SEDIMENT RECORD FROM BOG CORES IN THE SOUTHERNMOST CORDILLERA BLANCA, PERU

The Nevado Jeulla Rajo massif (10°00'S, 77°16'W, peaks ca. 5600 masl) lies at the southern end of the Cordillera Blanca and the Callejon de Huaylas valley in the central Peruvian Andes. The Conococha Plain (ca. 4050 masl) borders the western side of the massif. The massif still hosts a few small glaciers, but geomorphic evidence indicates that greater ice cover existed in the past. Large lateral moraines extend onto the Conococha Plain from the west-facing valleys while multiple moraine loops lie upvalley, closer to active ice margins. Surface-exposure dating with cosmogenic ¹⁰Be indicates that the largest lateral moraines from Jeullesh Valley are compound features deposited during the local last glacial maximum (ca. 30 ka) and a late-glacial readvance (ca. 15 ka). Peat bogs (pampas) have developed in low-lying areas partially enclosed by lateral moraines along the western side of the massif. In 2007, we used a square-rod piston corer to collect two sediment cores (approximately 2 m and 3 m depth) in the pampa located between moraines bordering Jeullesh and Quenua Ragra Valleys. The upper portions of the cores consist of fibrous peat, whereas the lower portions comprise sequences of sediment layers of different grain sizes. The corer hit refusal at the base of both cores. Macroscopic plant material within the sediment layers is being radiocarbon-dated. We will present the results of a detailed analysis of both sediment cores.