HR: 0830h
AN: NS41A-04    [Abstracts]
TI: GPR Surveys at Los Naranjos, an Early Formative Mesoamerican Site in Central Honduras
AU: * Lisman, T
EM: tal28@cornell.edu
AF: Department of Earth and Atmospheric Sciences, Cornell University, 3120 Snee Hall , Ithaca, NY 14853 United States
AU: Tchakirides, T F
EM: tft5@cornell.edu
AF: Department of Earth and Atmospheric Sciences, Cornell University, 3120 Snee Hall , Ithaca, NY 14853 United States
AU: Brown, L
EM: brown@geology.cornell.e.du
AF: Department of Earth and Atmospheric Sciences, Cornell University, 3120 Snee Hall , Ithaca, NY 14853 United States
AU: Henderson, J
EM: jsh6@cornell.edu
AF: Latin American Studies Program, Cornell University Uris Hall , Ithaca, NY 14853 United States
AB: Extensive GPR surveys were carried out in the summer of 2003 at the Early Formative Mesoamerican archeological site of Los Naranjos, on the shore of Lake Yojoa, in central Honduras. Sensors and Software's Pulse EKKO 100, equipped with 50, 100 and 200 MHz antennae and a Noggin 250 MHz were both used to collect 2D grids and linear profiles. The surveys were located on lacustrine and volcanic soils. Penetration was generally excellent even at the higher frequencies (eg. 200-250 MHz), and clutter problems from nearby canopy were minimal. Features were routinely mapped at 2-5 meters depth. The surveys covered both apparent archeological and natural features. Three-dimensional volume images reveal clear deformation of the youngest strata, including possible fault offsets that may mark paleoseismic events. Reflection amplitudes within the strata were highly variable; local radar bright spots remain to be explained. Numerous individual diffractors were mapped within the geological strata, especially at shallow depths. Some of these are likely to be generated from natural rockfall; however, some may well mark archeological artifacts or features. Identification remains to be provided by excavation. GPR surveys over the major monumental structure at this site encountered much more limited penetration than through the surrounding geological strata. This suggests the use of radar absorptive building materials or coatings. A GPR transect over a topographic high that appeared to be a manmade wall of volcanic rocks indicates that it is a natural rather than an artificial feature. In contrast, GPR profiles near a large isolated rock outcrop indicate that it is not in place, but was transported to its current location. GPR surveys at Lake Yojoa proper demonstrated excellent penetration, suggesting that GPR should be a useful tool in delineating quaternary stratigraphy, and perhaps paleoclimatology, recorded by this central water body. Future geological dating of the strata should help constrain the age of deformation of both natural and artificial markers associated with this early Mesoamerican settlement.
DE: 0600 ELECTROMAGNETICS
DE: 9350 North America
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly