Article: Middle Cretaceous wood from the Nanushuk Group, central North Slope, Alaska

Analysis of growth rings in Albian and Cenomanian (late Cretaceous) coniferous wood from the North Slope of Alaska (74-85° N. palaeolatitude) has shown that tree growth was rapid and steady during the growing season, resulting in wide growth rings and few false rings, that narrow late wood, as little as one cell wide, indicates that tree growth ceased abruptly at the end of the growing season owing to rapid onset of winter darkness, and that inter-annual growth was variable. Water being in abundant supply, this variability was likely to have been caused by fluctuations in soil drainage or in summer mean temperatures.