CCZO -- Soil Geochemistry -- Calhoun 70m deep well -- (2010-2010)

Geochemical analysis summary table for samples collected during drilling of 70m deep borehole. On 17-18 November 2010 a 70-m deep borehole was drilled at the Calhoun Long Term Soil Experiment site to examine soil properties down to the bedrock. These results were published as Table 1 in Bacon et al. 2012.

We sampled a residual soil, classified as Oxyaquic Kanhapludult of the Cataula series, and underlying granite gneiss on a broad interfluve with
Date Range Comments: Samples collected during a single event, the drilling of 70m deep borehole.

We collected 3 continuous cores (10 m apart), each to a depth of 6.1 m, and collected deeper samples from a single point 30 m away. Saprolite from 6.1–18.3 m was sampled with a three-wing auger bit, and unweathered granite gneiss, contacted at 30.5 m, was sampled to 67.1 m with a roller-cone bit. We separated samples by horizon and depth, and air-dried all samples. We sieved soil and/or saprolite with a 2 mm screen, and found coarse fragments in only 8 of the 52 samples. By volume, these fragments composed 1%–11% (mean = 7%) of the 8 samples, and were removed from our analysis. We measured total elemental concentrations of all samples by inductively coupled plasma–atomic emission spectroscopy or flame atomic absorption spectroscopy (AAS) after LiBO2 fusion, and measured texture, pH in 0.01 M CaCl2, total carbon (C), exchangeable base cations (Ca, Mg, K, and Na), and exchangeable acidity on all soil and/or saprolite samples (Carter, 1993; Dane and Topp, 2002; Sparks, 2002).

We composited (by horizon) across the continuous cores, extracted the composited samples and samples from 6.1–18.3 m with hydroxylamine hydrochloride (1 M NH2OH·HCl in 1 M HCl; Wiederhold et al., 2007), and measured Be and Fe in solution by furnace and flame AAS, respectively. By complete dissolution of oxide minerals at low pH, hydroxylamine hydrochloride extractable (hhe) metals are an operationally defined pool that have been weathered from primary minerals and retained in the soil, and in our analyses are akin to the familiar dithionite citrate bicarbonate extractable metals (Fig. DR2) popularized by Mehra and Jackson (1958). We further composited these samples across horizons (Table 1), isolated meteoric 10Be with a method modified from Stone (1998), and measured 10Be/9Be isotopic ratios by accelerator mass spectrometry (AMS).