Geophysical methods employed in urban archaeology prospecting: the Basílica de Nuestra Señora de la Salud, Patzcuaro, México

Abstract

The purpose of this investigation is to locate the foundations of an ancient neve annex to the main building of today’s Basilica of Nuestra Señora de la Salud built in the middle of the XVI century, situated in the City of Patzcuaro, Michoacán. A series of Vertical Magnetic Field and Ground Penetrating Radar profiles were carried out. These included 20 equidistant GPR profiles in the interior of the church’s atrium. Also, 16 vertical magnetic gradient profiles were surveyed, with a station separation of 0.4 m, and profiles 0.8 m apart. GPR images defined a reflector, whose depth varied between 1.4 m and 2.2 m beneath the atrium’s floor, with a NE-SW direction making an angle of 45º, approximately related to the geographic north. Magnetic results confirmed the presence of some structures defined by the GPR, but also the presence of an anomalous pattern of rectangular shape could be observed, after a filtering process was applied. These structures could be related to ancient pre-Hispanic remains, older than the church’s foundations of the expected wing.