Browne, G.H.; Field, B.D. 1985 The lithostratigraphy of Late Cretaceous to Early Pleistocene rocks of northern Canterbury, New Zealand. Lower Hutt: New Zealand Geological Survey. Record / New Zealand Geological Survey 6 63 p.
Abstract: Eight lithologic groupings are used to subdivide the Cretaceous- Cenozoic sedimentary and volcanic rocks of northern Canterbury: Mt Somers Volcanics Group (oldest), Mandamus Igneous Complex, Iwitahi Group, Eyre Group, Late Cretaceous-Middle Oligocene Limestone, Cookson Volcanics Group, Porter Group and Motunau Group (new - youngest). The Late Cretaceous-Middle Oligocene Limestone, and the Eyre and Motunau Groups are the most extensive stratigraphic units The Eyre Group (Piripauan to Whaingaroan stages) represents a broadly transgressive phase in the development of the basin and is characterised by siltstone, conglomerate, and quartzose sandstone (with lignite seams/beds near the base) which passes up into mudstone, greensand and detrital sandstone. Seventeen formations are recognised in northern Canterbury. The Late Cretaceous - mid Oligocene limestone (Piripauan to Whaingaroan) has the maximum lateral extent of rocks in the basin, when sedimentation was dominated by fine grained carbonate rocks. These rocks include the well known Amuri Limestone. The final regressive phase is recorded in the Motunau Group (new; Duntroonian to Castlecliffian). This group consists of sandstone, conglomerate, bioclastic linestone and siltstone and comprises 9 formations. Many of these formation names have previously appeared in the geological literature, most have been poorly defined, and have required formal designation in this paper. Regional time- equivalence stratigraphic correlation diagrams indicate the distribution, age, and nature of contacts between these formations