there ‧ up ‧ on /ˌðeərəˈpɒn, ˈðeərəpɒn $ ˌðerəˈpɒːn, -ˈpɑːn, ˈðerə-/ BrE AmE adverb formal
1 . immediately after something else has happened, and usually as a result of it SYN then :
Thereupon the whole audience began cheering.
2 . relating to a subject that has just been mentioned:
I read your article, and wish to comment thereupon.