154 research outputs found
molybdenum and sulfur incorporation as oxyanion substitutional impurities in calcium carbonate minerals: density functional theory data
No full text<p>Provided here are density functional theory research datasets generated using the Vienna Ab Initio Simulation Package. Data relates to publication in Chemical Geology, entitled, Molybdenum and sulfur incorporation as oxyanion substitutional impurities in calcium carbonate minerals: A computational investigation. By Scott D Midgley, James O Taylor, Dominik Fleitmann, Ricardo Grau-Crespo. </p>
<p>We include here final geometries in .cif format, as well as full OUTCAR files generated in VASP. Using this file, readers can access all details of the DFT simulations reported. </p>
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Late Holocene onset of intensive cultivation and introduction of the falaj irrigation system in the Salut oasis (Sultanate of Oman)
No full textThis paper discusses the time and steps of the introduction of intensive agriculture and evolution of irrigation systems to sustain crops in the palaeo-oasis of Salut in the northern Sultanate of Oman. Various geoarchaeological methods allow reconstructing the exploitation of the natural resources of the region and technological development of irrigation methods since the Mid-Holocene. Intensive agriculture started during the Bronze Age and continued with some spatial and intensity fluctuations up to the Islamic period. Cultivations were initially sustained by surface irrigation systems and later replaced by a dense net of aflaj, the typical surface/underground system adopted in the Levant, Arabian Peninsula and western Asia to collect water from deep piedmont aquifers and redistribute it to the fields located in the lowlands. Our results indicate that the aflaj were in use for a long period in the palaeo-oasis formed along Wadi Sayfam and surrounding the citadel of Salut. Uranium-Thorium dating of calcareous tufa formed in the underground tunnels of the aflaj suggests that they were used between ∼540 BCE and ∼1150 CE. After ∼1150 CE Wadi Sayfam were abandoned and the size of the oasis shrank substantially. During the late Islamic period, a surface aqueduct descending from the piedmont of Jabal Shams secured water supply. Our work confirms that in arid lands archaeological and historical communities were able to actively modulate their response to climate changes by using a variety of technological strategies
sulphate and molybdate incorporation at calcite-water interface - ab initio molecular dynamics data
No full textProvided here are ab initio molecular dynamics data files generated in CP2K, relating to the publication entitled
Sulphate and Molybdate Incorporation at the Calcite-Water Interface: Insights from Ab Initio Molecular Dynamics. By Scott D. Midgley, Devis Di Tommaso, Dominik Fleitmann, Ricardo Grau-Crespo.
We have provided the CP2K input file (.inp), the CP2K energy file (.ener), and a single geometry snapshot from the simulation (.xyz).
It is not possible to share the fully dynamics trajectory, because each file is extremely large.
N.B. for the sulphate ion in water, a corruption in the .ener file meant that it was not possible to share. Instead a list of MD energies are given as a .txt file, with energies in eV
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Inverse modelling of the 14C bomb pulse in stalagmites to constrain the dynamics of soil carbon cycling at selected European cave sites
No full textThe decomposition of soil organic matter (SOM) is temperature dependent, but its response to a future warmer climate remains equivocal. Enhanced rates of decomposition of SOM under increased global temperatures might cause higher CO2 emissions to the atmosphere, and could therefore constitute a strong positive feedback. The magnitude of this feedback however remains poorly understood, primarily because of the difficulty in quantifying the temperature sensitivity of stored, recalcitrant carbon that comprises the bulk (>90%) of SOM in most soils. In this study we investigated the effects of climatic conditions on soil carbon dynamics using the attenuation of the 14C ‘bomb’ pulse as recorded in selected modern European speleothems. These new data were combined with published results to further examine soil carbon dynamics, and to explore the sensitivity of labile and recalcitrant organic matter decomposition to different climatic conditions. Temporal changes in 14C activity inferred from each speleothem was modelled using a three pool soil carbon inverse model (applying a Monte Carlo method) to constrain soil carbon turnover rates at each site. Speleothems from sites that are characterised by semi-arid conditions, sparse vegetation, thin soil cover and high mean annual air temperatures (MAATs), exhibit weak attenuation of atmospheric 14C ‘bomb’ peak (a low damping effect, D in the range: 55–77%) and low modelled mean respired carbon ages (MRCA), indicating that decomposition is dominated by young, recently fixed soil carbon. By contrast, humid and high MAAT sites that are characterised by a thick soil cover and dense, well developed vegetation, display the highest damping effect (D = c. 90%), and the highest MRCA values (in the range from 350 ± 126 years to 571 ± 128 years). This suggests that carbon incorporated into these stalagmites originates predominantly from decomposition of old, recalcitrant organic matter. SOM turnover rates cannot be ascribed to a single climate variable, e.g. (MAAT) but instead reflect a complex interplay of climate (e.g. MAAT and moisture budget) and vegetation development
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Orbital- and millennial-scale environmental changes between 64 and 20 ka BP recorded in Black Sea sediments
No full textHigh-resolution pollen and dinoflagellate cyst records from sediment core
M72/5-25-GC1 were used to reconstruct vegetation dynamics in northern
Anatolia and surface conditions of the Black Sea between 64 and 20 ka BP.
During this period, the dominance of Artemisia in the pollen record indicates a
steppe landscape and arid climate conditions. However, the concomitant
presence of temperate arboreal pollen suggests the existence of glacial
refugia in northern Anatolia. Long-term glacial vegetation dynamics reveal
two major arid phases ~64–55 and 40–32 ka BP, and two major
humid phases ~54–45 and 28–20 ka BP, correlating with higher
and lower summer insolation, respectively. Dansgaard–Oeschger (D–O) cycles
are clearly indicated by the 25-GC1 pollen record. Greenland interstadials
are characterized by a marked increase in temperate tree pollen, indicating
a spread of forests due to warm/wet conditions in northern Anatolia,
whereas Greenland stadials reveal cold and arid conditions as indicated by
spread of xerophytic biomes. There is evidence for a phase lag of
~500 to 1500 yr between initial warming and forest expansion,
possibly due to successive changes in atmospheric circulation in the North
Atlantic sector. The dominance of Pyxidinopsis psilata and
Spiniferites cruciformis in the dinocyst record indicates
brackish Black Sea conditions during the entire glacial period. The decrease
of marine indicators (marine dinocysts, acritarchs) at ~54 ka
BP and increase of freshwater algae (Pediastrum, Botryococcus) from 32 to 25 ka BP reveals
freshening of the Black Sea surface water. This freshening is possibly
related to humid phases in the region, to connection between Caspian Sea and
Black Sea, to seasonal freshening by floating ice, and/or to closer position
of river mouths due to low sea level. In the southern Black Sea, Greenland
interstadials are clearly indicated by high dinocyst concentrations and
calcium carbonate content, as a result of an increase in primary
productivity. Heinrich events show a similar impact on the environment in the
northern Anatolia/Black Sea region as Greenland stadials
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New online method for water isotope analysis of speleothem fluid inclusions using laser absorption spectroscopy (WS-CRDS)
No full textA new online method to analyse water isotopes of speleothem fluid inclusions
using a wavelength scanned cavity ring down spectroscopy (WS-CRDS) instrument
is presented. This novel technique allows us simultaneously
to measure hydrogen and oxygen isotopes for
a released aliquot of water. To do so, we designed a new simple line that
allows the online water extraction and isotope analysis of speleothem
samples. The specificity of the method lies in the fact that fluid inclusions
release is made on a standard water background, which mainly improves the
δ D robustness.
To saturate the line, a peristaltic pump continuously injects standard water
into the line that is permanently heated to 140 °C and flushed with
dry nitrogen gas. This permits instantaneous and complete vaporisation of the
standard water, resulting in an artificial water background with well-known
δ D and δ18O values. The speleothem sample is placed in a
copper tube, attached to the line, and after system stabilisation it is crushed
using a simple hydraulic device to liberate speleothem fluid inclusions
water. The released water is carried by the nitrogen/standard water gas
stream directly to a Picarro L1102-i for isotope determination. To test the
accuracy and reproducibility of the line and to measure standard water during
speleothem measurements, a syringe injection unit was added to the line.
Peak evaluation is done similarly as in gas chromatography to obtain &delta
D; and δ18O isotopic compositions of measured water aliquots.
Precision is better than 1.5 ‰ for δ D and 0.4 ‰ for
δ18O for water measurements for an extended range (−210 to
0 ‰ for δ D and −27 to 0 ‰ for δ18O)
primarily dependent on the amount of water released from speleothem fluid
inclusions and secondarily on the isotopic composition of the sample. The
results show that WS-CRDS technology is suitable for speleothem fluid
inclusion measurements and gives results that are comparable to the isotope
ratio mass spectrometry (IRMS) technique
Modelling Climate and Societal Resilience in the Eastern Mediterranean in the Last Millennium
No full textXoplaki, Elena/0000-0002-2745-2467; Wagner, Sebastian/0000-0001-5603-3897; Luterbacher, Juerg/0000-0002-8569-0973; Bozkurt, Deniz/0000-0003-1021-8241WOS: 000436107000008PubMed ID: 29997409This article analyses high-quality hydroclimate proxy records and spatial reconstructions from the Central and Eastern Mediterranean and compares them with two Earth System Model simulations (CCSM4, MPI-ESM-P) for the Crusader period in the Levant (1095-1290 CE), the Mamluk regime in Transjordan (1260-1516 CE) and the Ottoman crisis and CelA cent lI Rebellion (1580-1610 CE). During the three time intervals, environmental and climatic stress tested the resilience of complex societies. We find that the multidecadal precipitation and drought variations in the Central and Eastern Mediterranean cannot be explained by external forcings (solar variations, tropical volcanism); rather they were driven by internal climate dynamics. Our research emphasises the challenges, opportunities and limitations of linking proxy records, palaeoreconstructions and model simulations to better understand how climate can affect human history.National Programme for the Development of the Humanities, Poland; Swiss National Science FoundationSwiss National Science Foundation (SNSF) [PP002-110554/1]; German Science Foundation (DFG) project AFICHEGerman Research Foundation (DFG); Belmont Forum; JPIClimate; Collaborative Research ActionAdam Izdebski acknowledges the funding received through the National Programme for the Development of the Humanities, Poland, for the years 2016-2019. Dominik Fleitmann acknowledges Support of the Swiss National Science Foundation (grant PP002-110554/1 to D. Fleitmann). Jurg Luterbacher was supported from the German Science Foundation (DFG) project AFICHE and the Belmont Forum and JPIClimate, Collaborative Research Action "INTEGRATE, An integrated data-model study of interactions between tropical monsoons and extratropical climate variability and extremes"
Quantitative reconstruction of temperature changes during the last ~13500 years in Georgia through stable isotopes (δ2H-δ13C-δ18O) from speleothems fluid inclusions and calcite
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Provenance of marbles from Naxos based on microstructural and geochemical characterization
No full textA detailed quantitative microstructural study coupled with cathodoluminescence and geochemical analyses on marbles from Naxos demonstrates that the analysis of microstructures is the most sensitive method to define the origin of marbles within, and between, different regions. Microstructure examination can only be used as an accurate provenance tool if a correction for the second-phase content is considered. If second phases are not considered, a large spread of different microstructures occurs within sample sites, making a separation between neighbouring outcrops difficult or impossible. Moreover, this study shows that the origin of a marble is defined more precisely if the microstructural observations are coupled with cathodoluminescence data
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