THE LANDSCAPE

The French Guiana coastal zone is part of the large Quaternary sedimentary plain stretching some 1,600 km between the mouth of the Amazon and the Orinoco Delta. It is relatively narrow in French Guiana where it measures between 5 and 40 km wide (Figure 13.1). Outcrops of the rocky shelf emerge only on the French Guiana coast in the shape of small hills

Handbook of South American Archaeology, edited by Helaine Silverman and William H. Isbell.

Springer, New York, 2008

Figure 13.1. Map of the main concentrations of raised fields of the Guianas (shown in black), within coastal zone (shown in grey). (after Boomert 1976: fig. 1 and Rostain 1994: fig. 75).

In Oyapock Bay, Cayenne Island and the lower Kourou. The landscape is a low swampy plain bordered by mangroves on the mud flats along the seashore and by the hinterland at the south. The marshes are cut by narrow and elongated sandy ridges parallel to the seashore that represent old beaches. These dry sandy ridges were preferred locations for the Indians to build their villages.

In 1988-90, numerous small earth mounds in the seasonally flooded savannas were reported and studied (Rostain 1991). They have remarkable characteristics (Figure 13.2): they are always located in flooded or seasonally flooded areas; are frequently interrupted by parallel and perpendicular rows in a grid; organized groups of rounded or rectangular fields are often associated with nearby sandy ridges; the shape of the fields (round, square, rectangular or elongated) seems to be related to the depth of the water; artificial ditches are frequently associated with these fields.

The first question is to determine if these mounds were natural or made by humans. In temperate climates, natural micro-mounds with a grid-like pattern called gilgais can be produced by swelling clay containing a lot of montmorillonite under the influence of strong rain and significant temperature variations. Gilgais are a series of micro-basins and micromounds on a flat surface, or micro-valleys and micro-crests of several centimeters to 2 m high running along a slope (Lozet and Mathieu 1986: 94). However, in French Guiana they cannot occur because of the slight temperature difference during the year and because the clay does not contain montmorillonite, but kaolinite, illite, smectite and chlorite. There are sometimes small and low natural micro-mounds along the degraded sandy ridges of French Guiana, but they are never so symmetrically distributed as raised fields are. So there can be no doubt that these fields are earthworks made in pre-Columbian times for agricultural purposes.

Figure 13.2. Raised fields in the Diamant site, east of Kourou River. (Stephen Rostain)