C-<up> runs the command emacspeak-mark-backward-mark (found in
global-map), which is an interactive byte-compiled Lisp function in
‘emacspeak-speak.el’.
It is bound to C-<up>.
(emacspeak-mark-backward-mark)
Cycle backward through the mark ring.
To cycle forward, use pop-to-mark-command bound to C-<down> #Emacs#Emacspeak