Stratigraphy of Late Pleistocene coastal deposits in Northern Spain

Resumen

Stratigraphical and sedimentological analysis, geological mapping and geochronological dating (luminescence, uranium/thorium, and radiocarbon) were undertaken on Late Pleistocene coastal deposits (raised beaches and periglacial deposits) in north-west Spain. Correlation of the 26 outcrops studied and their geometric relationships allowed the establishment of four stratigraphic units: Unit 1, sandy and gravelly raised beaches located above a rocky abrasion platform 1.5 –3.5 m above the modern mean sea level; Unit 2, matrix-supported breccias of head deposits; Unit 3, muddy peats formed in swamp depressions; and Unit 4, clast-supported conglomerates, breccias, and sands, deposited by intermittent current activity. Thermoluminescence (TL) and infrared-stimulated luminescence dating (IRSL) assigned Unit 1 to OIS 5; Unit 2 to OIS 4/3; and Unit 4 to OIS 3–2. Radiocarbon dating confi rmed the results obtained for Units 2 and 4 and that Unit 3 was contemporaneous with Unit 2. Comparison of these outcrops with others from raised beaches located in the central part of the northern Spanish coast (Cantabria) showed that the Cantabrian sector has been uplifted 2–3 m more than the north-west coast since the Last Interglacial. It is probable that Galicia acted as a hinge line between the uplifting north and the active, faulted atlantic margin of the Iberian Peninsula.