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The influence of time on the magnetic properties of late Quaternary periglacial and alluvial surface and buried soils along the Delaware River, USA
Abstract and Figures
Magnetic susceptibility of soils is a common proxy for rainfall, but other factors can contribute to magnetic enhancement in soils. Here we explore influence of century- to millennial-scale duration of soil formation on periglacial and alluvial soil magnetic properties by assessing three terraces with surface and buried soils ranging in exposure ages from <0.01 to ~16 kyrs along the Delaware River in northeastern USA. The A and B soil horizons have higher Xlf, Ms, and S-ratios compared to parent material, and these values increase in a non-linear fashion with increasing duration of soil formation. Magnetic remanence measurements show a mixed low- and high-coercivity mineral assemblage likely consisting of goethite, hematite, and maghemite and/or magnetite that contributes to the magnetic enhancement of the soil. Room-temperature and low-temperature field-cooled and zero field-cooled remanence curves confirm the presence of goethite and magnetite and/or maghemite and show an increase in magnetization with increasing soil age. These data suggest that as the Delaware alluvial soils weather, the concentration of secondary ferrimagnetic minerals increase in the A and B soil horizons. We then compared the time-dependent Xlf from several age-constrained buried alluvial soils with known climate data for the region during the Quaternary. Contradictory to most studies that suggest a link between increases in magnetic susceptibility and high moisture, increased magnetic enhancement of Delaware alluvial soils coincides with dry climate intervals. Early Holocene enhanced soil Xlf (9.5–8.5 ka) corresponds with a well-documented cool-dry climate episode. This relationship is probably related to less frequent flooding during dry intervals allowing more time for low-coercive pedogenic magnetic minerals to form and accumulate, which resulted in increased Xlf. Middle Holocene enhanced Xlf (6.1–4.3 ka) corresponds with a wet to dry transitional phase and a previously documented incision event along the valley bottom. In this case the incision and terrace development resulted in prolonged surface exposure and more time for the accumulation of secondary ferrimagnetic minerals, enhancing Xlf. The results of this study agree with previous modeling efforts, and show that in Quaternary (and possibly pre-Quaternary) periglacial and alluvial soils and paleosols that weathered for 101–104 years, duration of pedogenesis, rather than climate, is an important control on magnetic enhancement.
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... Reference soil samples CX1 and CX2 were associated with clusters "c" and "e" and were collected in the A and B horizons from a Haplic Cambisol in a dry forest environment. A dry forest is a vegetation community that hosts frequent natural fires, and the data prove the capacity of wildfire to produce magnetic signatures in the natural soil, as previously shown by Ketterings et al. (2000) and Stinchcomb and Peppe (2014). ...
This study provides the first survey of Brazilian magnetic susceptibility (MS) data from varying archaeological and geological contexts, including open‐air sites, quartzite, and limestone rockshelters, and Amazonian dark earths. Our MS analyses associated with archaeological findings allow us to propose MS values as proxies of intense anthropogenic burning activities for archaeological sites with (i) systematic use of large hearth lit in the same places; (ii) systematic burns and highly diverse uses; (iii) higher diversity use with few fire activities and knapping playing an essential role; and (iv) incipient human activities and the initial use of the archaeological site. Our data are limited to understanding anthropogenic burning activities and cannot be extended to reveal other archaeological aspects. The results have implications for understanding human occupation in a large area with numerous archaeological sites. This study was the first step in distinguishing archaeological fires from natural fires and provided a new perspective for further research that attempts to identify distinct types of human fires.
... As mentioned earlier, magnetic enhancement was observed in the upper horizons of all the pedons, as was also found by other authors (Stinchcomb and Peppe 2014;Mahmoodi et al. 2016). Researchers have ascribed this enhancement to a number of origins. ...
In order to investigate the development of forest soils formed on loess, six representative modern soil pedons were selected along a precipitation gradient extending from eastern Golestan (mean annual precipitation, MAP = 500 mm) to eastern Mazandaran Provinces (MAP = 800 mm). Physiochemical, micromorphological and magnetic properties, as well as clay mineralogy of soils were studied using standard methods. Soils are mainly classified as Alfisols and Mollisols. Downward decalcification and the subsequent clay illuviation were the main criteria of soil development in all study areas. Pedogenic magnetic susceptibility of pedons studied varied systematically across the precipitation gradient in Northern Iran, increasing from 14.66 × 10⁻⁸ m³ kg⁻¹ at the eastern part to 83.75 × 10⁻⁸ m³ kg⁻¹ at the western margin of this transect. The frequency-dependent magnetic susceptibility showed an increasing trend with rainfall as well. The micromorphological study of soils indicated that there is a positive relationship between climate gradient (increasing rainfall) and the micromorphological index of soil development (MISECA). The area and thickness of clay coatings showed an increasing trend with rainfall. Grain size analysis indicates that pedogenic processes are responsible for changing original grain size distribution of loess in our soils. The correlation achieved among modern soil properties and precipitation could be applied to the buried paleosols in the whole study area to refer degree of paleosol development and to reconstruct the paleoclimate.
... The formation of magnetic minerals in soils due to factors other than the change in pH and Eh caused by the oscillation of the water table was reported by Viana et al. (2006), who detected the presence of magnetite in the surface horizons of savanna (Cerrado) soils and attributed the genesis of the magnetite to natural and frequent burnings. Stinchcomb and Peppe (2014) also reported the genesis of magnetite in burnt soils along the Delaware River in the USA. In paleoenvironmental studies, magnetite and magnetic minerals are commonly reported (Bourne et al., 2015;Dong et al., 2015;Hu et al., 2015;Maxbauer et al., 2016), Marmet et al. (1999) mentioned the production of magnetite and maghemite due to the heating of soils, resulting in the increase in the magnetic susceptibility of the soil. ...
... PET is dependent on a variety of factors including climate and vegetation 8 . Targeted studies investigating the influence of other soil factors have improved our understanding into how the duration of soil development [22][23][24][25] , parent material [26][27][28] , and topography 29,30 impact the magnetic mineralogy of soils. Yet, the role of vegetation on magnetic mineral assemblages in soils remains largely unconstrained. ...
Pedogenesis produces fine-grained magnetic minerals that record important information about the ambient climatic conditions present during soil formation. Yet, differentiating the compounding effects of non-climate soil forming factors is a nontrivial challenge that must be overcome to establish soil magnetism as a trusted paleoenvironmental tool. Here, we isolate the influence of vegetation by investigating magnetic properties of soils developing under uniform climate, topography, and parent material but changing vegetation along the forest-prairie ecotone in NW Minnesota. Greater absolute magnetic enhancement in prairie soils is related to some combination of increased production of pedogenic magnetite in prairie soils, increased deposition of detrital magnetite in prairies from eolian processes, or increased dissolution of fine-grained magnetite in forest soils due to increased soil moisture and lower pH. Yet, grain-size specific magnetic properties associated with pedogenesis, for example relative frequency dependence of susceptibility and the ratio of anhysteretic to isothermal remanent magnetization, are insensitive to changing vegetation. Further, quantitative unmixing methods support a fraction of fine-grained pedogenic magnetite that is highly consistent. Together, our findings support climate as a primary control on magnetite production in soils, while demonstrating how careful decomposition of bulk magnetic properties is necessary for proper interpretation of environmental magnetic data.
... A study of alluvial vertisols in Texas documented magnetic enhancement that developed over the course of centuries ( Fig. 7; Lindquist et al., 2011). However, recent observations of magnetism in alluvial soils developed on differently aged river terraces along the Delaware River Valley suggest that time does influence magnetic mineralogy in this system (Stinchcomb and Peppe, 2014). ...
Magnetic properties of soil are widely utilized to study soil development in a variety of settings due to the formation of strongly magnetic iron oxides during pedogenesis. Similarly, soil organic matter (SOM) is commonly measured in soil surveys conducted on agricultural lands due to the essential role SOM plays in the soil ecosystem. Here, we present data from two agricultural fields in southeastern Minnesota that demonstrate a relationship between soil magnetic properties and SOM. In each field, we collected 100 topsoil samples along a 40 m by 20 m grid to determine spatial variability in soil magnetic properties and SOM, as well as two soil cores to constrain variability with depth (∼0–60 cm). Magnetic susceptibility, low-field remanence, and hysteresis properties were used to characterize magnetic mineral abundance and grain-size in the soils. There are strong positive correlations between SOM and three magnetic properties: the frequency dependence of susceptibility (χfd), anhysteretic remanent magnetization (ARM), and the ratio of ARM to isothermal remanent magnetization (ARM/IRM). All three of these magnetic properties (χfd, ARM, and ARM/IRM) are sensitive to the concentration (or relative abundance) of fine-grained (<75 nm) magnetite/maghemite known to form in well-drained soils during pedogenesis. Correlation between SOM and magnetic properties persist in each field despite differences in the management strategy over the past three decades. Our results support a functional link between SOM and soil-formed magnetite/maghemite, where increasing SOM (up to a threshold) enhances the production and stability of soil-formed magnetite due to its role in soil redox processes and iron-organic complexes. Agricultural soils seem particularly well suited to demonstrate correlations between SOM and pedogenic magnetic minerals due to their relatively low SOM and typically well-drained environments, supporting the utility of soil magnetism in agricultural soil survey studies.
Mass magnetic susceptibility (χ) was measured on samples taken from horizons from 27 northern California soils to determine the amount and vertical distribution of χ, and if the observed χ distribution could be related to parent material, climate, topography and time. In most of the soils with vertical morphological distinctions, eluvial horizon χ was greater than illuvial, R or CR χ. This susceptibility enhancement was interpreted as being due to pedogenic processes. Soils formed on parent material rich in Fe‐bearing minerals (e.g. basalt) had higher absolute χ and greater χ enhancement than did soils formed on Fe‐poor parent material (e.g. siltstone). Enhancement was greater in soils from areas of high (>1000 mm) mean annual precipitation compared with areas of low (<500 mm) mean annual precipitation, and soils formed under mean annual temperature ≤6 °C had less distinct enhancement than soils formed in warmer temperature regimes provided the precipitation was the same. Two soils with poor and somewhat‐poor drainage classes had distinctly lower absolute χ than associated well‐drained soils. Both absolute χ in eluvial horizons and susceptibility enhancement of eluvial over illuvial, and eluvial over C horizons increased as soils became older. Older soils were enhanced to a greater depth than younger soils. Eluvial and illuvial χ was greater than parent material χ in most profiles because non‐ or weakly magnetic minerals were converted to maghemite, which accumulated in eluvial horizons. In young soils with little morphological differentiation formed on transported parent material, χ measurements help to locate lithologic discontinuities.
Pollen and plant macrofossil studies at 11 sites in New Jersey, southern and eastern Pennsylvania, West Virgina, and Virginia, USA reveal the character of the stable vegetation of the unglaciated eastern United States while the Wisconsin ice sheet was still at its outer limit. The stable flora of the periglacial region was different from the pioneer flora of the deglaciated area and from the vegetation of the modern tundra. Persistent tundra made the higher mountains of central Appalachia an important phytogeographical barrier to tree migration until about 12 500 yr BP. -from Author
The study of buried soil archives in alluvial settings can be used to characterize floodplain and terrace habitats and complement other paleoenvironmental and archaeological archives study examines the early Holocene alluvial paleopedology along the Delaware River Valley in the northeastern USA. Chronological and alluvial stratigraphic data show that a widespread loam alluvial paleosol formed from 10.7 to 9.3 ka, herein referred to as the Jennings Lane Pedocomplex (JLP). The JLP at the Jennings Lane locality along the Delaware River, NJ, is a loam to silt loam soil that formed on mixed alluvium and windblown and/or reworked dust, likely sourced from nearby periglacial fines. This finding supports previous interpretations of late Quaternary dust deposition and reworking in the region. Fragic properties (e.g., firm peds with brittle manner of failure and rapid slaking in water) and cryogenic micromorphological features (lenticular pores, stone jacking and shattered grains) present within the JLP suggest cryoturbation. Soil mass-balance modeling suggests that the strain (ɛ) in immobile elements Ti and Zr show a dilation–collapse profile. These data indicate that organic matter and/or dust addition, and freeze-thaw created soil dilation at the JLP paleosurface. Mass-balance additions in Fe, K, and Mg are consistent with illuviated Fe-rich clay coatings present in thin section. The X-ray diffraction results show that these clays are illite, vermiculite, and kaolinite. Paleosol data presented here suggest that the JLP was overprinted by later pedogenic processes during the middle Holocene. τTi,Na shows minimal loss throughout much of the profile. Although rapid thaws may have promoted downward translocation of fines, the cold environment impeded base loss through either minimal release of cations from primary minerals or negligible water flux, as suggested by τTi,Na profiles and gains in τTi,K and τTi,Mg. This silt-rich JLP pedofacies experienced minimal chemical depletion over the course of ∼1200–3500 years. This cold-climate weathering coincides with rapid temperature fluctuations (10.5, 9.3, 8.2 ka) during the early Holocene in northeastern USA. This soil cryoturbation evidence has archaeological implications as well. The cryoturbation in this early Holocene pedocomplex suggests that vertical and lateral artifact redistribution is possible. Archaeologists should use caution when interpreting archaeological stratigraphy and intrasite artifact patterns at mid- to high-latitude archaeological sites.