Your work incorporating the Wikipedia material appears to be an "Adaptation" as defined in [CC-BY-SA 3.0 Unported](https://creativecommons.org/licenses/by-sa/3.0/legalcode) 1.a:

> "Adaptation" means a work based upon the Work, or upon the Work and
> other pre-existing works, such as a translation, adaptation,
> derivative work, arrangement of music or other alterations of a
> literary or artistic work, or phonogram or performance and includes
> cinematographic adaptations or any other form in which the Work may be
> recast, transformed, or adapted including in any form recognizably
> derived from the original, except that a work that constitutes a
> Collection will not be considered an Adaptation for the purpose of
> this License. For the avoidance of doubt, where the Work is a musical
> work, performance or phonogram, the synchronization of the Work in
> timed-relation with a moving image ("synching") will be considered an
> Adaptation for the purpose of this License.

Now see 4.b:

> You may Distribute or Publicly Perform an Adaptation only under the
> terms of: (i) this License; (ii) a later version of this License with
> the same License Elements as this License; (iii) a Creative Commons
> jurisdiction license (either this or a later license version) that
> contains the same License Elements as this License (e.g.,
> Attribution-ShareAlike 3.0 US)); (iv) a Creative Commons Compatible
> License.

4.b(ii) clearly gives you the right to relicense the work as CC-BY-SA 4.0 which in turn, I believe, allows you to relicense the work as GPLv3.

4.b(iv), at least on my interpretation, allows you to relicense the work directly as GPLv3.

Either way, you appear to have a valid route to license the resulting combined work as GPLv3.

See also [@unor](https://opensource.stackexchange.com/users/138/unor)'s answer on [FOS.SE](https://opensource.stackexchange.com/a/2213/3451), which reaches a different conclusion.