The central part of Lower Taylor Valley consists of a thick, nearly vertical sequence of faulted metasedimentary rocks in sharp contact on the west with banded granitic rock. An Ar40/K40 date of 500 ± 20 m.y. obtained on biotite separated from carbonate material indicates an Upper Cambrian-Lower Ordovician period of orogeny. A monzonitic gneiss sample from the west flank of Mt. Nussbaum yielded an Ar40/K40 age of 425 ± 20 m.y.
Four systems of lamprophyric dikes cut both the granitic and metasedimentary rocks, whereas several smaller pegmatitic and aplitic dikes are largely restricted to the granitic rocks. A sample collected from one of the lamprophyres gave an Ar40/K40 date of 458 ± 20 m.y.
Much of Taylor Valley is blanketed by morainal material deposited by Taylor Glacier and its tributaries.