Iron and aluminum soil/paleosol extractions as age/environment indicators: Some examples from a catchment in southern Ontario, Canada

A Summary of Radiocarbon Measurements of Fluvial and Colluvial Deposits in Catchments of South-Central Ontario, Canada

“…AMS 14 C measurements gave ages to within a range of several centuries, which is consistent with the release of secondary Fe-Al oxides and hydroxides reported by Mahaney et al (2016). We expect most of the age discrepancy between conventional and AMS dates are due to the different sample sizes, for AMS, smaller samples are used and the conventional ages were just “bulk dates”.…”

“…The Ah horizon in R15 on the older high terrace (<11 ka) (Mahaney and Sanmugadas 1986; Mahaney et al 2016) is ∼15 cm thick, similar to the Ah horizon in R71 (not previously published) on the younger 3-m terrace (∼1.0 ka). Both sites, previously dated by RD methods (R15 in Mahaney et al 2016 and R71), show close agreement in Ah horizon thickness. This suggests that both surface horizons, despite their disparate ages, reach near maturity in a matter of a few centuries, at least with a steady-state input-output of organic carbon and nitrogen achieved.…”

“…This suggests that both surface horizons, despite their disparate ages, reach near maturity in a matter of a few centuries, at least with a steady-state input-output of organic carbon and nitrogen achieved. Previous work attests to the ∼1.0–1.5 kyr value of organic matter in local Ah horizons to reach equilibrium where input equals output (Mahaney and Sanmugadas 1986; Mahaney et al 2016). However, both the basal Ah horizons R15 and R71 (see Table 1) show post-bomb radiocarbon dates.…”

“…The mid-section (5 cm) of the Ahk horizon in the ground soil, gives a post-bomb value of F 14 C of ∼1.645, only consistent with formation in the 1960s. The paleosol, formed in the colluvial beds of the section, with its 2Ahbk/3Bmbk/3Cbk/3Cubk profile (Figure 6)—the combined ground-paleosol, approximately 120-cm thick—correlates with the thickness of postglacial Late Holocene paleosols in other catchments of central Southern Ontario (Mahaney et al 2016). The one-century spread (for both raw and calibrated ages) for development of the 2Ahbk horizon is probably a minimum given that the uppermost part of this horizon was likely eroded (truncated) when it was over-topped by colluvial emplacement—the deposit in which the ground soil formed.…”

“…Soil color assessment based on Oyama and Takehara’s (1970) soil color chips, essentially the same as the Munsell System (Macbeth 1992). Site selection was based on previous stratigraphic assessment (Mahaney and Sanmugadas 1986; Mahaney and Hancock 1993b; Mahaney et al 2016), and on new sites intended to put an RD age fix on common 3 m terraces (R71). RD terrace age in both the Rouge and West Duffins Creek catchments is determined by terrace height above stream flow, using the amended relationship of Bufe et al (2017) where time of incision (Delta ti) = depth of incision (Di)/incision rate (Evi).…”