Wyniki wyszukiwania - BazTech

1

A fossil diatom-based reconstruction of sea-level changes for the Late Pleistocene and Holocene period in the NW South China Sea

Zhang Jinpeng, Tomczak Michał, Witkowski Andrzej, Zhen Xia, Li Chao

Oceanologia

|

2023

|

Vol. 65 (1)

211-229

EN

Marine transgressions-regressions have profoundly shaped marginal seas following global sea-level fluctuations driven by climate change. This study on a sedimentary core profile SO219/31-4 from the Beibu Gulf, northwestern South China Sea (SCS), reveals information about paleoenvironment, paleoceanography and paleoclimate changes through fossil diatom assemblages and grain size distributions during the last ca. 12900 cal. yr. BP. Eight local diatom assemblage zones were distinguished and assigned to paleoenvironmental fluctuations recording sea-level and depositional environment changes in eight stages, ca. 12900–11700 (stage 1), ca. 11700–9500 (stage 2), ca. 9500–7200 (stage 3), ca. 7200–5800 (stage 4), ca. 5800–3800 (stage 5), ca. 3800–2400 (stage 6), ca. 2400–800 (stage 7) and ca. 800–0 (stage 8), cal. yr. BP. After the low sea level of stage 1 within the last deglaciation, rapid increases in sea level in stages 2 and 3 were recorded as meltwater events pulse-1B and pulse-1C resulting in marine transgression rates of ca. 16 m/kyr and 8 m/kyr, respectively. The high sea level, above the present level, in stages 4 and 5, in the Middle Holocene Climatic Optimum period, was clearly documented by more significant open sea/tropical diatom species and coastal planktonic species percentages, respectively. The late Holocene regression of sea levels was marked by a pronounced reversion of diatom taphocoenosis, responding to neoglacial climate. Fossil diatom assemblages outlined responded to paleoclimate of global warming in the deglacial and early Holocene. This study provides additional insights into the late Pleistocene and Post-glacial history of a tropical-subtropical shallow water gulf, in the NW-SCS.

2

Flowstones from the Račiška Pečina Cave (SW Slovenia) Record 3.2-Ma-long history

Sierpień P., Pawlak J., Hercman H., Pruner P., Zupan Hajna N., Mihevc A., Bosák P.

Geochronometria

|

2021

|

Vol. 48, no.1

31--45

EN

Establishing a chronology of events is a critical step in reconstructing the palaeoclimate and it is important for all types of environmental records, including speleothems. Here, we analysed a unique series of flowstones deposited between 3.2 Ma (marine isotope stage (MIS) Km3) and 0.08 Ma (MIS 5). The studied flowstones are located in a classic karstic environment, the Račiška Pečina Cave in south-western Slovenia. Further, a detailed chronology of events was constructed based on oxygen isotope stratigraphy (OIS), combined with magnetostratigraphy and U-series dating. Two curves were selected as reference records where the LR04 record was used as the global curve and a Mediterranean record was used as the regional curve. The Račiška Pečina profile was divided into two segments separated by a principal disconformity. The lower segment correlated better with the regional Mediterranean curve, while the upper segment was with the global LR04 curve. These findings suggest that the main factors controlling environmental conditions in the cave area changed between 3.2 and 0.8 million years ago.

3

A continuous stable isotope record of last interglacial age from the Bulgarian Cave Orlova Chuka

Pawlak Jacek, Błaszczyk Marcin, Hercman Helena, Matoušková Šárka

Geochronometria

|

2019

|

Vol. 46, no. 1

87--101

EN

Recent research shows that the last interglacial climate was more unstable in comparison to Holocene. Lack of suitable dating techniques and precisely defined absolute age benchmarks is one from main problems for present LIG studies. Therefore many of LIG chronologies base on indirect dating techniques like record alignment strategies. In this context, speleothems are valuable paleoclimate archives because of their capability to be dated by U-series method. In Europe LIG speleothem records are known mostly from western and central part of the continent. In this paper we present a 1,650 mm long stalagmite (ocz-6) from Bulgarian Cave Orlova Chuka. The ocz-6 stalagmite records the period of time ca. 129–112 ka. Ocz-6 stalagmite was analyzed in terms of stable isotopic composition of calcite and trace elements content. All analyzed geochemical proxies point to dynamic changes in the environment during the Last Interglacial time. At the time of interglacial development (129–126.5 ka), ocz-6 records shows systematic change in proportion of moisture delivered from Atlantic source and other sources. The beginning of last interglacial optimum is connected with a rapid change to more humid and warm conditions. During interglacial demise local climate become more dependent from regional settings.

4

Low to middle Pleistocene paleoclimatic record from the Kraków-Częstochowa Upland (Poland) based on isotopic and calcite fabrics analyses

Błaszczyk M., Hercman H., Pawlak J., Gąsiorowski M., Matoušková Š., Aninowska M., Kicińska D., Tyc A.

Geochronometria

|

2018

|

Vol. 45, no. 1

185--197

EN

The quality of paleoenvironmental reconstruction based on speleothem records depends on the accuracy of the used proxies and the chronology of the studied record. As far as the dating method is concerned, in most cases, the best solution is the use of the U-series method to obtain a precise chronology. However, for older periods (i.e., over 0.5 Ma), dating has become a serious challenge. Theoretically, older materials could be dated with the U-Pb dating method. However, that method requires a relatively high uranium content (minimum of several ppm), whereas typical speleothems from Poland (and all of Central Europe) have uranium concentrations below 0.1 ppm. Because the materials in Polish caves are problematic, we applied oxygen isotope stratigraphy (OIS) as a tool for speleothem dating. By using OIS as an alternative tool to create a chronology of our flowstone, it was found that the studied flowstone crystallized from 975 to 470 ka with three major discontinuities, so obtained isotopic record can be correlated with oxygen isotopic stages from MIS 24 to MIS 12. The observed isotopic variability was also consistent and confirmed with the petrographic observations of the flowstone.

5

The Late Quaternary vegetational and environmental history of western tropical Africa - the eastern Benin Basin, Lagos, Nigeria

Adeonipekun P. A., Adeniyi T. A., Mateawo J., Agbalaya B.

Geology, Geophysics and Environment

|

2017

|

Vol. 43, no. 4

277--291

EN

A palynological study of a 30 m borehole within the Akoka campus of the University of Lagos, Akoka, Nigeria revealed Late Quaternary paleo-vegetational, climatic and environmental changes. Sixteen samples at a regular interval of 2 m were subjected to standard palynological and sedimentological techniques. Six pollen zones representing six paleoclimatic phases within the Late Quaternary period were recognized. The age model is based on two radiocarbon dates (6 m: 5,495 ± 25 ¹⁴C yr and 12 m: 15,660 ± 40 ¹⁴C yr) and, by extrapolation, the sequence spans approximately the last 35,000 yr BP. The African maximum transgression and the African Humid Period (wet paleoclimate maximum) – the Nouaktchottian, and Pre-Nouaktchottian respectively – were recognized, while the Ogolian II (Erg II) was stratigraphically recognized and the Upper Inchirian extrapolated. Recovered diatom frustules with other proxies were employed for paleoclimatic and paleoecological deductions. Four hydrological cycles and three paleoecological settings were identified. Results from this work indicate the co-eval record of paleoclimatic events across Africa, suspected cooling during the African maximum transgression in Nigeria and the usefulness of coastal freshwater swamp sediments for paleoclimate studies.

6

Facies and fauna proxies to reconstruct the MIS 5 and MIS 7 coastal environments in Eastern Tunisia

Chakroun A., Zaghbib-Turki D.

Geological Quarterly

|

2017

|

Vol. 61, No. 1

186--204

EN

This study is based on the analysis of the sedimentology and the fossil assemblages of the Pleistocene deposits in Eastern Tunisia. It aims to establish the different fauna assemblages in order to highlight their paleoenvironments and discuss the importance of the Persististrombus latus distribution especially in the MIS 5e deposits around the Mediterranean Basin. The stratigraphic succession has been divided into two main units. The lower unit is quartz-rich sediment. Its lower marine term revealed well preserved species (Bivalves, Gastropods, Echinoids and Scirripedia) dominated by Acanthocardia, Cerastoderma, Parvicardium, Arca, Donax, Glycymeris, Loripes, Tellina and Cerithium. This fauna is representative of a typical association/biocenosis which may be developed in a sheltered bay, where the hydrodynamism is regularly moderate to low and/or quickly post-mortem buried. The upper unit is carbonated. Its basal term is also rich marine fauna which contains the extant tropical West African species Persististrombus latus. The occurrence of Persististrombus latus in this unit compared to its presence in the whole Mediterranean basin in the Late Pleistocene leads to question its importance in the interpretation of the climate warming during the Late Pleistocene, and to suggest its Atlantic origin.

7

An 854-year tree-ring chronology of scots pine for south-west Finland

Helama S., Holopainen J., Timonen M, Mielikainen K

Studia Quaternaria

|

2014

|

Vol. 31, Nr 1

61--68

EN

A near-millennial tree-ring chronology (AD 1147-2000) is presented for south-west Finland and analyzed using dendroclimatic methods. This is a composite chronology comprising samples both from standing pine trees (Pinus sylvestris L.) and subfossil trunks as recovered from the lake sediments, with a total sample size of 189 tree-ring sample series. The series were dendrochronologically cross-dated to exact calendar years to portray variability in tree-ring widths on inter-annual and longer scales. Although the studied chronology correlates statistically significantly with other long tree-ring width chronologies from Finland over their common period (AD 1520-1993), the south-west chronology did not exhibit similarly strong mid-summer temperature or spring/early-summer precipitation signals in comparison to published chronologies. On the other hand, the south-west chronology showed highest correlations to the North Atlantic Oscillation indices in winter/spring months, this association following a dendroclimatic feature common to pine chronologies over the region and adjacent areas. Paleoclimatic comparison showed that tree-rings had varied similarly to central European spring temperatures. It is postulated that the collected and dated tree-ring material could be studied for wood surface reflectance (blue channel light intensity) and stable isotopes, which both have recently shown to correlate notably well with summer temperatures.

8

Geofizyczne oraz hydrogeologiczne warunki pozyskiwania energii geotermicznej w Polsce

Szewczyk J.

Przegląd Geologiczny

|

2010

|

Vol. 58, nr 7

566-573

EN

In result of drilling works carried out for over the past several decades in Poland, over 7,500 boreholes were completed to depths exceeding 1,000 m. The works were mainly connected with exploration for oil and gas and, therefore, the range and quality of the bulk of the obtained borehole data appear to be of very limited value and often even misleading in analyzing geothermal potential. This makes Polish Geological Institute’s exploratory boreholes especially important for geothermal studies thanks to their relatively regular distribution, large cored intervals and numerous hydrogeological and petrophysical tests and analyses. The Polish Geological Institute has been conducting long-term systematic studies aimed at obtaining uniform and the most detailed knowledge of environmental factors determining possibilities to use geothermal energy in Poland. Generation and compilation of uniform map of heat flow density in the area of Poland including southern Baltic Sea have been completed in 2009. The paper presents newly completed map of undisturbed temperature at the depth of 2,000 m for that area. This map along with the above mentioned uniform map of heat flow density provide important indices for evaluating perspectives of obtaining geothermal energy. The paper also presents hitherto obtained results of determinations of hydrogeological parameters of deep aquifers mainly extending throughout the Polish Lowlands.

9

Ślady zmian klimatycznych plejstocenu oraz holocenu w profilach temperatury w głębokich otworach wiertniczych na Niżu Polskim

Szewczyk J.

Przegląd Geologiczny

|

2002

|

Vol. 50, nr 11

1109-1114

PL

Zmiany klimatu jakie miały i mają miejsce na Ziemi mogą pozostawiać swoje ślady w postaci zmian temperatury obserwowanych obecnie w profilach otworów wiertniczych. Analiza głębokościowej zmienności tych temperatur może być źródłem informacji o warunkach klimatycznych jakie istniały na badanym obszarze w różnych okresach. Czynnik ten wpływa równocześnie na obserwowaną wielkość ziemskiego strumienia cieplnego i jego uwzględnienie może mieć istotny wpływ na poprawność wyznaczenia tego parametru. Na podstawie przedstawionych w pracy wyników analiz badań geotermicznych opartych zarówno na metodzie konstrukcji syntetycznych profilowań termicznych (Ts), jak i wykonanych modelowaniach geotermicznych przeanalizowano wpływ czynnika paleoklimatycznego związanego ze zlodowaceniem późnoplejstoceńskim na wartości temperatur obserwowanych obecnie w otworach wiertniczych na obszarze Niżu Polskiego. Wstępna interpretacja danych geotermicznych z ponad 30 głębokich otworów z tego obszaru pozwoliła między innymi na stwierdzenie obecności efektu paleoklimatycznego, a także naokreślenie średniej wartości temperatury warstwy przypowierzchniowej (GST) istniejącej na tym obszarze w okresie tego zlodowacenia. (-6.85 deg C).

EN

Past and current climatic changes on the Earth may be recorded in the subsurface temperature profiles observed in deep boreholes. Analysis of such profiles measured in boreholes few thousand metres deep may provide information on past climatic conditions existing in on the studied area. Terrestial heat flow data may be considerably influenced by this factor and should be corrected for all data accordingly. Results of analysis based both on constructions of synthetic thermal logs (Ts) and on the results of further modelling show that the last glaciation has left evident paleoclimatic temperature signals in nearly all observed subsurface temperature profiles in deep boreholes from the Polish Lowlands. Preliminary results on the average annual ground surface temperature for the Polish Lowlands in the Late Pleistocene have been obtained (GST = -6.8°C).

10

Fauna osadów interglacjalnych z Koczarek koło Mrągowa

Skompski S.

Przegląd Geologiczny

|

2002

|

Vol. 50, nr 7

615-619

PL

Analiza paleontologiczna 46 próbek z otworu wiertniczego w Koczarkach wykazała obecność różnorodnych szczątków zwierząt: mięczaków, małżoraczków, ryb i owadów. Na tej podstawie określono warunki paleoekologiczne i paleoklimatyczne w jakich powstawały osady z fauną oraz ich stratygrafię. Znalezione tu charakterystyczne gatunki mięczaków: Corbicula fluminalis i Lithoglyphus jahni oraz małżoraczka Scottia browniana pozwalają określić wiek osadów z fauną na interglacjał mazowiecki.

11

Climate reconstruction fromstable-isotope composition of the Mazovian Interglacial (Holsteinian) lake sediments in eastern Poland

Nitychoruk J.

Acta Geologica Polonica

|

2000

|

Vol. 50, no. 2

247-294

EN

Sediments of palaeolakes located in eastern Poland representing the Mazovian Interglacial (Holsteinian) and the initialpart of the succeeding Middle-Polish glaciation (Saalian) are unique in Europe. These sediments are very thick (up to 55 m) and homogeneous, composed of lake marl and calcareous gyttja. They are thoroughly interpreted in terms of geological and palaeobiological studies (palynology, macrofossils, diatoms and malacofauna) and represent continuous deposition. Analysis of stable oxygen and carbon isotopes in these deposits and of the shells of the malacofauna enables interpretation of the changes in the palaeoclimate and sedimentary environment that occurred in lake basins during this part of the Pleistocene. Maximum [delta]^18O (-3,6 promille) and minimum values of [delta]^13C (-6,4 promile) correspond to the first part of the interglacial optimum, while minimum delta^18O values (-10,1 promile) and maximum delta^13C values (10,0 promile) correspond to the coldest period, directly preceding the following glaciation. Climatic changes are well ducumented by isotopic curves correlated with the result of pollen analysis. The isotopic curves indicate relatively cool climatic conditions at the climaticoptimum of the Mazovian Interglacial. This may have been caused by increased atmospheric precipitation that led to deepening of the lakes and/or by influx of ground waters enriched in light isotopes. In the upper part of the successions,coresponding to the initial stage of the following glaciation, the concentration of 18^O and 13^C increases, which was probably associated with the lake shallowing and with enrichment in heavy isotopes through evaporation under conditions of a cool steppe climate and/or with the redeposition of "warm" interglacial deposits from shore areas exposed as the result of lake shallowing. The isotopic curves clearly illustrate changes in the relative influence of maritime and continental air circulation during the Mazovian Interglacial. The studied lakes were oligo- or mesotropic with dominant influence of continental air circulation before the interglacial climatic optimum. Maritime air circulation prevailed during the interglacial climatic optimum and the lakes became eutrophic. Cyclic climatic cooling during the post-interglacial period is recorded in oxygen isotopic curves trending towards their lower values. The carbon isotopic curves reach higher values, which is related to climatic cooling and shallowing of the lakes, caused by their infilling with deposits.