At http://wattsupwiththat.com/2015/05/28/study-finds-severe-cold-snap-durin… … this piece was on Phys Org a few days ago and has now popped up at Anthony's place. Scientists in Frankfurt, Germany, and Ottawa, Canada, have had a look at the Arctic climate during the Cretaceous era – between 145 and 66 million years ago. The Cretaceous, as most geologists will tell you, was one of the warmest periods in the history of the Earth – when global warming was rampant. In Britain's Midlands the climate resembled Florida – and in the near Arctic there were trees growing. Basically, this is why global warming in the Cretaceous is a matter of faith – as movement of the Poles is out of the question (as far as settled science is concerned). Well, it seems some of that warmth may very well have gone through the roof – literally. It seems to have disappeared out of the atmosphere and into space as they have detected a cold snap of around 6 million years duration smack bang in the middle of the Cretaceous.
The Cretaceous is regarded as extremely warm with the Poles devoid of ice and average temperatures of 35 degrees Celsius in the oceans. It was s typical greenhouse climate – or so the consensus theory goes. Some geologists even refer to it as a 'super greenhouse' climate – but how much is really known about the Cretaceous?
Samples were taken from the Arctic Fjiord glacier and from Axel Heiberg Island (at intervals of 5 to 10m) and they found what are called glendonites (star shaped calcite minerals). These are only formed below 8 degrees Celsius (which is a bit on the chilly side) and they metamorphise into calcite at warmer temperatures. Hence, sedimentology and age dating combine to provide an indication of environmental condition in the Arctic during the Cretaceous. So what was going on to cause temperatures to dramatically plummet?
Two research expeditions were undertaken, in 2011 and 2014, and 1700 rock samples were taken back to Frankfurt where they were analysed. See http://geology.gsapubs.org/content/early/2015/03/19/G36439.1.full.pdf