I would do this by inserting a column to the left of each filled
series, and numbering the rows from 1 to 2500, so they would look like
this:
Col A Col B
1 50000
2 50001
etc
2500 52499
....
1 60000
2 60001
etc
2500 62499

I would then copy the first set of numbers (A1:B2500) into the desired
location, and copy the second set of numbers directly under the first
set. Highlight the entire range, and sort on column A and secondarily
on column B.

Just one way to skin this cat.