Geologos, 2015, 21, 1


Recent Submissions

Now showing 1 - 4 of 4
  • Item
    Cyclic sedimentation pattern in Lake Veetka, southeast Estonia: a case study
    (Bogucki Wydawnictwo Naukowe, 2015-03) Saarse, Leili
    A sediment core from Lake Veetka, southeast Estonia, 1077 cm in length and covering 10,500 calibrated years, was examined using loss-on-ignition, grain-size distribution and AMS 14 C dating to reconstruct depositional dynamics. The studied core, recovered from the northern part of the lake, shows a cyclic pattern of organic and mineral matter concen -tration with cycle durations of 100-400 years. Cyclicity is displayed better in sediments laid down between 9,200 and 5,600 cal BP. Within two time windows (5,600–5,100 cal BP and from 1,200 cal BP to the present), sediment composition changed drastically on account of a high and fluctuating mineral matter content, obviously driven by different factors. Little Ice Age cooling is characterised by the highest proportion of mineral matter, and the Medieval Warm Period is typified by high organic matter content. The cyclic change of organic and mineral matter has been related to climate dynamics, most likely an alternation of wet and dry conditions, changes in the water level of the lake and differences in bioproduction.
  • Item
    New data on middle and late Albian foraminifera and biostratigraphy of the northern palaeobiogeographical district of western Siberia
    (Bogucki Wydawnictwo Naukowe, 2015-03) Podobina, Vera M.
    The present paper discusses foraminiferal assemblages and biozones established on the basis of studies of samples from ten borehole sequences of the Khanty-Mansiysk Horizon in the Samotlor area of the northern palaeobiogeograph -ical district of western Siberia (Russia). In this region, middle and late Albian foraminiferal assemblages were first distinguished in western Siberia. Levels from which these assemblages have been recovered, are here referred to the following foraminiferal zones, the Ammobaculites fragmentarius–Gaudryinopsis filiformis Zone (middle Albian) and the Ammotium braunsteini–Verneuilinoides borealis assanoviensis Zone (upper Albian). Zonal assemblages are dominated by representatives of the orders Ammodiscida, Textulariida and Ataxophragmiida. Species of the ataxophragmiid genera Verneuilinoides, Pseudoverneuilina and Gaudryinopsis are the most characteristic, inclusive of several key index forms. Foraminiferal tests consist of agglutinated quartz-silica, the wall microstructure being almost exclusively medium and coarse grained. In specific composition, the Albian assemblages from the Samotlor area are similar to those from Tran -suralia (Russia) and to the Canadian Province, which, together with West-Siberian Province, forms the Arctic palaeo -biogeographical realm.
  • Item
    Factors controlling sedimentation in the Toruń-Eberswalde ice-marginal valley during the Pomeranian phase of the Weichselian glaciation: an overview
    (Bogucki Wydawnictwo Naukowe, 2015-03) Pisarska-Jamroży, Małgorzata
    During the Pleistocene the Scandinavian ice sheet drained huge quantities of sediment-laden meltwaters. These meltwaters supplied ice-marginal valleys that formed parallel to the front of the ice sheet. Not without significance was the supply of ice-marginal valleys from extraglacial rivers in the south. Moreover, periglacial conditions during and after sedimentation in ice-marginal valleys, the mor -phology of valley bedrocks, and erosion of older sediments played important roles in the depositional scenarios, and in the mineralog -ical composition of the sediments. The mechanisms that controlled the supply and deposition in ice-marginal valleys were analysed on the basis of a Pleistocene ice-marginal valley that was supplied by northern and southern source areas in the immediate vicinity. Investigations were conducted in one of the largest ice-marginal valleys of the Polish-German lowlands, i.e., the Toruń-Eberswalde ice-marginal valley, in sandurs (Drawa and Gwda) supplied sediments and waters from the north into this valley, and on extraglacial river terraces (pre-Noteć and pre-Warta rivers), formed simultaneously with the sandurs and ice-marginal valley (Pomeranian phase of Weichselian glaciation) supplied sediments and waters from the south into this valley. A much debated question is how similar, or different, depositional processes and sediments were that contributed to the formation of the Toruń-Eberswalde ice-marginal valley, and whether or not it is possible to differentiate mostly rapidly aggraded sandur sediments from ice-marginal valley sediments. Another question addresses the contribution of extraglacial feeding of the Toruń-Eberswalde ice-marginal valley. These matters were addressed by a wide range of analyses: sediment texture and structure, architectural elements of sediments, frequency of sedimentary successions, heavy-mineral analysis (both transparent and opaque heavy minerals), analysis of rounding and frosting of quartz grains, and palaeohydrological calculations. Additionally, a statistical analysis was used. The specific depositional conditions of distribution of sediments in ice-marginal valley allow to distinguish new environment of ice-marginal valley braided river. The spectrum of depositional conditions in the Toruń-Eberswalde ice-marginal valley and their specific palaeohydraulic parameters allow to distinguish three coexisting zones in the ice-marginal valley braided-river system: (1) deep gravel-bed braided channel zone with extensive scours, (2) deep sand-bed braided channel zone with transverse bars, and (3) marginal sand-bed and gravel-bed braided channel zone with diamicton and breccia deposition, which were characterised in detail. Some of the results have been published previously, which is why they are discussed in the present paper within the context of new data.
  • Item
    Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran)
    (Bogucki Wydawnictwo Naukowe, 2015-03) Taghipour, Batoul; Ahmadnejad, Farhad
    The Qolqoleh gold deposit is located in the northwestern part of the Sanandaj–Sirjan Zone (SSZ), within the NE–SW trending Qolqoleh shear zone. Oligocene granitoids, Cretaceous meta-limestones, schists and metavolcanics are the main lithological units. Chondrite-normalised REE patterns of the ore-hosting metavolcanics indicate REE enrichment relative to hanging wall (chlorite-sericite schist) and footwall (meta-limestone) rocks. The pattern also reflects an enrich -ment in LREE relative to HREE. It seems that the LREE enrichment is related to the circulation of SO 4 2- and CO 2 -bearing fluids and regional metamorphism in the Qolqoleh shear zone. Both positive and negative Eu anomalies are observed in shear-zone metavolcanics. These anomalies are related to the degree of plagioclase alteration during gold minerali -sation and hydrothermal alteration. In progressing from a metavolcanic protomylonite to an ultramylonite, significant changes occurred in the major/trace element and REE concentration. Utilising an Al-Fe-Ti isocon for the ore-hosting metavolcanics shows that Sc, Y, K, U, P, and M-HREE (except Eu) are relatively unchanged; S, As, Ag, Au, Ca, LOI, Rb and LREE are enriched, and Sr, Ba, Eu, Cr, Co and Ni decrease with an increasing degree of deformation. Based on geochemical features and comparison with other well-known shear zones in the world, the study area is best classified as an Isovolume-Gain (IVG) type shear zone and orogenic type gold mineralisation. Based on the number of phases observed at room temperature and their microthermometric behaviour, three fluid in -clusion types have been recognised in quartz-sulphide and quartz-calcite veins: Type I monophase aqueous inclusions, Type II two-phase liquid-vapour (L-V) inclusions which are subdivided into two groups based on the homogenisation temperature (Th): a) L-V inclusions with Th from 205 to 255°C and melting temperature of last ice (Tm) from –3 to –9°C. b) L-V inclusions with higher Th from 335 to 385°C and Tm from –11 to –16°C. Type III three-phase carbonic-liquid in -clusions (liquid water-liquid CO2-vapour CO2) with Th of 345–385°C. The mean values of the density of ore-forming fluids, pressure and depth of mineralisation have been calculated to be 0.79–0.96 gr/cm 3, 2 kbar and 7 km, respectively. The δ18O water and δD values of the gold-bearing quartz-sulphide veins vary from 7.2‰ to 8‰ and –40.24‰ to –35.28‰, respectively, which are indicative of an isotopically heavy crustal fluid and likely little involvement of meteoric fluid. The δ18O water values of the quartz-calcite veins have a range of –5.31‰ to –3.35‰, and the δD values of –95.65‰ to –75.31‰, which are clearly lower than those of early-stage quartz-sulphide-gold veins, and are close to the meteoric water line. Based on comparisons of the D–O isotopic systematics, the Qolqoleh ore-mineralising fluids originated from metamorphic devolatilisation of Cretaceous volcano-sedimentary piles. Devolatilisation of these units occurred either synchronously with, or postdates, the development of penetrative (ductile) structures such as shear zones and during overprinting brittle deformation.