Abstract:
The Wanganui District is built of sediments of Pliocene and Pleistocene age, which contain the type localities of most stages of the Wanganui Series. These sediments occupy a structural basin of considerable size and depth, coincident with one of the largest Bouguer gravity anomalies measured in New Zealand.(Robertson, 1953). This structure, known as the Wanganui Basin, (Fleming, 1953), is broadly oval in outline, elongate in the east-north-east direction, and extends from the western side of the the Ruahine Ranges, southwest into the Taranaki Bight.
The maximum thickness of sediments, as a cumulative column, is along the Wanganui River, where the Superior Oil Company recorded over 15,000 feet from the base of the Waitotaran Stage to near the top of the Gastlecliffian Stage. (Fleming, 1953). During that time, sedimentation kept pace with subsidence, so that most of the sediments in the basin are marine, and were deposited at relatively shallow depths, although a small proportion are freshwater sediments, deposited slightly above sea level.
