Environment of deposition of the Maungataniwha Sandstone (Late Cretaceous), Te Hoe River area, western Hawke's Bay, New Zealand

Abstract

Abstract The Maungataniwha Sandstone is a remarkably thick (c. 400 m), poorly bedded, transgressive, sandstone-dominated unit of Campanian-Maastrichtian age (late Piripauan to early Haumurian). It was deposited during continued slow subsidence, and possibly records onlap over a dissected coastal plain and/or stacking of several minor transgressive and regressive cycles. It contains a diverse, dominantly marine vertebrate and invertebrate fauna, but includes terrestrial vertebrates, invertebrates, and plants. Marine fossils were probably not significantly transported or mixed prior to burial, and indicate deposition in a fully marine, nearshore, shallow water, moderate to high energy environment, possibly within an estuary, bay, or inlet. Three benthic invertebrate assemblages are recognised, and these may correspond to different habitats within such an environment. A nearby river mouth or delta is implied by the abundance of terrestrially derived material. Information on environment of deposition from sedimentary structures, grain-size analyses, and trace fossils is consistent with faunal evidence. In addition, it indicates that the lowest part of the Maungataniwha Sandstone was deposited mainly on the foreshore or shoreface, above fair-weather wave-base, and that the bulk of this unit was deposited under gradually deepening conditions on the inner shelf, above storm wave-base. Rare phosphatic concretions, of diagenetic origin, are considered to be derived from decaying organic matter.