Geology of the Waikato-King Country Region
Encyclopedia
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 Taupo Volcanic Zone
. Large amounts of pumice
from the Taupo Volcanic Zone have been deposited in the Waikato Basin and Hauraki Plains
.
, siltstone
and mudstone
).
The Waipa Fault passes north–south through the Waikato-King Country region, from Taupiri
, along the Waipa River
, and south to near Ohura
. It represents a major dividing line between different terrane
s.
Murihiku Terrane greywacke lies beneath the Waikato-King Country region on the western side, and outcrops to the west of the Waipa Fault, from south of Waikato Heads
to Awakino
. The Murihiku Terrane is considered to be an accretionary wedge of mainly volcanogenic forearc
sediments. It was formed in Late Triassic
to Late Jurassic
times (220-145 Ma).
A line of Maitai-Dun Mountain Terrane rocks are assumed to pass north–south along the Waipa Fault, through the centre of the Waikato-King Country region, separating the Murihiku Terrane and Waipapa Composite Terrane, and produce a detectable junction magnetic anomaly
, but only outcrops at one place, at Wairere. Some Murihiku rocks occur to the east of the junction magnetic anomaly, forming the Taupiri and Hakarimata
Ranges, but it is assumed that these rocks have been shifted to their present position.
The Waipapa Morrinsville Terrane greywacke lies beneath the Waikato-King Country region on the eastern side, south of the Hunua Ranges
, and east of the Waipa Fault. It was formed in Late Jurassic to Early Cretaceous
times (160-120 Ma).
, 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 sunk and the sea transgressed, and calcareous
sandstone, mudstone, and limestone were deposited in Oligocene
times (34-24 Ma).
The coal deposits outcrop near Huntly
and Maramarua, where they are mined.
Limestone exists in the area south and west of the Waikato River
, down to Piopio
and Te Kuiti
, producing impressive bluffs around Port Waikato, Raglan Harbour, Kawhia Harbour, Otorohanga, Waitomo, Te Kuiti, etc. The Karst landscape around Waitomo contains many cave systems, including the Waitomo Glowworm Cave
.
times (14-11 Ma), and contributed to the sandstone and mudstone deposits that formed around that time.
, near Raglan and Kawhia Harbours, are large stratovolcano
es composed of andesite
and basalt
, that erupted about 2.5 Ma ago. Other volcanoes in this group include Kakepuku, Te Kawa, and Tokanui
.
Maungatautari, west of Te Awamutu, is a volcano, composed of andesite and dacite
, that erupted about 1.8 Ma.
have deposited ignimbrite
s over the area East of Te Kuiti. Some of the largest deposits are from the Whakamaru eruption, north of Taupo, around 330,000 years ago. The ignimbrite deposits from the Oruanui eruption 26,500 years ago, and the Taupo eruption, 1800 years ago are also major deposits. They form impressive cliffs in many areas.
The Hauraki Plains
and Hauraki Gulf
are believed to represent a rift valley
. The rift valley is assumed to have developed about 2 Ma ago, due to the clockwise rotation of the Eastern North Island, that stretched the land between Auckland and East Cape. The Waikato River used to flow from Lake Karapiro
, through the Hinuera Gap, and Hauraki Plains, to come out on the east coast in the Hauraki Gulf. The sediment from the 26.5 ka Oruanui eruption
of Lake Taupo
caused the river to change direction, and come out to the west. In fact, the Waikato River changes its route quite regularly, as eruptions occur in the Taupo Volcanic Zone, and the river channel becomes blocked. Many lakes and swamps in the Waikato Basin represent old routes.
Pumice from the Taupo Volcanic Zone has been deposited throughout the Waipa and Waikato Basins, and the Hauraki Plains, forming excellent soils and swampland.
Harbours.
GNS provides a free Map of New Zealand's Geological Foundations.GNS Map of New Zealand's Geological Foundations
The main maps are the 1 : 250 000 QMap series, which will be completed as a series of 21 maps and booklets in 2010. Low resolution versions of these maps (without the associated booklet) can be downloaded from the GNS site for free. The map for the Waikato Area was published in 2005.
King Country
The King Country is a region of the western North Island of New Zealand. It extends approximately from the Kawhia Harbour and the town of Otorohanga in the north to the upper reaches of the Whanganui River in the south, and from the Hauhungaroa and Rangitoto Ranges in the east to near the Tasman...
regions of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
are built upon a basement of greywacke
Greywacke
Greywacke or Graywacke is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found...
rocks, which form many of the hills. Much of the land to the west of the Waikato River
Waikato River
The Waikato River is the longest river in New Zealand. In the North Island, it runs for 425 kilometres from the eastern slopes of Mount Ruapehu, joining the Tongariro River system and emptying into Lake Taupo, New Zealand's largest lake. It drains Taupo at the lake's northeastern edge, creates the...
and in the King Country to the south has been covered by limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
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
Ignimbrite
An ignimbrite is the deposit of a pyroclastic density current, or pyroclastic flow, a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere....
deposits from the Taupo Volcanic Zone
Taupo Volcanic Zone
The Taupo Volcanic Zone is a highly active volcanic V shaped area in the North Island of New Zealand that is spreading east -west at the rate of about 8mm per year...
. Large amounts of pumice
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
from the Taupo Volcanic Zone have been deposited in the Waikato Basin and Hauraki Plains
Hauraki Plains
The Hauraki Plains are a geographical feature and non-administrative area located in the northern North Island of New Zealand, at the lower end of the Thames Valley...
.
Basement rocks
As with most of New Zealand, the basement rocks of the Waikato Region and King Country are composed of greywacke (indurated sandstoneSandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
, siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
and mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
).
The Waipa Fault passes north–south through the Waikato-King Country region, from Taupiri
Mount Taupiri
Mount Taupiri is a sacred mountain and burial place for the Tainui Māori People based in the Waikato in the town of Taupiri.Taupiri is a small township on State Highway 1 and the Waikato River north of the town of Ngaruawahia and south of Huntly in the Waikato Region...
, along the Waipa River
Waipa River
The Waipa River is in the Waikato region of the North Island of New Zealand. The headwaters are in the Rangitoto Range east of Te Kuiti. It flows north for 115 kilometres, passing through Otorohanga and Pirongia, before flowing into the Waikato River at Ngaruawahia...
, and south to near Ohura
Ohura
Ohura is a small town in the west of the North Island of New Zealand. It is located to the west of Taumarunui in the area known as the King Country, in inland Manawatu-Wanganui...
. It represents a major dividing line between different terrane
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
s.
Murihiku Terrane greywacke lies beneath the Waikato-King Country region on the western side, and outcrops to the west of the Waipa Fault, from south of Waikato Heads
Port Waikato
Port Waikato is on the south bank of the Waikato River at its outflow into the Tasman Sea, in northern New Zealand. Now a small town with a population of under 300, it was an important port during the New Zealand Land Wars of the 19th century...
to Awakino
Awakino
Awakino is a settlement in the south of Waitomo District, in the North Island of New Zealand. It is located on State Highway 3 at the mouth of the Awakino River, five kilometres north of Mokau. It is 79 km southwest of Te Kuiti, and 98 km northeast of New Plymouth.North of Awakino, State...
. The Murihiku Terrane is considered to be an accretionary wedge of mainly volcanogenic forearc
Forearc
A forearc or forarc, also called arc-trench gap is a depression in the sea floor located between a subduction zone and an associated volcanic arc. It is typically filled with sediments from the adjacent landmass and the island arc in addition to trapped oceanic crustal material...
sediments. It was formed in Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
to Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
times (220-145 Ma).
A line of Maitai-Dun Mountain Terrane rocks are assumed to pass north–south along the Waipa Fault, through the centre of the Waikato-King Country region, separating the Murihiku Terrane and Waipapa Composite Terrane, and produce a detectable junction magnetic anomaly
Magnetic anomaly
In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying material...
, but only outcrops at one place, at Wairere. Some Murihiku rocks occur to the east of the junction magnetic anomaly, forming the Taupiri and Hakarimata
Hakarimata Range
Hakarimata Range is the name of the hills on the western edge of Ngaruawahia township in the Waikato region of New Zealand, lying along the Waikato River and Waipa River....
Ranges, but it is assumed that these rocks have been shifted to their present position.
The Waipapa Morrinsville Terrane greywacke lies beneath the Waikato-King Country region on the eastern side, south of the Hunua Ranges
Hunua Ranges
The Hunua Ranges form a block of hilly country to the southeast of Auckland in New Zealand's North Island. They cover some 250 square kilometres , containing 178 km² of parkland, and rise to 688 metres at Kohukohunui...
, and east of the Waipa Fault. It was formed in Late Jurassic to Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
times (160-120 Ma).
Te Kuiti Group coal and limestone
The Te Kuiti Group rocks overlie the basement rocks, and are present in Northland, AucklandAuckland
The Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...
, 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 sunk and the sea transgressed, and calcareous
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
sandstone, mudstone, and limestone were deposited in Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
times (34-24 Ma).
The coal deposits outcrop near Huntly
Huntly, New Zealand
Huntly is a town in the Waikato region of the North Island of New Zealand. It is on State Highway 1, 93 kilometres south of Auckland and 35 kilometres north of Hamilton. It is situated on the North Island Main Trunk Railway and straddles the Waikato River.Huntly was called Rahui Pokeka when...
and Maramarua, where they are mined.
Limestone exists in the area south and west of the Waikato River
Waikato River
The Waikato River is the longest river in New Zealand. In the North Island, it runs for 425 kilometres from the eastern slopes of Mount Ruapehu, joining the Tongariro River system and emptying into Lake Taupo, New Zealand's largest lake. It drains Taupo at the lake's northeastern edge, creates the...
, down to Piopio
Piopio, New Zealand
Piopio is a small town in the Waitomo District. Situated on State Highway 3 approximately 23km from Te Kuiti.-External links:* *...
and Te Kuiti
Te Kuiti
Te Kuiti is a small town in the south of the Waikato region of the North Island of New Zealand. It lies at the junction of State Highways 3 and 30 and on the North Island Main Trunk Railway, 80 km south of Hamilton....
, producing impressive bluffs around Port Waikato, Raglan Harbour, Kawhia Harbour, Otorohanga, Waitomo, Te Kuiti, etc. The Karst landscape around Waitomo contains many cave systems, including the Waitomo Glowworm Cave
Waitomo Glowworm Cave
The Waitomo Glowworm Caves attraction is a cave at Waitomo on the North Island of New Zealand, known for its population of glowworms, Arachnocampa luminosa. These glowworms are found exclusively in New Zealand and around the size of an average mosquito...
.
Miocene sediment
In early Miocene times (24 Ma), plate convergence caused regional compression. The land eroded, and was deposited throughout the Miocene (24-5 Ma) in rapidly subsiding basins. These soft sandstones and mudstones remain to the southwest of Te Kuiti.Mohakatino Volcanic Arc
The volcanic arc that developed to the west of Northland and Auckland extended further south towards Taranaki. These andesitic and basaltic volcanoes were mostly active in middle MioceneMiocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
times (14-11 Ma), and contributed to the sandstone and mudstone deposits that formed around that time.
Recent volcanic activity
Karioi and PirongiaPirongia
Pirongia is a small town in the Waipa District of the Waikato region of New Zealand's North Island.It is 12 kilometres to the west of Te Awamutu, on the banks of the Waipa River, close to the foot of the 962 metre Mount Pirongia, which lies in a forest park to the west of the town.Pirongia was...
, near Raglan and Kawhia Harbours, are large stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
es composed of andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
and basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
, that erupted about 2.5 Ma ago. Other volcanoes in this group include Kakepuku, Te Kawa, and Tokanui
Tokanui
Tokanui is a community in the eastern portion of Southland District Council, located on the Southern Scenic Route about 55 km east of Invercargill and 109 km southwest of Balclutha, New Zealand....
.
Maungatautari, west of Te Awamutu, is a volcano, composed of andesite and dacite
Dacite
Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...
, that erupted about 1.8 Ma.
Ignimbrite and pumice deposits
Over the last 2 million years, pyroclastic flows from the Taupo Volcanic ZoneTaupo Volcanic Zone
The Taupo Volcanic Zone is a highly active volcanic V shaped area in the North Island of New Zealand that is spreading east -west at the rate of about 8mm per year...
have deposited ignimbrite
Ignimbrite
An ignimbrite is the deposit of a pyroclastic density current, or pyroclastic flow, a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere....
s over the area East of Te Kuiti. Some of the largest deposits are from the Whakamaru eruption, north of Taupo, around 330,000 years ago. The ignimbrite deposits from the Oruanui eruption 26,500 years ago, and the Taupo eruption, 1800 years ago are also major deposits. They form impressive cliffs in many areas.
The Hauraki Plains
Hauraki Plains
The Hauraki Plains are a geographical feature and non-administrative area located in the northern North Island of New Zealand, at the lower end of the Thames Valley...
and Hauraki Gulf
Hauraki Gulf
The Hauraki Gulf is a coastal feature of the North Island of New Zealand. It has a total area of 4000 km², and lies between the Auckland Region, the Hauraki Plains, the Coromandel Peninsula and Great Barrier Island...
are believed to represent a rift valley
Rift valley
A rift valley is a linear-shaped lowland between highlands or mountain ranges created by the action of a geologic rift or fault. This action is manifest as crustal extension, a spreading apart of the surface which is subsequently further deepened by the forces of erosion...
. The rift valley is assumed to have developed about 2 Ma ago, due to the clockwise rotation of the Eastern North Island, that stretched the land between Auckland and East Cape. The Waikato River used to flow from Lake Karapiro
Lake Karapiro
Lake Karapiro is an artificial reservoir lake on the Waikato River in the North Island of New Zealand. The lake, near Cambridge and some south-east of the city of Hamilton, was created in 1947 to store water for the Karapiro Power Station, the last of the eight hydroelectric power stations on the...
, through the Hinuera Gap, and Hauraki Plains, to come out on the east coast in the Hauraki Gulf. The sediment from the 26.5 ka Oruanui eruption
Oruanui eruption
The Oruanui eruption of New Zealand's Taupo Volcano was the world's largest known eruption in the past 70,000 years, with a Volcanic Explosivity Index of 8...
of Lake Taupo
Lake Taupo
Lake Taupo is a lake situated in the North Island of New Zealand. With a surface area of , it is the largest lake by surface area in New Zealand, and the second largest freshwater lake by surface area in geopolitical Oceania after Lake Murray ....
caused the river to change direction, and come out to the west. In fact, the Waikato River changes its route quite regularly, as eruptions occur in the Taupo Volcanic Zone, and the river channel becomes blocked. Many lakes and swamps in the Waikato Basin represent old routes.
Pumice from the Taupo Volcanic Zone has been deposited throughout the Waipa and Waikato Basins, and the Hauraki Plains, forming excellent soils and swampland.
Coastal dunes
Substantial sand dunes with high iron content have formed around the Kawhia and AoteaAotea
Aotea can refer to:*Great Barrier Island*Aotea Square, a square in downtown Auckland*Aotea Harbour, a natural harbour in New Zealand*Aotea , traditional canoe by which some Māori settled New Zealand...
Harbours.
Geological sites worth visiting
- Hinuera Gap, State Highway 29, between Lake Karapiro and Matamata is the course of the Waikato River, before it changed to go through Hamilton. The cliffs on either side show how big the river was.
- Much of the Western hill country from Waikato Heads down to Te KuitiTe KuitiTe Kuiti is a small town in the south of the Waikato region of the North Island of New Zealand. It lies at the junction of State Highways 3 and 30 and on the North Island Main Trunk Railway, 80 km south of Hamilton....
contains interesting limestone countryside, with impressive bluffs. However, you need to take the small, unsealed roads to see much. - The Waitomo Area contains excellent examples of a Karst landscape, and several tourist caves, including the most famous Waitomo Glowworm CaveWaitomo Glowworm CaveThe Waitomo Glowworm Caves attraction is a cave at Waitomo on the North Island of New Zealand, known for its population of glowworms, Arachnocampa luminosa. These glowworms are found exclusively in New Zealand and around the size of an average mosquito...
. - The Raglan, Aotea, and Kawhia Harbours are worth a visit, especially the dissected hill country around Raglan formed on greywacke basement rocks, the limestone countryside, the sand dunes and beach near Kawhia, and Albatross Point west of Kawhia Harbour.
- Karioi and Pirongia volcanoes are well worth climbing, for those with sufficient fitness. A drive around Karioi has impressive scenery, especially the Te Toto Gorge.
- Wairere has the one outcrop of serpentine in the North Island.
- Mangpehi Mine, near Benneydale is an abandoned coal mine.
- The coastal highway down to Taranaki has rugged sandstone cliffs, and black sand beaches.
- The road from Te Kuiti through to Atiamuri has impressive Whakamaru Group welded ignimbrite cliffs.
Maps
Geological maps of New Zealand can be obtained from the New Zealand Institute of Geological and Nuclear Science (GNS Science), a New Zealand Government Research Institute.GNS provides a free Map of New Zealand's Geological Foundations.GNS Map of New Zealand's Geological Foundations
The main maps are the 1 : 250 000 QMap series, which will be completed as a series of 21 maps and booklets in 2010. Low resolution versions of these maps (without the associated booklet) can be downloaded from the GNS site for free. The map for the Waikato Area was published in 2005.
Further reading
- Graham, Ian J. et al.; A continent on the move : New Zealand geoscience into the 21st century - The Geological Society of New Zealand in association with GNS Science, 2008. ISBN 9781877480003