Trends in δ18O and δ13C values in lacustrine tufa mounds: Palaeohydrology of Searles Lake, California

Sedimentology ◽  
2013 ◽  
Vol 61 (1) ◽  
pp. 221-237 ◽  
Author(s):  
Xuan Guo ◽  
Henry S. Chafetz
Keyword(s):  
Δ13c Values ◽  
Δ18o And Δ13c

scholarly journals Monitoring of a fast-growing speleothem site from the Han-sur-Lesse cave, Belgium, indicates equilibrium deposition of the seasonal δ<sup>18</sup>O and δ<sup>13</sup>C signals in the calcite

2014 ◽  
Vol 10 (5) ◽  
pp. 1871-1885 ◽  
Author(s):  
M. Van Rampelbergh ◽  
S. Verheyden ◽  
M Allan ◽  
Y. Quinif ◽  
E. Keppens ◽  
...  
Keyword(s):  
Water Temperature ◽  
Single Layer ◽  
Δ13c Values ◽  
Drip Water ◽  
Fast Growing ◽  
Cave System ◽  
Water Recharge ◽  
Opposite Behavior ◽  
Calcite Saturation ◽  
Δ18o And Δ13c

Abstract. Speleothems provide paleoclimate information on multimillennial to decadal scales in the Holocene. However, seasonal or even monthly resolved records remain scarce. Such records require fast-growing stalagmites and a good understanding of the proxy system on very short timescales. The Proserpine stalagmite from the Han-sur-Less cave (Belgium) displays well-defined/clearly visible darker and lighter seasonal layers of 0.5 to 2 mm thickness per single layer, which allows a measuring resolution at a monthly scale. Through a regular cave monitoring, we acquired a good understanding of how δ18O and δ13C signals in modern calcite reflect climate variations on the seasonal scale. From December to June, outside temperatures are cold, inducing low cave air and water temperature, and bio-productivity in the soil is limited, leading to lower pCO2 and higher δ13C values of the CO2 in the cave air. From June to December, the measured factors display an opposite behavior. The absence of epikarst water recharge between May and October increases prior calcite precipitation (PCP) in the vadose zone, causing drip water to display increasing pH and δ13C values over the summer months. Water recharge of the epikarst in winter diminishes the effect of PCP and as a result the pH and δ13C of the drip water gradually decrease. The δ18O and δ13C signals of fresh calcite precipitated on glass slabs also vary seasonally and are both reflecting equilibrium conditions. Lowest δ18O values occur during the summer, when the δ13C values are high. The δ18O values of the calcite display seasonal variations due to changes in the cave air and water temperature. The δ13C values reflect the seasonal variation of the δ13CDIC of the drip water, which is affected by the intensity of PCP. This same anticorrelation of the δ18O versus the δ13C signals is seen in the monthly resolved speleothem record that covers the period between 1976 and 1985 AD. Dark layers display lower δ18O and higher δ13C values. The cave system varies seasonally in response to the activity of the vegetation cover and outside air temperature between a "summer mode" lasting from June to December and a "winter mode" from December to June. The low δ18O and high δ13C values of the darker speleothem layers indicate that they are formed during summer, while light layers are formed during winter. The darker the color of a layer, the more compact its calcite structure is, and the more negative its δ18O signal and the more positive its δ13C signal are. Darker layers deposited from summer drip water affected by PCP are suggested to contain lower Ca2+ concentration. If indeed the calcite saturation represents the main factor driving the Proserpine growth rate, the dark layers should grow slower than the white layers.

scholarly journals Beachrock as a Paleoshoreline Indicator: Example from Wadi Al-Hamd, South Al-Wajh, Saudi Arabia

2021 ◽  
Vol 9 (9) ◽  
pp. 984 ◽  
Author(s):  
Ammar A. Mannaa ◽  
Rabea A. Haredy ◽  
Ibrahim M. Ghandour
Keyword(s):  
Saudi Arabia ◽  
Volcanic Rocks ◽  
Skeletal Remains ◽  
Heavy Minerals ◽  
Coarse Grained ◽  
Coralline Algae ◽  
Sea Level Changes ◽  
Pore Filling ◽  
Δ13c Values ◽  
Δ18o And Δ13c

The present study concerns the Holocene inland beachrocks that are exposed in the Red Sea coastal plain at the mouth of Wadi Al-Hamd, South Al-Wajh City, Saudi Arabia, and their utility as an indicator for Holocene climate and sea level changes. In addition, the framework composition, and carbon and oxygen isotopic data, are employed to interpret the origin of their cement. The beachrock consists mainly of gravel and coarse-grained terrigenous sediments dominated by lithic fragments of volcanic rocks, cherts and rare limestones along with quartz, feldspars and traces of amphiboles and heavy minerals. In addition, rare skeletal remains dominated by coralline algae, benthic foraminifera and mollusca remains are recognized. The allochems are cemented by high Mg-calcite (HMC) formed mainly in the intertidal zone under active marine phreatic conditions. The cement takes the form of isopachous to anisopachous rinds of bladed crystals, micritic rim non-selectively surrounding siliciclastic and skeletal remains, and pore-filling micrite. Pore-filling micrite cement occasionally displays a meniscus fabric, suggesting a vadose environment. The δ18O and δ13C values of carbonate cement range from −0.35‰ to 1‰ (mean 0.25‰) and −0.09‰ to 3.03‰ (mean 1.85‰), respectively, which are compatible with precipitation from marine waters. The slight depletion in δ18O and δ13C values in the proximal sample may suggest a slight meteoric contribution.

scholarly journals Novel method for determining <sup>234</sup>U–<sup>238</sup>U ages of Devils Hole 2 cave calcite (Nevada)

Geochronology ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 49-58
Author(s):  
Xianglei Li ◽  
Kathleen A. Wendt ◽  
Yuri Dublyansky ◽  
Gina E. Moseley ◽  
Christoph Spötl ◽  
...  
Keyword(s):  
The Novel ◽  
Time Intervals ◽  
Δ13c Values ◽  
Devils Hole ◽  
Calcite Deposition ◽  
Dating Method ◽  
Novel Method ◽  
Multi Linear Regression ◽  
Δ18o And Δ13c

Abstract. Uranium–uranium (234U–238U) disequilibrium dating can determine the age of secondary carbonates over greater time intervals than the well-established 230Th–234U dating method. Yet it is rarely applied due to unknowns in the initial δ234U (δ234Ui) value, which result in significant age uncertainties. In order to understand the δ234Ui in Devils Hole 2 cave, Nevada, we have determined 110 δ234Ui values from phreatic calcite using 230Th–234U disequilibrium dating. The sampled calcite was deposited in Devils Hole 2 between 4 and 590 ka, providing a long-term look at δ234Ui variability over time. We then performed multi-linear regression among the δ234Ui values and correlative δ18O and δ13C values. The regression can be used to estimate the δ234Ui value of Devils Hole calcite based upon its measured δ18O and δ13C values. Using this approach and the measured present-day δ234U values of Devils Hole 2 calcite, we calculated 110 independent 234U–238U ages. In addition, we used newly measured δ18O, δ13C, and present-day δ234U values to calculate 10 234U–238U ages that range between 676 and 731 ka, thus allowing us to extend the Devils Hole chronology beyond the 230Th–234U-dated chronology while maintaining an age precision of ∼ 2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 ± 11 kyr ago. The novel method presented here may be applied to future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.

Comparison of δ18O and δ13C values between tree-ring whole wood and cellulose in five species growing under two different site conditions

2015 ◽  
Vol 29 (23) ◽  
pp. 2233-2244 ◽  
Author(s):  
Rosemarie B. Weigt ◽  
Stephanie Bräunlich ◽  
Lothar Zimmermann ◽  
Matthias Saurer ◽  
Thorsten E. E. Grams ◽  
...  
Keyword(s):  
Tree Ring ◽  
Site Conditions ◽  
Δ13c Values ◽  
Δ18o And Δ13c

scholarly journals Oxygen and Carbon Stable Isotope Composition of Cretaceous to Pliocene Calcareous Paleosols in the Tian Shan Region (Central Asia): Controlling Factors and Paleogeographic Implications

Geosciences ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 330 ◽  
Author(s):  
Marc Jolivet ◽  
Philippe Boulvais ◽  
Laurie Barrier ◽  
Cécile Robin ◽  
Gloria Heilbronn ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Central Asia ◽  
Isotope Composition ◽  
Time Range ◽  
Large Lakes ◽  
Δ13c Values ◽  
Late Mesozoic ◽  
Oxygen And Carbon Isotope ◽  
Δ18o And Δ13c ◽  
Tian Shan

The Late Mesozoic–Cenozoic topographic and climate evolution of Central Asia remains highly debated. The final retreat of the proto-Paratethys Sea from the western Tarim Basin is thought to correspond in time with the onset of tectonic uplift in the Pamir, Tian Shan and Altai ranges, as well as with regional aridification. The oxygen and carbon isotope compositions of the sediment deposits in the various Central Asian basins have already been used to decipher both the topographic and climatic changes that occurred in that region during the Cenozoic, generally concentrating on one sedimentary section and/or on a limited time range and either using multiple-type samples including sandstone calcitic cements, marine carbonates, fossils, or paleosols. In order to get a homogeneous dataset, minimizing variations in the isotopic composition of the material depending on its type and/or depositional environment, we selected only calcareous paleosols sampled in several continuous sections covering a wide time range from the Late Jurassic to the Pliocene. Our sampling also covers a wide area encompassing the whole Tian Shan region, which allows detecting regional variations in the δ18O and δ13C values. We show that the influence of the distance to the proto-Paratethys Sea on the paleosol δ18O record was not significant. Besides local factors such as the occurrence of large lakes that can have a significant effect on the isotopic composition of the calcareous paleosols, the long-term evolution of both the δ18O and δ13C values possibly reflects the hypsometry of the river drainage systems that bring water to the basins. However, as it is commonly accepted that the δ18O of soil carbonates is controlled by the δ18O of in-situ precipitation, this last conclusion remains to be further investigated.

Subannual stable isotope records reveal climate warming and seasonal anoxia associated with two extinction intervals across the Cretaceous-Paleogene boundary on Seymour Island, Antarctica

Geology ◽  
2020 ◽  
Vol 48 (11) ◽  
pp. 1131-1136
Author(s):  
Rachel C. Mohr ◽  
Thomas S. Tobin ◽  
Sierra V. Petersen ◽  
Andrea Dutton ◽  
Elizabeth Oliphant
Keyword(s):  
High Resolution ◽  
Stable Isotope ◽  
Climate Warming ◽  
Rapid Change ◽  
Low Oxygen ◽  
Δ13c Values ◽  
Oxygen Conditions ◽  
Seymour Island ◽  
Δ18o And Δ13c ◽  
Bivalve Shells

Abstract High-resolution stable isotope (δ18O and δ13C) sclerochronology of accretionary carbonate bivalve shells can provide subannual environmental records useful for understanding intervals of extinction, which are commonly periods of rapid change and instability. Here, we present results from high-resolution serial sampling of Lahillia larseni bivalve shells across the Cretaceous-Paleogene boundary (KPB) on Seymour Island, Antarctica. These data highlight two intervals of anomalous δ18O and δ13C values that coincide with condensed fossil last occurrences: one at the KPB and one at an apparent extinction event 150 k.y. earlier. We interpret these two intervals to represent periods of both climate warming, as indicated by lower δ18O, and seasonal anoxia or euxinia, as evidenced by anomalously low (−21.6‰ to −3.0‰ VPDB [Vienna Peedee belemnite]) δ13C values with high (2‰ to 19‰ in magnitude) seasonal variation. Low-oxygen conditions may have acted as a kill mechanism at the earlier extinction interval and possibly prolonged recovery from the KPB extinction.

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