Tillaceous geo-puzzle
A quick contest:
What is the origin of these red polka-dots on this apparently white sample?
Hint: this cobble was photographed at the "half drumlin bluff" site I detailed yesterday!
First one to answer correctly is entitled to a free "GEOLOGY ROCKS" bumper sticker!
What is the origin of these red polka-dots on this apparently white sample?
Hint: this cobble was photographed at the "half drumlin bluff" site I detailed yesterday!
First one to answer correctly is entitled to a free "GEOLOGY ROCKS" bumper sticker!
1 Comments:
The white stuff is caliche, a calcium carbonate residue deposited (probably on the bottom surface of the cobble) by rainwater percolating down through the till. The red spots are contact points where the cobble was resting on pebbles, preventing deposition of the caliche at those points.
--Howard
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