Search results for "PELE"

Effects of dating errors on nonparametric trend analyses of speleothem time series

2012

A fundamental problem in paleoclimatology is to take fully into account the various error sources when examining proxy records with quantitative methods of statistical time series analysis. Records from dated climate archives such as speleothems add extra uncertainty from the age determination to the other sources that consist in measurement and proxy errors. This paper examines three stalagmite time series of oxygen isotopic composition (δ18O) from two caves in western Germany, the series AH-1 from the Atta Cave and the series Bu1 and Bu4 from the Bunker Cave. These records carry regional information about past changes in winter precipitation and temperature. U/Th and radiocarbon dat…

New insights on secondary minerals from Italian sulfuric acid caves

2018

Sulfuric acid minerals are important clues to identify the speleogenetic phases of hypogene caves. Italy hosts ~25% of the known worldwide sulfuric acid speleogenetic (SAS) systems, including the famous well-studied Frasassi, Monte Cucco, and Acquasanta Terme caves. Nevertheless, other underground environments have been analyzed, and interesting mineralogical assemblages were found associated with peculiar geomorphological features such as cupolas, replacement pockets, feeders, sulfuric notches, and sub-horizontal levels. In this paper, we focused on 15 cave systems located along the Apennine Chain, in Apulia, in Sicily, and in Sardinia, where copious SAS minerals were observed. Some of the…

2018

Abstract. Here we present a sensitive method to analyze lignin oxidation products (LOPs) in speleothems and cave drip water to provide a new tool for paleo-vegetation reconstruction. Speleothems are valuable climate archives. However, compared to other terrestrial climate archives, such as lake sediments, speleothems contain very little organic matter. Therefore, very few studies on organic biomarkers in speleothems are available. Our new sensitive method allows us to use LOPs as vegetation biomarkers in speleothems. Our method consists of acid digestion of the speleothem sample followed by solid-phase extraction (SPE) of the organic matter. The extracted polymeric lignin is degraded in a m…

Aleksandr Prochanov, o la Crimea come antidoto al postmoderno

2019

When Aleksandr Prokhanov’s Mr. Hexogen appeared in 2001 most critics perceived it as a postmodern novel – a totally unexpected move from this author, a long-standing Soviet writer and a leader of the Stalinist-nationalist opposition. The work shows indeed some features in common with, for instance, Babylon by Viktor Pelevin, one of the most popular Russian postmodern writers. Both novels demonstrate a phantasmagoric picture of the hidden side of Russian political life: if, however, in Pelevin’s case the intent is clearly ironic, Mr. Hexogen can be read as a book aimed to convey the view that the Moscow terrorist attacks of winter 1999 were designed in order to ensure Putin’s raise to presid…

Plazmas trimetilamīna N-oksīda koncentrācijas novērtēšana eksperimentālajā 2.tipa diabēta modelī

2016

Bakalaura darbā tika analizēti bioķīmiskie marķieri diabēta attīstības raksturošanai un pētītas trimetilamīna N-oksīda (TMAO) un L-karnitīna koncentrācijas izmaiņas diabēta gadījumā. Iegūtie rezultāti parāda, ka db/db pelēm, kam raksturīga aptaukošanās un 2. tipa cukura diabēts, bija ievērojami paaugstināta TMAO koncentrācija asins plazmā un tā palielinājās laika gaitā. L-karnitīna koncentrācija asins plazmā bija ticami zemāka nekā kontroles grupai tikai 12 nedēļas vecām db/db pelēm. Tika novērots, ka 8 nedēļu laikā db/db pelēm bija ticami palielināta ķermeņa masa, plazmas glikozes un insulīna koncentrācijas, kā arī attīstījusies insulīna rezistence. Pētījuma rezultāti liecina, ka diabēta g…

Little Egret Egretta garzetta (Linnaeus, 1766) ( Pelecaniformes Ardeidae) and Eurasian crag martin Ptyonoprogne rupestris (Scopoli, 1769) (Passerifor…

2021

For the first time, the nesting of Eurasian crag martin Ptyonoprogne rupestris (Scopoli, 1769) (Passeriformes Hirundinidae) and Little egret Egretta garzetta (Linnaeus, 1766) (Pelecaniformes Ardeidae) in the Aegadian Islands (W-Sicily, Italy) is reported. Of particular interest is the nesting of the Little egret on the island of Maraone resulting in the first report for Sicily of a heronry on a marine island. Although this nesting environment has already been established in Sardinia, it should be emphasized that until now the establishment of a heronry has never been detected on an islet so far from the mainland.

Sensitivity of Bunker Cave to climatic forcings highlighted through multi-annual monitoring of rain-, soil-, and dripwaters

2017

The last two decades have seen a considerable increase in studies using speleothems as archives of past climate variability. Caves under study are now monitored for a wide range of environmental parameters and results placed in contextwith speleothemdata. The present study investigates trends froma seven year longmonitoring of Bunker Cave, northwestern Germany, in order to assess the hydraulic response and transfer time of meteoric water fromthe surface to the cave. Rain-, soil-, and dripwaterwere collected fromAugust 2006 to August 2013 at a monthly to bimonthly resolution and their oxygen and hydrogen isotope composition wasmeasured. Furthermore, drip rates were quantified. Due to differe…

230Th/U-dating of a late Holocene low uranium speleothem from Cuba

2010

We present 22 U-series ages for a stalagmite from north-western Cuba based on multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and thermal ionisation mass spectrometry (TIMS). Our results reveal that the stalagmite continuously grew within the last ~1400a. Low uranium content of the sample and thus, extremely low 230Th concentrations limit the precision and accuracy of 230Th/U-dating by TIMS. Samples measured by MC-ICPMS show a high variability of 232Th content along the growth axis with some sections significantly affected by initial 230Th from a detrital phase. An a-priori bulk earth ratio for (238U/232Th) cannot be used to accurately account for this initial 230Th.…

Caribbean hydroclimate and vegetation history across the last glacial period

2019

Abstract We present a new speleothem trace element and stable isotope record, which extends previous paleoclimate evidence from Cuban speleothems to the last 96 ka. Multiple proxies were used to reconstruct Caribbean hydroclimate and vegetation variability on orbital to millennial timescales. In particular, our proxies indicate a shift to more abundant C4 (compared to C3) vegetation and/or reduced soil activity during the Last Glacial Maximum. Our results confirm the close link of Caribbean precipitation to North Atlantic climate variability, insolation and the strength of the AMOC. The associated variations in Caribbean SSTs and the shift of the ITCZ led to substantial changes of the hydro…

Climate variations of Central Asia on orbital to millennial timescales

2016

AbstractThe extent to which climate variability in Central Asia is causally linked to large-scale changes in the Asian monsoon on varying timescales remains a longstanding question. Here we present precisely dated high-resolution speleothem oxygen-carbon isotope and trace element records of Central Asia’s hydroclimate variability from Tonnel’naya cave, Uzbekistan and Kesang cave, western China. On orbital timescales, the supra-regional climate variance, inferred from our oxygen isotope records, exhibits a precessional rhythm, punctuated by millennial-scale abrupt climate events, suggesting a close coupling with the Asian monsoon. However, the local hydroclimatic variability at both cave sit…