Submarine Morphology East of the North Island, New Zealand
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ISSN 2538-1016; 14 NEW ZEALA D DEPARTME T OF SCIENTIFIC AND INDU TRIAL RESEAR H BULLETI 149 SUBMARINE MORPHOLOGY EAST OF THE NORTH ISLAND, NEW ZEALAND by H. M. PA TI Ne� Zealand Oceanographic In tituLe Wellington ew Zealand Oceanographic Institute Memoir No. 14 1963 @©@© Whites A via1io11Ltd. photograph Frontispiece View north from Castlepoint (Castle Rock centre foreground) to Cape Turnagain. Castle Rock is made up of Waitotaran limestone (upper Pliocene) overlying Opoitian siltstone (lower Pliocene); the reef immediately to the north is composed dominantly of Waitotaran limestone. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ NEW ZEALAND DEPARTMENT OF SCIENTIFIC AND INDUSTRIAL RESEARCH BULLETIN 149 SUBMARINE MORPHOLOGY EAST OF THE NORTH ISLAND, NEW ZEALAND by H. M. PANTIN New Zealand Oceanographic Institute Wellington New Zealand Oceanographic Institute Memoir No. 14 1963 Price 25s. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ FOREWORD THE resurvey of the New Zealand coastline by the Royal New Zealand Navy is providing a valuable opportunity for the accumulation of data of concern to the marine sciences. The bathymetric analysis of some of the information made available from surveys of HMNZS Lach/an is not only the basis for the present geological study but provides a definition of the morphology of shelf and slope directly applicable to problems in other fields of marine science. Mrs P. M. Cullen has been responsible for the preliminary editing of the manuscript. Final editing of the material for publication has been carried out by Mr M. O'Connor, Information Bureau, D.S.I.R. J. w. BRODIE, Director' New Zealand Oceanographic Institute. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ CONTENTS Page INTRODUCTION 9 Materials 9 Area Covered 9 Coastal Topography 9 Coastal Geology .. 15 SUBMARINE MORPHOLOGY 17 Morphological Zones 17 Continental Shelf .. 17 Width and Gradient 17 Depth and Trend of Shelf Edge 17 Banks 28 Continental Slope 29 Submarine Canyons . 29 Sea Valleys .. 29 Slope Depressions 30 Slope Highs .. 30 HikurangiTrench 30 DISCUSSION 32 The Shelf 32 General Morphology . 32 Benches and Banks 32 Sinuous Portions of the Shelf Edge 34 Faulting 34 The Slope . 34 Introduction . 34 The Submarine Canyons 34 The Sea Valleys . 36 The Slope Highs and Depressions 36 Cross Faults .. 38 The Hikurangi Trench 38 COMPARISON WITH SOUTHERN CALIFORNlA .. 40 /..(:KNOWLEDGMENTS .. 40 REFERENCES .. 41 INDEX .. 42 This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ FIGURES Page Locality map 8 2 Simplified geology of the eastern part of the North Island 10 3 Major morphological zones and canyon axes, east coast, North Island 18 4 Locations of depth profiles and echo sounding traverses 19 5 Depth profiles 20-25 6 (a) and (b) Echo-sounding traverses 26,27 7 Locations of small banks offCape Turnagain 28 8 Ritchie Banks 31 9 A small enclosed basin on the shelf offWhareonga in Poverty Bay 33 10 Zones of relative uplift and subsidence on the east coast shelf 35 11 Zones of relative uplift and subsidence on the continental slope offthe east coast 37 12 Alternative hypotheses to account for the morphology along section GG' (figs.4 and 5) 39 PLATES Frontispiece: View north from Castlepoint I Marine terraces around Cape Kidnappers, Hawke Bay 11 II The tombolo at Opoutama connecting Mahia Peninsula to the mainland 12 III Panoramic view of the coast near Honeycomb Rock . 13 IV Oblique projection of shelf and slope off the east coast, from Cape Palliser north to Gable End Foreland . 13 V Large-scale slumping of Nukumaruan beds forming high coastal cliffs 2 miles SW of the Mohaka River mouth 14 CHARTS New Zealand Oceanographic Institute Chart I, Coastal Series I : 200,000 Bathymetry - Palliser. 2, Coastal Series I : 200,000Bathy metry - Turnagain. 3, Coastal Series I : 200,000 Bathymetry - Mahia. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ Fig. I. Locality map. (Bathymetry from New Zealand Oceanographic Institute Bathymetric Charts I : 219,400; 1960.) This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ SUBMARINE MORPHOLOGY EAST OF THE NORTH ISLAND, NEW ZEALAND INTRODUCTION MATERIALS coast of the North Island, and extends 230 miles The materials on which the present analysis is from the mouth of the Opouawe River, near Cape founded are the extensive lines of echo soundings Palliser, to Gable End Foreland, north of Poverty obtained by the Royal New Zealand Navy Survey Bay (fig. 1). The coast, which forms the western Ship Lach/an in the course of her present hydro boundary of the area, is very regular in trend for graphic resurvey of the coastal waters of New the first150 miles, running steadily north-eastward Zealand. Under Commander J. M. Sharpey from Cape Palliser to Cape Kidnappers with only Schafer, R.N., 1949-51; Captain C. C. Lowry, minor promontories and indentations. Between R.N., 1951-54; Captain G. S. Ritchie, R.N., Cape Kidnappers and Mahia Peninsula, the coast 1954-57; and Commander F. W. Hunt, R.N., swings westward to form the great re-entrant of 1957-60, the survey of the eastern coastal waters Hawke Bay, which extends up to 25 miles north of the North Island has been carried from Cook west of the general line of the coast, and measures Strait to Poverty Bay. 45 miles across the entrance between Cape The surveys were carried out at larger scales to Kidnappers and Mahia Peninsula. North of the produce charts on a scale of I : 200,000. The irregular Mahia Peninsula, the coast trends lines of echo soundings were run E-W roughly steadily northward to the smaller re-entrant of normal to the coastline and ½ mile apart out to Poverty Bay and thence north-eastward to Gable 100 fathoms followed by lines 2 miles apart, then End Foreland. by lines 5 miles apart to the limits of the area surveyed. Through the cooperation of the Com COASTAL TOPOGRAPHY manding Officer, additional lines were run for deep bathymetric control in a number of cases. In the sector between Cape Palliser and Cape In Hawke Bay the sounding lines were traversed Kidnappers the shore topography is uniformly as a series of parallel arcs concentric on either rugged, with a highly dissected fluvial morphology Cape Kidnappers or Portland Island. The original containing numerous summits over 1,500 ft in echo soundings and collector tracings of unpub height. Many of these summits are situated only lished soundings have been made available to the a few miles from the coast. The landscape around New Zealand Oceanographic Institute. Hawke Bay is variable, being fairly rugged The bathymetric charts which accompany this between Cape Kidnappers and the mouth of the Memoir were compiled from contourings of the Tukituki River (plate I), and between Tangoio large-scale survey collector sheets· of soundings; Bluff and Waikokopu, whereas the ground these contoured sheets were then reduced to fit a between the Tukituki River and Tangoio Bluffis base prepared on the same scale as the published comparatively low-lying. In this sector a stretch of hydrographic chart. alluvial plain some 20 miles wide (the Heretaunga Plains) reaches the coast and extends 20-30 miles AREA inland. It has been built by three of the major COVERED rivers draining southern Hawke's Bay, and still The area to be described is that covered by the carries the seaward portions of these rivers. In Mahia and Turnagain charts, and the Palliser the hilly areas surrounding Hawke Bay summits chart east of longitude 175° 25'. It forms a belt in the immediate vicinity of the coast are not that extends 50-80 miles out to sea from the east quite as high as in the country further south, and 9 This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ Sig. 2 17S0 E LEGEND r---- ----+- Greywacke -----41•s Jurassic Cretaoeous •?::m SCALE Tertiary 0 10 20 lO SO Miles IE=i:r:§1 Quaternary mn:�:@ Mesoroic CapePalliser Volcanics Fig. 2. Simplified geology of the eastern part of the North Island (adapted from New Zealand Geological Survey "Geological Map of New Zealand" 1958.) 10 This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ Whites Aviation Ltd. photograph Plate I. Marine terraces around Cape Kidnappers, Hawke Bay. Cape Kidnappers consists of Opoitian siltstone; white cliffs of Castlecliffian pumiceous sandstone can be seen in the right middle distance, with the Heretaunga Plains beyond and a scarp of Waitotaran limestone in the left centre background. The Ruahine Range (Mesozoic greywacke) is just visible on the skyline. 11 This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.