Sorry... I'm really bad with titles apparently.

So a long while ago I created this overland map in Photoshop CS2. What I want to do is take a region of the original map and make an independent map out of it. I'm trying to zoom in and have more detail (like taking a map of the U.S. and zooming in on Washington State). I had a problem with the resolution, but figured that part out. Now I want to add more detail, but I'm having trouble. What I did was copy the region out of the original map and paste it in a new document. However, now all the layers are blended together, and the map doesn't really look right - the river's are still pencil thin etc.

Does anyone have any tips or know of a tutorial on how to do what I'm trying?

Any help is appreciated, thanks.