How about 12,000 years of overlapping ring patterns from paleo trees?
Live trees, dead trees in buildings, bogs, tidal zones, etc.
There's also sedimentation layers from multiple scattered bore samples that will reveal more about patterns of particle fall from the skies and layered flows from years past.
I specifically meant live trees, didn't really occur to me that dead trees could be relevant. Not sure how common it is to find 12000 year old dead trees either but I guess it's more common than live ones.
And of course geological surveys would definitely tell you something about the past
The real problem with tree rings here in this specific case is ... Ethiopia .. not a lot of big trees now, nor in the recent past when it was grasslands - but not really my field - there's likely to be very slow growing unassuming trees that are surprisingly old there .. and remains of older trees that have overlapping ring sequences.
But yes - geological / geophysical clues are likely more relevant here.
Live trees, dead trees in buildings, bogs, tidal zones, etc.
There's also sedimentation layers from multiple scattered bore samples that will reveal more about patterns of particle fall from the skies and layered flows from years past.