, and was deposited at the close of the Matuyama Chron. Galt Island tephra has an age of 0.49 ± 0.05 Ma, a normal magnetic polarity, and was deposited during the early Brunhes Chron. Rich fossil vertebrate faunas occur in sediments close to them. Major- and trace-element concentrations in their glass shards indicate a source in the Cascade Range of the Pacific Northwest, USA, but differences in trace-element ratios suggest they are not consanguineous.

The Matuyama—Brunhes boundary in the loess-palaeosol sequence of Dolynske, southern Ukraine

We present the results of a palaeomagnetic study of the Early—Middle Pleistocene deposits exposed on the left bank of the River Danube at Dolynske, southern Ukraine. A thick succession of water-lain facies is succeeded by stratigraphically complete loess-palaeosol sequence; these constitute a unique palaeoclimate archive in the southern margin of the East European loess province. The Matuyama—Brunhes boundary (MBB) has been detected at the bottom of the Lower Shyrokyne (S7S3) subunit and not in the Martonosha (S6) unit as previously thought. New data align with previous results from the Roksolany and Vyazivok sections, where the MBB was determined at the same stratigraphical level in the S7S3 soil. In contrast to terrestrial Pleistocene records in China and сentral Europe, where the MBB was regularly determined in a loess layer (representing a cold period), the MBB in the Ukrainian subaerial succession is located in the soil unit (representing a warm period). Furthermore, eight, and not seven, glacial-interglacial cycles are recorded in the Brunhes chron. This may indicate the stratigraphic completeness of the loess-soil succession of Ukraine, which can be compared with the reference global marine and terrestrial palaeoclimatic archives. Further palaeomagnetic studies of loess-palaeosol sequences of other regions of Ukraine will allow revision and correlation of still inconsistent stratigraphic and magnetostratigraphic schemes of the Pleistocene deposits.

The feature of P- and S-waves propagation inside the inner G-core of the Earth

В статье приводится объяснение причины, почему скорости P- и S-волн во внутреннем ядре Земли не возрастают по мере приближения к центру ядра, как им положено при увеличении плотности и внешнего давления. Причина может состоять только в том, что вещество внутреннего ядра Земли находится в состоянии квантовой сцепленности, которое возникло при образовании Земли. Оно исчезнет сразу после того, как закончится период Брюнеса, при этом прекратится существование геомагнитного поля. The article explains why despite the increasing density and external pressure the velocities of P-and S-waves do not increase as they approach the center of the inner G-core of the Earth. The reason can only be that the matter of the inner core of the Earth is in a state of quantum entanglement, which arose at the formation of the Earth and will disappear immediately after the end of the Brunhes chron when the geomagnetic field disappears.

Rock magnetic and palaeomagnetic studies of loess-palaesol sections — Lower Palaeolithic sites within the Southern Bug Valley (Medzhybizh, Holovchyntsi)

Combined rock magnetic and palaeomagnetic studies of loess-soil sections — Lower Paleolithic sites in the valley of the Southern Bug (Medzhybizh, Holovchintsi) — have been performed for the first time in order to determine the suitability of these objects for palaeomagnetic study and the establishment of magnetostratigraphic markers. Investigated sections by rock magnetic characteristics are closest to the sections of the Volynian Upland, and refer to the intermediate «Chinese» type of formation of magnetic properties, with an admixture of the «Alaskan» mechanism. These sections are characterized by a low concentration of ferrimagnetic material, the destruction of the primary sedimentary magnetic texture, which makes them unsuitable for qualitative magnetostratigraphic studies. According to the data of magnetic-mineralogical analysis, the samples are subdivided into three groups: the first group includes samples with new formation at 300 °C, which is associated with iron hydroxides or the presence of organic matter; in the second group, the thermomagnetic curves are not informative, which makes it difficult to determine the minerals-carriers; in some samples, the magnetization carrier is magnetite (with defects or finely dispersed). A zone of normal polarity, probably the Brunhes chron, has been reliably determined in the upper part (G-S7S1 soil) of the Holovchyntsi section. In the lower part of the M-S4 soil unit (MIS 11) at Medzhybizh, the Unnamed geomagnetic event at 430 ky has been detected. The paleomagnetic veracity of the remaining investigated layers is questioned. The analogies for the archaeological assemblages from the lower layers of Medzhybizh-A and Holovchintsi-1 are seen in archaic industries of mode 1, which in southeastern Europe are dated back from 800 ky and older. However, reliable data on the Matuyama—Brunhes boundary and, correspondingly, data on the >780 ky age of any layers with artifacts in the Medzhybizh and Holovchintsi sections were not obtained by the palaeomagnetic studies.

Subdivision of the Quaternary System: formal subseries and new corresponding stages for the Pleistocene and Holocene

<p>The Holocene and Pleistocene series/epochs have each long been divided into Early, Middle and Late subseries/subepochs, although their formalization had been complicated by the hitherto absence of this rank from the International Chronostratigraphic Chart.  On 14th June 2018, the Holocene was formally subdivided into the Greenlandian, Northgrippian and Meghalayan stages/ages and their corresponding Lower/Early, Middle, Upper/Late subseries/subepochs, each defined by a Global Boundary Stratotype Section and Point (GSSP). The GSSP for the lowermost stage, the Greenlandian, is that of the Holocene as previously defined in the NGRIP2 Greenland ice core, and dated at 11,700 yr b2k (before 2000 CE). The GSSP for the Northgrippian is in the NGRIP1 Greenland ice core, and dated at 8236 yr b2k, whereas that for the Meghalayan is located in a speleothem from Mawmluh Cave, Meghalaya, northeast India with a date of 4250 yr b2k (Walker et al., 2018).  The Pleistocene Series/Epoch of the Quaternary System/Period has been divided unofficially into three subseries/subepochs since at least the 1870s.  On 30th January 2020, two proposals were ratified: 1) the Lower Pleistocene Subseries, comprising the Gelasian Stage and the superjacent Calabrian Stage, with a base defined by the GSSP for the Gelasian Stage, the Pleistocene Series, and the Quaternary System, and currently dated at 2.58 Ma; and 2) the term Upper Pleistocene, at the rank of subseries, with a base currently undefined but provisionally dated at ~129 ka.  The Middle Pleistocene and its corresponding Chibanian Stage/Age had meanwhile been formalized on January 17, 2020 with a GSSP in the Chiba section, Japan.  The GSSP is placed 1.1 m below the directional midpoint of the Matuyama–Brunhes Chron boundary, at the base of a regional lithostratigraphic marker, the Ontake-Byakubi-E tephra bed, in the Chiba section. The GSSP has an astronomical age of 774.1 ka and is placed just below the top of Marine Isotope Substage 19c.  These ratifications nominally complete the official division of the Quaternary into subseries/subepochs, although the Upper Pleistocene and its corresponding stage remain to be defined by GSSP.  The Anthropocene is currently an unofficial unit, while analysis of potential candidate GSSP locations is progressing in preparation for a formalization proposal.  If approved, it would terminate the Holocene at around the year 1952, assuming it is defined at series/epoch rank.</p><p>Head, M.J., Pillans, B., and Zalasiewicz, J.A., in press. Formal ratification of subseries/subepochs for the Pleistocene Series/Epoch of the Quaternary System/Period. Episodes</p><p>Suganuma, Y., Okada, M., Head, M.J., et al., in press. Formal ratification of the Global Boundary Stratotype Section and Point (GSSP) for the Chibanian Stage and Middle Pleistocene Subseries of the Quaternary System: the Chiba Section, Japan.  Episodes</p><p>Walker, M., Head, M.J., Berkelhammer, M. et al., 2018.  Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period): two new Global Boundary Stratotype Sections and Points (GSSPs) and three new stages/subseries. Episodes 41(4): 213–223. </p>

Effects of atmospheric CO₂ variability of the past 800 kyr on the biomes of southeast Africa

Very little is known about the impact of atmospheric carbon dioxide pressure (pCO2) on the shaping of biomes. The development of pCO2 throughout the Brunhes Chron may be considered a natural experiment to elucidate relationships between vegetation and pCO2. While the glacial periods show low to very low values (∼220 to ∼190 ppmv, respectively), the pCO2 levels of the interglacial periods vary from intermediate to relatively high (∼250 to more than 270 ppmv, respectively). To study the influence of pCO2 on the Pleistocene development of SE African vegetation, we used the pollen record of a marine core (MD96-2048) retrieved from Delagoa Bight south of the Limpopo River mouth in combination with stable isotopes and geochemical proxies. Applying endmember analysis, four pollen assemblages could be distinguished representing different biomes: heathland, mountain forest, shrubland and woodland. We find that the vegetation of the Limpopo River catchment and the coastal region of southern Mozambique is influenced not only by hydroclimate but also by temperature and atmospheric pCO2. Our results suggest that the extension of mountain forest occurred during those parts of the glacials when pCO2 and temperatures were moderate and that only during the colder periods when atmospheric pCO2 was low (less than 220 ppmv) open ericaceous vegetation including C4 sedges extended. The main development of woodlands in the area took place after the Mid-Brunhes Event (∼430 ka) when interglacial pCO2 levels regularly rose over 270 ppmv.

Effects of atmospheric CO₂ variability of the past 800 ka on the biomes of Southeast Africa

Very little is known about the impact of atmospheric carbon dioxide pressure (pCO2) on the shaping of biomes. The development of pCO2 throughout the Brunhes Chron may be considered a natural experiment to elucidate relationships between vegetation and pCO2. While the glacial periods show low to very low values (~ 230 to ~ 190 ppmv, respectively), the pCO2 levels of the interglacial periods vary from intermediate to relatively high (~250 to ~ 270, respectively). To study the influence of pCO2 on the Pleistocene development of SE African vegetation, we used the pollen record of a marine core (MD96-2048) retrieved from Maputo Bay south of the Limpopo River mouth in combination with stable isotope and geochemical proxies. Applying endmember analysis, four pollen assemblages could be distinguished representing different biomes: heathland, mountain forest, shrubland and woodland. We find that the vegetation of the Limpopo River catchment and the coastal region of southern Mozambique is not only influenced by hydroclimate but by also temperature and atmospheric pCO2. Our results suggest that the extension of either open ericaceous vegetation including C4 sedges or mountain forest depended on glacial pCO2 levels, and that the main development of woodlands in the area took place after the Mid-Brunhes Event when interglacial pCO2 levels rose over 270 ppmv.

Magnetostratigraphic dating of the Linyi Fauna and implications for sequencing the mammalian faunas on the Chinese Loess Plateau

The Chinese Loess Plateau (CLP) in North China is an important terrestrial archive that witnessed the environmental changes and mammal and early human evolution in Asia over the past 2.6 Ma. Establishing precise ages for the Pleistocene faunas on the CLP is critical for better understanding of these environmental, biological, and archaeological issues. Here we report a new magnetostratigraphic record that places age constraints on the Linyi Fauna on the southeastern CLP. Our investigated 170-m-thick Linyi section mainly consists of two portions: (1) an overlying eolian Quaternary loess-paleosol sequence and (2) underlying fluvial-lacustrine sand and silty clay. Paleomagnetic results suggest that the composite section records the Brunhes chron, Jaramillo and Olduvai subchrons, and successive reverse polarity portions of the intervening Matuyama chron. The Linyi Fauna is located between Jaramillo and Olduvai subchrons in the fluvial-lacustrine interval, with an estimated age of ~1.5–1.6 Ma. Combining previously dated faunas, we establish a Pleistocene magnetochronology spanning from 2.54 to 0.65 Ma for the faunas on the CLP.