Discoverer of carbon dating
Both white spruce (Picea glauca) and black spruce (Picea mariana) were present, as was larch (Larix laricina).
(And how could you resist a face looking up at you through the sparkling water?After it all settled, the ice and floods had cobbled many sections of the clear riverbeds with smooth pebbles and stones - some rare and semiprecious.During this post-glacial flooding, smooth rocks with similar specific gravity had congregated in clusters at eddies on selected northern Illinois river bottoms.It is thought they brought Clovis point technology (earlier, similar points were found in France) and genetic diversity (such as red hair and large noses) to Native Americans.The exact date humans came to North America will not be found soon, but the Hebior and Schaefer Wisconsin mammoth sites about 350 miles northeast of our recovery site were recently carbon-dated to 15,000 to 16,500 years ago and contained artifacts that were basically cutting and skinning tools.What happens next is like something out of a Dooms-Day sci-fi movie: The exploding comet creates a giant white-hot tornado and sets forests ablaze killing off just about everything and everybody in North America.
The remaining vegetation would have been charred, forcing starvation upon surviving mega fauna. This comet melted a good portion the Laurentide Ice Sheet and the resultant flood waters changed the Atlantic currents.
During this time birch (Betula) and alder (Alnus) were also important components of the vegetation.[At that time, the summers here were one month shorter than today and rivers had dropped to their near present levels.
By the end of this Mini-Ice Age 11,700 years ago, the climate warmed. After the floods, gravity continued its work on the riverstones, again using water as a tool, albeit in less dramatic fashion: Since glaciers follow the course of rivers, the exposed rocks were washed down and further polished by flowing water.
Although the glaciers had retreated, the climate was still quite cold.
About 16,000 years ago, the spruce forest became denser, and closed forest developed.
This question has been hotly debated for over a century, especially now with the recent interest in the last Ice Age.