The full programme book (PDF) - Royal Geographical Society

T2
Optimising the use of marine tephrochronology in the North Atlantic: A detailed
investigation into the Faroe Marine Ash Zones II, III and IV
A.J. Griggs 1 *, S.M. Davies 1 , P.A. Abbott 1 , T.L. Rasmussen 2 , A.P. Palmer 3
1 Department of Geography, College of Science, Swansea University, Singleton Park, Swansea, SA2
8PP
2 Department of Geology, University of Trømso, NO9037, Trømso, Norway
3 Department of Geography, Royal Holloway, Egham Hill, Egham, TW20 0EX
Tephrochronology is central to the INTIMATE goals to test the degree of climatic
synchroneity during abrupt climatic events that punctuated the last glacial period. Since
their identification in North Atlantic marine sequences, the Faroe Marine Ash Zone II
(FMAZ-II), FMAZ-III and FMAZ-IV have received considerable attention due to their
potential for high-precision synchronisation with the Greenland ice-cores. In order to
optimise the use of these horizons as isochronous markers, a detailed re-investigation into
the geochemical composition, sedimentology and the processes that deposited each ash
zone is presented. Shard concentration profiles, geochemical homogeneity and microsedimentological
structures are investigated for each ash zone preserved within core
JM11-19PC, retrieved from the southeastern Norwegian Sea on the central North Faroe
Slope. This approach allows a thorough assessment of primary ash-fall preservation and
secondary depositional signals and demonstrates its values for assessing depositional
integrity in the marine environment. Results indicate that the FMAZ II and IV are wellresolved
primary deposits that can be used as isochrons for high precision correlation
studies. We outline key recommendations for future marine tephrochronolgical studies and
provide a protocol for optimising the application of marine tephras to meet the INTIMATE
synchronisation goals.
Keywords: cryptotephra; isochrones; taphonomy; palaeoclimatic correlation; Iceland