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Wyszukujesz frazę "fluvial deposits" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
A Miocene anastomosing river system in the area of Konin Lignite Mine, central Poland
Autorzy:
Widera, M.
Kowalska, E.
Fortuna, M.
Powiązania:
https://bibliotekanauki.pl/articles/191379.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
sedimentology
fluvial deposits
palaeochannel pattern
anastomosing river
sand-filled channels
Opis:
This sedimentological study of the Wielkopolska Member of the Miocene Poznań Formation in the Jóźwin IIB opencast lignite-mining field, central Poland, reveals a late mid-Miocene anastomosing fluvial system with ribbon-shaped channels filled mainly by sandy and muddy deposits. The fluvial system, extending across the eastern flank of the post-Mesozoic Kleczew Graben, was tributive in its eastern upper reaches, but was increasingly distributive and northwards deflected in its lower reaches near the graben axis. Lithofacies analysis of a representative palaeochannel indicates that the river discharge significantly fluctuated and that the channels were filled with mud-bearing stratified fine-grained sand by low-density tractional turbulent flow during the high and low water stages and with a massive mud or sandy mud by a high-density flow during the rising and falling stages. The spatial pattern of fluvial channels and deformation channel-fill sandbodies were controlled by the graben topography and the differential compaction of peat substrate, with possible influence of bedrock faults. The fluvial system is thought to have drained to an endorheic ‘terminal’ basin to the north, rather than into the hypothetical Baltic River and further westwards to the distant North Sea basin, as postulated by some previous authors. The present case study contributes to the known spectrum of anastomosing river systems as a sand- to mud-dominated end-member.
Źródło:
Annales Societatis Geologorum Poloniae; 2017, 87, 2; 157-168
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sand- and mud-filled fluvial palaeochannels in the Wielkopolska Member of Neogene Poznań Formation, central Poland
Autorzy:
Widera, M.
Powiązania:
https://bibliotekanauki.pl/articles/191168.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
fluvial lithosomes
floodplain deposits
channel-fill facies
channel width-depth ratio
hyperconcentrated flow
anastomosing river system
Opis:
This study focuses on the single- and multi-storey fluvial palaeochannel lithosomes encased in mud- rich floodplain deposits in the alluvial succession of the late Neogene Wielkopolska Member of the Poznań For- mation, central Poland, well-exposed in the lignite mining pits of the region. The fluvial lithosomes include both sand-filled and mud-filled channel varieties. The channel-fill facies are not diagnostic for any particular type of fluvial system, as the fine- to very fine-grained sandy deposits are massive to trough cross-stratified and also the muddy deposits are massive to weakly flat-laminated. The scarcity of lateral accretion bedding precludes the possibility of meandering rivers, whereas the low width/thickness ratios of the palaeochannels preclude braided rivers. The width/thickness ratio is in the range of 4.5–14 (averaging 7.5) for sand-filled channels and in the range of 6–10 (averaging 9) for mud-filled ones, which indicates narrow ribbons in general classification of fluvial channel belts. The origin of the alluvial succession is attributed to a W-/NW-directed anastomosing river system characterized by laterally inactive cut-and-fill channels with cohesive and vegetated banks. The sand-filled chan- nels conveyed water and sediment discharges on a perennial basis, whereas the mud-filled conduits are thought to have been the cut-and-abandoned branches of the system, filled by overbank flooding from adjacent active channels. Minor lateral migration of channels occurred probably during periods of minimum subsidence rate, when the fluvial system was forced to develop lateral accommodation for its discharges.
Źródło:
Annales Societatis Geologorum Poloniae; 2013, 83, 1; 19-28
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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