Though most environments present today were represented during the Devonian, evidence of glacial deposits is questionable. It is clear that if polar ice caps did exist, they were very much smaller than they are today. It is thus concluded that Earth was warmer during Devonian time than at present.
Warm and equable climates were common, as shown by the wide distribution of evaporite basins in the Northern Hemisphere, by coal deposits in Arctic Canada and Spitsbergen, and by widespread desert conditions and carbonate reefs. Devonian salt deposits indicative of high evaporation rates, and thus of high temperatures, range from western Canada to Ukraine and Siberia and are found locally in Australia. Evidence of cooler average temperatures is provided by annual tree rings in Archaeopteris trunks from New York state that record seasonal growth patterns characteristic of higher latitudes.
Studies of growth lines on Devonian corals indicate that the Devonian year was longer, about 400 days. The lunar cycle, about 301/2 days, was one day longer than it is now.
Warm and equable climates were common, as shown by the wide distribution of evaporite basins in the Northern Hemisphere, by coal deposits in Arctic Canada and Spitsbergen, and by widespread desert conditions and carbonate reefs. Devonian salt deposits indicative of high evaporation rates, and thus of high temperatures, range from western Canada to Ukraine and Siberia and are found locally in Australia. Evidence of cooler average temperatures is provided by annual tree rings in Archaeopteris trunks from New York state that record seasonal growth patterns characteristic of higher latitudes.
Studies of growth lines on Devonian corals indicate that the Devonian year was longer, about 400 days. The lunar cycle, about 301/2 days, was one day longer than it is now.
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