Marine-lacustrine stratigraphy of raised coastal basins and postglacial sea-level change at Lyngen and Vanna, Troms, northern Norway

Abstract

and diatom analysis of core samples from 10 raised lake basins from an inner (Lyngen) and outer (Vanna) coastal area of Troms, northem Norway, was made in order to reconstruct relative sea-level change during the Holocene and Late Weichselian. A variety of facies types and facies sequences, controlled primarily by sea-level change and inftuenced also by climatic factors, is recognized. Main facies types are: (I) Marine (mud and sand), (Il) Transitional (laminated gyttja or gyttja and silt), (Ill) Lacustrine (gyttjajplant detritus), and (IV) Mixed (gyttja, mud and sand/gravel). Laminated transitional facies li, in nearly all cases, is interpreted as having formed under meromictic limnic conditions following basin isolation from the sea, whereas heterolithic mixed facies IV forms usually under littoral inftuence during ingression. Sea-level displacement curves are constructed for Lyngen and Vanna based on radiocarbon-date d isolation and ingression contacts, elevation/inferr ed-age data for prominent raised shorelines, and other data,. The evidence suggests that the Tapes transgression at Lyngen had a minimum amplitude of 2-3m and peaked at ca. 7000 BP. Average rates of pre-Tapes (before 8500 BP) and post-Tapes (after 6000 BP) regression are approximately 15 and 3 mm/year respectively at Lyngen, and lO and 1.5 mm/year respectively at Vanna.