Geologos, 2016, 22, 1


Recent Submissions

Now showing 1 - 6 of 6
  • Item
    Loess encounters of three kinds: Charles Lyell talks about, reads about, and looks at loess
    (Instytut Geologii UAM, 2016-04) Smalley, Ian; Kels, Holger; Gaudenyi, Tivadar; Jovanovic, Mladjen
    Charles Lyell (1797–1875) was an important loess pioneer. His major contribution was to distribute information on the nature and existence of loess via his influential book ‘The Principles of Geology’. He was obviously impressed by loess when he encountered it; the initial encounter can be split into three phases: conversations about loess; confronting the actual material in the field; and reading about loess in the literature. Detail can be added to an important phase in the scientific development of the study of loess. Significant events include conversations with Hibbert in 1831, conversations and explorations with von Leonhard and Bronn in 1832, the opportunity to include a section on loess in vol. 3 of ‘Principles’ for publication in 1833, a substantial Rhineland excursion in 1833, the reporting of the results of this excursion in 1834, discussions at the German Association for the Advancement of Science meeting in Bonn in 1835. Of all the people encountered perhaps H.G. Bronn was the most significant. Lyell eventually listed eleven people as relevant to the loess writings: Bronn, von Leonhard, Boue, Voltz, Steininger, Merian, Rozet, Hibbert, Noeggerath, von Meyer, Horner – of these Bronn, von Leonhard, Hibbert and Horner appear to have been the most significant, viewed from 2015.
  • Item
    Peat decomposition – shaping factors, significance in environmental studies and methods of determination; a literature review
    (Instytut Geologii UAM, 2016-04) Drzymulska, Danuta
    A review of literature data on the degree of peat decomposition – an important parameter that yields data on environmental conditions during the peat-forming process, i.e., humidity of the mire surface, is presented. A decrease in the rate of peat decomposition indicates a rise of the ground water table. In the case of bogs, which receive exclusively atmospheric (meteoric) water, data on changes in the wetness of past mire surfaces could even be treated as data on past climates. Different factors shaping the process of peat decomposition are also discussed, such as humidity of the substratum and climatic conditions, as well as the chemical composition of peat-forming plants. Methods for the determination of the degree of peat decomposition are also outlined, maintaining the division into field and laboratory analyses. Among the latter are methods based on physical and chemical features of peat and microscopic methods. Comparisons of results obtained by different methods can occasionally be difficult, which may be ascribed to different experience of researchers or the chemically undefined nature of many analyses of humification.
  • Item
    New data on Callovian (Middle Jurassic) belemnites and palynomorphs from the Northern Caucasus, southwest Russia
    (Instytut Geologii UAM, 2016-04) Dzyuba, Oksana S.; Goryacheva, Anna A.; Ruban, Dmitry A.; Gnezdilova, Victoria V.; Zayats, Pavel P.
    Palaeontological data on the Caucasus are highly important for large-scale stratigraphical and palaeobiogeographical assessment of the northern Tethyan margin, but this information is often scarce and not available in English. Field studies in the Northern Caucasus have now permitted to amass some new data. Two belemnite species are described from the stratotype section of the Kamennomostskaja Formation (Callovian, Middle Jurassic) near the town of Kamennomostskij in Adygeja (Northern Caucasus). These are Belemnopsis subhastata (von Zieten, 1831) and Rhopaloteuthis ominosa Gustomesov, 1968. The latter is a rare species, and the present find allows new insights into its taxonomy. A palynological analysis of the belemnite-bearing sample was carried out, and a diverse assemblage of dinocysts, acritarchs and prasinophytes, plus pollen and spores recognised. The most abundant palynomorphs are Micrhystridium and Classopollis. Data on belemnites coupled with those on palynomorphs indicate the early Callovian age of the sample level. This interpretation differs slightly from previous conclusions based on ammonites and dinocysts. If this age is correct, the degree of condensation of Callovian deposits in the section studied was lesser than previously assumed.
  • Item
    Geochemistry of rare earth elements in the Baba Ali magnetite skarn deposit, western Iran – a key to determine conditions of mineralisation
    (Instytut Geologii UAM, 2016-04) Zamanian, Hassan; Radmard, Kaikosrov
    The Baba Ali skarn deposit, situated 39 km to the northwest of Hamadan (Iran), is the result of a syenitic pluton that intruded and metamorphosed the diorite host rock. Rare earth element (REE) values in the quartz syenite and diorite range between 35.4 and 560 ppm. Although the distribution pattern of REEs is more and less flat and smooth, light REEs (LREEs) in general show higher concentrations than heavy REEs (HREEs) in different lithounits. The skarn zone reveals the highest REE-enriched pattern, while the ore zone shows the maximum depletion pattern. A comparison of the concentration variations of LREEs (La–Nd), middle REEs (MREEs; Sm–Ho) and HREEs (Er–Lu) of the ore zone samples to the other zones elucidates two important points for the distribution of REEs: 1) the distribution patterns of LREEs and MREEs show a distinct depletion in the ore zone while representing a great enrichment in the skarn facies neighbouring the ore body border and decreasing towards the altered diorite host rock; 2) HREEs show the same pattern, but in the exoskarn do not reveal any distinct increase as observed for LREEs and MREEs. The ratio of La/Y in the Baba Ali skarn ranges from 0.37 to 2.89. The ore zone has the highest La/Y ratio. In this regard the skarn zones exhibit two distinctive portions: 1) one that has La/Y >1 beingadjacent to the ore body and; 2) another one with La/Y < 1 neighbouring altered diorite. Accordingly, the Baba Ali profile, from the quartz syenite to the middle part of the exoskarn, demonstrates chiefly alkaline conditions of formation, with a gradual change to acidic towards the altered diorite host rocks. Utilising three parameters, Ce/Ce*, Eu/Eu* and (Pr/Yb)n, in different minerals implies that the hydrothermal fluids responsible for epidote and garnet were mostly of magmatic origin and for magnetite, actinolite and phlogopite these were of magmatic origin with low REE concentration or meteoric water involved.
  • Item
    Unravelling the complex nature of the Upper Weichselian till section at Gdynia Babie Doły, northern Poland
    (Instytut Geologii UAM, 2016-04) Woźniak, Piotr Paweł; Czubla, Piotr
    The complexity of glacial sequences may increase when these formed underneath ice sheets despite subsequent changes in their extent that are accompanied by alterations in the direction of the ice flow. Our aim was to determine whether or not changes in ice sheet dynamics during the Late Weichselian are also recorded in sediments formed north of the area of its fluctuating margin (i.e., where the ice sheet prevailed independent of such fluctuations). It is shown that in these areas such a record could have occurred, as documented by results of till studies at Babie Doły. The examination was carried out using several analyses: lithofacies properties of sediments, petrographic till composition (fine gravel fraction, indicator erratics), till matrix CaCO3 content, till fabric, as well as orientation of striae on the top surfaces of large clasts. In parallel, datings of sub- and supra-till sediments using the TL method were carried out. The basal till at Babie Doły represents almost the entire Upper Weichselian, but it can be divided into subunits whose features indicate different ice flow directions and debris supply. The lower subunit developed as a result of the palaeo-ice stream along the main axis of the Baltic Sea (from the north), expanding to areas adjacent to the depression of the Gulf of Gdańsk. The upper subunit developed when the influence of the palaeo-ice stream in the study area decreased, the main role having been taken over by the ice flowing from the northwest. The till analysed also shows considerable lateral variation, indicative of the mosaic nature of subglacial sedimentation. We consider the diversity of permeability of deposits over which the ice sheet extended to be the prime factor that determined such a situation.
  • Item
    River response to climate and sea level changes during the Late Saalian/Early Eemian in northern Poland – a case study of meandering river deposits in the Chłapowo cliff section
    (Instytut Geologii UAM, 2016-04) Moskalewicz, Damian; Sokołowski, Robert J.; Fedorowicz, Stanisław
    Fluvial sediments in the Chłapowo cliff section were studied in order to reconstruct their palaeoflow conditions and stratigraphical position. Lithofacies, textural and palaeohydraulic analyses as well as luminescence dating were performed so as to achieve the aim of study. Sedimentary successions were identified as a record of point bar cycles. The fluvial environment probably functioned during the latest Saalian, shortly after the retreat of the Scandinavian Ice Sheet. Discharge outflow was directed to the northwest. The river used the older fluvioglacial valley and probably was directly connected to the Eem Sea. Good preservation and strong aggradation of point-bar cycles were related to a rapid relative base level rise. The meandering river sediments recognised showed responses to climate and sea level changes as illustrated by stratigraphical, morphological and sedimentological features of the strata described. The present study also revealed several insights into proper interpretation of meandering fluvial successions, in which the most important were: specific lithofacies assemblage of GSt (St, Sp) → Sl → SFrc → Fm (SFr) and related architectural elements: channel/sandy bedforms CH/SB → lateral accretion deposits LA → floodplain fines with crevasse splays FF (CS); upward-fining grain size and decreasing content of denser heavy minerals; estimated low-energy flow regime with a mean depth of 1.6–3.3 m, a Froude number of 0.2–0.4 and a sinuosity of 1.5.
Uniwersytet im. Adama Mickiewicza w Poznaniu
Biblioteka Uniwersytetu im. Adama Mickiewicza w Poznaniu
Ministerstwo Nauki i Szkolnictwa Wyższego