The Creek People have a long, and well documented history.
There is no tribe known as "Blackcreek".
As both your father and grandfather are deceased, then it might be an idea to begin looking at your family history by obtaining their death certificates, obituaries, and their original SS Applications.
This will provide you with additional information to enable to go back another generation.
Your recent ancestors are documented in the Federal Census.
It is only by following the documented history of your ancestors that you will discover who they were, and where they were from.
However, as I know from my own experience, tracing one's African (Slave) ancestors does present some dificulties.
Tanzania was, I believe, created relatively recently (1964 ?) and I also believe the importation of Africans ended in the early 1800's.
Both the Cherokee and Creek Nations that flourished in the southeast were forced to cede their homelands in the early 1800's. Again, there is abundant documented history on this.
The Brighton Reservation is part of the Seminole Nation.