Crossing the Borders: New Methods and Techniques in the Study of Archaeological Materials from the Caribbean

46 / Knippenberg and Zijlstra
on La Désirade (Bodu 1984; Bouysse et al. 1983; De Waal 1999b; Montgomery et al.
1992), and in the eastern part of Puerto Rico (Rodríguez Ramos personal communication
2000).
Given the occurrence of a broad range of chert types in the northern Lesser
Antilles, a choice was made about which material varieties were to be included
in the characterization study and which were not. This choice was necessary to
avoid having the series of source locations be too large, which would make success
in petrographically or chemically distinguishing the different source types less
probable. As the first group includes the large majority of available chert sources
and prehistorically used materials in the northern Lesser Antilles, it will be the
focus of this research. Sources can be found on Antigua, St. Kitts, and in the southwestern
part of Puerto Rico.
On these three islands, chert is most common on Antigua and moreover still occurs
in the rocks where it formed. On St. Kitts and Puerto Rico chert is less abundant
and has only been found ex- situ. The rocks of Antigua can be subdivided
into three types. In the southwest, one finds siliciclastic rocks of the early Tertiary
Volcanic Suite (Figure 4.2) (Weiss 1994). They formed when the Atlantic plate
subducted under the Caribbean plate and molten, relatively low density magma
moved to the surface, depositing volcanic deposits above sea level. Subsequently,
during the Eocene, the subsurface cooled and while the island slowly sank below
sea level, the volcanic rocks were eroded and erosion products were deposited as
near- coastal volcanic siliciclastic sediments of the Central Plain Group, which
forms the central part of the island. During the Oligocene, most of the island was
submerged again, and shallow- marine sediments were deposited, which received
little volcanic siliciclastic sediment from land, and therefore consist mainly of very
pure biogenic carbonates that presently form the northeast part of the island, and
that belong to the Antigua Formation (Weiss 1994). As a consequence of Miocene
tectonics, the island was uplifted again and tilted toward the northeast. During
the Pliocene to Pleistocene Ice Ages, southwest- northeast- oriented river valleys
were repeatedly eroded and filled with alluvial sediments derived from Volcanic
Suite, Central Plain Group, and Antigua Formation, while the soluble carbonates
of the Antigua Formation experienced also karstic dissolution and were covered by
insoluble eluvial residue.
Also at St. Kitts, early Tertiary siliciclastic volcanic rocks crop out; however,
limestone is absent, apart from a small patch of relatively young Pleistocene limestone
(Figure 4.3). Puerto Rico exposes Mesozoic volcanic rock and limestone,
which is covered again by early Tertiary volcanic rock covered by marine limestone
(Figure 4.4).
From eight localities on Antigua, two on St. Kitts 1 and five on Puerto Rico, 15
in total, a source description was made and chert samples were collected for mac-
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