Stable Isotope Studies of the Water Cycle and Terrestrial Environments

This volume is devoted to Earth surface environmental reconstructions and environmental changes that may be deciphered and modelled using stable isotopes along with mineralogical/chemical, sedimentological, palaeontological/biological and climatological methodologies. The book is divided into two sections, both using stable isotopes (δD, δ18O, δ13C, d15N, δ34S, clumped isotopes Δ47) in various samples and phases as the main research tool. The first section is devoted to studies focusing on the distribution of isotopes in precipitation, groundwater, lakes, rivers, springs, tap water, mine water and their relationship with terrestrial environments at regional to continental scale. In relation to this, the second section includes case studies from a range of continental settings, investigating cave deposits (stalagmites, bat guano), animal skeletons (dinosaurs, alligators, turtles, bivalves), present and past soils (palaeosols) and limestones. The sections focus on the interaction between the surficial water cycle and underground water storage with deposits acting as archives of short- to long-term climatic and environmental changes. Examples from the Early Cretaceous to present time come from Europe, Asia, Africa, North and South America.
Stable isotope geochemistry of pedogenic carbonates in calcareous materials, Iran: a review and synthesis
Correspondence: Omid.bayat@gmail.com, omid_bayat@ag.iut.ac.ir
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Published:October 28, 2021
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CiteCitation
Omid Bayat, Alireza Karimi, Ronald Amundson, 2021. "Stable isotope geochemistry of pedogenic carbonates in calcareous materials, Iran: a review and synthesis", Stable Isotope Studies of the Water Cycle and Terrestrial Environments, A.-V. Bojar, A. Pelc, C. Lécuyer
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Abstract
The stable isotopic composition of pedogenic carbonate forms in equilibrium with environmental parameters and, thus, records palaeoenvironmental signals. The aims of this study are to synthesize available data on the stable isotopic composition of Quaternary pedogenic carbonates in calcareous parent materials of Iran and to decipher paleoenvironmental implications of the isotopic data for the country. Isotopic composition and microfabric of pedogenic carbonates in 18 pedons in both gravelly (calcareous alluvium in central Iran) and non-gravelly deposits (calcareous loess in northeastern Iran) have been investigated. The results indicate that in limestone-derived soils of central Iran in situ weathering of calcareous pebbles is a major source of Ca for genesis of the carbonates, and carbonate features consist of micritic calcite crystals. In the loessic soils of northeastern Iran, pedogenic carbonates show a dominance of nodule morphology and are classified as orthic nodules. Microfabric analysis reveals that most of the carbonates have not been altered by diagenetic processes, especially the Holocene carbonates, and are suitable for isotopic study and palaeoreconstructions. In limestone-derived soils within the arid region of central Iran, the δ18O and the δ13C values of carbonates indicate their enrichment due to the effects of evaporative water loss, a decline in plant density and the entrance of atmospheric CO2 into the soils. In semi-arid ecosystems of central and northeastern Iran, most of the Holocene carbonates have formed in equilibrium with the ambient environment and are suitable for palaeoenvironmental reconstructions. The combination of carbon and oxygen isotopic data demonstrates the dominant role of climate in determining the δ13C values of carbonates. There is a strong relationship between the δ13C values of carbonates and rainfall, and between O isotopes and aridity indices. Stable isotope patterns in Holocene soils appear to provide data for models that can then be used to interpret the many localities where Pleistocene-aged soils and associated carbonate exist.
- annual variations
- Asia
- C-13/C-12
- calcareous composition
- calcite
- carbon
- carbonates
- Cenozoic
- chemical composition
- correlation
- ecosystems
- environmental analysis
- geochemistry
- Holocene
- hydrology
- Iran
- isotope ratios
- isotopes
- land cover
- micromorphology
- Middle East
- morphology
- O-18/O-16
- oxygen
- paleoenvironment
- parent materials
- pedogenesis
- pedons
- Pleistocene
- Quaternary
- rainfall
- reconstruction
- seasonal variations
- semi-arid environment
- soils
- stable isotopes
- terrestrial environment
- vegetation