This story has more plotholes than the average byroad in Romania...starting with the "fossilized horseshit".
If - as you had claimed - the dark lumps in that pic is what you said, they must have had driven the horses by the hundreds for decades over this way.
Now, I happen to live in a village where you can find the one or another pile of horse feces on the roads. Per usual, these piles are gone within two weeks, be it eaten by insects, washed away by rain or melting snow or blown away by the wind once it had dried.
Now combine this with another facts, like the fact that a glacier does take a looong time to build. Or that the typical Viking dwelling rarely consisted of more than a handful of dozens of inhabitants, thus also limiting the number of horses which they were able to keep.
See, I do think that we are do our our part in influencing climate changes, though I'm all against "climate hysterics". But to pin the warnings only on Liberals as a mean to denounce them is ridiculous - as, if you are interested in science sure know, a number of Republicans are concerned about the climate as well.