The only way I can see of acquiring “palimpsest” is by looking at the slabs that have Morse between them.
Acquiring “palimpsest” from the Morse itself I find to be tenuous at best,
The slabs that appear to be sinking into the pond are how I imagine Quagmire is to be determined as the encryption method, as they are sinking into a “quagmire”.
As for “abscissa”, again, parts of the Morse slabs have been “cut away”. An alternative is to say “Absence” from K1, with Subtle Shading, to give ABS and SS, and then insert CIA, but again, this seems tenuous.