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In Ikka Fjord in Southwest Greenland, tufaceous material is found
ikaite (calcium carbonate hexahydrate) over alkaline submarine springs.
forms where mixing of alkaline spring water and cold seawater leads to
and instant precipitation. The submarine springs are fed by meteoric water
was percolated through a carbonatite cored, alkaline ring complex, known as
Grønnedal-Ika complex, belonging to the rift-related Proterozoic Gardar
Ikka tufa structures grow into a variety of forms, predominantly columns
Ikka columns, many up to 18 m high. Distribution and form of the tufa
the submarine environment in Ikka Fjord have been mapped for the first time
echo-sounder traverses, lines of side-scan sonar imagery and seismic
profiles from a
‘pinger’ sediment profiler. The maps show the extent of Ikka tufa
distributional trends within the deposits. Hundreds of observations and
made by divers within the fjord, together with the maps, have enabled us to
tufas into five morphotypes: columns, fin-like structures, mounds, and hard
Many of the tufas are arranged into lines and clusters. GIS analysis has
the outcrop of the Grønnedal-Ika Complex, the proximity to stream mouths
bedrock exposures all control the distribution of the tufa deposits. Field
have also shown that carbonatite dykes passing under the fjord are
column location. Where ikaite tufas form in abundance, maps of their
indicate the pattern of submarine springs about the fjord bed.
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