The formation of iron oxides and magnetic enhancement mechanisms in northern Iranian loess-paleosol sequences: Evidence from diffuse reflectance spectrophotometry and temperature dependence of magnetic susceptibility

Ghafarpour, Amin; Khormali, Farhad; Balsam, William; Forman, Steven L.; Cheng, Liangqing; Song, Yougui

doi:10.1016/j.quaint.2021.02.019

Cited by 6 publications

(7 citation statements)

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“…In addition, by comparing loess units at Mobarakabad, including the OSL ages of unit 4, with stratigraphy and previously published luminescence ages from other sections at NFAM, this unit 1 at Mobarakabad correlates well with MIS 5e (Particle Size Parameters of Loess Units). Corroborating this assignment, based on magnetic depletion in the paleosol of unit 1 at Mobarakabad, Ghafarpour et al (2021) concluded that the paleosol formation was accompanied by high (winter) rainfall in which dissolution of pedogenic maghemite-magnetite occurred. As such, one way of explaining these observations is high rainfall in winters, probably in MIS 5e, followed by dry and hot summers in which evaporative soil water loss predominates with little meteoric recharge, resulting in enriched δ 18 O bc and δ 18 O pc values of the upper horizons (Btb and Btkb) compared to those of Bkb and BCb horizons in unit 1 (Figure 2A).…”

Section: Particle Size Measurementsmentioning

confidence: 99%

“…These deposits represent outstanding archives of past climate in a region highly sensitive to changes in hydroclimate and potentially important in past human migrations (Shoaee et al, 2021) but otherwise poorly represented by past climate records. The loess units in the area are separated by paleosols showing various development degrees, providing valuable sedimentary archives of loess accumulation, soil, and paleosol formation within the loess units (Kehl et al, 2005;Frechen et al, 2009;Kehl, 2010;Khormali and Kehl, 2011;Ghafarpour et al, 2016Ghafarpour et al, , 2021Vlaminck et al, 2016Vlaminck et al, , 2018Lauer et al, 2017a;Lauer et al, 2017b;Shahriari et al, 2017;Pourmasoumi et al, 2019;Sharifigarmdareh et al, 2020;Kehl et al, 2021). These previous studies of loess-paleosol sequences in northern Iran mainly focused on dating of the deposits, particle size distributions, and paleosol formation in response to paleoprecipitation and paleopedogenic process, with little emphasis on phases of eolian deposition, meaning that additional detailed analyses of the loess units in particular are essential.…”

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 Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…4). Therefore, compared with χ lf and χ fd %, the a* value might be a more reliable paleoclimatic indicator (Hu et al, 2014) in the loess–paleosol sequences of the NILP and NFAM (Ghafarpour et al, 2021a). We also ascribe the increased hematite content and χ fd % values in the modern soil and paleosols (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…1). These loess deposits are separated by buried soils that formed under relatively moist and warm climatic conditions (e.g., Frechen et al, 2009; Kehl, 2010; Karimi et al, 2011; Lauer et al, 2017b; Ghafarpour et al, 2021a; Kehl et al, 2021). Regressions and transgressions of the Caspian Sea (e.g., Yanina, 2014; Yanina et al, 2018; Krijgsman et al, 2019; Leroy et al, 2020) may have affected loess formation in the Caspian Lowlands by changing the size of the dust source area and by their influence on regional climate (Vlaminck et al, 2018; Kehl et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Geophysical sediment properties of a late Pleistocene loess–paleosol sequence, Chenarli, northeastern Iran

et al. 2023

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We present stratigraphic, magnetic, diffuse reflectance spectrophotometric analyses, and chronologic data for the Chenarli loess–paleosol sequence in northeastern Iran. Eight loess units (LU) are identified, described, and constrained in time based on relative stratigraphy and luminescence dating from >130 ± 9.1 ka to ~9.8 ± 0.7 ka. Our data indicate that pedogenic magnetite/maghemite formation gives rise to magnetic enhancement in modern soil and paleosols. The top of LU 7 is demarcated by the well-developed last interglacial soil in which magnetic depletion occurred. We infer that magnetic depletion in this paleosol was produced by reducing conditions in a seasonally waterlogged soil during a warm and wet phase within Marine Isotope Stage (MIS) 5e. Units LU 6 to 1 record several episodes of dust accumulation and soil formation during the last glacial and Holocene. Increased dust accumulation rates occurred during middle-late MIS 3 and lasted into the late MIS 2, with a peak during the last glacial maximum (LU 2). These findings could be applicable to understanding magnetic enhancement/dissolution mechanism in the loess–paleosol sequences in study area. We infer paleoenvironmental changes in northeastern Iran relative to northern Iran, Eurasia, and China.

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“…Rock magnetism (magnetic properties of rocks) and palaeomagnetic (magnetostratigraphy) methods, especially in combination with lithological-palaeopedological and palynological analyses, serve as a powerful tool in the reconstruction of palaeoenvironmental changes [120][121][122]. Magnetic susceptibility is a sensitive, fast and accurate technique to detect soil pedogenic processes and features and can improve the understanding of soil-forming and, correspondingly, palaeoclimate factors [86,[123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140].…”

Section: Introductionmentioning

confidence: 99%

Early–Middle Pleistocene Magnetostratigraphic and Rock Magnetic Records of the Dolynske Section (Lower Danube, Ukraine) and Their Application to the Correlation of Loess–Palaeosol Sequences in Eastern and South-Eastern Europe

Hlavatskyi

Бахмутов

2021

Quaternary

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We present new palaeomagnetic and rock magnetic results with a stratigraphic interpretation of the late Early–Middle Pleistocene deposits exposed on the left bank of the River Danube at Dolynske, southern Ukraine. A thick succession of water-lain facies is succeeded by reddish-brown clayey soils, topped by a high-resolution loess–palaeosol sequence. These constitute one of the most complete recently discovered palaeoclimate archives in the Lower Danube Basin. The suggested stratigraphy is based on the position of the Matuyama–Brunhes boundary, rock magnetic, palaeopedological and sedimentological proxies, and it is confidently correlated with other loess records in the region (Roksolany and Kurortne), as well as with the marine isotope stratigraphy. The magnetic susceptibility records and palaeosol characteristics at Dolynske show an outstanding pattern that is transitional between eastern and south-eastern European loess records. Our data confirm that the well-developed S4 soil unit in Ukraine, and S5 units in Romania, Bulgaria and Serbia, correlate with the warm MIS 11. Furthermore, we suggest the correlation of rubified S6 palaeosols in Romania and Bulgaria and the V-S7–V-S8 double palaeosol in Serbia with S6 in Ukraine, a strong Mediterranean-type palaeosol which corresponds to MIS 15. Our new results do not support the hypothesis of a large magnetic lock-in depth like that previously interpreted for the Danube loess, and they prove that the Matuyama–Brunhes boundary is located within the palaeosol unit corresponding to MIS 19. The proposed stratigraphic correlation scheme may serve as a potential basis for further regional and global Pleistocene climatic reconstructions.

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The formation of iron oxides and magnetic enhancement mechanisms in northern Iranian loess-paleosol sequences: Evidence from diffuse reflectance spectrophotometry and temperature dependence of magnetic susceptibility

Cited by 6 publications

References 118 publications

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

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

Geophysical sediment properties of a late Pleistocene loess–paleosol sequence, Chenarli, northeastern Iran

Early–Middle Pleistocene Magnetostratigraphic and Rock Magnetic Records of the Dolynske Section (Lower Danube, Ukraine) and Their Application to the Correlation of Loess–Palaeosol Sequences in Eastern and South-Eastern Europe

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