Clumps of dandruff on my dogs head?

My dog is about 8 weeks. I was petting him and scratching his head when all of a sudden I feel these weird clumps. As I look onto the top of his head I see these clumps, they look like dandruff I took a bit of one off and it looks reddish white. I'm not sure what it really is. Can anyone tell me how to treat this or what it really is? I would really appreciate the help, as would my puppy Oso. Thanks.