9th August 2008, 01:10 PM
"Ferrugination: (L: ferro= iron; ferruginis= rust) iron sesquioxides adhere firmly to sand and gravel, giving them a red colour, and may cement them to form a subsurface iron pan." Iron pans form in a few ways and since I'm not a soil scientist I'm not going to try to describe them.
The iron panning you described would have occured after the dark silty clay fills were deposited in the cut feature. Iron panning commonly occurs at an interface between ferrous and non-ferous deposits (not getting into the sediments vs soils debate here)that are quite damp. This phenomenom is fairly common in ditches in some parts of the country.
The important thing to remember in archaeology is that iron panning is frequently an indicator of a high level of cess in one of the deposits. The clay-like nature of the upper deposit seems a good indication of this. (Does it feel soapy and is there a slight gloss to it?)
Ironically, although water passing through the deposits creates the iron pan in the first place as it accretes it becomes more difficult for the water to pass through and the above deposit frequently becomes water-logged. That's one of the reasons raised bogs are wet. (I hope your other half got lots of samples from the dark deposits.)
Physically the iron pan deposit belongs to the redeposited natural series, sequentially it comes at least after the initial dark deposit above it. Oh, how I love matrices!
I'm not going to hazard a guess as to what the feature is without knowing what's nearby. Hope this helps.
The iron panning you described would have occured after the dark silty clay fills were deposited in the cut feature. Iron panning commonly occurs at an interface between ferrous and non-ferous deposits (not getting into the sediments vs soils debate here)that are quite damp. This phenomenom is fairly common in ditches in some parts of the country.
The important thing to remember in archaeology is that iron panning is frequently an indicator of a high level of cess in one of the deposits. The clay-like nature of the upper deposit seems a good indication of this. (Does it feel soapy and is there a slight gloss to it?)
Ironically, although water passing through the deposits creates the iron pan in the first place as it accretes it becomes more difficult for the water to pass through and the above deposit frequently becomes water-logged. That's one of the reasons raised bogs are wet. (I hope your other half got lots of samples from the dark deposits.)
Physically the iron pan deposit belongs to the redeposited natural series, sequentially it comes at least after the initial dark deposit above it. Oh, how I love matrices!
I'm not going to hazard a guess as to what the feature is without knowing what's nearby. Hope this helps.