Introduction and significance: Many intercrater plains and degraded impact craters in the Noachian highlands contain flat-lying, relatively high thermal inertia (TI) surfaces (“bedrock”) that commonly show modest enrichments in olivine and/or pyroxene compared to surrounding materials (Fig. 1). These surfaces have maximum TI values above 500 J m K s in THEMIS images; some units exhibit TI values well above 900 J m K s. These physicochemically distinctive units occur in dozens of isolated exposures ranging from ~2x10 to ~3x10 km in area and exhibit morphologies indicating reduced/minimal sediment mantling. The units lack evidence of fine-scale layering in HiRISE imagery, and also lack evidence of aqueous alteration in spectral data [1-7].