The Loess-Paleosol Sequence at the Krasnogorskoye Section, the Low-Hill Zone of the Northeastern Altai Mountains

The loess-paleosol sequence of the Krasnogorskoye section in the low-altitude area of the northeastern Altai Mountains, can provide a yardstick for estimating the age of the Paleolithic sites and reconstructing environmental and climatic changes. Its correlation with the respective sequence of the southern part of the West Siberian Plain is evaluated. Five pedocomplexes are studied in detail, evidencing the evolution of the Middle and Late Pleistocene soil formation from the Shadrikha interglacial to the Karga interstadial. Buried soils of the Shadrikha, Shipunovo, Koinikha, and Kazantsevo warm stages formed under a climate that was warmer and more humid than today. After the Kazantsevo interglacial, both the range and the frequency of climatic oscillations show marked changes. It is demonstrated that the warm stages of this interval differ from the earlier ones by lesser warming and shorter duration by a cooler and more arid climate. Seven loess horizons dividing pedocomplexes are established. Nonmetric and metric analyses of quartz sand grains support the eolian origin of loess horizons under cryoarid conditions. The size of grains in the Late Pleistocene portion of the Krasnogorskoye section attests to the intensifi cation of the loess processes. Higher magnetic susceptibility during the cool stages and higher frequency-dependent susceptibility during the warm stages evidence marked climatic oscillations. After the Kazantsevo interglacial, the amplitude fades and the pattern of paleoclimatic signal recorded by the magnetic properties of loess and paleosol in the section are close to the “Alaskan” type.

Quaternary volcanic ash of Kharkiv region

Formulation of the problem. The article is devoted to detail geological and mineralogical description of quaternary volcanic ash in Kharkiv region. The purpose of the article is to ground its origin. Presentation of the main material. Quaternary volcanic ash was discovered in Kharkiv region in the middle of last century. There are a few Late Neo-Pleistocene deposits of volcanic ash in Kharkiv region now. They are located in Kharkiv and near such villages as Russki Tishki, Novoselivka, Levkivka, Donetzke and Krasnokutsk. Such deposits of volcanic ash were found in the neighboring regions of the Eastern Ukraine - Lugansk, Donetsk, Dnieperpetrovsk and some other regions. Volcanic ash forms the elongated lenticular deposits in the loess loam strata. The contact of ash beds is clear with underlying loess and gradual with overlying loess. The ash lies 3-5 m below the surface of loess. These ashes are light-grey with feeble yellow or brown shades. Its thickness is up to 0.4 m. The particles of the ash are volcanic colourless isotropic glass with refraction index 1,517. Its forms are various. Plate isometric and elongated ash particles with even straight or cambered sides are the most widespread. Predominance of 0.005-0.1 mm particles in this ash rocks is confirmed by the results of mechanical analyses. This tephra is badly sorted. Their sort factor is 4.2-5.9. The ash deposits were formed by wind transportation of ash particles to wind shadow zones. The results of X-ray investigation are typical for glass. IR-spectra investigation revealed molecular water and hydroxyl groups in the volcanic ash. Chemical composition of the volcanic ash of Kharkiv region is characterized by the average percentage of SiO2 – 58.88, Al2O3 – 18.79, Na2O – 5.03, K2O – 6.30, Na2O+K2O – 11.33. Relation of Na2O to K2O is 0.80 and Na2O+K2O to Al2O3 is 0.60. It corresponds to trachyte and phonolite and is confirmed by the refraction index of glass particles. The volcanic glass particles are angular and non-rounded. This fact signifies the eolian origin of ash deposits. Moreover, numerous manifestations of volcanic ash scattered in loess loams are found in Kharkiv region. These loams contain only a few per cents of poorly rounded volcanic ash particles. The loess loams with scattered volcanic ash and volcanic ash deposits belong to the same stratigraphic datum - to the Bugskij horizon, which correspond to Wurmian stage. Conclusions. All tephra deposits of Kharkiv region are in the ash plume of the super-eruption, which occurred in Southern Italy about 39280 years ago (Campanian Ignimbrite eruption). Kharkiv objects fill territory in this plume between the ash depositions of Romania and Russian Voronezh region. They are similar to all other tephra localities of this plume. The volcanic ash was taken by air from the Phlegraean Fields though the distance between Kharkiv and this volcano is over 2000 km. Scientific novelty and practical significance. We can affirm that Kharkiv ash deposits are the result of distant ashfall of Phlegraean Fields super-eruption. The volcanic ash is a horizon marker in the Neo-Pleistocene strata and a datum mark for archaeological study of the Paleolithic cultures. Volcanic ash is a remarkable component of Kharkiv region geological monuments. Russki Tishki locality of volcanic ash is the best object in Kharkiv region. It is situated in 22 km north from Kharkiv. These geological sights have been used as objects of scientific tourism and native land study. Their protection is of highly necessity.

Clima Seco e Formação de Dunas Eólicas durante o Holoceno Médio em Taquaruçu, Mato Grosso do Sul

Holocene sandy deposits interpreted as of eolian origin were studied at Taquaruçu, MS (22º30’ S / 53º20’ W). That area is constituted of hills with 5 to 12 m of height over the regional surface, with lightly asymmetric profile, which, morphologically remind eolian dunes quite dissipated, covered by scattered shrub-arboreal vegetation. The deposits are mainly composed of fine to very fine (35 and 54%), medium quartzose sand (7%), with rare granules in the basal interval and clay (4%). Sediment is almost totally massive, probably, by intensive root bioturbation. Structures generated by dissipation and fluidization were also identified. The studied profiles are very similar and presented a temporal hiatus between 3,3 and 3,7 ka BP. The curve of magnetic susceptibility also displays a coincident inflection with the identified discontinuity in the age curve. It was possible to conclude that the area was submitted to a drier climate than the current during the Middle Holocene. Under this climate there was reduction in the vegetable covering and the consequent mobilization of the sand generating an erosive surface and the formation of small dune field. This dry period at the end of Middle Holocene is also identified in other localities such as in SE and Central area of Brazil, and in NE of Argentina. However, this is the first time that eolian processes of such intensity were described in the studied area, and a revision in the definition of aridity intensity of the short dry period of the Holocene is suggested.

Boulder Deposits from Large Waves during the Last Interglaciation on North Eleuthera Island, Bahamas

Seven boulders measuring 100 to 1000 m3 are scattered along the coastal ridge of north Eleuthera. Some are situated on ridge crests up to 20 m above present sea level. The boulders were probably deposited during oxygen-isotope substage 5e or 5d, as shown by their stratigraphic setting and by amino acid racemization ratios. D-alloisoleucine/L-isoleucine ratios were determined for land snails, and oolite of both marine and eolian origin was associated with the boulders. Like the boulders, the probable source rocks exposed in the adjacent cliffs are composed of marine and eolian limestone of oolitic and peloidal composition. The source beds are correlated with stage 9 or 11. The largest boulder is about 10 times the size of the largest Holocene ones moved by waves in the area. Tsunamis are a reasonable possibility as a transporting mechanism of the Pleistocene boulders. However, if deposited instead by storms during the last interglaciation, the storms were of much greater intensity than those occurring in the region during the late Holocene.

Holocene Paleofloods of the Ross River, Central Australia

The rivers of central Australia rise in the MacDonnell Ranges and flow out across broad, low-relief plains into the surrounding desert. The stratigraphy of the Ross River plain records the areal extent and frequency of Holocene floods. This floodout plain is underlain by deeply weathered alluvial deposits, characterized by red earth soils dated by thermoluminesence at >59,000 yr. This old alluvium is covered by a sheet-like deposit of very silty sand of probable eolian origin dated by thermoluminesence at 9200 ± 900 yr. The oldest Holocene alluvium occurs as broad, low-relief bars and levee deposits flanking the modem channel and as low-relief long-wavelength bedforms that fan out across the plain. This deposit resulted from a flood flow, up to 10 km wide, that covered the entire plain. Evidence for several large floods between 1500 and 700 yr B.P. is also preserved in a 500- to 1500-m-wide paleochannel. Thus, the surface features on the floodout plains are the product of a few rare large flood events. This paleohydrologic record is additional evidence of the dynamic nature of the hydrometerological regime of central Australia.