Search results for "Glacial period"
showing 10 items of 196 documents
Accumulation of metals and changes in composition of freshwater lake organic sediments during the Holocene
2020
Abstract The distribution of metals in the strata of sediments deposited in the freshwater environment formed during the Holocene in the territory of Latvia has been studied rather insufficiently. Considering the large volume of accumulated organic matter in sediments, studies on the content of metallic elements in sediments can help to determine the peculiarities of the metal accumulation process in limnic systems and the biogeochemical cycling of metals. Lake Pilvelis, which is located in the eastern part of Latvia (the northern part of Europe), was selected as the main study site. Lake Pilvelis is a small lake of a glacial origin, and >90% of its depression is filled with organic-rich se…
Cryogenic cave carbonate – a new tool for estimation of the Last Glacial permafrost depth of the Central Europe
2012
Abstract. Cryogenic cave carbonate (CCC) represents a specific type of speleothems, whose precipitation is triggered by freezing of mineralized karst water. Coarse-crystalline CCC, which formed during slow freezing of water in cave pools, is known in 20 Central European caves located in Germany, the Czech Republic, Slovakia and Poland. All these caves are situated in an area, which was glacier-free during the Weichselian. Whereas the formation of usual types of speleothems in caves of this region usually ceased during glacials, CCC precipitation was restricted to glacial periods. Since CCC represents a novel, useful paleoclimate proxy, data from Weichselian CCC occurrences in caves in Centr…
Mediterranean coccolith ecobiostratigraphy since the penultimate Glacial (the last 145,000years) and ecobioevent traceability
2015
The Mediterranean Sea is a miniature ocean ideal to test the response of marine ecosystems to amplified orbital and suborbital climate changes. Here we present coccolith data from a Sardinia Channel gravity core (Arcose C_33) analysed over the last 145,000 years, with a mean resolution of about 900 years. The study highlights that regional phytoplankton assemblages underwent significant modifications between the penultimate glacial and the last interglacial, as well as between the last glacial and the Holocene. The N ratio palaeoproductivity index suggests reduced productivity levels and the development of a deep nutricline during the last interglacial and the Holocene. Within the last glac…
Palaeoclimate has a major effect on the diversity of endemic species in the hotspot of mountain biodiversity in Tajikistan.
2021
AbstractIn a period of ongoing climate changes, identifying drivers of overall and endemic species diversity is a key element in constructing new ecological patterns and determining the main goals of conservation. Such studies are especially crucial if they concern biodiversity hotspot areas. In this study, we explore patterns and drivers of plant endemism (the proportion of endemic plant species to overall plant species richness; PE) in Tajikistan. We used three groups of climatic measures featuring the contemporary and glacial climates as well as climatic changes since the Last Glacial Maximum in the Pleistocene (LGM). To explore relationships between PE and climatic groups, and the most …
Glacial survival and post-glacial recolonization of an arctic-alpine freshwater insect (Arcynopteryx dichroa, Plecoptera, Perlodidae) in Europe
2012
Aim General models for understanding the climate-driven processes of post-glacial colonization in European arctic–alpine species are mainly derived from studies on temperate terrestrial taxa. However, cold-adapted freshwater species may tolerate or even thrive under colder climatic conditions as flowing water habitats are thermally buffered against freezing and extremely cold temperatures. Here, we investigate the European Pleistocene and Holocene history of the arctic–alpine stonefly Arcynopteryx dichroa. Location Europe. Methods We used two genetic data sets (mitochondrial sequence data and nuclear microsatellite data) to investigate the glacial survival and post-glacial recolonization ro…
Maars of the Westeifel, Germany
2008
Within the Westeifel Volcanic Field 27% of the 250 Quaternary eruptive centers are maars. Maars form as a result of a highly explosive interactive process between rising melt and groundwater. In the Westeifel, probably thermal water plays an important role for the productive phreatomagmatic interaction process and, con-sequently, the high number of maars. The Westeifel maars show all transitions to scoria cones. Only the youngest maars are filled by a maar lake or a raised bog, and are well preserved. The older maars show a low diameter to depth ratio. Nearly one third of the Westeifel maars were formed during the Weichselian glaciation period. The isostatic movements during the increasing …
Quaternary development and evolution of the sedimentary environments in the Central Mediterranean Spanish coast
1995
Abstract The reconstruction of the evolutive phases of the Mediterranean Spanish Central sector during the Late Quaternary is the aim of this work. From geomorphological, sedimentological and chronometrical studies, different morphostratigraphic units are determined. Results point out the development of several transgressive phases. The older one go back to isotope stage 7. The Eemian transgression is broadly recorded, and its coastline was near the present one. During the Flandrian episode, the sea surpassed the current coastline in the northern coastal plain, while in the meridional littoral erosive notches were formed between +1 and +2 m. During the regressive events, we find the prograd…
Yttrium and REE signature recognized in Central Mediterranean Sea (ODP Site 963) during the MIS 6–MIS 5 transition
2010
Abstract The Mediterranean Sea acts as a miniature ocean with the development of its own conveyor belt. It constitutes an ideal location to study and forecast how the marine environment responds to rapid climatic change. Here we present a palaeoenvironmental study carried out on the sediments of ODP Site 963, recovered in the Sicily Channel, the sill which divides the western from the eastern Mediterranean basin. We focused on the transition between the penultimate glacial (MIS 6) and the last interglacial (MIS 5), between approximately 130 and 115 kyr BP. A novel approach is proposed, taking into account centennial-scale geochemical data on major elements, selected trace elements, and yttr…
Tropical Atlantic temperature seasonality at the end of the last interglacial
2015
The end of the last interglacial period, ~118 kyr ago, was characterized by substantial ocean circulation and climate perturbations resulting from instabilities of polar ice sheets. These perturbations are crucial for a better understanding of future climate change. The seasonal temperature changes of the tropical ocean, however, which play an important role in seasonal climate extremes such as hurricanes, floods and droughts at the present day, are not well known for this period that led into the last glacial. Here we present a monthly resolved snapshot of reconstructed sea surface temperature in the tropical North Atlantic Ocean for 117.7±0.8 kyr ago, using coral Sr/Ca and δ18O records. W…
Antarctic erosion history reconstructed by Terre Adélie moraine geochronology
2020
AbstractWe report apatite fission-track and 10Be terrestrial cosmogenic nuclide (TCN) dating of 14 moraine boulders originating from inland Terre Adélie, East Antarctica. These data show cooling of the Proterozoic Terre Adélie craton at < ~120°C between 350 and 300 Ma, suggesting > 4 km temperate glacial erosion during the Late Palaeozoic Ice Age, followed by nearly null Mesozoic erosion and low glacial erosion (< 2 km) in the Cenozoic. Based on glacial flux maps, the origin of the boulders may be located ~400 km upstream. Preliminary TCN (10Be) datings of moraine boulders cluster within the last 30 ka. Cosmogenic ages from the Lacroix Nunatak suggest a main deglaciation after the …