How huge numbers of millions of years-old giant glendonite crystals did manage to form has been a geological puzzle in Denmark for several years. The answer may be that major volcanic eruptions resulted in episodes of much cooler prehistoric climates than once thought. Read how Danish scientists unravel occurrence of “impossible” crystals.
These uncommon calcium carbonate crystals – that need temperatures lower than 4 degrees Celsius to frame – are formed from the mineral ikaite and found in several millions on the Danish islands of Fur and Mors. They have been dated to 56-54 million years back. “Why we find glendonites from a hot period, when temperatures arrived at the midpoint of over 35 degrees, has for quite some time been a mystery,” says geologist Nicolas Thibault, an associate professor at the University of Copenhagen’s Department of Geosciences and Natural Resource Management.
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After a detailed chemical analysis of glendonite samples by Thibault and department colleagues Madeleine Vickers, Christian Bjerrum and Christoph Korte, using a technique called clumped isotope thermometry to trace temperatures back millions of years, there might be an answer: the Eocene was perhaps not as uniformly warm as previously thought.
The possibility of colder Eocene spells has been advanced already, however the proof has been uncertain up until this point. The new chemical breakdown assists specialists with argueing the case for cooler conditions, with models recommending the glendonites framed in waters under 5 degrees Celsius (41 degrees Fahrenheit) at a profundity of around 300 meters (984 feet).
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Sedimentary layers of ash on the island of Fur point to the possibility that volcanic eruptions may well have been responsible for these chillier episodes in the Eocene, localized around specific regions, which would help to explain the cooler waters and the rock record.
“There were presumably an enormous number of volcanic emissions in Greenland, Iceland and Ireland during this period,” says Thibault. These delivered sulphuric corrosive beads into the stratosphere, which might have stayed there for quite a long time, concealing the planet from the sun and reflecting daylight away. It assists with clarifying how provincially cool zones were conceivable, which is the thing that influenced the climate in early Eocene Denmark.
The new study backs the hypothesis that colder Eocene periods are more likely than the alternative – which is that the science is wrong about the sort of temperatures that ikaite-based rock is able to form at.
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The presence of volcanic activity is revealed by, among other things, sedimentary layers visible on Fur, where layers of volcanic ash are clearly visible as bands in the coastal bluffs.
Next, the group needs to see comparative examinations completed to perceive how inescapable the cooling found in the Danish Basin really was. Other geological records – including those from the Arctic – recommend this dunk in temperature wasn’t going on everywhere on the globe through the Eocene. As with any discovery about our climate past, the study is going to help scientists map out our climate future.
The study was conducted in collaboration with researchers from England, Switzerland and Norway, and has been published in the scientific journal Nature Communications.
Feature image (on top) Furs and Mors. Photo: University of Copenhagen
Danish Scientists Unravel Occurrence of “Impossible” Crystals, written by Tor Kjolberg