REGISTRO HISTÓRICO Y EVOLUCIÓN DE LA BARRA ARENOSA DE PUNTARENAS, GOLFO DE NICOYA, COSTA RICA

Abstract

The Puntarenas sand spit appears in maps from the XVIII century. The 600 m-wide, 7 km-longspit trends E-W with an average elevation of 3 m above sea level. The spit forms part of the Gulf of Nicoyaestuarine system. A geomorphologic analysis of historical maps and aerial photographs reveals systematicgrowth of the spit over the past 137 years. Puntarenas is part of an estuarine system growing southwards. Thesand bar shows lateral growing, basically in La Punta. The spit growth ceased 50 years ago with the onset ofcoastal engineering. Based on previous photogeological and geophysical studies and new geophysical surveyswe identify two paleochannels west of the current Barranca river channel. We infer a NW to SE migration of theBarranca channel, driven by neotectonic activity on the Barranca fault. The lateral growing rate of thePuntarenas spit for the period 1860-1945 (prior to human control) is 14 m per year; extrapolating this rate backin time yields an origin for the spit approximately 500 years ago.