scholarly journals The Potential of Tufa as a Tool for Paleoenvironmental Research—A Study of Tufa from the Zrmanja River Canyon, Croatia

Geosciences ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 376
Author(s):  
Jadranka Barešić ◽  
Sanja Faivre ◽  
Andreja Sironić ◽  
Damir Borković ◽  
Ivanka Lovrenčić Mikelić ◽  
...  
Keyword(s):  
Radiocarbon Dating ◽  
Isotope Composition ◽  
Flow Direction ◽  
Stable Carbon Isotope ◽  
Oxygen Isotopic Composition ◽  
Organic Residue ◽  
Present Level ◽  
The Holocene ◽  
Mis 3 ◽  
River Bed

Tufa is a fresh-water surface calcium carbonate deposit precipitated at or near ambient temperature, and commonly contains the remains of macro- and microphytes. Many Holocene tufas are found along the Zrmanja River, Dalmatian karst, Croatia. In this work we present radiocarbon dating results of older tufa that was found for the first time at the Zrmanja River near the Village of Sanaderi. Tufa outcrops were observed at different levels, between the river bed and up to 26 m above its present level. Radiocarbon dating of the carbonate fraction revealed ages from modern, at the river bed, up to 40 kBP ~20 m above its present level. These ages fit well with the hypothesis that the Zrmanja River had a previous surface connection with the Krka River, and changed its flow direction toward the Novigrad Sea approximately 40 kBP (Marine Isotope Stage 3). Radiocarbon AMS dating of tufa organic residue yielded a maximum conventional age of 17 kBP for the highest outcrop position indicating probable penetration of younger organic material to hollow tufa structures, as confirmed by radiocarbon analyses of humin extracted from the samples. Stable carbon isotope composition (δ13C) of the carbonate fraction of (−10.4 ± 0.6)‰ and (−9.7 ± 0.8)‰ for the Holocene and the older samples, respectively, indicate the autochthonous origin of the carbonate. The δ13C values of (−30.5 ± 0.3)‰ and (−29.6 ± 0.6)‰ for organic residue, having ages <500 BP and >5000 BP, respectively, suggest a unique carbon source for photosynthesis, mainly atmospheric CO2, with an indication of the Suess effect in δ13C during last centuries. The oxygen isotopic composition (δ18O) agrees well with deposition of tufa samples in two stages, the Holocene (−8.02 ± 0.72‰) and “old” (mainly MIS 3 and the beginning of MIS 2) (−6.89 ± 0.34‰), suggesting a ~4 °C lower temperature in MIS 3 compared to the current one.

scholarly journals The Ice-Rich Permafrost Sequences as a Paleoenvironmental Archive for the Kara Sea Region (Western Arctic)

2021 ◽  
Vol 9 ◽  
Author(s):  
I. D. Streletskaya ◽  
A. A. Pismeniuk ◽  
A. A. Vasiliev ◽  
E. A. Gusev ◽  
G. E. Oblogov ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Marine Sediments ◽  
Isotope Composition ◽  
Kara Sea ◽  
Coastal Sediments ◽  
Organic Carbon Content ◽  
Ground Ice ◽  
Geochemical Composition ◽  
The Holocene ◽  
Mis 3

The Kara Sea coast and part of the shelf are characterized by wide presence of the ice-rich permafrost sequences containing massive tabular ground ice (MTGI) and ice wedges (IW). The investigations of distribution, morphology and isotopic composition of MTGI and IW allows paleoenvironmental reconstructions for Late Pleistocene and Holocene period in the Kara Sea Region. This work summarizes result of long-term research of ice-rich permafrost at eight key sites located in the Yamal, Gydan, Taimyr Peninsulas, and Sibiryakov Island. We identified several types of ground ice in the coastal sediments and summarized data on their isotopic and geochemical composition, and methane content. We summarized the available data on particle size distribution, ice chemical composition, including organic carbon content, and age of the enclosing ice sediments. The results show that Quaternary sediments of the region accumulated during MIS 5 – MIS 1 and generally consisted of two main stratigraphic parts. Ice-rich polygenetic continental sediments with syngenetic and epigenetic IW represent the upper part of geological sections (10–15 m). The IW formed in two stages: in the Late Pleistocene (MIS 3 – MIS 2) and in the Holocene cold periods. Oxygen isotope composition of IW formed during MIS 3 – MIS 2 is on average 6‰ lower than that of the Holocene IW. The saline clay with rare sand layers of the lower part of geological sections, formed in marine and shallow shelf anaerobic conditions. MTGI present in the lower part of the sections. The MTGI formed under epigenetic freezing of marine sediments immediately after sea regression and syngenetic freezing of marine sediments in the tidal zone and in the conditions of shallow sea.

When animals are not quite what they eat: diet digestibility influences 13C-incorporation rates and apparent discrimination in a mixed-feeding herbivore

2011 ◽  
Vol 89 (6) ◽  
pp. 453-465 ◽  
Author(s):  
Daryl Codron ◽  
Jacqui Codron ◽  
Matt Sponheimer ◽  
Stefano M. Bernasconi ◽  
Marcus Clauss
Keyword(s):  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Food Sources ◽  
Capra Hircus ◽  
Stable Carbon ◽  
Animal Tissues ◽  
Themeda Triandra ◽  
Low Protein ◽  
Medicago Sativa L ◽  
Discrimination Factors

The stable carbon isotope composition of animal tissues represents the weighted sum of the variety of food sources eaten. If sources differ in digestibility, tissues may overrepresent intake of more digestible items and faeces may overrepresent less digestible items. We tested this idea using whole blood and faeces of goats ( Capra hircus L., 1758) fed different food mixtures of C3 lucerne ( Medicago sativa L.) and C4 grass ( Themeda triandra Forssk.). Although blood and faecal δ13C values were broadly consistent with diet, results indicate mismatch between consumer and diet isotope compositions: both materials overrepresented the C3 (lucerne) component of diets. Lucerne had lower fibre digestibility than T. triandra, which explains the results for faeces, whereas underrepresentation of dietary C4 in blood is consistent with low protein content of the grass hay. A diet switch experiment revealed an important difference in 13C-incorporation rates across diets, which were slower for grass than lucerne diets, and in fact equilibrium states were not reached for all diets. Although more research is needed to link digestive kinetics with isotope incorporation, these results provide evidence for nonlinear relationships between consumers and their diets, invoking concerns about the conceptual value of “discrimination factors” as the prime currency for contemporary isotope ecology.

Climate and land-use effects on hydrological and vegetation signals during the last three millennia: Evidence from sedimentary leaf waxes in southwestern Morocco

The Holocene ◽  
2021 ◽  
pp. 095968362098805
Author(s):  
Asmae Baqloul ◽  
Enno Schefuß ◽  
Martin Kölling ◽  
Lydie Dupont ◽  
Jeroen Groeneveld ◽  
...  
Keyword(s):  
Land Use ◽  
Carbon Isotope ◽  
Vegetation History ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Economic Stress ◽  
Published Data ◽  
Leaf Waxes ◽  
Argan Tree ◽  
Precipitation Changes

The southwest of Morocco is considered to be an area of refuge within the Mediterranean region, hosting the endemic tropical Argan tree. This region is presently subject to severe droughts, desertification and land degradation, and likely facing increased climate variability and socio-economic stress in the future. Here, we use the stable hydrogen and carbon isotope composition (δD and δ13C) of plant-waxes in a high-resolution marine sediment core (GeoB8601-3) collected off Cape Ghir in southwestern Morocco, in combination with published data on pollen and XRF element ratios from the same archive. We aim to reconstruct the hydroclimate and vegetation history during the last 3000 years. Stable carbon isotope compositions of leaf waxes (δ13Cwax) show that natural vegetation in southwestern Morocco consists of C3 plants. Minor variations in δ13Cwax were positively correlated to changes in stable hydrogen isotope compositions of leaf waxes (δDwax) before 700 CE. Changes in rainfall amounts and water use efficiency indicate a clear vegetation response to precipitation changes and thus to climate forcing. After 700 CE, δDwax and δ13Cwax became de-coupled suggesting that the plant wax discharge and their isotope signals were no longer solely controlled by climate; the waxes likely mainly originate from the lowlands and carry an enriched (dry) δD signal but a depleted 13C signature. The depletion of δ13Cwax correlates with the increase of Argan pollen concentration in the record. The period between ~700 and 900 CE coincides with the Arabization of Morocco which had an impact on the demographic composition of the country leading to new agricultural habits and, as a result, on the land-use triggering a higher erosion of lowland material by the Souss River.

Factors affecting 13C/12C ratios of inland halophytes. I. Controlled studies on growth and isotopic composition of Puccinellia nuttalliana

1986 ◽  
Vol 64 (11) ◽  
pp. 2693-2699 ◽  
Author(s):  
Robert D. Guy ◽  
David M. Reid ◽  
H. Roy Krouse
Keyword(s):  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Isotope Analysis ◽  
Research Problem ◽  
Carbon Isotope Composition ◽  
Stable Carbon ◽  
Factors Affecting ◽  
Plant Parts ◽  
High Level ◽  
Puccinellia Nuttalliana

Studies on various factors affecting the growth and stable carbon isotope composition of the graminaceous C3 halophyte Puccinellia nuttalliana (Schultes) Hitch. were initiated as a step towards interpreting δ13C variations in nature. For isotope analysis, combustion at 900 °C resulted in higher CO2 yield than at 550 °C but did not affect δ13C values. Differences in δ13C between leaves of different insertion level were unimportant, but roots were about 1‰ more positive than shoots. Trends in δ13C with salinity were the same in all plant parts. Depressions of growth by NaCl or Na2SO4 were similar, but plants grown in Na2SO4 displayed a greater shift in δ13C relative to controls. Growth rates were affected more by salinity than were previously reported photosynthetic rates. At typical salinities, δ13C changed linearly with salinity. The supply of nitrate to stressed and unstressed plants had no important influence on δ13C. Growth in polyethylene glycol produced δ13C values consistent with a high level of stress. After a salinity step-up, changes in δ13C were complete within 10 days. During winter, data were found to be heavily influenced by unintentional, human-respired CO2 enrichment. This represents a potentially serious research problem in laboratories of temperate climes.

scholarly journals Speleothem Stable Isotope Records from Eastern Europe & Turkey

2018 ◽  
Author(s):  
Zoltán Kern ◽  
Attila Demény ◽  
István Gábor Hatvani
Keyword(s):  
Stable Isotope ◽  
Eastern Europe ◽  
Oxygen Isotope ◽  
Temporal Resolution ◽  
Isotope Composition ◽  
Precipitation Amount ◽  
Temporal Distribution ◽  
Elevation Gradients ◽  
The Holocene ◽  
Carbon And Oxygen Isotope

The region of Eastern Europe &amp; Turkey contributed to the SISAL (Speleothem Isotopes Synthesis and AnaLysis) global database with stable carbon- and oxygen isotope time-series from 18 entities from 14 cave systems. The currently available oldest record from this region is the ABA-2 flowstone record (Abaliget Cave; Hungary) reaching back to MIS 6. The temporal distribution of the compiled 18 entities points out a ~20-kyr-long period, centering around 100 ka, lacking speleothem stable isotope record in the region. The regional subset of SISAL_v1 records displays a continuous coverage for the past ~90 kyr for both &delta;18O and &delta;13C, with a mean temporal resolution of ~12 yr for the Holocene, and &gt;50 yr for the pre-Holocene period. The highest temporal resolution both for the Holocene and the pre-Holocene was achieved in the So-1 record (Sofular Cave; Turkey). Assessing the data, an important split was found regarding the climatic interpretation of speleothem &delta;18O. While the oxygen isotope composition of more continental formations is thought to reflect mainly temperature variations and changes in moisture transport trajectories, it may strongly reflect fluctuations of precipitation amount in the southern part of the region. Variations of &delta;13C primarily interpreted as humidity changes reflecting dry/wet periods across the region. Elevation gradients from three non-overlapping time periods from the region - for the last 5kyr - indicated systematically prevailing elevational gradients around -0.26&permil;&nbsp;100m-1 in &delta;18O. The regional comparison of SISAL_v1 speleothem &delta;18O and the temporal distribution of coarsely crystalline cryogenic cave carbonate occurrences back to 45ka does not appear to confirm the finding that occurrence of the latter coincides with the warming from stadial to interstadial conditions.

scholarly journals Timing of Medieval Fluvial Aggradation at Bremgarten in the Southern Upper Rhine Graben – a Test for Luminescence Dating

2009 ◽  
Vol 57 (3/4) ◽  
pp. 411-432
Author(s):  
Manfred Frechen ◽  
Dietrich Ellwanger ◽  
Daniel Rimkus ◽  
Astrid Techmer
Keyword(s):  
Little Ice Age ◽  
Radiocarbon Dating ◽  
Experimental Studies ◽  
Luminescence Dating ◽  
Ice Age ◽  
Upper Rhine Graben ◽  
River Rhine ◽  
Fluvial Sediments ◽  
The Holocene ◽  
Short Period

Abstract. The Holocene flood plain of the River Rhine is a complex dynamic sedimentary system. A series of geochronological results for the Bremgarten section including optically stimulated luminescence (OSL) and radiocarbon dating was determined to improve the understanding of part of the Holocene evolution of the River Rhine. The applied single aliquot regenerative (SAR) protocols and the applied experimental studies to find the best luminescence behaviour leave us with confidence that OSL dating is a suitable method for dating fluvial sediments from large river systems. Insufficient bleaching of the sediments from Bremgarten prior to deposition seems to be not as dramatic as previously thought. OSL and radiocarbon dating results give evidence for a short period of major erosion and re-sedimentation of fluvial sediments from the “Tiefgestade” at the Bremgarten section between 500 and 600 years before present. This time period correlates with the beginning of the Little Ice Age at about AD 1450. Several severe floods occurred in Southern Germany between AD 1500 and 1750; all those floods correlate to the period of the Little Ice Age, including the destruction of the village of Neuenburg AD 1525.

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