A small slightly pedantic point, but that should be 'a Senior Marketing Manager' rather than 'the Senior Marketing Manager'.
The Senior Marketing Manager is, I imagine, a very important person. A Senior Marketing Manager is, well, a manager in the marketing department who is in some sense 'Senior'.
The Senior Marketing Manager is, I imagine, a very important person. A Senior Marketing Manager is, well, a manager in the marketing department who is in some sense 'Senior'.