440 PROCEEDINGS OF SECTION C. 



11.— THE PHYSIOGRAPHY OF WEST WANGANUI INLET, 



NEW ZEALAND. 



By JAMES MACKINTOSH BELL. Director of the Geological Survey of New 



Zealand. 



[With Map.] 



The Inlet of West Wanganui occupies a prominent bight in the 

 western seashore of the extreme north-western corner of the South 

 Island of New Zealand. It presents many physiographic features 

 of interest, and exhibits a scenery of rare beauty and charm. 



The inlet has an extreme length from north-east to south-west, in 

 which direction its main axis lies, of about nine miles, and an extreme 

 width in the opposite direction of rather less than three miles. It is 

 connected with the open sea, about half-way along its western border, 

 by a narrow strait of water, rather less than three-quarters of a mile 

 in width at high tide, though only a few chains wide at low tide. The 

 coast line of the inlet, with its numerous deep and irregular bays, is 

 very intricate, and is said to be no less than 110 miles around. 



The extreme rise of the tide at West Wanganui Inlet is about 16ft. 

 At high tide the inlet is a beautiful sheet of water, almost completely 

 landlocked, while at low tide the basin is occupied by a spacious mud 

 flat, through which ramify the narrow tortuous channels from the 

 numerous entering streams. 



The stratigraphical geology of the country surrounding West 

 Wanganui Inlet is simple, the rocks consisting entirely of strata, classi- 

 fied as Cretaceo-Tertiary by former New Zealand geologists. These 

 strata have a gradual though decided inclination to the north-west- 

 ward from the rugged eastern hinterland of Palaeozoic rocks and in- 

 trusive granites. The Cretaceo-Tertiary rocks may be loosely divided 

 into two series — a, lower poorly consolidated and easily weathering 

 series of shales, sandstones, and coal seams, and an upper more com- 

 pact and more resistant series of calcareous sandstones and limestones. 

 The shallow basin, occupied by West Wanganui Inlet and the broad 

 valley stretching south-west from that feature beyond the Patarau 

 River indicate physiographically the location of the friable series, 

 while the ridge of rugged bluffs rising abruptly close to the western 

 margin of West Wanganui Inlet and the valley marking its south- 

 western continuation show topographically the presence of the more 

 resistant series. These bluffs form a typical cuesta, or ridge of rock, 

 presenting a steep escarpment in a direction opposite to that of the 

 dip of the strata and a gradual slope corresponding closely to the in- 

 clination of the strata in the contrary direction. 



West Wanganui Inlet is probably but a portion of a more majestic 

 feature, and formerly it seems to have stretched south-westward along 

 the broad valley already mentioned beyond the Patarau River, as far 

 south at least as Lake Otahie, or a distance of some 10 miles from its 



