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[Michaelangelica]

Here pottery shards litter the ground. At one of the site’s two excavations, the broken bits stick out from the earthen walls of a large square pit. The layers of protruding pottery are so tight and thick they look almost like wall coverings.

Black Gold of the Amazon | Archaeology | DISCOVER Magazine

Cultural mosaic

Climbing to the top of Ibibaté, a forested loma (mound) 18 meters higher than the surrounding savanna, Erickson comes to a bare patch of earth created by a fallen tree. Bending over the uncovered ground, he points out the dark, almost black soil, which is filled with fragments of pottery.

Several pieces of pot rim are visible, along with the leg of a vessel shaped like a human foot. Both the richness of the soil and the abundance of the potsherds are typical, in Erickson's view. "Many of the lomas are almost nothing but enormous heaps of sherds," he says. "I've never seen anything like it—10, 20, 30 feet of sherds"

Earthmovers of the Amazon

The firing of the potteries occur in open atmosphere (Fig. 6), possibly in the same primitive way as the actual Indians and caboclos still do. The firing temperature didn't exceed 600 ºC, as demonstrated by partial dehydroxylation of clay material and the formation of maghemite. This phase formed the ceramic minerals: dehydroxylation of clay giving rise to burned clay, maghemite and recrystallization of anatase. Maghemite promotes the slightly brown to red color of the potteries.
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Chemical elements such P, Mg, Ca, Mn, Ba, Zn, Pb, etc. are fixed partly and concentrated in the organic humus of ABE soils and possibly is partly absorved in the ceramic fragments, contributing to formation of phosphates and Mn oxyhydroxides in less extension.

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Rich in humus, pieces of pre-Columbian unfired clay pottery, and black carbon, it's like a "microbial reef" that promotes and sustains mycorrhizae growth and other beneficial microbes, and it has been shown to retain its fertility for thousands of years.


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South American terra preta soils are also full of pieces (sherds) of unfired pottery. It is generally believed that the pottery was introduced into the soil much as modern growers add perlite or sand to potting mix, as a way of keeping the soil from baking completely tight under the tropical sun before a cover of vegetation could grow over it. Much is made of these sherds as "proof" that terra preta deposits are really prehistoric trash piles, but Charles C. Mann asserts there are indications that much of this pottery was actually made specifically for incorporation into the soil.

TERRA: Living Soil

T

he above described minerals and organic substances led to identify the following materials as raw materials for the ceramics:

1) clay material derived from weathering (saprolite/mottling zone) of fine crystalline and less frequent sedimentary rocks (indicated by clay-derived minerals and iron oxy-hydroxides, anatase and quartz );

2) fresh crystalline rocks crushed (feldspars, quartz and rock fragments);

3) organic materials (cauixi and burned cariapé).

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