Tephra stratigraphy on the north icelandic shelf: Extending tephrochronology into marine sediments off north iceland

Tephra stratigraphical and tephrochronological studies of marine core MD99-2275 on the North Icelandic shelf have revealed 58 new tephra horizons within the last 7050 cal. a BP, bringing the total number of identified tephra layers to 76. So far, over 100 tephra layers have been identified in the entire core spanning the last 15000 years. The majority of the newly identified tephra layers are basaltic in composition and originate from the most active volcanic systems in Iceland, namely Grímsvötn, Veidivötn-Bárdarbunga and Katla. A total of 40 tephra layer land-sea correlations have been made within this time period, of which 16 represent absolutely dated tephra markers. In addition, two tephra marker series are revealed in the marine sediments and in the terrestrial tephra stratigraphy, located between c. 2300-2600 and between 5700-5900 years. For the last 15000 years, 21 tephra markers have been recognized. The marine tephra layer frequency (TLF) reveals two peaks, within the last 2000 years, and between 5000 and 7000 years ago. It shows the same general characteristics as the terrestrial TLF curve in Iceland, which indicates that marine sediments can yield important information about volcanism in Iceland. This is useful in time segments in which terrestrial records are poor or non-existent. The study contributes to a high-resolution tephrochronological framework on the North Icelandic shelf, with core MD99-2275 representing a potential stratotype section in the area, and for the northern North Atlantic-Nordic Seas region, as well as being an important contribution to the Lateglacial-early Holocene volcanic history of Iceland.