The oldest known record of a ground sloth (Mammalia, Xenarthra, Folivora) from Hispaniola: evolutionary and paleobiogeographical implications

Sloths were among the most diverse groups of land vertebrates that inhabited the Greater Antilles until their extinction in the middle-late Holocene following the arrival of humans to the islands. Although the fossil record of the group is well known from Quaternary deposits in Cuba, Hispaniola, and Puerto Rico, remains from older units are scarce, limiting our understanding of their evolution and biogeographic history. Here we report the oldest known fossil ground sloth from Hispaniola, represented by an unassociated partial tibia and scapula that are recognized as a single taxon from the late Miocene-early Pliocene of the Dominican Republic. The combination of characters observed on the tibia suggests a close relationship with Megalocnus, otherwise only known from the Pleistocene–Holocene of Cuba. These fossils fill a temporal gap between those previously known from the early Miocene of Cuba and those from Pleistocene–Holocene deposits in the region and provide additional support for a continuous presence of the group in the Greater Antilles since the Oligocene.

SOME ASPECTS OF POLISH-UKRAINIAN GEOLOGICAL AND GEOMORPHOLOGICAL RESEARCHES OF WESTERN VOLYN-PODILLIA DURING THE POLISH INVASION

The proposed article is based on an analysis of publications on field observations published in the then Polish and Ukrainian periodicals, collections of materials from scientific forums at various levels, works collections of individual Polish and foreign scientific institutes, etc. The purpose of the article was an attempt to analyze and generalize the research results of the study area in the field of Quaternary geology and geomorphology. It should also be noted that publications from the listed sections of physical geography are encountered quite sporadically and in significantly smaller numbers than articles on purely geological disciplines such as mineralogy, petrography, lithology, tectonics, etc. The study of geological and geomorphological objects and processes was carried out on the territory of Western Volyn-Podillia, which at that time was a part of the Polish-Lithuanian Commonwealth. The works mainly concerned the study of the stratigraphy of anthropogenic sediments distributed in the Podillia loess and loess soils, continental glaciations and related glacial and fluvial-glacial deposits, surface and underground karst, etc. It was established that significant in volume and depth of generalization of works on the geological and geomorphological structure the region features at that time was not. The studies that were carried out were not systematic, they were often carried out on the researchers initiative and without adequate funding, with localization mainly in the territory with open at that time deposits of certain minerals types. Analysis of publications can be stated as follows: the study of Quaternary deposits of the region and loess in particular was carried out with extensive use of laboratory studies, paleontological method, chemical, particle size distribution mineralogical and petrographic analyzes, the method of separation of loess minerals in heavy liquids, paleontological and archaeological observations, etc., were progressive at that time. It should be noted that individual reports on the determination of the age of the Quaternary strata were poorly synchronized with each other and a reliable generally accepted scale for the division of these deposits in this period was not agreed. During this period, factually substantiated schemes of geomorphological zoning of both the Podillia region as a whole and its individual components were proposed. Regular relationships of the relief features of the region with the lithogenic base, neotectonic movements, glacial and fluvial-glacial processes are traced. Significant progress is noted in the study of stratigraphy, lithology of local loess strata, problematic issues of their genesis are discussed. Among the few works on the study of the loess cover of Volyn-Podillia, the work of Yu. Polianskyi and Yu. Tokarskyi attracts attention first of all. The works on the study of loess are important due to: a) their almost ubiquitous distribution in the described territories; b) value for stratigraphic subdivision of the Pleistocene; c) controversial genesis; d) widespread use for the production of bricks and tiles. Work on the study of surface and underground forms of the Podillia karst has spread. Systematic mapping of individual underground cavities begins which gave impetus to their use in the future as objects of tourism. The largest number of works is devoted to the problems of studying the relief and modern physical and geographical processes in the interwar period. At the same time, along with purely descriptive publications, works appear where conclusions are based on the use of cartographic materials, which allowed researchers to identify significant patterns in the morphological features of the region. In the period under study, numerous publications by soil scientists also appeared, in which Quaternary sediments are considered as parent rocks on which soils were formed, the dependence of the type of soil on the lithology of the underlying rocks is established. In general, the works of Polish and Ukrainian researchers in the characterized period laid a reliable foundation for modern ideas about the geological and geomorphological features of the region. Keywords: geomorphological studies, Quaternary deposits, glacial deposits, stratigraphy, morphology, loess deposits.

PROBLEMS OF AGE AND GENETIC DIAGNOSTICS OF QUATERNARY DEPOSITS IN THE VALLEY OF THE YENISEI RIVER MIDDLE COURSE (YENISEI – LOWER ANGARA STRATIGRAPHIC REGION AND THE MINUSINSK BASINS AREA)

The article is devoted to the state of stratigraphic exploration maturity of the Eopleistocene – Neo-Рleistocene Quaternary deposits on the boundary of mountain and plain territories in the non-glacial area. The material analysis shows an inadequate rationale of the existing stratigraphic schemes, according to which the ladder of alluvial terraces of these territories was formed sequentially during the Eopleistocene, Neo-Pleistocene and Holocene. The revising of representative sections was carried out, the provision of them with geochronological data, the accuracy of age and genetic diagnostics were evaluated.

GOSUDAREV LOG REFERENCE SECTION OF THE GELASIAN AND EOPLEISTOCENE

An integrated analysis of Quaternary deposits of the Gosudarev Log section near Krasnoyarsk was carried out. In the wall of the ancient ravine, deposits of the two highest river terraces of the Yenisei River embedded in accumulative formations of the so-called Batoisky uval [ridge] were uncovered. In the axial part of this ridge, lacustrine Eopleistocene formations overlie river gravel of the Gelasian and are overlain by subaerial cover loess-like formations. This section is proposed as a reference one for the Gelazian and Eopleistocene deposits of the extraglacial zone of the Pre-Yenisei Siberia.

Landscape, Soil, Lithology, Climate and Permafrost Control on Dissolved Carbon, Major and Trace Elements in the Ob River, Western Siberia

In order to foresee possible changes in the elementary composition of Arctic river waters, complex studies with extensive spatial coverage, including gradients in climate and landscape parameters, are needed. Here, we used the unique position of the Ob River, draining through the vast partially frozen peatlands of the western Siberia Lowland and encompassing a sizable gradient of climate, permafrost, vegetation, soils and Quaternary deposits, to assess a snap-shot (8–23 July 2016) concentration of all major and trace elements in the main stem (~3000 km transect from the Tom River confluence in the south to Salekhard in the north) and its 11 tributaries. During the studied period, corresponding to the end of the spring flood-summer baseflow, there was a systematic decrease, from the south to the north, of Dissolved Inorganic Carbon (DIC), Specific Conductivity, Ca and some labile trace elements (Mo, W and U). In contrast, Dissolved Organic Carbon (DOC), Fe, P, divalent metals (Mn, Ni, Cu, Co and Pb) and low mobile trace elements (Y, Nb, REEs, Ti, Zr, Hf and Th) sizably increased their concentration northward. The observed latitudinal pattern in element concentrations can be explained by progressive disconnection of groundwaters from the main river and its tributaries due to a northward increase in the permafrost coverage. A northward increase in bog versus forest coverage and an increase in DOC and Fe export enhanced the mobilization of insoluble, low mobile elements which were present in organo-ferric colloids (1 kDa—0.45 µm), as confirmed by an in-situ dialysis size fractionation procedure. The chemical composition of the sampled mainstream and tributaries demonstrated significant (p < 0.01) control of latitude of the sampling point; permafrost coverage; proportion of bogs, lakes and floodplain coverage and lacustrine and fluvio-glacial Quaternary deposits of the watershed. This impact was mostly pronounced on DOC, Fe, P, divalent metals (Mn, Co, Ni, Cu and Pb), Rb and low mobile lithogenic trace elements (Al, Ti, Cr, Y, Zr, Nb, REEs, Hf and Th). The pH and concentrations of soluble, highly mobile elements (DIC, SO4, Ca, Sr, Ba, Mo, Sb, W and U) positively correlated with the proportion of forest, loesses, eluvial, eolian, and fluvial Quaternary deposits on the watershed. Consistent with these correlations, a Principal Component Analysis demonstrated two main factors explaining the variability of major and trace element concentration in the Ob River main stem and tributaries. The DOC, Fe, divalent metals and trivalent and tetravalent trace elements were presumably controlled by a northward increase in permafrost, floodplain, bogs, lakes and lacustrine deposits on the watersheds. The DIC and labile alkaline-earth metals, oxyanions (Mo, Sb and W) and U were impacted by southward-dominating forest coverage, loesses and eluvial and fertile soils. Assuming that climate warming in the WSL will lead to a northward shift of the forest and permafrost boundaries, a “substituting space for time” approach predicts a future increase in the concentration of DIC and labile major and trace elements and a decrease of the transport of DOC and low soluble trace metals in the form of colloids in the main stem of the Ob River. Overall, seasonally-resolved transect studies of large riverine systems of western Siberia are needed to assess the hydrochemical response of this environmentally-important territory to on-going climate change.

The results of a complex study of the Turchu limestone hollow (polje). Western Georgia, Caucasus

Based on the complex studies (geographical-geological, karst-speleological, and geophysical studies), conducted by the authors in the study area, karst forms such as sinkholes and ponors were identified, the width (2-17 m) of the Quaternary deposits located on the limestones were determined, the average and maximum discharges of the streams flowing on the bottom of the hollow were calculated. Studies have also shown that relatively heavy rains and snowmelt periodically flood the relatively low, western part of the hollow and create a temporary lake that soon dries up through the ponors at the bottom of the hollow, where the water stream are discharged. The closed shape of the Turchu hollow the limestone bottom covered with Quaternary deposits and the events described above indicate the corrosive origin of the hollow, which has been practically confirmed by our georadiological and electrometric studies. It is notable that the role of tectonic movements in the origin of the hollow along with the corrosive processes, which had a periodic character, and together with the uplifting of the area caused the lowering of the levels of underground waters and, consequently, the activation of karst processes.

GEOQUÍMICA E PETROGRAFIA DE DEPÓSITOS QUATERNÁRIOS DA PORÇÃO SW DA PRAIA BRAVA, ARMAÇÃO DOS BÚZIOS, RJ, BRASIL: EDFRX E DIFRAÇÃO A LASER

Resumo: Este artigo apresenta os dados geoquímicos e petrográficos de sedimentos praiais da região SW da Praia Brava (PB) em Armação dos Búzios-RJ. Buscamos discutir os processos de intemperismo químico e proveniência, bem como, analisar o ambiente geoquímico e a sua relação com as fontes autóctones. Neste estudo foram utilizadas análises petrográficas, parâmetros texturais na distribuição de partículas, geoquímica e estatística com auxílio de Laser Difraction e Fluorescência de Raios-X com Energia Dispersiva. Os sedimentos estudados são compostos essencialmente de granadas, biotita, piroxênio (diopsídio e augita?), epidoto, monazita, hornblenda, ilmenita, zircão, rutilo, titanita, silimanita, cianita, além de quartzo. Os sedimentos investigados são reflexo dos litotipos encontrados regionalmente, indicando possivelmente uma forte correlação entre as rochas-fonte e os depósitos sedimentares. O ambiente de oxirredução é demarcado pela presença de óxidos de Fe, provavelmente hematita. O índice de alteração calculado suporta um grau moderado, onde micas são preservadas, totalmente ou em partes. Palavras-Chave: Sedimentos Inconsolidados; Depósitos Praiais; Intemperismo Químico. GEOCHEMISTRY AND PETROGRAPHY OF QUATERNARY DEPOSITS FROM SW OF PRAIA BRAVA BEACH, ARMAÇÃO DOS BÚZIOS, RJ, BRAZIL: EDFRX AND LASER DIFRACTION Abstract: This article presents the geochemical and petrographic data of beach sediments from the SW region of Praia Brava (PB) in Armação dos Búzios-RJ. We seek to discuss the processes of chemical weathering and provenance, as well as to analyze the geochemical environment and its relationship with autochthonous sources. In this study, petrographic analyzes, textural parameters in particle distribution (Laser Difraction), geochemistry (X-Ray Fluorescence with Dispersive Energy) and statistics were used. The studied sediments are essentially composed of garnets, biotite, pyroxene (diopside and augite?), epidote, monazite, hornblende, ilmenite, zircon, rutile, titanite, silimanite, kyanite, and quartz. The investigated sediments are similar to the lithotypes found regionally, thus possibly indicating a strong correlation between source rocks and sedimentary deposits. The redox environment is marked by the presence of Fe oxides, probably hematite. The alteration index supports a moderate degree, where micas are preserved, in whole or in part. Keywords: Unconsolidated Sediments, Beach Deposits; Chemical watering. GEOQUÍMICA Y PETROGRAFÍA DE DEPÓSITOS CUTERNARIOS DE LA PORCIÓN SW DE PRAIA BRAVA, ARMAÇÃO DOS BÚZIOS, RJ, BRASIL: EDFRX Y DIFFRACCIÓN LÁSER Resumen: Este artículo presenta los datos geoquímicos y petrográficos de sedimentos de playa de la región SO de Praia Brava (PB) en Armação dos Búzios-RJ. Buscamos discutir los procesos de meteorización química y procedencia, así como analizar el entorno geoquímico y su relación con fuentes autóctonas. En este estudio se utilizaron análisis petrográficos, parámetros texturales en distribución de partículas, geoquímica y estadística con la ayuda de Difracción Láser y Fluorescencia de Rayos X con Energía Dispersiva. Los sedimentos estudiados están compuestos fundamentalmente por granate, biotita, piroxeno (¿diópsido y augita?), Epidota, monacita, hornblenda, ilmenita, circón, rutilo, titanita, silimanita, cianita, además de cuarzo. Los sedimentos investigados son un reflejo de los litotipos encontrados regionalmente, lo que posiblemente indique una fuerte correlación entre las rocas generadoras y los depósitos sedimentarios. El entorno redox está delimitado por la presencia de óxidos de Fe, probablemente hematita. El índice de cambio calculado admite un grado moderado en el que se conservan las micas, ya sea total o parcialmente. Palabras clave: Sedimentos no consolidados; Depósitos en la playa; Meteorización química.