Answer:
a surface of contact between two groups of unconformable strata.
"erosion beneath the Hercynian unconformity has removed most of the Westphalian strata"
the condition of being unconformable.
Explanation:
Seen from Desert Tower, the Great Unconformity is the boundary between the flat-lying Tapeats sandstone (and overlying Paleozoic rocks) and tilted rocks of the Grand Canyon Supergroup (GCS).
thats all I know so i hope this helps
