Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: varves

Sortuj według:

Ogranicz wyniki do:

Diatom-based reconstruction of trophic status changes recorded in varved sediments of Lake Żabińskie (northeastern Poland), AD 1888-2010

Witak M., Hernández-Almeida I., Grosjean M., Tylmann W.

Oceanological and Hydrobiological Studies

2017

Vol. 46, No. 1

1--17

We investigated diatom assemblages in surface sediments of 46 lakes in northern Poland and developed a diatom-based transfer function to infer epilimnetic total phosphorus (TP) concentrations. Multivariate ordination techniques (DCA, CCA) were used to identify major environmental gradients and to evaluate the effect of environmental parameters on the distribution of diatoms in the modern diatom dataset. The transfer function was developed using PLS, WA and WA-PLS models, and applied to a varved sediment core from Lake Żabińskie, AD 1888-2010. Annually-resolved quantitative reconstruction of TP concentrations shows that multidecadal changes in the TP level reflect the local settlement history, land-use changes and development of agriculture and tourism. The period of high trophic levels with maximum values of TP was documented until the late 1920s. In the 1930s-1970s period, TP generally decreased and eutraphentic flora was partly replaced by oligotraphentic and oligo-mesotraphentic diatom taxa. The reconstructed TP concentrations have started to increase from the 1970s. After the 1950s, strong short-term fluctuations of TP values were noted and explained by interactions between meteorological conditions, water column mixing and nutrient cycling in the lake.

The evolution of a Weichselian proglacial lake in NW Poland as revealed by static penetration tests

Wierzbicki Jędrzej, Paluszkiewicz Renata, Paluszkiewicz Ryszard

Geologos

2011

Vol. 17, No. 2

111--119

The lithology, structure and geophysical characteristics of the glaciolacustrine clays deposited in the Wierzchowo proglacial lake were determined using static penetration tests (CPTU) in combination with standard lithological measurements. The deposits are divided into four lithological units (R1 to R4) on the basis of overconsolidation. Units R3 and R4 are separated by mass-flow deposits. The depositional conditions history of the lake result represent four phases: (1) an initial (low-energy) phase with the deposition of the rhythmically laminated sediments of units R1 and R2, which are divided by an erosional interval; (2) a phase of non-deposition with some desiccation structures and extended consolidation of sediments; (3) the main phase characterised by deposition of the rhythmically laminated sediments of unit R3; and finally, (4) the youngest phase, which represents alternations of deposition and erosion. The results show that sedimentation in the Wierzchowo proglacial lake was less continuous, and that the depositional processes were more complex than in the neighboring Złocieniec glacial lake.

Stable isotopes as record of climatic changes of Daniglacial in Lithuania

Gaigalas A., Pazdur A., Hałas S., Pawlyta J., Kazakauskas V.

Geochronometria

2001

Vol. 20

81-86

Development of glaciolacustrine basins and varved clay sedimentation in Lithuania are closely connected with the course of ice retreat during Daniglacial time from 16,000 till 13,000 BP. Isotopic composition (delta 13C and delta 18O) of chemogenic carbonaceous samples from glaciolacustrine varved clays, which spread near glacier edge of South-Lithuanian (Balbieriýkis section), Middle-Lithuanian (Girininkai section) and North-Lithuanian (Joniškelis section) Phases of the Baltija (Pomeranian) Stage of Nemunas (Vistulian) Glaciation, has been studied. The obtained stable isotope data well confirm climatic changes of Daniglacial time in Lithuania. The gradual warming of climate is connected with the South-Lithuanian to Middle-Lithuanian and the Middle-Lithuanian to North-Lithuanian Interphasials as well as with the South Lithuanian interoscillations. The Interphasial lacustrine sedimentation with rhythmical lamination of carbonaceous sediments was observed in the middle part of the Balbieriýkis section (at a depth of 3.1-5.9 m). The following climatic changes of Daniglacial time in Lithuania are distinguished: (1) stadial (3000-6000), (2) glaciophasial (500-1000), (3) glaciooscillation (500-1000) years and (1) interstadial (1000-2000), (2) interphasial (250-450), (3) glacio-interoscillation (20-40) years. Regular succession of Daniglacial climatic and sedimentation changes in the local periglacial glaciolacustrine lakes, conditioned by recession of the last Scandinavian ice sheet, was revealed in the glaciolacustrine-lacustrine sediments for the first time.