Pedogenic carbonate nodules from a forested region of humid climate in central Tennessee, USA, and their implications for interpretation of C3-C4 relationships and seasonality of meteoric precipitation from carbon isotope (δ13C) data

Railsback, L. Bruce

doi:10.1016/j.catena.2021.105169

Cited by 4 publications

(4 citation statements)

References 49 publications

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“…The presence of soil carbonate in some of the wettest parts of central Myanmar, and their growth during possibly wetter conditions, is contrary to the traditional wisdom that soil carbonates do not form in environments with MAP >1,000 mm/year (Retallack, 2005). While this occurrence is rare, soil carbonates have been observed in “wet” localities such as northern India (Singh & Singh, 1972) and Tennessee, USA (Railsback, 2021). Quaternary pedogenic nodules are also found in multiple localities near the equator in Java (latitude ca.…”

Section: Discussionmentioning

confidence: 99%

Dynamics of Pedogenic Carbonate Growth in the Tropical Domain of Myanmar

Licht

Kelson

Bergel

et al. 2022

Geochem Geophys Geosyst

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Pedogenic carbonate is widespread at mid latitudes where warm and dry conditions favor soil carbonate growth from spring to fall. The mechanisms and timing of pedogenic carbonate formation are more ambiguous in the tropical domain, where long periods of soil water saturation and high soil respiration enhance calcite dissolution. This paper provides stable carbon, oxygen and clumped isotope values from Quaternary and Miocene pedogenic carbonates in the tropical domain of Myanmar, in areas characterized by warm (>18°C) winters and annual rainfall up to 1,700 mm. We show that carbonate growth in Myanmar is delayed to the driest and coldest months of the year by sustained monsoonal rainfall from mid spring to late fall. The range of isotopic variability in Quaternary pedogenic carbonates can be solely explained by temporal changes of carbonate growth within the dry season, from winter to early spring. We propose that high soil moisture year‐round in the tropical domain narrows carbonate growth to the driest months and makes it particularly sensitive to the seasonal distribution of rainfall. This sensitivity is also enabled by high winter temperatures, allowing carbonate growth to occur outside the warmest months of the year. This high sensitivity is expected to be more prominent in the geological record during times with higher temperatures and greater expansion of the tropical realm. Clumped isotope temperatures, δ13C and δ18O values of tropical pedogenic carbonates are impacted by changes of both rainfall seasonality and surface temperatures; this sensitivity can potentially be used to track past tropical rainfall distribution.

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Section: Discussionmentioning

confidence: 99%

Dynamics of Pedogenic Carbonate Growth in the Tropical Domain of Myanmar

Licht

Kelson

Bergel

et al. 2022

Geochem Geophys Geosyst

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“…Regarding the responsible factors determining the δ 13 C values of pedogenic carbonates, several potential causes may be responsible for the disequilibrium between soil carbonates and modern vegetation: (1) contamination of soil carbonates with inherited calcareous material, especially marine limestone (Amundson et al, 1989;Khademi and Mermut, 1999), (2) diagenetic alteration of the pedogenic carbonates by post-depositional processes (Budd et al, 2002), (3) diffusion of atmospheric gas having high δ 13 C values into the soil due to a low vegetation cover and low respiration rates (Amundson et al, 1989;Pendall et al, 1994;Monger et al, 1998;Ebeling et al, 2016;Bayat et al, 2018) and (4) changes in the proportion of C 3 /C 4 plants in the local ecosystem (Cerling, 1984;Cerling and Quade, 1993;Andrews et al, 1998;Monger et al, 1998;Achyuthan et al, 2007;Railsback, 2021; Frontiers in Earth Science frontiersin.org Sarangi et al, 2021;Fernández et al, 2022). Since the carbonates of the Baharan palaeosol are developed on non-calcareous clasts and are in the early stages of development, we can exclude causes 1 and 2.…”

Section: Stable Carbon Isotopesmentioning

confidence: 99%

“…Furthermore, soil carbonates formed around deeprooting plants can alter the chronology of syngenetic carbonate of palaeosols (Gocke et al, 2014). Moreover, recent studies have emphasised a seasonal bias in the formation of soil carbonates (Breecker et al, 2009;Kelson et al, 2020;Railsback, 2021;Sarangi et al, 2021;Domínguez-Villar et al, 2022). Therefore, palaeoclimatic signatures of soil carbonates may rather indicate the conditions of a particular part of the year than average annual parameters.…”

Section: Introductionmentioning

confidence: 99%

High-resolution record of stable isotopes in soil carbonates reveals environmental dynamics in an arid region (central Iran) during the last 32 ka

et al. 2023

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Although central Iran is pivotal for palaeoclimatic correlations, palaeoenvironmental data for this region is very sparse and a reliable chronology for pedogenic features is lacking. We therefore tried to answer the question how the environmental conditions and, in particular, the climate developed over time by using the isotopic signatures of pedogenic carbonates. We present a chronology of pedogenic carbonates in association with stable carbon and oxygen isotopes in both the matrix and coating carbonates of a relict palаeosol (Baharan palaeosol) in central Iran to understand the dynamics of environmental changes in this region during the late Quaternary. The palаeosol experienced several episodes of leaching during pedogenesis as reflected in its morphology (carbonate coatings under the rock fractions) and geochemical characteristics (Ba/Sr ratios). The δ18O values of both the matrix and coating carbonates in the upper 60 cm (especially in the upper 20 cm) of the pedon are enriched (∼4‰) compared to the subsoil and are mainly related to the impact of evaporation. Moreover, the δ13C values of the carbonates are in isotopic disequilibrium with the modern vegetation cover (desert shrubs) of the study area and are enriched in different degrees. The carbonates in the top 60 cm are formed by the input of atmospheric CO2 and calcareous dust while deeper carbonates formed in an environment exhibiting a higher contribution of C4 plants. Based on the radiocarbon chronology of carbonate coatings, it seems that three main stages of palaeoenvironmental changes occurred in the region during the last 32 ka. The first stage lasted ca. 5,000 years (between 31.6 and 26.0 ka) and was accompanied by deep leaching under sub-humid climatic conditions and the expansion of C4 plants. Under the dominance of semi-arid conditions during the second stage until the late Holocene, a gradual increase in the δ18O values and aridity occurred in the region. The last phase in the late Holocene was characterised by the establishment of an arid and evaporative environment with a sparse vegetation cover. A climatic correlation using the oxygen isotopic composition of secondary carbonates from the Baharan palaeosol, Soreq Cave (the Levant) and Hoti Cave (Oman; both having speleothems records) suggested a climatic connection between central Iran and the eastern Mediterranean during the late Pleistocene and between central Iran and northern Oman during the late Holocene.

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“…Researchers believe that carbonate concretions have the potential to provide valuable information about the ancient Earth (Clifton, 1957;Melendez et al, 2013;Dale et al, 2014;Mavotchy et al, 2016). During and after the formation of carbonate concretions, an enclosed microsystem that is independent of and distinct from surrounding rocks is generated (Raiswell and Fisher, 2000;Railsback, 2021). Paleoenvironmental and paleontological information on the synsedimentary to the early diagenetic stage is sealed within this protected microsystem.…”

Section: Introductionmentioning

confidence: 99%

Preservation of molecular fossils in carbonate concretions in cretaceous shales in the songliao basin, northeast China

Lin

Fang²,

Xu³

2023

Front. Earth Sci.

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Paleoenvironmental information is better preserved in carbonate concretions. In this study, carbonate concretions in the Cretaceous Nenjiang shale, Songliao Basin, were examined to determine whether molecular fossils reflective of the paleoenvironment were better preserved at these sites. Organic and inorganic geochemical characteristics of the concretions and surrounding rocks were analyzed using a series of techniques, including SEM, LA-ICP-MS, GC-MS-MS, and GC-IRMS. The concretions are composed of high content microcrystalline dolomite. The δ13Ccarb and δ18Ocarb values of the concretionary dolomite were significantly higher than those of the surrounding rocks. The dolomite show enrichment in the LREEs and have a negative Eu anomaly. The concretion biomarkers showed distribution characteristics similar to those of surrounding rocks. This suggested that the molecular fossils preserved in concretions were mainly inherited from surrounding rocks. However, the concretions contained more C27 sterane and hopanes, with the hopane/sterane ratio being significantly higher than that of surrounding rocks (1.49 v. 0.86). Moreover, the relative content of 2-methylhopane was 2.4–6.6 times that of the surrounding rocks. This indicated changes in the biological equilibrium of source organisms within and outside the concretions. It was possible that the unstable organic matter at the core increased the bacterial concentration and activity inside the concretions. Both the hydrogen index and biomarker-derived indicators implied that the transformation of organic matter in concretions was minimized when compared with their host rock. The isotope δ13C16-30 was 1‰–3‰ more prevalent in individual N-alkane hydrocarbons in the concretions than in surrounding rocks, likely owing to differences in lithology, bacterial action, and degree of weathering. The study concluded that carbonate concretions could preserve molecular fossils better than the surrounding rocks, and the in-depth organic geochemical analysis of concretions could provide a valuable reference for research into early life forms.

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Pedogenic carbonate nodules from a forested region of humid climate in central Tennessee, USA, and their implications for interpretation of C3-C4 relationships and seasonality of meteoric precipitation from carbon isotope (δ13C) data

Cited by 4 publications

References 49 publications

Dynamics of Pedogenic Carbonate Growth in the Tropical Domain of Myanmar

Dynamics of Pedogenic Carbonate Growth in the Tropical Domain of Myanmar

High-resolution record of stable isotopes in soil carbonates reveals environmental dynamics in an arid region (central Iran) during the last 32 ka

Preservation of molecular fossils in carbonate concretions in cretaceous shales in the songliao basin, northeast China

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