Rock magnetic properties of a soil developed on an alluvial deposit at Buttermilk Creek, Texas, USA

Abstract

[1] The evolution of magnetization within a floodplain soil begins with initial deposition of magnetic particles during sedimentation and continues via subsequent alteration and growth of iron-bearing compounds by pedogenic and biologic processes. Measurements of soil magnetic properties capture information about the developmental history of the soil and are a convenient method by which to investigate environmental change and pedogenesis. Using a range of magnetic measurements, a comprehensive scenario for soil development was constructed for floodplain sediments at the Debra L. Friedkin site, an important archeological site near Buttermilk Creek, Texas. Floodplain deposits have traditionally been avoided for soil magnetism studies because it is thought that the episodic input of sediment would form soils characterized by discrete sedimentary units rather than a continuous record of pedogenesis. We demonstrate that alluvial deposits can sometimes carry a straightforwardly interpretable magnetic signal similar to those typically seen in loess deposits. Smooth variation of rock magnetic parameters as a function of depth also leads us to conclude that the soil at this site is largely undisturbed and that the age of lithic artifacts found within the soil may be interpreted within stratigraphic context.

The influence of time on the magnetic properties of late Quaternary periglacial and alluvial surface and buried soils along the Delaware River, USA

“…Because the T v is absent in the ZFC/FC plots, we suggest that maghemite, not magnetite, is the magnetically soft SD grain primarily responsible for much of the increased magnetic susceptibility in the soil horizons. Lindquist et al (2011) document a similar ZFC/FC pattern from alluvial soils in Texas and suggested it could be the results of goethite and SP maghemite. In this study however, the RT-SIRM suggests the presence of stoichiometric magnetite in the T3 terrace and the irreversible warming of all RT-SIRM analyses indicates the presence of PSD maghemite in all terraces (Figure 6), suggesting a difference in magnetic mineralogy between our Delaware River valley soils and those of Lindquist et al (2011).…”

“…The ratio of ARM to IRM (ARM/IRM) provides a relative estimate of the fine-grained SD-like particle concentration (King et al, 1982;Geiss et al, 2004;Lindquist et al, 2011). Because the S-ratio and backfield remanence suggest the presence of a lowcoercivity mineral such as magnetite or maghemite, we can infer the ARM/IRM ratio indicates changes in the relative concentration of fine-grained magnetite/maghemite.…”

“…Although alluvial soils are subject to burial, erosion, and pedofacies evolution, recent research demonstrates that the rock magnetic properties of an alluvial Vertisol forming in central Texas is interpretable in a similar manner as loessal soils (Lindquist et al, 2011). Lindquist et al (2011) also noted that magnetic enhancement can mature over centuries.…”

“…Although alluvial soils are subject to burial, erosion, and pedofacies evolution, recent research demonstrates that the rock magnetic properties of an alluvial Vertisol forming in central Texas is interpretable in a similar manner as loessal soils (Lindquist et al, 2011). Lindquist et al (2011) also noted that magnetic enhancement can mature over centuries. The implications of this work are that magnetic properties of soils can be used to estimate duration of soil formation for buried soils at a much higher resolution than previously studied (Singer and Fine, 1989;Singer et al, 1992;Vidic et al, 2004).…”

Understanding Australia’s cultural history through archaeological geophysics

“…At GS1, the χfd% (~10%) resembles percentages typical of modern soils rich in organic carbon. While most natural soils show a progressive decrease in the abundance of SP grains with depth (Lindquist et al 2011), the samples at GS1 show consistently elevated and stable SP concentrations. This further indicates that the sediments are not an expression of natural environmental processes but that human occupation played an important role in the formation of the magnetic assemblage.…”