New Zealand's Northland Region is built upon a basement consisting mainly of greywacke rocks, which are exposed on the eastern side of the peninsula. In-place Eocene coal measures crop out at Kamo, near Whangarei, and Oligocene limestone crops out at Hikurangi, near Whangarei.
A subduction zone is believed to have existed to the northeast of Northland in early Miocene times, causing the Northland Allochthon to thrust over much of the peninsula and volcanic belts to develop on either side of the peninsula. Intra-plate basaltic volcanic activity has occurred around Kaikohe, the Bay of Islands, and Whangarei since late Miocene times. Sand dunes sourced from volcanoes further south occupy much of the western coast, and the Aupouri Peninsula joins previously separate islands to the mainland to form a large tombolo.
Murihiku Terrane rocks lies beneath the Northland Region on the western side, but do not crop out. The Murihiku Terrane was formed in Late Triassic to Late Jurassic times (220–145 Ma).[2]
A line of Dun Mountain-Maitai Terrane rocks pass NNW-SSE through the centre of the Northland Region, separating the Murihiku Terrane from the more easterly terranes, and produce a detectable Junction Magnetic Anomaly (JMA), but do not crop out.[2]
Caples Terrane rocks crop out to form the Waipapa Horst (Omahuta and Puketi forest area). The Caples Terrane was formed in Permian to Triassic times (300–200 Ma).
Hunua Terrane rocks (part of the Waipapa Composite Terrane) crop out throughout much of eastern Northland, south of Whangaroa. The rocks are generally fine grained and highly deformed. The Hunua Terrane was formed in Triassic to Jurassic times (250–145 Ma).
Mount Camel Terrane rocks crop out near Mount Camel and the Karikari Peninsula. They were formed in the early Cretaceous (131–104 Ma).
Te Kuiti group coal and limestone
The Te Kuiti Group Rocks overlie the basement rocks, and are present in Northland, Auckland, the Waikato, and King Country, although they have often been eroded or covered. Rocks containing coal were formed from swampland in Late Eocene times (37–34 Ma). The land sank, the sea transgressed, and calcareous sandstone, mudstone, and limestone were deposited in Oligocene times (34–24 Ma).
Eocene coal measures crop out in the east, between Kerikeri and Waipu. Coal has been mined around Kamo, north of Whangarei.[3]
Limestone crops out around Whangarei, with an interesting display at the Waro Rocks Scenic Reserve, north of Hikurangi.
Northland Allochthon
Map of selected surface volcanic features of Northland Region. Clicking on the map enlarges it, and enables panning and mouseover of volcano name/wikilink and ages before present. Key for the volcanics that are shown with panning is: '"`UNIQ--templatestyles-00000004-QINU`"'basalt (shades of brown/orange), '"`UNIQ--templatestyles-00000005-QINU`"'monogenetic basalts, '"`UNIQ--templatestyles-00000006-QINU`"'
'"`UNIQ--templatestyles-00000007-QINU`"'arc basalts,'"`UNIQ--templatestyles-00000008-QINU`"'arc ring basalts, '"`UNIQ--templatestyles-00000009-QINU`"'
and '"`UNIQ--templatestyles-0000000D-QINU`"'plutonic. White shading is selected caldera features.
In Early Miocene times (24–21 Ma), a series of thrust sheets was emplaced over Northland,[2] extending as far south as the Kaipara Harbour and Albany areas. The rocks came from the northeast (perhaps beyond the Vening Meinesz Fracture Zone), and were emplaced in reverse order, but the right way up. The original rocks are of Cretaceous to Oligocene age (90–25 Ma), and include mudstone, limestone and basalt lava. These rocks outcrop around Silverdale, Warkworth, and Wellsford, reaching as far south as Albany.[2] The allochthon includes displaced Te Kuiti group rocks. The basalt lava of the Tangihua Complex is believed to represent sea floor, that has been obducted onto Northland to form high standing massifs, such as the Reinga, Ahipara, Warawara, Mangakahia, and Maungataniwha massifs. Isolated bodies of serpentine occur at North Cape, and south of Maungaturoto.[4]
The Northland and East Cape Allochthons are assumed to constitute part of a single allochthon, that have later separated, due to the clockwise rotation of the eastern part of the North Island, relative to the western part.
Early Miocene volcanism
Bream Head is a remnant of one of the many Miocene volcanoes in the Northland Arc
A subduction-related volcanic belt became active to the west of the current land in Northland in Miocene times[2] (23 Ma), and gradually moved south down to Taranaki. It produced mainly andesiticstratovolcanoes. Most of these volcanoes have been eroded, but remnants form the Waipoua Plateau (basaltic, 19–18 Ma), and Waitākere Ranges (andesitic, 22–16 Ma).
An eastern volcanic belt formed mainly andesitic volcanoes around Karikari (22.3–19.8 Ma), Whangaroa (20.5–17.5 Ma), Whangarei Heads (21.5–16.1 Ma), Bream Head, and created the Hen and Chicken Islands (19.5–16.5 Ma).
Waitemata sandstone
Miocene volcanoes and the Northland Allochthon eroded to form the Waitemata sandstone, between Whangarei and Auckland, on the eastern side of Northland.[5]
Uplift
By middle Miocene, Northland was uplifted above sea level, with a slight westward tilt,[6] exposing basement rocks on the eastern side, and resulting in a tendency for rivers to flow in a westerly direction.
Recent basaltic volcanism
Intra-plate basaltic volcanism has occurred in Northland from late Miocene to Quaternary times. The Kerikeri volcanic group covered the area from Kaikohe, Kerikeri, to Whangarei. Activity began about 9 Ma, and the youngest cones are probably only tens of thousands of years old.
Little Barrier Island is the emergent part of a large dacitic-rhyodacitic stratovolcano, formed through two eruptive periods (3 Ma, and 1.6–1.2 Ma).[7]
Coastal dunes
Satellite photo of the Aupouri Peninsula, which connects former islands including Cape Reinga with the rest of the North Island
The coastal barriers north and south of the entry to the Kaipara Harbour, are essentially consolidated sand dunes, built up over the last few million years. Similar dunes have formed in the north from Ahipara to Cape Reinga, connecting what used to be isolated islands to the rest of the North Island, thus creating a large tombolo.[8][9] Sand on the eastern coast tends to be more pure quartz, and appears white.
Copper has been mined at Kaeo, silver, gold and mercury at Puhipuhi, and antimony at Russell.
Coal has been mined at Kawakawa, Hikurangi,[11] Kamo[3] and Kiripaka.
The Northland Basin, to the west of the Northland Peninsula is considered as having potential for oil and gas.
Halloysite clay is mined at Matauri Bay and Mahimahi.[12]
High quality quartz sand is dredged from near Parengarenga Harbour.
Geological hazards
The main geological hazard in Northland is the potential for landslides, particularly in mudstones and sandstones of the Northland Allochthon. Northland has the least incidence of earthquakes of anywhere in New Zealand. Volcanic activity is dormant rather than extinct.[13] However, tsunamis generated by earthquakes around the Pacific can occur on the east coast.[14]
Geological sites of interest
Hunua Terrane can be seen along much of the coast between the Bay of Islands and Whangarei. Mount Camel Terrane can be seen at Parerake Bay, Karikari Peninsula.[8]
Kamo coal measures can be seen near Kamo. Whangarei Limestone can be seen at Waro Rocks Scenic Reserve, north of Hikurangi.
Many of the hills in Northland are formed from the Tangihua Complex rocks of the Northland Allochthon.
Maungaraho, north of Tokatoka, gives a good example of a remnant of an early Miocene andesitic volcano. Whangarei Heads represents another example.
Sand dunes can be seen on either side of the coast between Kaitaia and Cape Reinga.[8]
Maps
Geological maps of New Zealand are now freely accessible on line from the New Zealand Institute of Geological and Nuclear Science (GNS Science), a New Zealand Government Research Institute. [15]
There is also a 1: 25 000 map of the Whangarei Urban Area, published in 2003.[16]
Whangārei is the northernmost city in New Zealand and the regional capital of Northland Region. It is part of the Whangarei District, a local body created in 1989 from the former Whangārei City, Whangārei County and Hikurangi Town councils, to administer both the city proper and its hinterland. The city population was estimated to be 56,900 in June 2023, an increase from 47,000 in 2001.
Hurupaki Mountain is in Kamo, Whangārei, New Zealand. The centre of Hurupaki Mountain lies between Three Mile Bush Road and Dip Road, approximately 1.5 kilometres west of Kamo township. Hurupaki Mountain is visible from State Highway 1.
The volcanism of New Zealand has been responsible for many of the country's geographical features, especially in the North Island and the country's outlying islands.
Hikurangi is a settlement in Northland, New Zealand. The city of Whangārei is 17 km (11 miles) to the south, and Kawakawa is 39 km (24 miles) northwest. The Glenbervie Forest is southeast of the settlement. State Highway 1 once passed through the town, but now bypasses it to the west. Mount Hikurangi is a volcanic dome rising 365 metres (1,198 ft) to the west of the town. It is 1.2 million years old, and part of the Harbour Fault which also includes Parakiore, near Kamo, and Parihaka in Whangarei.
The geology of New Zealand is noted for its volcanic activity, earthquakes and geothermal areas because of its position on the boundary of the Australian Plate and Pacific Plates. New Zealand is part of Zealandia, a microcontinent nearly half the size of Australia that broke away from the Gondwanan supercontinent about 83 million years ago. New Zealand's early separation from other landmasses and subsequent evolution have created a unique fossil record and modern ecology.
The Auckland Region of New Zealand is built on a basement of greywacke rocks that form many of the islands in the Hauraki Gulf, the Hunua Ranges, and land south of Port Waikato. The Waitākere Ranges in the west are the remains of a large andesitic volcano, and Great Barrier Island was formed by the northern end of the Coromandel Volcanic Zone. The Auckland isthmus and North Shore are composed of Waitemata sandstone and mudstone, and portions of the Northland Allochthon extend as far south as Albany. Little Barrier Island was formed by a relatively isolated andesitic volcano, active around 1 to 3 million years ago.
The Waikato and King Country regions of New Zealand are built upon a basement of greywacke rocks, which form many of the hills. Much of the land to the west of the Waikato River and in the King Country to the south has been covered by limestone and sandstone, forming bluffs and a karst landscape. The volcanic cones of Karioi and Pirongia dominate the landscape near Raglan and Kawhia Harbours. To the east, the land has been covered with ignimbrite deposits from the Taupō Volcanic Zone. Large amounts of pumice from the Taupō Volcanic Zone have been deposited in the Waikato Basin and Hauraki Plains.
The Taranaki Region of New Zealand is built upon the Median Batholith in the West, and Greywacke Rocks in the East. However, no rocks older than Miocene times are visible at the surface. The dominant feature of the Taranaki Region is the andesitic stratovolcano of Mount Taranaki, which is only about 130,000 years old. The dissected hill country to the East of the Taranaki Peninsula, and West of the Central Volcanic Plateau is composed of soft Miocene to Pleistocene sandstone and mudstone. The coastal lowlands around Wanganui to the South have well-developed Quaternary marine terraces, and coastal sand dunes.
The Raukumara Region of New Zealand corresponds to the East Cape of the North Island, and associated mountain ranges.
Canterbury in New Zealand is the portion of the South Island to the east of the Southern Alps / Kā Tiritiri o te Moana, from the Waiau Uwha River in the north, to the Waitaki River in the south.
The Tasman Region, and the small adjoining Nelson Region, form one of the more geologically interesting regions of New Zealand. It contains the oldest rocks of anywhere on New Zealand's main islands. It contains all the main terranes that make up New Zealand's basement. These basement rocks include Ultramafic rocks, such as Serpentine and Dunite, and valuable minerals, such as Gold. The Nelson Region is bordered to the south by the Alpine Fault, the main fault forming the boundary between the Pacific Plate and the Indo-Australian Plate, that generated the Southern Alps.
The recently active basaltic Kaikohe-Bay of Islands volcanic field in the Northland Region of New Zealand is associated geographically with an older region of extinct volcanism to its north the Wairakau Volcanic Centre, meaning eruptions in this region have occurred over the last 20 million years. All the cones older than 2 million years have eroded away, leaving plateaus from Ōkaihau to Kerikeri and north to Whangaroa from the old andesite/dacite stratovolcanoes of the Wairakau Volcanic Centre and the ten million year old or more recent volcanoes in field towards the south. In the southern part of the field, around 12 small basaltic scoria cones, and a rhyolite dome erupted in the last 500,000 years around Kaikohe. The field is considered dormant, rather than extinct.
This is a list of the units into which the rock succession of New Zealand is formally divided. As new geological relationships have been discovered new names have been proposed and others are made obsolete. Not all these changes have been universally adopted. This table is based on the 2014 New Zealand Stratigraphic Lexicon (Litho2014). However, obsolete names that are still in use and names postdating the lexicon are included if it aids in understanding.
The Banks Peninsula Volcano is an extinct volcanic complex to the east of Christchurch on New Zealand's South Island. While the volcano is highly eroded it still forms the majority of Banks Peninsula with a highest point of 919 m (3,015 ft). It is a composite of two main eruptive centres one originating at Lyttelton Harbour, the other at Akaroa Harbour. The eruptions were predominantly basaltic, with associated andesite and trachytes, with minor rhyolite. The volcanic activity occurred in the Late Miocene and possibly extended into the Early Pliocene. There are four volcanic groups, all of which are within the Māui Supergroup. The Christchurch earthquakes led to rumors of a possible eruption, however, there is no known magma chamber beneath the volcano and there has not been any sign of volcanic activity in the last 5 million years.
The Waitemata Group is an Early Miocene geologic group that is exposed in and around the Auckland Region of New Zealand, between the Whangarei Harbour in the North and the Raglan Harbour in the South. The Group is predominantly composed of deep water sandstone and mudstone (flysch). The sandstone dominated units form the cliffs around the Waitemata Harbour and rare more resistant conglomerates underlie some of Auckland's prominent ridges.
The Waitākere volcano, also known as the Manukau volcano, was a Miocene era volcano that formed off the west coast of the modern Auckland Region of New Zealand's North Island. Erupting intermittently between 23 million and 15 million years ago, the volcano was at one point one of the tallest mountains in New Zealand. The volcano alternated between periods as a seamount and as a volcanic island, before tectonic forces raised the volcano up from the seafloor 17 million years ago. Volcanism at the site ceased 15 million years ago and the cone has mostly eroded, however the modern Waitākere Ranges are formed from the remnants of the volcano's eastern slopes. A number of visible volcanic sites associated with the Waitākere volcano remain around Auckland, including Pukematekeo, Karekare and Lion Rock.
The South Auckland volcanic field, also known as the Franklin Volcanic Field, is an area of extinct monogenetic volcanoes around Pukekohe, the Franklin area and north-western Waikato, south of the Auckland volcanic field. The field contains at least 82 volcanoes, which erupted between 550,000 and 1,600,000 years ago.
The Auckland regional geologic faults have low seismic activity, compared to much of New Zealand, but do result in an earthquake risk to the Auckland metropolitan area, New Zealand's largest city. There is also evidence of past tectonic, volcanic associations in a city located within what is, at best, a very recently dormant Auckland volcanic field.
The Whangārei volcanic field is an area of intra-plate monogenetic volcanism located near the city of Whangārei, North Island, New Zealand. It was last active between 260,000 to 319,000 years ago and continues to be potentially active as a low-velocity seismic zone in the crust exists beneath Whangārei, which is interpreted to be a body of partial melt. This mantle source has been coupled to the lithosphere for about 8 million years. As the field has potentially been active at low frequency for millions of years, with 100,000 years or more between events it might best be regarded as dormant. The recent vents active in the last million years include some dacite in composition. Composition details are freely available for most of the field but many vents do not have ages.
Much of the volcanic activity in the northern portions of the North Island of New Zealand is recent in geological terms and has taken place over the last 30 million years. This is primarily due to the North Island's position on the boundary between the Indo-Australian and Pacific Plates, a part of the Pacific Ring of Fire, and particularly the subduction of the Pacific Plate under the Indo-Australian Plate. The activity has included some of the world's largest eruptions in geologically recent times and has resulted in much of the surface formations of the North Island being volcanic as shown in the map.
1 2 3 4 5 Spörli, K.B. and Hayward, B.W. (2002). Geological overview of NorthlandArchived 22 May 2010 at the Wayback Machine , pp. 3–10 in Smith, V. and Grenfell, H.R. (editors) (2002): Fieldtrip Guides, Geological Society of New Zealand Annual Conference “Northland 2002”, Geological Society of NZ Miscellaneous Publication 112B, 116 pp. ISBN0-908678-90-8. Accessed 23 May 2010.
1 2 Claudia Orange. Northland places – Kamo, Te Ara – the Encyclopedia of New Zealand. Updated 20 November 2009. Retrieved 3 June 2010.
↑ Edbrooke, S.W. (compiler) (2001). Geology of the Auckland Area, p. 39. Lower Hutt: GNS Science. ISBN0-478-09714-X.
1 2 3 Black, Philippa and Gregory, Murray (2002). Field trip 9: Geological gems of the Far NorthArchived 22 May 2010 at the Wayback Machine , in Smith, V. and Grenfell, H.R. (editors) (2002): Fieldtrip Guides, Geological Society of New Zealand Annual Conference “Northland 2002”, Geological Society of NZ Miscellaneous Publication 112B, 116 pp. ISBN0-908678-90-8. Accessed 23 May 2010.
Graham, Ian J. et al. (2008). A continent on the move: New Zealand geoscience into the 21st century. The Geological Society of New Zealand in association with GNS Science. ISBN978-1-877480-00-3
Hayward, Bruce W. (2017). Out of the Ocean, into the Fire: History in the rocks, fossils and landforms of Auckland, Northland and Coromandel. Geoscience Society of New Zealand. ISBN9780473395964.
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