A systematic survey was conducted of all river systems along a 100 km
segment of the coastal plain of Chiapas, Mexico, in order to find buri
ed archaeological sites. The survey was undertaken because the only kn
own sites of the Late Archaic Period were highly obtrusive shell heaps
situated in the littoral wetlands, but they seemed to have been forme
d by itinerant people; no coeval sites, presumed to have been left by
the same group, had been found farther inland on the coastal plain. It
is surmised that the ''missing sites'' had become buried by alluvium
but that some of these might be visible in river cuts. Twenty-two such
buried sites in river cuts were found and examined during this survey
, including one site that possibly dates to the Archaic Period. In add
ition, a greater understanding was gained of the fluvial processes in
the region and their roles as transformers of the archaeological recor
d. This information will be crucial for developing predictive models t
o locate buried early sites.