 The conglomerates are primarily orthoquartzite monomict vein-pebble conglomerates, or polymict pebble conglomerates.In low-strain zones they preserve graded bedding, cross-bedding and heavy mineral-rich horizons.These rocks provide the bulk of age determinations from the Narryer Gneiss Terrane from detrital zircons, with the bulk of readings bracketing 3.5 to 3.75 billion years old, 3.35 to 3.45 billion years old, and a population of 4.1 to 4.2 billion years, with outliers of up to 4.4 billion years old.