I hate to bust anyone's bubble-but, I would be looking in another State, North of NM.
"Begin it where warm waters halt"--Hot springs in South Dakota, Wyoming and Alaska. Any others?
"And take it in the canyon down" "not far, but too far to walk"--Take what? Do you need some type of vehicle because of the rough landscape and walking is next to impossible?
"From there it's no place for the meek" Tigers, lions, bears-oh my. No bears in South Dakota.
"Put in below the home of Brown"--"Put in" reference to landing or parking area? Capital "B", name of a person, place or animal?
"There'll be no paddle up your creek, Just heavy loads and water high"--Is the heavy load a backpack? Is the water high a lake up in the mountains, that has a stream coming down and passes where a person "put in" at., but is too small to use a canoe?
" If you've been wise and found the blaze"--He left some kind of mark to show the way or the location.
"But tarry scant with marvel gaze"--Does the location have a view that makes a person what to stop and admire? Near this view will be the treasure.
"Your effort will be worth the cold"--Some place that is fairly high and chilly all year. This leaves out South Dakota, again.
"If you are brave and in the wood"--Forest where others don't venture that often.
I'll' leave now and let you ponder this post.