Multi-method dating of the previously undated Óþoli Tephra of the Vestfírðir Peninsular, NW Iceland provides a unique chronological constraint for Quaternary landscape evolution, ice sheet extent, ice-sheet thickness and ice-free area hypotheses in Iceland. For the first time, a major age constraint has been placed on the glacially driven, macroscale landscape evolution processes of fjord network formation on the Vestfíröir Peninsula. The pre-¹⁴C. Quaternary era is a vital period in which current glacial/interglacial cycles developed and caused widespread environmental change. Dating controls for this era are limited because of widespread glacial erosion, but in Iceland certain tephra deposits have survived glacial overriding and can provide accurate age constraints and precise spatial correlation for stratigraphic sequences. This study focuses on two tephra deposits of great palaeoenvironmental significance: the aforementioned Óþoli Tephra and the þörsmórk Ignimbrite. The Óþoli Tephra rest unconformably 580-600 m.a.s.l. near the plateau surface of Skagafjall (NW Iceland). The 100-160 m thick sequence of ice-damned lake deposits beneath it were thought to have formed during the Last Glacial Maximum (LGM), 20-17 ka. The þörsmórk Ignimbrite þIG; S. Iceland) is the largest Quaternary-age ignimbrite deposit in Iceland and glass compositions have been geochemically linked with the highly silicic (SiO₂ >68 wt %) ignimbrite deposit in Iceland and glass compositions have been geochemically linked with the highly silicic (SiO₂ >68 wt %) component of North Atlantic Ash Zone-2 (NAAZ-2), 48-58 ka. Correlation fission-track (FT) and thermoluminescence (TL) methods were used to produce ages from the glass shards that overwhelmingly dominate the highly silicic airfall and/or surge ash components of these deposits. Dating glass shards is advantageous because they form during the magma-quenching phase of an eruption and nearly always reflect the ‘true’ eruption age. They are also the most far-travelled and geochemically diagnostic phase of Icelandic tephra.