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    Wyświetlanie 1-14 z 14
    Tytuł:
    Isotopic ages of selected magmatic rocks from King George Island (West Antarctica ) controlled by magnetostratigraphy
    Autorzy:
    Nawrocki, J.
    Pańczyk, M.
    Williams, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058738.pdf
    Data publikacji:
    2011
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Antarctica
    King George Island
    magnetostratigraphy
    isotopic ages
    Opis:
    Isotopic and palaeomagnetic studies were carried out in the central part of King George Island. Selected mafic to intermediate igneous rocks were sampled for this purpose. Single-grain U-Pb dating of zircons from basalts to dacites was controlled by a whole rock 40Ar-39Ar data and the magnetostratigraphy. Five magmatic activity phases were distinguished in the SE coast of King George Island. The oldest, late Cretaceous (Campanian) phase represented by basalts of the Uchatka Point Formation are followed by the early to middle Eocene (~53–43 Ma) phase documented by the lava flows whose ages decrease from SW to NE. Next younger magmatic activity phases were recorded by the lava flows or vertical intrusions emplaced in the late Eocene (~37–35 Ma), late Oligocene (~~28-25 Ma) and late Pliocene to Holocene. The early to middle Eocene magmatic activity phase was the most extensive, producing the largest volume of magma in the study area. The new age determinations allow a more precise and credible stratigraphic correlation of the interbeds of sedimentary rocks observed in some places within the magmatic succession. The glacial provenance of the Herv' Cove diamictite is not obvious. It might represent a mountain river environment. Intense volcanic activity could be additional factor modelling the climate conditions of Antarctica in Paleogene
    Źródło:
    Geological Quarterly; 2011, 55, 4; 301-322
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Calcareous nannofossils from the Upper Cretaceous of northern James Ross Island, Antarctica : a pilot study
    Autorzy:
    Švábenická, L.
    Vodrážka, R.
    Nývlt, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060496.pdf
    Data publikacji:
    2012
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Antarctica
    James Ross Island
    Upper Cretaceous
    calcareous nannofossils
    biostratigraphy
    Opis:
    The Czech scientific expedition to northern James Ross Island, Antarctica has tested the use of calcareous nannofossils as a possible tool for stratigraphic correlation of Cretaceous and Neogene strata. Only a few samples with poor nannofossil content gave useful information for biostratigraphy. The Lower Campanian Chiastozygus garrisonii Zone and Gephyrobiscutum diabolum Subzone, respectively, was established in the lower part of the Santa Marta Formation, Lachman Crags Member, from the common occurrence of Gephyrobiscutum diabolum associated with Broinsonia parca parca and Acuturris scotus. Deposits of the Late Miocene Mendel Formation yielded exclusively reworked nannofossils from the older Upper Cretaceous deposits. Nannofossils indicate at least two distinct stratigraphic levels: Middle Coniacian and Santonian–basal Campanian, and these must have been sourced from the immediate area. The majority of the marine deposit samples studied were barren of nannofossils, probably due to late diagenetic secondary decalcification.
    Źródło:
    Geological Quarterly; 2012, 56, 4; 765--772
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pliocene age of the oldest basaltic rocks of Penguin Island (South Shetland Islands, northern Antarctic Peninsula)
    Autorzy:
    Pańczyk, M.
    Nawrocki, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058747.pdf
    Data publikacji:
    2011
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Antarctica
    Penguin Island
    Pliocene
    40Ar-39Ar dating
    magnetostratigraphy
    basaltic rocks
    Opis:
    The Penguin Island volcano is located on the southern shelf of King George Island (South Shetland Islands, West Antarctica). Its activity is regarded as connected with the opening of the Bransfield Strait. Penguin Island is dominated by a 180 m high basaltic stratocone (Deacon Peak) with a 350 m wide crater containing a small basaltic plug inside and radial dykes, and it has a second principal vent – the Petrel Crater maar – that was formed during a phreatomagmatic eruption about 100 years ago. A low-potassium, calc-alkaline sequence of basaltic lava flows with intercalations of beach deposits (Marr Point Formation) forms the basement of the stratocone. The Marr Point Formation lava flows have never been dated before. Combined whole rock 40Ar-39Ar isotopic dating and magnetostratigraphy were applied for this purpose. We obtained an isotopic 40Ar-39Ar plateau age of 2.7 š0.2 Ma, and together with the palaeomagnetic data, middle Pliocene age (Piacenzian) is implied for the basaltic plateau of Penguin Island.
    Źródło:
    Geological Quarterly; 2011, 55, 4; 335-344
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Eocene sedimentary facies in volcanogenic succession on King George Island, South Shetland Islands : a record of pre-ice sheet terrestrial environments in West Antarctica
    Autorzy:
    Mozer, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060603.pdf
    Data publikacji:
    2013
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Antarctica
    King George Island
    Eocene
    preglacial environments
    plant fossils
    Opis:
    About 34 Ma ago there was a radical change of climate that led to the formation of Antarctic ice sheet. King George Island, located in the South Shetland Islands volcanic arc (northern Antarctic Peninsula region), is one of a few places in West Antarctica which shows a geological record of sedimentary environments preceding development of the ice sheet. The Eocene sedimentary facies occur in the dominantly volcanogenic succession of King George Island. They have been recognized in the Arctowski Cove and Point Thomas formations (Ezcurra Inlet Group) and in the Mount Wawel Formation (Point Hennequin Group) in Admiralty Bay, and in the Mazurek Point Formation (Chopin Ridge Group) and Lions Cove Formation (Polonia Glacier group) in King George Bay. They record a cooling trend in terrestrial environments that began at termination of the Early/Middle Eocene Climatic Optimum, and was followed by a significant deterioration of climate during Late Eocene and earliest Oligocene, directly preceding glacial conditions in the northern Antarctic Peninsula region. The ongoing research confirms the existence of three preglacial climatic stages (PGS-1 – PGS-3) during Eocene – earliest Oligocene, from humid, warm to moderate climate (PGS-1), through cool and dry climate (PGS-2), up to cold and humid conditions (PGS-3). Studies were carried out on usually fine-grained volcanoclastic sediments, containing Podocarpaceae–Araucaria–Nothofagus plant fossils assembly. Beds of reworked pyroclastic material alternate with lava flows or volcanic agglomerates, as well as ex situ blocks of Eocene volcanogenic sediments on a moraine. Calculated geochemical indices of weathering (CIA, PIA and CIW) confirm moderate to high chemical weathering under warm and humid climate conditions at the beginning and deterioration of conditions in the end of Eocene.
    Źródło:
    Geological Quarterly; 2013, 57, 3; 385--394
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Eocene relatives of cod icefishes (Perciformes: Notothenioidei) from Seymour Island, Antarctica
    Autorzy:
    Bieńkowska-Wasiluk, M.
    Bonde, N.
    Møller, P. R.
    Gaździcki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060314.pdf
    Data publikacji:
    2013
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Notothenioids
    cod icefishes
    Eocene
    Seymour IsIand
    Antarctica
    Opis:
    Fragmentary skull bones and vertebra from the Upper Eocene La Meseta Formation on Seymour (Marambio) Island, Antarctic Peninsula have been described as gadiform fishes, informally named “Mesetaichthys”. Here we describe jaws as Mesetaichthys jerzmanskae n. g. and n. sp., and refer this taxon to the perciform suborder Notothenioidei. This group is almost unknown as fossils. Similarities to the living, ‘primitive’ nototheniid Dissostichus eleginoides are indicated in the dentition. Gadiform evolution in the Paleocene-Eocene, and the possibility of a correlation between the origin and evolution of notothenioids in connection with the deterioration of the climate in Antarctica during the Late Eocene-Oligocene is discussed.
    Źródło:
    Geological Quarterly; 2013, 57, 4; 567--582
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Geochronology of selected andesitic lavas from the King George Bay area (SE King George Island)
    Autorzy:
    Pańczyk, M.
    Nawrocki, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058742.pdf
    Data publikacji:
    2011
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    West Antarctica
    Eocene
    40Ar-39Ar dating
    magnetostratigraphy
    volcanic rocks
    Opis:
    Volcanic rocks from the Lions Rump area, which are the basement for a sequence of glaciomarine sediments of the Polonez Cove Formation, and lava flows from the Turret Point–Three Sisters Point area were sampled for thermogeochronological and palaeomagnetic investigations. Generally, andesitic lavas from King George Bay area consist mainly of clinopyroxene (Ti-augite) orthopyroxene (hyperstene) and plagioclase phenocrysts. The groundmass comprises mostly plagioclase laths, clinopyroxene, titanomagnetite and rare orthopyroxene crystals. However, the modal content, size, shape and distribution of phenocrysts are variable and specific for each sample. The Ar-Ar plateaus ages calculated for lavas from the Lions Rump area are very homogenous and point to middle Eocene age (Lutetian, ~44.5 Ma). The similar and consistent ages for volcanic basement for that area excluded the thesis about separate tectonic evolution of the Warszawa and Kraków blocks at least since the middle Eocene. The lavas from Turret Point and Three Sister Point are younger and were emplaced during the late Eocene (Bartonian/Priabonian: 37.3 š0.4 Ma and Priabonian: 35.35 š0.15 Ma, respectively). The results of isotopic investigations are consistent with magnetic polarities of the rocks indicating that the samples from the Lions Rump area are coeval with the lower part of the C20 polarity chron whereas the sample from Turret Point can be correlated with the upper part of the C17 polarity chron
    Źródło:
    Geological Quarterly; 2011, 55, 4; 323-334
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Eocene bryozoan assemblages from the La Meseta Formation of Seymour Island, Antarctica
    Autorzy:
    Hara, U.
    Mörs, T.
    Hagström, J.
    Requero, M. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060414.pdf
    Data publikacji:
    2018
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Cyclostomata
    Cheilostomata
    taxonomy
    Paleogene
    James Ross Basin
    Antarctic Peninsula
    Opis:
    Early to Late Eocene bryozoans from the La Meseta Formation of Seymour Island were collected at two localities within the Cucullaea I Allomember (Telm4 and Telm5) on the northwestern side of the island and in two localities within the Submeseta Allomember (Telm6 and Telm7) on the northeastern side. This fauna is represented by cyclostomes of the suborders Tubuliporina and Cerioporina and suborders of Neocheilostomata, among which nine species have been recognized. The following new species are introduced: Micropora nordenskjoeldi sp. nov., Lunulites marambionis sp. nov., Otionellina antarctica sp. nov. and Otionellina eocenica sp. nov. Some other taxa recognized in the studied material, such as Reticrescis plicatus, Uharella seymourensis and Celleporaria mesetaensis, were previously described from the lowermost (Telm1) or uppermost parts (Telm6-7), thus their stratigraphical ranges within the La Meseta Formation are extended. The diverse growth-forms of the bryozoans include a sole ball-shaped celleporiform colony and reticulated and bilamellar-foliaceous colony, as well as rich encrusting and free-living forms (so-called sand faunas), indicating the existence of locally restricted shallow-marine environments. This is particularly true in the middle and upper parts of the La Meseta Formation (Telm4-7). Reticulated, spheroidal and robust, branched colonies, which thrived in the environmental conditions of the lower part (Telm1), are represented only by a sparse bryozoan biota in the upper part of the La Meseta Formation. Lunulitiforms, such as Lunulites and Otionellina which are warm water, free-living bryozoans, dominate in the siliciclastic sediments of Telm5, but erect folded sheets forming a shell bed composed of ?Goodonia occur in Telm6-7. These three genera are recognized in Antarctica for the first time. The austral genus Otionellina has its earliest fossil record here, showing close biogeographical links with the Late Eocene-Miocene faunas of Australia and New Zealand. The taxonomic composition of the studied fauna together with their growth forms is a very good tool for reconstructing palaeoenvironmental conditions in the middle and upper parts (Telm4-7) of the La Meseta Formation, deposited during the Late Ypresian-Priabonian.
    Źródło:
    Geological Quarterly; 2018, 62, 3; 705--728
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Groundwater conditions along the seawater/freshwater interface on a volcanic island and a depositional area in Japan
    Autorzy:
    Marui, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058825.pdf
    Data publikacji:
    2003
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    submarine groundwater discharge
    seawater/freshwater interface
    groundwater flow
    far-east area
    Opis:
    Fresh groundwater comes in contact with seawater at the downstream end of its flow system. Most previous work has discussed the shape of the seawater/freshwater interface on the basis of Ghyben-Herzberg’s law. The groundwater, however, pushes the seawater farther offshore side than predicted by the law, giving rise to freshwater flows even below the bottom of the sea. A previous study found that the distribution of submarine groundwater discharge and the point of the seawater/freshwater interface on the marine floor are closely related. The cross-sectional shape of the interface onshore is clarified by using electrical tomography and observation of groundwater and soil samples taken from observation wells located in the coastal area (by a volcanic island and associated deposits). In both fields, diving was carried out to find the submarine groundwater discharge on the sea-floor and to take water samples. From the analysis of the water discharged on the marine floor and/or electric conductivity measurements in the marine sands, it is shown the freshwater flows (discharges) along the interface, even in the submarine deposits. The understanding of groundwater flows at the downstream end of the groundwater flow system (from mountainous to marine) will facilitate the development of water resources and the evaluation of environments.
    Źródło:
    Geological Quarterly; 2003, 47, 4; 381-388
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The origin of the Popiel peridotite (Western Sudetes, SW Poland) : metamorphism of the island arc tholeiitic cumulate
    Autorzy:
    Kukuła, A.
    Puziewicz, J.
    Ntaflos, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060292.pdf
    Data publikacji:
    2015
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    peridotite
    cumulate
    supra-subduction
    Intrasudetic Fault
    Bohemian Massif
    Opis:
    A small (280 x 140 m) outcrop of peridotite occurs on Popiel Hill (Sudetes, SW Poland) within the low-grade metabasic rocks of the Rudawy Janowickie Complex, which form the eastern and north-eastern cover of the Variscan Karkonosze granite. The peridotite is situated on the Intra-Sudetic Fault, one of the major Variscan dislocations in the region. The rock consists of strongly tectonised olivine (Fo84-88) and orthopyroxene (Mg# 0.84–0.88) aggregates, overgrown by tremolite-magnesiohornblende, locally forming large crystals, embedded in serpentine. Spinel and magnetite are subordinate; ilmenite, Fe-sulfide, and apatite are accessories. The bulk-rock chemical composition suggests a lherzolitic composition and the occurrence of primary clinopyroxene, now completely replaced by tremolite and magnesiohornblende. Rare Earth Element patterns are flat, slightly enriched relatively to primitive mantle, as is typical of island arc tholeiites. Olivine, orthopyroxene, and spinel were the first to crystallize, and they represent relics of a primary igneous assemblage. They were followed by tremolite and serpentine, formed during uplift and related metamorphism. The last mineral to crystallize was magnesiohornblende, which originated due to contact metamorphism by the Karkonosze granite magma. The Popiel peridotite probably represents a small slice of lherzolitic cumulate, which originated in a tholeiitic magma chamber at the roots of a supra-subduction volcanic arc.
    Źródło:
    Geological Quarterly; 2015, 59, 2; 239--247
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Relative sea level changes and development of the Hiiumaa Island during the Holocene
    Autorzy:
    Vassiljev, J.
    Saarse, L.
    Grudzinska, I.
    Heinsalu, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059662.pdf
    Data publikacji:
    2015
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Litorina Sea
    Limnea Sea
    lithology
    diatoms
    AMS 14C dates
    Estonia
    Opis:
    Three sediment cores (Loopsoo, Tihu, Prassi) from Hiiumaa Island (Estonia) were investigated using diatoms, lithological proxies, magnetic susceptibility, geochronological dates and incorporated with the previously studied Kõivasoo site, aiming to reconstruct the development of the island and shoreline changes during the Litorina Sea and the Limnea Sea. The highest level of the Litorina Sea shoreline near Kõivasoo is at 27.6 m a.s.l., and it occurred during the Initial Litorina Sea. Within the Litorina Sea transgression, 7800 cal yr BP, relative sea level reached 24.9 m a.s.l. at Kõivasoo, 24.1 m a.s.l. at Loopsoo, 23.6 m a.s.l. at Tihu, and 21.5 m a.s.l. at Prassi. Kõivasoo became isolated from the sea about 8500 cal yr BP, Loopsoo between 7100 and 6800 cal yr BP, Tihu around 4800 cal yr BP, and Prassi about 2500 cal yr BP. Presently gained data from Hiiumaa Island confirm that the Litorina Sea regressed consistently during the last 8000 years due to progressively declining isostatic rebound. The present study is also illustrated by 3-dimensional palaeogeographic maps of the Hiiumaa Island development.
    Źródło:
    Geological Quarterly; 2015, 59, 3; 517--530
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The facies and biota of the oldest exposed strata of the Eocene La Meseta Formation (Seymour Island, Antarctica)
    Autorzy:
    Tatur, A. E.
    Krajewski, K. P.
    lvalle de, R. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058745.pdf
    Data publikacji:
    2011
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Antarctica
    Seymour
    Eocene
    sediments
    goethite
    thanatocoenosis
    Opis:
    La Meseta Formation is made up of estuarine and shallow marine, fossiliferous clastic deposits 720 m thick that provides a unique record of marine and terrestrial biota of Antarctic ecosystems preceding continental glaciation in the Oligocene. The lower limit of this formation has been poorly known, and therefore it has been carefully investigated. The lowest part of the La Meseta Formation, at the southern bank of a palaeodelta, is represented by relics of a prograding sequence of sediments deposited in the wave-dominated part of a deltaic system in the offshore and lower and upper shoreface environments. The sequence is completed landwards by younger tidal plain sediments deposited at 40 m lower altitude in a relatively protected, central estuarine basin, which was dominated by tidal activity and influenced by periodic fluvial inflow. These strata were deposited during a late Paleocene or Ypresian/Lutetian lowstand of sea level, which might reflect a glaciation event or glacioisostatic rebound of land following deglaciation of hypothetic Antarctic inland glaciers. Forced regression of sea level and seaward expansion of a deltaic freshwater environment, led to local extinction of a unique assemblage of marine echinoderms, bryozoans, corals and brachiopods. These marine fossils, representing a thanatocoenosis, are perfectly preserved due to syngenetic goethite permineralisation. This process owed its origin to excess reactive iron coming from sulphide-rich bedrock through weathering processes and acid sulphate drainage of the neighbouring land area.
    Źródło:
    Geological Quarterly; 2011, 55, 4; 345-360
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dumpstones as records of overturning ice rafts in a Weichselian proglacial lake (Rügen Island, NE Germany)
    Autorzy:
    Pisarska-Jamroży, M.
    Van-Loon, A. J. T.
    Bronikowska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060089.pdf
    Data publikacji:
    2018
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    dumpstones
    dropstones
    ice-rafted debris
    Weichselian
    glaciolacustrine sediments
    Opis:
    Dumpstones and dropstones up to 0.8 m in size occur in a silty/sandy Weichselian glaciolacustrine succession near Dwasieden on Rügen Island in the SW Baltic Sea (NE Germany). The deposits are exceptional because two levels of dumpstones and dropstones are present, suggesting two dumping phases interrupting characteristic fine-grained glaciolacustrine sedimentation. Plastic downwarping of sediments below the dumpstones and dropstones result in soft-sediment deformation structures. The distribution and orientation of the long axes of the clasts are useful tools for the reconstruction of the state of the lake bottom, as well as for the water depth. The horizontal position of the gravels and boulders (parallel to the bedding) suggests deposition in relatively shallow-water. The dumping events are linked to iceberg rafting in a glacial lake during the Weichselian Glaciation (MIS 2).
    Źródło:
    Geological Quarterly; 2018, 62, 4; 917-924
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Probable root structures and associated trace fossils from the Lower Pleistocene calcarenites of Favignana Island, southern Italy : dilemmas of interpretation
    Autorzy:
    Uchman, A.
    Ślączka, A.
    Renda, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060614.pdf
    Data publikacji:
    2012
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    ichnology
    root structures
    burrows
    carbonates
    Quaternary
    Mediterranean Sea
    Opis:
    Two types of large, branched structures from the Lower Pleistocene (Calabrian) high-energy calcarenites of Favignana Island are described: Faviradixus robustus gen. et sp. nov. and Egadiradixus rectibrachiatus gen. et sp. nov. They may be interpreted as root structures of large plants, trees and trees or shrubs, respectively. The former taxon co-occurs with the marine animal trace fossils Ophiomorpha nodosa, Ophiomorpha isp., Thalassinoides isp. and Beaconites isp. The interpretation as root structures although tentative is probable and can be related to short emergence episodes for the formation of E. rectibrachiatus or to longer emergence, responsible for the discontinuity at the base of the overlying Tyrrhenian deposits, for F. robustus. Calcified root mats of smaller plants associated with the Tyrrhenian or younger emergence surfaces are common.
    Źródło:
    Geological Quarterly; 2012, 56, 4; 745--756
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Black sand properties in beach-dune system, Patea Beach, North Island, New Zealand
    Autorzy:
    Dłużewski, Maciej
    Hilton, Mike
    Muszyński, Andrzej
    Rotnicka, Joanna
    Woronko, Barbara
    Powiązania:
    https://bibliotekanauki.pl/articles/2060113.pdf
    Data publikacji:
    2021
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    titanomagnetite
    black sand
    beach-dune deposits
    grain size distribution
    grain shape
    microtexture
    aeolian sorting
    Opis:
    The study focuses on sand grain properties in different parts of a beach-dune system built entirely of heavy mineral particles. These properties are related to: (1) resistance of particular minerals to weathering and abrasion, (2) hydraulic sorting in the swash zone, and (3) aeolian sorting during grain transport inland from the upper beach. The main waterlain and windlain sand properties depend on settling velocity which results from grain density (reflecting grain mineralogy), size, shape and roundness. The study was performed on the beach and dunes at Patea on the west coast of the North Island of New Zealand, which are comprised of heavy minerals assemblage containing a ferromagnetic (dominated by titanomagnetite) and non-ferromagnetic (mainly pyroxene and amphibole) fractions. The result demonstrates that three zones of different sand properties can be distinguished: (1) a lower swash zone dominated by non-ferromagnetic, larger and more angular particles which are carried back from the upper swash zone down the foreshore by the backwash; (2) an uppermost swash zone and beach with almost 100% of ferromagnetic, smaller and more rounded particles deposited at the back of the beach by the uprush, which during high tide and storms can reach the cliff toe, and can be reworked by wind; and (3) a climbing dune composed of a more poorly sorted mixture of non- and ferromagnetic particles. In terms of both mineralogy and grain size and shape, the dune sand is less uniform than the beach sand. Aeolian segregation resulted here in sand textural features opposite to those found in dune sands composed of light minerals. The results highlight the density-dependent variability of grain size and shape of beach-dune deposits consisting of only heavy minerals, and broaden our understanding of mechanisms of sedimentary processes which is particularly important when reconstructing older sedimentary successions.
    Źródło:
    Geological Quarterly; 2021, 65, 3; 65: 35
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-14 z 14

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