this is an image of the marks above the carpeting on the floorboard. The carpet and floorboards were replaced a couple months ago. Any and all information would be greatly appreciated. No moisture is present in the carpeting....
I do realize that you said no moisture in the carpet, but the discoloration does look very much like at some point there was water in/under that carpet close to the corner, and it has now evaporated. It is hard to tell what the source of the water was without knowing anything about what part of the house that is. Is there plumbing in that wall or above it? A vent pipe? Is this in the basement by chance?
You say, 'strange' marks........like, how strange? Do they look like they were caused by aliens or what? Or, are they simply scratches? What type of wood is the floor made from?
More specific info, please.