{{Short description|Terrane found in New Zealand}} {{Infobox rockunit | name = Torlesse composite terrane | image = Aoraki (Mount Cook) from Hooker Glacier Lake.jpg | caption = View of Torless composite terrane at [[Aoraki / Mount Cook]] | type = [[Terrane]] | age = [[Carboniferous]]-[[Cretaceous]]<br>~{{fossil range|320|130}}<!--rough range, needs to be refined--> | period = Mesozoic | prilithology = [[Greywacke]], [[schist]], [[basalt]] | otherlithology = | namedfor = [[Torlesse Range]] | namedby = | region = [[Canterbury, New Zealand|Canterbury]], [[Marlborough region|Marlborough]] & [[Otago region]]s | country = New Zealand | coordinates = | unitof = [[Stratigraphy of New Zealand#Basement rocks (Austral superprovince)|Austral superprovince]] | subunits = [[Kaweka terrane|Kaweka]], [[Rakaia terrane|Rakaia]] & [[Pahau terrane]]s, [[Esk Head Belt]], [[Pahaoa Group|Pahaoa]] & [[Clent Hills Group]]s | underlies = [[Caples terrane]], [[Momotu Supergroup|Momotu]], [[Waka Supergroup|Waka]] & [[Haerenga Supergroup]]s | overlies = | thickness = | extent = | area = | map = Cross Section New Zealand geology.jpg | map_caption = Cross-section of New Zealand's stratigraphy }}
The '''Torlesse composite terrane''' is a plate tectonic [[terrane]] forming part of the [[South Island]] of New Zealand. It contains the Rakaia, Aspiring and Pahau terranes and the Esk Head Belt.<ref>{{cite web |url=https://data.gns.cri.nz/ |title= New Zealand Stratigraphic Lexicon |last= |first= |date=|website= |publisher=GNS Science |access-date=|quote=}}</ref> [[Greywacke]] (or '''Torlesse Greywacke''') is the dominant rock type of the composite terrane; [[argillite]] is less common and there are minor basalt occurrences. The Torlesse composite terrane is found east of the [[Alpine Fault]] in the [[Southern Alps (New Zealand)|Southern Alps]] of New Zealand. Its southern extent is a cryptic boundary with the [[Caples terrane]] within the [[Haast Schist]]s in Central Otago.<ref>{{cite web |url= https://www.geotrips.org.nz/downloads/Ballance_NZ_Geology-V2.pdf |title= New Zealand Geology: an illustrated guide |website= www.geotrips.org.nz}}</ref> It is named for the Torlesse Range in [[Canterbury, New Zealand|Canterbury]].
== Description == The Rakaia terrane rocks, of Permian to late Triassic age (300–200 Ma), occur south of [[Rangiora]]. The Pahau terrane rocks, of [[Late Jurassic]] to [[Early Cretaceous]] age (160–100 Ma), occur to the north, and are probably derived from the Rakaia terrane. At the boundary between these two terranes is the Esk Head Belt, an {{convert|11|km|mi|abbr=|adj=on}} wide [[mélange]] of broken and deformed rocks. The Aspiring terrane (Aspiring lithologic association) is officially included within the Torlesse composite terrane; however, it has a higher proportion of igneous rocks and a different sedimentary source.<ref name="JugumNorris2013">{{cite journal|last1=Jugum|first1=D|last2=Norris|first2=RH|last3=Palin|first3=JM|title=Late Jurassic detrital zircons from the Haast Schist and their implications for New Zealand terrane assembly and metamorphism|journal=New Zealand Journal of Geology and Geophysics|volume=56|issue=4|year=2013|pages=223–228|issn=0028-8306|doi=10.1080/00288306.2013.815639|bibcode=2013NZJGG..56..223J|s2cid=128551272|doi-access=free}}</ref> Its original relationship with the Rakaia terrane is obscured by the Haast Schist.
== Deposition == The greywacke of the Torlesse composite terrane was deposited on the eastern side of New Zealand from the [[Late Carboniferous]] through to the Middle [[Cretaceous]]. It was deposited in giant [[deep sea fan]]s that extended beyond the ends of ancient submarine canyons. A fan starts with a [[submarine canyon]] on the [[continental shelf]]. Then [[turbidity current]]s rush down the canyon like giant undersea avalanches. They carry all sorts of sediments from the shallower [[seafloor]] of the continental shelf. At the end of the canyon the turbidity current spreads out and creates giant fans of sediment that blanket the deep seafloor. These sediments may have derived in part from the [[granite|granitic]] rocks of northeastern [[Australia]], as suggested by studies of the mineral grains.<ref>{{Cite web|url=http://www.teara.govt.nz/en/geology-overview/page-4|title=Building a continent – Te Ara Encyclopedia of New Zealand}}</ref>
== Metamorphism == The Torlesse composite terrane has undergone [[metamorphism]] and been transformed into Haast Schist. In the Haast Schists, the [[mineral]]s that make up greywacke became coarser grained and altered to other minerals including quartz, feldspar and biotite.<ref>{{cite web |url=https://www.gns.cri.nz/Home/Our-Science/Earth-Science/Regional-Geology/The-Geology-of-New-Zealand/Stratigraphy/Greywacke |last= |first= |date=|website=www.gns.cri.nz| title=The Geology of New Zealand: Greywacke |publisher=GNS Science |access-date=|quote=}}</ref> Rare pods of [[pounamu]] ([[jade]]) are found in the higher metamorphic grades near the Alpine Fault.<ref name="CooperIreland2015">{{cite journal|last1=Cooper|first1=Alan F.|last2=Ireland|first2=Trevor R.|title=The Pounamu terrane, a new Cretaceous exotic terrane within the Alpine Schist, New Zealand; tectonically emplaced, deformed and metamorphosed during collision of the LIP Hikurangi Plateau with Zealandia|journal=Gondwana Research|volume=27|issue=3|year=2015|pages=1255–1269|issn=1342-937X|doi=10.1016/j.gr.2013.11.011|bibcode=2015GondR..27.1255C}}</ref>
==Fossil content== * ''[[Torlessia]]''<ref name="auto">{{Cite journal | url=https://paperspast.natlib.govt.nz/periodicals/TRSGEO19650722.2.2 | title=Fossil Localities of the Torlesse Group in the South Island | author1=J. D. Campbell | author2=Guyon Warren | journal=Transactions of the Royal Society of New Zealand: Geology | volume=3 | issue=8 | date=1965-07-22 | page=99}}</ref> * ''[[Monotis]]''<ref name="auto"/> * [[Hector's Ichthyosaur]]<ref>{{cite web | url=https://icebergdb.com/hectors-ichthyosaurtrue-organism-size-parameters-2/ | title=Hectors Ichthyosaur(True Organism Size Parameters) | date=29 March 2022 }}</ref> * [[Nothosaur]]<ref>{{cite web | url=https://sci.waikato.ac.nz/evolution/FossilEvidence.shtml | title=Fossil Evidence }}</ref> * [[Conodont]]<ref>{{Cite web|url=https://teara.govt.nz/en/fossils/page-2|title=Oldest fossils – Paleozoic – Te Ara Encyclopedia of New Zealand}}</ref>
== See also == * [[Geology of the Canterbury region]] * [[Geology of the Tasman District]] * [[Stratigraphy of New Zealand]] ** [[Takaka terrane]] ** [[Dun Mountain–Maitai terrane]]
== References == {{Reflist}}
== Further reading == * The Rise and Fall of the Southern Alps, G. Coates published 2002
[[Category:Terranes]] [[Category:Geologic formations of New Zealand]] [[Category:Paleozoic Oceania]] [[Category:Jurassic System of Oceania]] [[Category:Cretaceous System of Oceania]] [[Category:Geography of the Canterbury Region]] [[Category:Geography of the Marlborough District]] [[Category:Geography of Otago]]