Electrical resistivity tomography and magnetometry surveying of a
~500-1532 CE Manteño culture archeological site close to
Puerto Lopez, Ecuador
Abstract
Geophysical methods are very useful in archeological prospection by
providing an inexpensive, non-invasive view of the subsurface, and,
helping the archeologists to better target their excavation efforts.
Ecuador’s past is very rich, with many archeological sites still
unexplored. Manteño culture prevailed in the province of Manabí in a
series of large coastal towns and along the river valleys and ridges of
the Chongón-Colonche coastal mountains of what is now Ecuador from
around 500 CE to 1532 CE. They were one of the last prehistoric cultures
and the Inca Empire never conquered them directly, which meant their
culture developed independently. Thousands of carefully arranged stone
foundation have been documented across the abrupt landscape that has
been intentionally modified for large scale agriculture. In this work,
we present the results of Electrical Resistivity Tomography (ERT) and
magnetometry surveys at the Río Blanco archeological area close to the
coastal city of Puerto Lopez. The area includes one of the largest
unexcavated archeological remains known in Ecuador. It consists of
alluvial terraces modified by the Manteño people scattered with numerous
ruins. The archeological structures are often delimited by buried rock
blocks that sometimes outcrop in the surface. We made 2 ½ D ERT with
dipole-dipole array configuration and ground magnetometry surveys at
three locations which were identified earlier by archeologists as buried
buildings, with one of them being previously partially excavated. The
measurement grid for each structure was designed according to their
size. For magnetometry, a base station measurement was taken after
finishing each survey line in order to be able to remove diurnal
variations from the magnetometry readings. All tested structures showed
internal variations within them related to differences in electrical
resistivity and magnetic susceptibility. According to our preliminary
interpretation, some of these anomalies are from the wall rocks and some
suggest the presence of buried objects as well as potential locations of
fireplaces. The locations of the buried objects are intended to be later
verified by archeological excavation.