A05_P02

Pollen and bulk radiocarbon ages from  a montane lake core – Yagour Plateau, High Atlas, Morocco

Cornelissen H¹, Fink D ²,  Fletcher W¹, Hughes P¹, Bell B¹, Rhoujjati A³, Ewague A⁴

¹Department of Geography, University of Manchester, Manchester, United Kingdom, ²ANSTO, Sydney, Australia, ³Faculté des Sciences et Techniques, Université Cadi Ayyad, Marrakech, , Morocco, ⁴Université Chouaib Doukkali, El Jadida, , Morocco

The Yagour plateau in the Marrakech High Atlas, Morocco (31.31°N, 7.60°W, 2460 masl.) supports a montane (sub-alpine) wetland. It contains a rich collection of petroglyphs and pastoral usage on the plateau by surrounding villages is maintained by adherence to an historic cultural and community-based system called Agdal  that regulates annual grazing access. We retrieved a 290 cm sediment core with excellent preservation from a marginal lake that spans 13 ka BP providing a high-resolution palaeo-environmental Holocene record and insights into the archaeological and cultural heritage of the region. Our age-depth model rests on a 28-sample radiocarbon Bayesian analysis of common depth pollen concentrates, charcoal and bulk organic sediment. We find significant age differences between these C-bearing materials which are thought to be due to site-specific processes. We surmise that old-carbon from a variety of possible sources is likely driving the age differences throughout the Holocene period. The  most likely two sources would be secondary carbonate accumulation in the porous and faulted Triassic sandstone and surface pedogenic carbonates produced during drier conditions. Increased groundwater pressure due to Holocene niche snowpack melt in the nearby mountains drove a larger input of spring water at Yagour.  However, unknown factors drive a reversal in the chronological trend in the Late-Glacial period. The age-differences between sample-types highlight the importance of a cohesive understanding of lithostratigraphy and hydrology of previously undated sites in order to underpin robust chronologies used for environmental and cultural research.