okay last CHALLENGE while i'm out in the field trying to find lost quarrys of francis slate.
i saved up a hard one for the finale of this the first round of challenges... time to prove you have a bigger brain that me!
above is a nice picture of the badlands, with a rather ugly green line (added by me in paint to the photo) running along the top. there is a key difference between the layers above and below this line.
now before you take a guess... i'm sure some of you are thinking it must be the KT boundary!... there is a difficult catch. i only want to know what is special about the top layer... which is hint right away. it is only a single layer above the green line, compared to many many below it!
the layers below the line are of the horseshoe formation, and contain the sorts of dinosaurs and other fossils you'd expect to find in those rocks. however the rocks above it are not from the horseshoe canyon formation, and the horseshoe are the only cretaceous layers around drumheller (where this photo was taken!).
how can you explain this layer as per the law of superposition?!?
next the really hard part, and a prize winning answer if you can get it (there is a prize for this part if you can get it). how is the source of this single top layer (possibly) responsible for my finding fossils in the bottom layers, as the bottom layers came before it?
(this is not a trick question! the bottom layers were laid down before this top one for the record. somehow this layer explains why i today can find fossils in this area).
double good luck to you, and be sure to check back on feb. 21st when i get back and figure out who got this one and the first two challenges right!