PAGE(S) 4: Paleosols

2 Sep 2016
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This is my second year working on the geology of Armenia, and I am happy to be back in Yerevan as part of the PAGES project.

I have been working at geoarchaeological sites in East Africa for the past six years, and I am excited to expand this research on the past environments of our early ancestors to the Southern Caucasus. 

My role in the project has two parts: one is serious, the other is not.

First, as a geologist I have been lending my expertise in mapping the complex geology and also identifying the many paleosols or fossilized soils in the Hrazdan Valley. Second, as the only American geologist, my role is to tally how many times my British colleagues slip up and properly pronounce garage, basalt, and lacustrine.

Soils form at the ground surface in stable conditions and as a result of weathering of the surface geology; paleosols are simply ancient soils that are usually preserved through burial by later sediments.

There are paleosols at almost every site we have identified in the Hrazdan Valley, and at one site close to the village of Solak we have found twelve. My goal in characterizing these paleosols is to understand the climate and environment in which they formed and any effects soil formation might have had on the archaeological sites we find within them. This involves describing any changes in the sediments (size, shape, or sorting) in which the soils formed, recording any soil features, and identifying soil horizons (the latter develop as a soil develops maturity).

I also collect samples of the paleosols to determine the chemistry and mineralogy, which have been analyzed extensively in modern soils as analogs and related to soil properties such as precipitation, temperature, and pH that can be used to reconstruct past environments in great detail.

I will also be looking at microscopic features of these paleosols.

Because they are so friable, samples of the paleosols are wrapped in a sophisticated mixture of plaster, toilet paper, and finally duct tape in order to get them back to the laboratories where I work in the United States in a solid block. In the US, these samples will be hardened using epoxy resin, sawn into 3x5 cm blocks, and cut into very thin slivers of rock known as thin sections. The latter are only 30 μm thick, which is thin enough for light to pass through. This technique know as micromorphology or petrography allows for identification of minerals as well as morphological features that can yield information on how the soil formed or what animals were living in the paleosol in the past.

So far, we know that most of the paleosols in the Hrazdan valley represent soils forming on the floodplain near the ancestral River, but there are also paleosols forming along former lake margins.

Over the next couple of years as PAGES progresses, the data collected from geochemistry, mineralogy, and micromorphology will allow for a detailed reconstruction of the environment and help our team understand why this area was so attractive to early humans, but as far as this human is concerned, Armenia is a great place to work.

About the author

Dr Emily Beverly is Postdoctoral researcher in the Department of Geosciences at Georgia State University.

Read more about Dr Beverly's work here

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