A new monograph published in GEUS Bulletin describes and defines the Tertiary volcanic succession on Svartenhuk Halvø, West Greenland.
“We have established a connection to the southernly volcanic areas in the basin and have indicated a likely connection to the large volcanic areas on the West Greenland shelf” says co-author Lotte Melchior Larsen, Emeritus at GEUS.
The research documents the rock types and structures in the northern Nuussuaq Basin – an important area for understanding the entire West Greenland shelf, says Melchior Larsen.
“The Tertiary volcanic rocks here are pieces of the puzzle of the entire continental breakup in the North Atlantic when large-scale volcanism occurred, and the current basins were formed.”
Hand drawing and no GPS
The monograph was years in the making. Asked how the work came about, Melchior Larsen replies “It is a long story!”.
“This manuscript is a sort of developed or expanded map description. The mapping took place between 1974 and 1983, in connection with a large regional effort to map the entire area, both the Precambrian bedrock around Maarmorlik and the younger sediments and volcanics in the Nuussuaq Basin, which were of interest in the exploration for hydrocarbons.”
Lead-author Jørgen Gutzon Larsen was at that time employed as a summer geologist with the Geological Survey of Greenland (GGU) when he completed the mapping “the classic way”, explains Melchior Larsen.
They setup field camps and worked from a ship. They had very little helicopter support and no GPS or electronics. Field observations were drawn on aerial photographs and a regional grid of measured profiles was established, from which they took samples of each lava flow so that they could systematically document and define each of the rock types found.
Fills a 'black hole' in published geological record
It was not until 2020, that they were able to combine the results of the mapping with extensive geochemical analyses to fully define and describe the volcanics of this part of West Greenland.
“In 2020, after having already published three volumes in GEUS Bulletin on the stratigraphy and sediments in the Nuussuaq Basin (vol. 19) and the volcanics of Disko and Nuussuaq (vols. 39 and 40), it was clear that the volcanics in the northern part of the Nuussuaq Basin represented a black hole in the published knowledge.”
This gap is now filled, with the publication of this new monograph in the GEUS Bulletin series.
“In the Svartenhuk area the overall volcanic evolution, and the major mantle sources, show strong similarities to the southern parts of the Nuussuaq Basin. However, the basalts of the newly-defined Svartenhuk Formation are compositionally different from the southern basalts, probably because some minor mantle components of local northern origin took part in the melting processes.”