Which preposition to use with tympans

of Occurrences 4%

The other bas-relief of Holland vanquished and in tears, has been struck by balls, as have also the figures of Fame in the tympans of the arcades.

over Occurrences 1%

The ornament is nearly confined to the tympan over the portal, the capitals of columns, and to the choir with its seven absidal chapels.

Which preposition to use with  tympans