Papers by Ieva Grudzinska
Peat Stratigraphy and Changes in Peat Formation During the Holocene in Latvia
STRATI 2013, 2014
An overview of peatland development and peat formation during the Holocene in Latvia is presented... more An overview of peatland development and peat formation during the Holocene in Latvia is presented. Altogether, 24 peatlands each with at least three 14C dates, plant macrofossil data and degree of peat decomposition were assembled in order to compare and discuss spatial and temporal changes. A series of 2000-year time windows for the entire Holocene were produced, showing peatland development processes as reflected by peat composition. The results show that the oldest peatlands started to develop at the beginning of the Early Holocene (11,600e8200 cal. BP), mainly in depressions in the uplands. Peat macrofossil composition is characterised by remains of plants growing under conditions of excess humidity, represented by various Hypnum species and sedges (Carex lasiocarpa, Carex appropinquata and Carex teretiuscula), and less frequently by woody plants. The degree of peat decomposition indicates a wetedryewet pattern for the Holocene climate, which accords with other regional climatic studies. Climate change influenced groundwater and lake levels, promoting the establishment of peatlands during the Early Holocene.Warm and dry conditions resulted in low peat accumulation rates throughout the Middle Holocene (8200e4200 cal. BP). The present study shows that a large number of bogs became established in the Late Holocene (4200e0 cal. BP), formed by a wide variety of various raised-bog-type peats (cotton grasseSphagnum, Sphagnum fuscum and cotton grass peat), which continue to accumulate at the present day. The Early, Middle and Late Holocene as recognised in the present study correspond closely to a recent global scheme suggested by the INTIMATE-SQS working group on the subdivision of the Holocene.
Estonian Journal of Earth Sciences, 2012
The marine-freshwater environmental transition, i.e. basin isolation from the Limnea Sea, has bee... more The marine-freshwater environmental transition, i.e. basin isolation from the Limnea Sea, has been identified in two short sediment cores with respect to their diatom composition, loss-on-ignition and magnetic susceptibility content. The isolation level of the basins was dated by accelerator mass spectrometry radiocarbon measurements. The basins are situated on the southern coast of the Gulf of Finland between altitudes 5.5 and 3.9 m above sea level. The Lohja basin became isolated from the sea around 2300 cal yr BP and Käsmu basin around 1800 cal yr BP as a result of glacio-isostatic uplift. The total land upheaval rate that has been 2.6 mm yr -1 since 2500 cal yr BP has currently decreased to 2.0 mm yr -1 . We present a GIS-based 3D palaeogeographic reconstruction of the palaeocoastline changes in northern Estonia for two peninsulas, Pärispea and Käsmu, as well as compose a shoreline displacement curve for the study area, which is a compilation of previous and ongoing investigations.
Three sediment cores (Loopsoo, Tihu, Prassi) from Hiiumaa Island, Estonia) were investigated usin... more 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 Koivasoo 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 shore line near Koivasoo 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 Koivasoo, 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. Koivasoo 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 Is land con firm 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.
Bulletin of the Geological Society of Finland
In response to glacio-isostatic rebound in Estonia, a relative sea level fall occurred during the... more In response to glacio-isostatic rebound in Estonia, a relative sea level fall occurred during the mid- and late-Holocene, and as a result, lowland regions in northern Estonia have experienced an evolution from sea to land. The mid- and late-Holocene shoreline changes along the southern coast of the Gulf of Finland were reconstructed, using litho-, bio- and chronostratigraphical proxies from four lakes. The lakes are located within the Gulf of Finland drainage system at different altitudes between 18 and 4 m above the present sea level. The isolation from the sea and the onset of freshwater lacustrine sedimentation occurred in Tänavjärv basin at 5400 cal yr BP, in Klooga basin at 4200 cal yr BP, in Lohja basin at 2200 cal yr BP and in Käsmu basin at 1800 cal yr BP. Through the application of GIS-based analysis, a modern digital terrain model and reconstructed past water level surfaces, we present a series of scenarios of shoreline and palaeogeography changes occurring since 7800 cal ...
Baltica, 2014
The paper presents diatom, loss-on-ignition, magnetic susceptibility, and radiocarbon data to rec... more The paper presents diatom, loss-on-ignition, magnetic susceptibility, and radiocarbon data to reconstruct the depositional history and evolution of Lake Harku, a former Limnea Sea lagoon. Harku is one of the youngest isolated lakes that has been studied bio-and chronostratigraphically in Estonia to date. Based on changes in diatom assemblages, four evolutionary stages in basin development have been recognized (lagoon, semi-enclosed lagoon, transitional and closed lake). Shoreline positions at 2000, 1500, 1000 and 800 cal BP have been reconstructed and displayed on 3D palaeogeographic maps. Lake Harku became isolated from the Limnea Sea at ~800 cal BP, followed by occasional seawater incursions over the next 300 years. Plain landscape, low-lying threshold, and proximity to the sea contributed to extended basin isolation.
Estonian Journal of Earth Sciences, 2012
The marine-freshwater environmental transition, i.e. basin isolation from the Limnea Sea, has bee... more The marine-freshwater environmental transition, i.e. basin isolation from the Limnea Sea, has been identified in two short sediment cores with respect to their diatom composition, loss-on-ignition and magnetic susceptibility content. The isolation level of the basins was dated by accelerator mass spectrometry radiocarbon measurements. The basins are situated on the southern coast of the Gulf of Finland between altitudes 5.5 and 3.9 m above sea level. The Lohja basin became isolated from the sea around 2300 cal yr BP and Käsmu basin around 1800 cal yr BP as a result of glacio-isostatic uplift. The total land upheaval rate that has been 2.6 mm yr -1 since 2500 cal yr BP has currently decreased to 2.0 mm yr -1 . We present a GIS-based 3D palaeogeographic reconstruction of the palaeocoastline changes in northern Estonia for two peninsulas, Pärispea and Käsmu, as well as compose a shoreline displacement curve for the study area, which is a compilation of previous and ongoing investigations.
The Lake Rāzna is the second largest lake by area and the biggest by volume in Latvia. It is loca... more The Lake Rāzna is the second largest lake by area and the biggest by volume in Latvia. It is located in the central part of the Latgale Upland and occupies the lower part of the extensive glacial depression formed as a result of the activity of the Rāzna glacier tongue over the course of the last deglaciation. The results of the composition of the sediments study and the changes in composition confirm the hypothesis that Lakes Rāzna and Zosna were part of a single large
palaeolake in the late stage of the Late Glacial. With the lowering of the water level and more active overgrowth processes, the palaeolake was gradually divided into two separate lakes. The results of the research lead to the conclusion that the palaeolake started overgrowing about 8000 years ago; initially starting with the shallower area separating the two lakes, and the palaeolake ceased to
exist, being replaced by two separate lakes, Rāzna and Zosna.
The paper presents diatom, loss-on-ignition, magnetic susceptibility, and radiocarbon data to rec... more The paper presents diatom, loss-on-ignition, magnetic susceptibility, and radiocarbon data to reconstruct the depositional history and evolution of Lake Harku, a former Limnea Sea lagoon. Harku is one of
the youngest isolated lakes that has been studied bio- and chronostratigraphically in Estonia to date. Based on
changes in diatom assemblages, four evolutionary stages in basin development have been recognized (lagoon,
semi-enclosed lagoon, transitional and closed lake). Shoreline positions at 2000, 1500, 1000 and 800 cal BP
have been reconstructed and displayed on 3D palaeogeographic maps. Lake Harku became isolated from the Limnea Sea at ~800 cal BP, followed by occasional seawater incursions over the next 300 years. Plain landscape, low-lying threshold, and proximity to the sea contributed to extended basin isolation.
Mid and late-Holocene shoreline changes along the southern coast of the Gulf of Finland
In response to glacio-isostatic rebound in Estonia, a relative sea level fall occurred during the... more In response to glacio-isostatic rebound in Estonia, a relative sea level fall occurred during the mid- and late-Holocene, and as a result, lowland regions in northern Estonia have experienced an evolution from sea to land. The mid- and late-Holocene shoreline changes along the southern coast of the Gulf of Finland were reconstructed, using litho-, bio- and chronostratigraphical proxies from four lakes. The lakes are located within the Gulf of Finland drainage system at different altitudes between 18 and 4 m above the present sea level. The isolation from the sea and the onset of freshwater lacustrine sedimentation occurred in Tänavjärv basin at 5400 cal yr BP, in Klooga basin at 4200 cal yr BP, in Lohja basin at 2200 cal yr BP and in Käsmu basin at 1800 cal yr BP. Through the application of GIS-based analysis, a modern digital terrain model and reconstructed past water level surfaces, we present a series of scenarios of shoreline and palaeogeography changes occurring since 7800 cal yr BP. The land uplift rate, which was approximately 2.8 mm yr-1 7800 cal yr BP in the surroundings of Tänavjärv, has decreased to 2.2 mm yr-1 at present and that at Lohja from 2.4 to ca 2.0 mm yr-1, respectively. The relative sea level curves show a land uplift decrease, which is nearly linear since the mid-Holocene.
The marine-freshwater environmental transition, i.e. basin isolation from the Limnea Sea, has be... more The marine-freshwater environmental transition, i.e. basin isolation from the Limnea Sea, has been identified in two short sediment cores with respect to their diatom composition, loss-on-ignition and magnetic susceptibility content. The isolation level of the basins was dated by accelerator mass spectrometry radiocarbon measurements. The basins are situated on the southern coast of the Gulf of Finland between altitudes 5.5 and 3.9 m above sea level. The Lohja basin became isolated from the sea around 2300 cal yr BP and Kasmu basin around 1800 cal yr BP as a result of glacio-isostatic uplift. The total land upheaval rate that has been 2.6 mm yr 1 since 2500 cal yr BP has currently decreased to 2.0 mm yr 1. We present a GIS-based 3D palaeogeographic reconstruction of the palaeocoastline changes in northern Estonia for two peninsulas, Parispea and Kasmu, as well as compose a shoreline displacement curve for the study area, which is a compilation of previous and ongoing investigations.
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Papers by Ieva Grudzinska
palaeolake in the late stage of the Late Glacial. With the lowering of the water level and more active overgrowth processes, the palaeolake was gradually divided into two separate lakes. The results of the research lead to the conclusion that the palaeolake started overgrowing about 8000 years ago; initially starting with the shallower area separating the two lakes, and the palaeolake ceased to
exist, being replaced by two separate lakes, Rāzna and Zosna.
the youngest isolated lakes that has been studied bio- and chronostratigraphically in Estonia to date. Based on
changes in diatom assemblages, four evolutionary stages in basin development have been recognized (lagoon,
semi-enclosed lagoon, transitional and closed lake). Shoreline positions at 2000, 1500, 1000 and 800 cal BP
have been reconstructed and displayed on 3D palaeogeographic maps. Lake Harku became isolated from the Limnea Sea at ~800 cal BP, followed by occasional seawater incursions over the next 300 years. Plain landscape, low-lying threshold, and proximity to the sea contributed to extended basin isolation.
palaeolake in the late stage of the Late Glacial. With the lowering of the water level and more active overgrowth processes, the palaeolake was gradually divided into two separate lakes. The results of the research lead to the conclusion that the palaeolake started overgrowing about 8000 years ago; initially starting with the shallower area separating the two lakes, and the palaeolake ceased to
exist, being replaced by two separate lakes, Rāzna and Zosna.
the youngest isolated lakes that has been studied bio- and chronostratigraphically in Estonia to date. Based on
changes in diatom assemblages, four evolutionary stages in basin development have been recognized (lagoon,
semi-enclosed lagoon, transitional and closed lake). Shoreline positions at 2000, 1500, 1000 and 800 cal BP
have been reconstructed and displayed on 3D palaeogeographic maps. Lake Harku became isolated from the Limnea Sea at ~800 cal BP, followed by occasional seawater incursions over the next 300 years. Plain landscape, low-lying threshold, and proximity to the sea contributed to extended basin isolation.