Iron and magnesium rich rock formed at depth. Tt 200,694 acres. Thick sequence of rhythmically bedded sandstone with thinly bedded mudstone. Low porosity of water infiltration except along joints. Moderate to steep slopes occur.
High debris flow potential on steep slopes.
Low groundwater potential. Weathers to sandy silt. Tmss 59,080 acres. Fine to coarse grained sandstone held together by solidified muds. Easily eroded, weathers to a gentle slope consisting of fine to coarse grained muds and sands.