Cent. Eur. J. Geosci. • 5(1) • 2013 • 12-27 DOI: 10.2478/s13533-012-0117-8 Central European Journal of Geosciences Pleistocene glacial morphology and timing of Last Glacial Cycle in Cantabrian Mountains (Northern Spain): new chronological data from the Asón Area Research Article Manuel Frochoso 1* , Raquel González-Pellejero 1† , Fernando Allende 2‡ 1 Department of Geography, Urbanism and Regional Planning, University of Cantabria, Santander 39005, Cantabria, Spain 2 Department of Geography, University Autónoma de Madrid, Madrid, 28049, Spain Received 4 October 2012; accepted 12 January 2013 Abstract: The timing of the local last glacial maximum in the mountains of the Northern Iberian Peninsula is not synchronous with the global Last Glacial Maximum (LGM) probably due to the marginal position of the Northern Iberian Penin- sula within the European continent. The study of a Cantabrian massif, the Asón platform and summits, provides new data on the extent and timing of the local last glaciation. Here we can place the last maximal extent of glaciers during Early Würm, according to OSL dating on till samples. The main glaciers developed at least between 78- 65 ka BP, well centred on MIS 4 and even the transition to MIS 5. The erosive efficacy of these glaciers decreased later, ca. 45-40 ka BP, until they abruptly disappeared from the edges of the massif. A new ice advance left well- defined moraines at the edges of the massif’s internal depressions, indicating a tongue disjunction phase with two glacier sub-stages, probably one at the beginning of the cooling ca. 27-25 ka BP, followed by a retreat and another glacial advance ca. 21-18 ka BP. After these episodes the glaciers disappeared from the Asón Mountains and only some residual glaciers were formed that may be related to the LGM. Keywords: Iberian Peninsula • Cantabrian Mountains • Last Glacial Maximum (LGM) • Late Pleistocene • glacial landforms • geochronology • dating. © Versita sp. z o.o. 1. Introduction The Cantabrian Mountains in Northern Spain extend the European continent about 500 km to the west in a succes- sion of massifs aligned parallel to the coast. The marginal, southern continental position of these mountains induced * E-mail: manuel.frochoso@unican.es † E-mail: raquel.gonzalez@unican.es ‡ E-mail: fernando.allende@uam.es small glaciers to form in them during the Late Pleis- tocene. Our research is focused on a sector of the Central Cantabrian Mountains, the Asón Area of the Castro Val- nera Massif. Evidence of Pleistocene glaciation in the Cantabrian Mountains was recognized relatively early [1] but it was not until the twentieth century that systematic glaciation study began. Obermaier [2] distinguished two glaciations in the Picos de Europa and his scheme was repeated for the Cantabrian Mountains, e.g. [3–7], including Castro Valnera (1718 m) and the karstic Asón platform and sum- 12 Author copy