This thick sedimentary sequence comprises sandstones, mudstones, siltstones and numerous thin limestones. It contains non-red lithologies, green mudstones, siltstones, fine sandstones and yellow sandstones. The formations are a mix of mudstones, siltstones, sandstones and halites. Well sorted volcanoclastic sandstones, siltstones and mudstones are found in this system. The Pico Member is mostly made of massive siltstones and sandstones interbedded with minor silty-sandstones. The strata composed of siltstones, shales and limestones were deposited in lagoonal and fluvial environments. The underlying lithology is dominated by Permian siltstones and sandstones. The Mokau Group is composed of shoreface sandstones with some interbedded siltstones. These were followed by dark marine shales, siltstones, and coarse sandstones of the Millstone Grit. The younger siltstones and mudstones are assigned to the Mercia Mudstone Group. It comprises (slightly smaller than Croatia) of Precambrian gneiss and Paleozoic siltstones and shales. The line will mainly be bored through East Coast Bays Formation of sandstones and siltstones. The basement rocks comprise slates, siltstones, greywackes and quartzite. It consists of siliceous siltstones, formed in deep water. Intercalated are reddish to light grey claystones and siltstones.