Pedogenic carbonates archive modern and past precipitation change – A transect study from soils and loess-paleosol sequences from northern Iran

Khormali, Farhad; Shahriari, Ali; Ghafarpour, Amin; Kehl, Martin; Lehndorff, Eva; Frechen, Manfred

doi:10.1016/j.quaint.2019.12.011

Cited by 16 publications

(12 citation statements)

References 67 publications

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“…The observed shift in average δ 13 C pc values from paleosols (−8.5‰) to modern soil (−6.1‰) suggests that the paleosols δ 13 C pc values were ∼2.5‰ lower than those of the modern soil. Additionally, the δ 13 C pc values of the modern soil of Mobarakabad are similar to the average δ 13 C pc values of loessic modern soils (−6.2‰) in the NFAM with forest cover, reported in Khormali et al (2020). Furthermore, the mean δ 13 C values of soil organic matter (−23.6‰) of the paleosols in Mobarakabad (Khormali et al, 2020) are within the same range as the δ 13 C values of modern soil organic matter, indicating a C 3 -dominated environment for both paleosols and the modern soil of Mobarakabad.…”

Section: Particle Size Measurementssupporting

confidence: 83%

“…Additionally, the δ 13 C pc values of the modern soil of Mobarakabad are similar to the average δ 13 C pc values of loessic modern soils (−6.2‰) in the NFAM with forest cover, reported in Khormali et al (2020). Furthermore, the mean δ 13 C values of soil organic matter (−23.6‰) of the paleosols in Mobarakabad (Khormali et al, 2020) are within the same range as the δ 13 C values of modern soil organic matter, indicating a C 3 -dominated environment for both paleosols and the modern soil of Mobarakabad. Therefore, we inferred a ∼2.5‰ increase in δ 13 C pc values of the modern soil of Mobarakabad and loessic modern soils in northern Iran (Khormali et al, 2020), as compared to paleosols of Mobarakabad section, might result from a drier climate in Holocene, as compared to the paleosol formation periods in late Pleistocene in the NFAM.…”

Section: Particle Size Measurementssupporting

confidence: 83%

“…Furthermore, the mean δ 13 C values of soil organic matter (−23.6‰) of the paleosols in Mobarakabad (Khormali et al, 2020) are within the same range as the δ 13 C values of modern soil organic matter, indicating a C 3 -dominated environment for both paleosols and the modern soil of Mobarakabad. Therefore, we inferred a ∼2.5‰ increase in δ 13 C pc values of the modern soil of Mobarakabad and loessic modern soils in northern Iran (Khormali et al, 2020), as compared to paleosols of Mobarakabad section, might result from a drier climate in Holocene, as compared to the paleosol formation periods in late Pleistocene in the NFAM. In contrast, the similarity in average δ 18 O pc values of both the modern soil and paleosols in Mobarakabad (−7.3‰) with the average δ 18 O pc values of loessic modern soils in the NFAM (−7.4‰) may reflect no shift in the source of late Pleistocene-to-Holocene regional precipitation in the NFAM.…”

Section: Particle Size Measurementsmentioning

confidence: 63%

“…In units 1-5, δ 13 C bc values decrease with increasing pedogenesis and vegetation cover from loessic C horizons to the paleosols (Figure 2A). Additionally, the vegetation in the paleosols of the section is dominated by C 3 plants, with a mean δ 13 C value of soil organic matter (−23.6‰) (Khormali et al, 2020). Thus, δ 13 C bc values of paleosols are very sensitive to changes in the precipitation-controlled vegetation density and can serve as a reliable proxy of paleoprecipitation.…”

Section: Particle Size Measurementsmentioning

confidence: 99%

“…Chinese loess δ 13 C bc variation therefore likely reflects the regional precipitation change and therefore can be regarded as a sensitive proxy for the summer monsoon intensity (Liu et al, 2011;Sun et al, 2015). Recently, Khormali et al (2020) investigated δ 13 C bc and δ 18 O bc as well as δ 13 C pc and δ 18 O pc and organic carbon from modern soils and paleosols in northern Iran along a west to east and south to north precipitation gradient. They concluded that δ 13 C bc and δ 18 O bc values showed a significant relationship with MAP, over the range from 200 to approximately 750 mm/yr, and also suggested a summer bias in carbonate nodule formation in the area.…”

Section: Introductionmentioning

confidence: 99%

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Late Pleistocene Climate and Dust Source From the Mobarakabad Loess–Paleosol Sequence, Northern Foothills of the Alborz Mountains, Northern Iran

et al. 2021

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Paleoclimatic investigation of loess-paleosol sequences from northern Iran is important for understanding past changes in a region highly sensitive to shifts in precipitation, and along potential routes of past human migration. Here, we present carbon and oxygen isotopic compositions of bulk carbonate (δ13Cbc and δ18Obc, respectively) coupled with particle size distributions of samples from the Mobarakabad section, northern Iran, to study past wind dynamics and hydroclimate. We also present new initial clay-sized Hf-Nd isotope results from key horizons in order to assess general dust sources. Variations of δ13Cbc and δ18Obc values of modern soils compared to paleosols allow reconstruction of late Pleistocene–Holocene climate change in the area. Our results show severe drought during a major eolian deposition phase (EDP) after 34 ka. The thickness and PSD of the C horizon of unit 5 suggest significant shifts in loess sources and depositional environments during this EDP after 34 ka. Indeed, based on our new clay-sized Hf-Nd data, we hypothesize that the loess unit 5 might originate from the young crustal source of the Alborz and Kopet Dagh mountains. In general, the PSD of C horizons in the section is bimodal in the silt fraction and the very small, very fine clay fraction, with a mode at c. 1 μm in the modern soil and paleosols possibly produced by weathering and pedogenic processes. There also appears to be a good correlation between δ13Cbc and δ18Obc values, differentiating phases of loess accumulation and paleosol formation and hence providing quantitative data for reconstructing paleoclimatic conditions in the study area.

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Section: Particle Size Measurementssupporting

confidence: 83%