The Southland Syncline is a major geological structure located in the

Southland Region Southland ( mi, Murihiku) is New Zealand's southernmost region. It consists mainly of the southwestern portion of the South Island and Stewart Island/Rakiura. It includes Southland District, Gore District and the city of Invercargill. The r ...

New Zealand's New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island country b ...

South Island. The

syncline In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimpose ...

folds the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

greywackes of the

Murihiku Terrane The Southland Syncline is a major geological structure located in the Southland Region of New Zealand's South Island. The syncline folds the Mesozoic greywackes of the Murihiku Terrane. The northern limb of the fold is steep to overturned, while ...

. The northern limb of the fold is steep to overturned, while the southern limb dips shallowly to the northeast. The axial plan dips to the northeast and the axis plunges to the southeast. The Murihiku Terrane is formed predominantly from

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

sedimentary rocks with minor igneous intrusions, and is marked by prominent strike ridges particularly on its northern limb due to the steeper dip. These are created from the erosion of alternating strata of sandstone and mudstone. The northern edge of this fold system is marked by the Murihiku Escarpment, at the southern extreme of the Waimea Plains. Many of the names of

stages Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * S ...

and

epochs In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

in the Permian, Triassic, and Jurassic periods in the

New Zealand geologic time scale While also using the international geologic time scale, many nations–especially those with isolated and therefore non-standard prehistories–use their own systems of dividing geologic time into epochs and faunal stages. In New Zealand, these epo ...

are named for places within or close to the Southland Syncline and Murihiku Terrane. The ridges run northwest from the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

coast in

the Catlins The Catlins (sometimes referred to as The Catlins Coast) comprises an area in the southeastern corner of the South Island of New Zealand. The area lies between Balclutha and Invercargill, straddling the boundary between the Otago and Southlan ...

to the Takitimu Range, and includes the

Hokonui Hills The Hokonui Hills, also known as ''The Hokonui Mountains'' or simply ''The Hokonui'', are a range of hills in central Southland, New Zealand. They rise to 600 metres above the surrounding Southland Plains, of which the hills mark a northern extre ...

, which rise above the otherwise flat land of the

Southland Plains The Southland Plains is a general name given to several areas of low-lying land in the South Island of New Zealand, separated by the rise of the Hokonui Hills in the north. It forms a sizeable area of Southland region and encompasses its two pr ...

(to the south) and Waimea Plains (to the north). The syncline dates from the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

, though the Hokonui Hills are caused by more recent uplift. In the west, the syncline meets the country's largest fault system, the

Alpine Fault The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island (c. 480 km) and forms the boundary between the Pacific Plate and the Indo-Australian Plate. The Southern Alps have been uplifted on the fa ...

. This fault is a

transform fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subductio ...

for much of its length, and as such the westernmost part of the Southland Syncline is not found in the

, but continues several hundred kilometres to the north in the Nelson-Tasman area. The same fold is found as far north as the

Auckland Region Auckland () is one of the sixteen regions of New Zealand, which takes its name from the eponymous urban area. The region encompasses the Auckland Metropolitan Area, smaller towns, rural areas, and the islands of the Hauraki Gulf. Containing ...

where it is called the Kaimango Syncline.

Notes

References

* * * * * *{{cite book , ref={{sfnRef, Turnbull & Allibone, 2003, last1=Turnbull , first1=Ian M. , last2=Allibone , first2=Andrew Harold , date=2003 , title=Geology of the Murihiku area , location=Wellington , publisher= New Zealand Institute of Geological and Nuclear Sciences , isbn=0-478-09800-6 Geography of Southland, New Zealand Geology of New Zealand Geologic formations of New Zealand

See also

Notes

References