Search results for "maar"

Dating Bulk Sediments from Limnic Deposits Using a Grain-Size Approach

2013

Radiocarbon measurements on bulk subaqueous sediments typically provide ages significantly older than actual time of deposition. This is generally caused by the presence of reworked organic compounds, which are depleted in 14C. To explore this issue of age heterogeneity, we collected 4 organic-rich samples from varying depths in a lake sediment core at the Gemündener Maar (Eifel, Germany), a lake of volcanic origin. We divided each sample into 5 standard grain-size fractions: gravel, sand, silt, clay, and 1 fraction smaller than 0.45 μm. These were cleaned separately using a standard acid-alkali-acid treatment. The highly organic gravel-size fraction provided the youngest 14C ages of all gr…

On the Volcanology of the West Eifel Maars

1987

The Quaternary alkali-basaltic volcanic field of the West Eifel is the classic maar region of the world. Related to the formation of the continental rift zone which extends through Central Europe, ultrabasic magmas rose from the upper mantle through the continental crust and fed 240 small volcanoes. Next to scoria cones with their lava flows, maars are most frequent and represent 25% of the volcanoes. Since 1820 and until 1970 their origin was mostly believed to be related to explosive exsolution of juvenile volatile phases. Since 1970, however, several authors have suggested that the West Eifel maars are phreatomagmatic in origin, i.e. rising magma contacted groundwater in near-surface lev…

Geochemical insight into differences in the physical structures and dynamics of two adjacent maar lakes at Mt. Vulture volcano (southern Italy)

2013

[1] We report on the first geochemical investigation of the Monticchio maar lakes (Mt. Vulture volcano, southern Italy) covering an annual cycle that aimed at understanding the characteristic features of the physical structures and dynamics of the two lakes. We provide the first detailed description of the lakes based on high-resolution conductivity-temperature-depth (CTD) profiles, chemical and isotopic (H and O) compositions of the water, and the amounts of dissolved gases (e.g., He, Ar, CH4, and CO2). The combined data set reveals that the two lakes, which are separated by less than 200 m, exhibit different dynamics: one is a meromictic lake, where the waters are rich in biogenic and man…

A new windstorm proxy from lake sediments: A comparison of geological and meteorological data from western Germany for the period 1965–2001

2009

[1] The feasibility of detecting windstorm layers in lake sediments is explored by comparing quartz grain size data from a freeze core obtained from the Schalkenmehrener Maar (Eifel region, western Germany) to recent meteorological wind data. The Schalkenmehrener Maar is appropriate for such a calibration study because the morphological settings of the lake allow the conservation of windstorm layers (in particular, there is no fluvial sediment inflow) and long-term wind measurements are available from nearby stations. The age model for the uppermost 30 cm of the sediment core is based on measurements of 137Cs and 210Pb concentrations. An ultra-high-resolution grain size analysis is performe…

Late Pleistocene aeolian dust provenances and wind direction changes reconstructed by heavy mineral analysis of the sediments of the Dehner dry maar …

2016

Abstract The study presents the results of a heavy mineral analysis from a 38 m long record of lacustrine Eifel maar sediments from a core section of the Dehner dry maar. The record encompasses the period from 29,000 to about 12,500 b2k. Statistical analyses enabled the distinction of local and regional source areas of aeolian material and revealed pronounced changes in the amounts of different heavy mineral species and corresponding changes in the grain size Index (GSI and CSI). The results indicate that during the early stages of MIS2 (39 to 30 m depth) aeolian sediments were supplied mostly from local sources. This period is characterized by low GSI and CSI ratios resulting from a reduce…

The ELSA-Flood-Stack: A reconstruction from the laminated sediments of Eifel maar structures during the last 60 000 years

2016

Abstract This study reconstructs the main flood phases in central Europe from event layers in sediment cores from Holocene Eifel maar lakes and Pleistocene dry maar structures. These reconstructions are combined with recent gauge time-series to cover the entire precipitation extremes of the last 60 000 years. In general, Eifel maar sediments are perfectly suited for the preservation of event layers since the deep water in the maar lakes is seasonal anoxic and therefore, bioturbation is low. However, the preservation of annual lamination is only preserved in Holzmaar and Ulmener Maar; the other cores are dated by 14C, magnetostratigraphy, tephra markers and ice core tuning. The cores were dr…

Fire–vegetation relationships during the last glacial cycle in a low mountain range (Eifel, Germany)

2021

Abstract Lake sediments can provide useful archives to reconstruct past vegetation changes or fire history. To comprehend how vegetation and fire history have correlated during the last 130,000 years, we used two lake sediment records with known patterns of pollen and botanical macro remains and supplemented this data by analyses of lignin-derived phenols as markers for local vegetation inputs and by benzene polycarboxylic acids (BPCAs) as markers for total fire residue inputs (black carbon, BC). The two sediment archives originated from two maar lakes in the Eifel, which is part of the low mountain ranges in central Germany. A lignin-derived phenol index showed woody angiosperms and gymnos…

Sankaruuden kahdet kasvot : sankarinarratiivit Maarit Verrosen novelleissa

2012

Eolian sedimentation in central European Auel dry maar from 60 to 13 ka

2021

AbstractThe climate in central Europe during the last 60 ka is characterized by rapid temperature and moisture changes and strong cold periods (Heinrich events). All these variations are preserved in sediments of marine and also some terrestrial archives. Here we present a continuous, terrestrial sediment record with almost all Greenland stadials and Heinrich events between 60 and 13 ka visible from carbonate roundness of the Eifel Laminated Sediment Archive Dust Stack-20 and CaCO3 data for central Europe. The carbonate roundness data show almost all stadials between 60 and 13 ka. CaCO3 data show a general transport system change with the beginning of Heinrich event 3. Since there are no ca…

Environmental geology and geochemistry of lake sediments (Holzmaar, Eifwl, Germany)

2008

Quaternary sediments of the lake Holzmaar comprise a well laminated, undisturbed sequence of diatomaceous gyttja, silt, clay laminites and tuff layers. The annually deposited gyttja has been dated by varve chronology yielding a continuous high-resolution time sequence for the Holocene and early Pleistocene. These organic-rich sediments provide an unique paleolimnological record on climatic changes, forest fires, volcanic eruptions, and anthropogenic influences on the sediment composition. Volcanic activity produced thin tephra layers (Laacher See Tephra 11,200±120 radiocarbon yrs BP; Ulmener Maar Tephra 9435±70 radiocarbon yrs BP) in the sedimentary column which possess elevated Ba, Sr, Zr,…