FLUVIAL DEPOSITION, EL NIñO AND LANDSCAPE CONSTRUCTION AT SAN JOSé DE MORO AND HUACA DEL SOL, PERU

The El Niño global climate anomaly can have far-reaching and serious impacts on human populations. Some of its most robust effects are felt in northern coastal Peru where strong El Niño events often cause catastrophic flooding and mass wasting, with significant social disruption. Consequently, records of El Niño rainfall and flooding are often found in association with archaeological sites in this region, as are floral and faunal markers of El Niño-driven environmental change. Nevertheless, our knowledge of the prehistoric chronology of El Niño is extremely limited. In an effort to address the timing and characteristics of past El Niño events, we investigated two alluvial stratigraphic sections at the archaeological sites of San José de Moro and Huaca del Sol. Both sites are adjacent to rivers and are located on floodplains composed of thick alluvial sequences. Each site represents activity during the highly complex Moche period (100-800 AD), and was the location of important ceremonial activity. Detailed sedimentological analyses from both sites indicate formation by largely fluvial processes. Due to the limited size of the Rio Chamán at San José de Moro, the floodplain was created solely by El Niño-driven alluvial aggradation, while at Huaca del Sol, the site is on a floodplain at least partially created as the result of El Niño flooding. These flat, broad surfaces above frequent flood levels were likely highly attractive for the occupation and ceremonialism that took place at each site. El Niño thus appears to have been important in the development of the landscapes that were chosen for the construction of at least two of the region’s important Moche sites. In turn, these sites have preserved sedimentary records of El Niño chronology and intensity from subsequent erosion.