Wyniki wyszukiwania - Biblioteka Nauki

1

Sezonowe zmiany skladu osadu laminowanego jeziora Gosciaz w najmlodszej czesci profilu

100%

Goslar T.

|

tom 08

2

Chronologia warwowa osadu laminowanego jeziora Gosciaz

100%

Goslar T.

|

tom 08

3

Komputerowe pomiary grubosci lamin

63%

Walanus A. , Goslar T.

|

tom 08

4

Vegetation changes caused by agricultural societies in the Great Mazurian Lake District

51%

Wacnik A. , Goslar T. , Czernik J.

Acta Palaeobotanica

|

2012

|

tom 52

|

nr 1

5

Comparing Varve Counting And 14C-Ams Chronologies In The Sediments Of Lake Żabińskie, Northeastern Poland: Implications For Accurate 14C Dating Of Lake Sediments

45%

Bonk A. , Tylmann W. , Goslar T. , Wacnik A. , Grosjean M.

|

tom Vol. 42, no.1

159--171

EN

Varved lake sediments from Lake Żabińskie (northeastern Poland) provide a highresolution calendar-year chronology which allows validation of 14C dating results. Microscopic analysis of the varve microfacies revealed that laminations found in Lake Żabińskie were biogenic (calcite) varves. Three independent counts indicated a good preservation quality of laminae in the 348 cm long sediment profile which contained 1000+12/-24 varves. The varve chronology was validated with the 137Cs activity peaks, the tephra horizon from the Askja eruption at AD 1875 and with the timing of major land-use changes of known age inferred from pollen analysis. 32 AMS 14C dates of terrestrial macrofossils distributed along the profile were compared with the varve chronology. After identification of outliers, the free-shape model performed with 21 14C dates provided the best possible fit with the varve chronology. We observed almost ideal consistency between both chronologies from the present until AD 1250 while in the lower part (AD 1000–1250) the difference increases to ca. 25 years. We demonstrate that this offset can be explained by too old radiocarbon ages of plant remains transported to the lake by the inflowing creek. Results of this study highlight that careful interpretation of radiocarbon age-depth models is necessary, especially in lakes where no annual laminations are observed and no independent method are used for cross-validation.

6

Stages of the formation of the Łeba Barrier-Lagoon system on the basis of the geological cross-section near Rąbka (southern Baltic coast, Poland)

45%

Rotnicki K. , Alexandrowicz S. W. , Pazur A. , Goslar T. , Borówka R. K.

|

2009

|

tom Vol. 26

3-24

EN

The article presents the results of a detailed study of the geological structure of the Łeba Barrier in the Rąbka cross-section (Southern Baltic, Poland). The barrier separates Lake Łebsko from the Baltic. Five sedimentary complexes were distinguished there (M2-M6). The spatial variability of the grain-size distribution was examined and succession stages of the mollusc fauna occurring in the individual sedimentary complexes were distinguished. Radiocarbon dating was used to establish the age of the most important events during the process of formation of the barrier, which took place in the course of several relative sea-level changes. The first sedimentary complex (M2) at Rąbka is connected with the second ingression (i2) of the Baltic Sea (ca. 6,700-6,000 14C years BP), sea-level stabilization (6,000-5,500 14C years BP), and at last sea-level lowering (5,500-5,000 14C years BP) in the region of the Gardno-Łeba Coastal Plain. The sedimentary complex M3 developed in a lagoonal environment when the barrier was situated north of its present position (5,000-3,000 14C BP). The next lowering of the sea-level made the lagoon shallower and caused the emergence of small but already subaerial stretches of barrier land with a freshwater fauna in the north (4,880š40 14C BP). With the next ingression stage (i3), which took place between 4,500 and 3,000 BP, the barrier shifted to its present-day position and the lagoon changed into a freshwater lake. From 3,000 to 1,700 14C BP fossil soil and peats developed on the barrier surface as a result of another sea-level lowering. The last ingression stages (i4 and i5), younger than 1,700 BP, built up the barrier, practically in its today's location (sedimentary complexes M4 and M5). The youngest sedimentary complex (M-6) is represented by present-day beach sands.

7

Climate change and human impact in the southern Baltic during the last millennium reconstructed from an ombrotrophic bog archive

38%

Lamentowicz M. , Gałka M. , Pawlyta J. , Lamentowicz Ł. , Goslar T. , Miotk-Szpiganowicz G.

|

tom Vol. 28

3-16

EN

We present the last millennium of history of a peatland located in northern Poland. Our results are based on two replicate monoliths taken from a Baltic raised bog. We applied a high-resolution approach and radiocarbon dating to the peat material to obtain a detailed palaeoenvironmental reconstruction. To reconstruct past peatland moisture, we used three proxies: testate amoebae, plant macrofossils and pollen. Despite different peat accumulation and extensive hiatus in the formerly studied core, both monoliths show a similar pattern of changes. However, the core from this study provides us with more detailed data on S. fuscum disappearance which correlates well with the data from the other Baltic bog, Słowińskie Błoto. Our research shows that pristine Baltic bogs can be dated to AD 1350. Słowińskie Błoto palaeohydrology confirms AD 1300 as the beginning of the hydrological disturbance. In the case of the Stążki and Słowińskie Błoto bogs, the Little Ice Age (LIA) is recorded between AD 1500 and AD 1800. However, this climatic change might have been blurred by human impact. In the case of the Baltic bogs, their reference virgin state can be dated to AD 1200. After this date, we observed increasing human impact and climatic instability connected with the LIA. However, between AD 1800 and 1900, bogs were wet, most possibly due to climatic forcing. This fact suggests that despite human impact, recent peat deposits can still reflect climate. Our research provided information related to the time of existence, location and characteristics of the natural/pristine state. High-resolution peatland palaeoecology is crucial for restoration activities, e.g., rewetting and environmental management. The palaeohydrological context (supported by other proxtes) of the last 1000 years provides a retiable answer to the question: 'To rewet or not to rewet?'