{{short description|Small tectonic plate located to the east of the island of New Guinea}} <!--much of text on this page as of 7th August 2023 is based on the same author's recent work in improving the page on Woodlark Basin in August 2023---> {{Infobox tectonic plate | image ={{maplink|frame=yes|frame-align=center|frame-width=280|frame-height=200|frame-long=153.7|frame-lat=-8|zoom=4|raw=[{{Wikipedia:Map data/Solomon Sea plate}},{{Wikipedia:Map data/New Britain subduction zone}}]|text={{Wikipedia:Map data/Solomon Sea plate/key}}, {{legend-line|blue solid 2px|Active trench subduction boundaries|inline=yes}}, {{legend-line|lightblue solid 2px|Inactive trench subduction boundaries|inline=yes}}, {{legend-line|yellow solid 3px|current spreading boundary|inline=yes}}. The Australian plate to the southeast and the Pacific plate to the northwest are not shown, but their complex collision has created these microplates. Click and then mouse over shows feature names.}} | alt = | type = microplate | move_direction = northeast | move_speed = 58 mm/year | geo_features = New Guinea, Pacific Ocean }} {{Annotated image | image = Coral Sea Topography.jpg | image-width = 1253<!--1,253 ----><!-- 1,253 × 776 pixels---> | image-left = -250 | image-top = -150 | width = 300 | height = 300 | float = right | annotations = {{Annotation |2|44|New Britain| text-align=left | font-size=16 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |110|138|Woodlark<br />Island| text-align=right | font-size=16 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |200|95|Solomon<br /> Islands| text-align=right | font-size=16 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |60|200|Louisiade Archipelago| text-align=left | font-size=16 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |80|260|{{colored link|#FFFFFF|Coral Sea Basin|Coral<br /> Sea<br />Basin}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}}
{{Annotation |202|135|W. P.| text-align=left | font-size=16 | font-weight=normal| font-family=Arial | background-color=| color=black}} {{Annotation |165|175|{{colored link|#FFFFFF|Woodlark Basin|Woodlark Basin}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color= }}
{{Annotation |50|0|{{colored link|#FFFFFF|Manus Basin|Manus<br />Basin}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color= }} {{Annotation |210|260|{{colored link|#FFFFFF|Louisiade Plateau|Louisiade<br />Plateau}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |220|0|{{colored link|#FFFFFF|Ontong Java Plateau|Ontong Java<br /> Plateau}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |80|54|{{colored link|#FFFFFF|New Britain Trench| Britain<br />New Trench}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |250|44|{{colored link|#FFFFFF|North Solomon Trough| North<br />Solomon<br /> Trough}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |30|145|{{colored link|#FFFFFF|Woodlark Rise|Woodlark Rise}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |0|195|{{colored link|#FFFFFF|Papuan Plateau|Papuan<br />Plateau}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |30|98|{{colored link|#FFFFFF|Trobriand Trough|Trobriand<br /> Trough}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |160|215|{{colored link|#FFFFFF|Pocklington Trough| Pock-<br /> lington<br />Trough}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |120|90|{{colored link|#FFFFFF|Solomon Sea|Solomon<br /> Sea}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} {{Annotation |100|215|{{colored link|#FFFFFF|Pocklinton Rise|Pocklinton Rise}}| text-align=left | font-size=12 | font-weight=normal| font-family=Arial | background-color=| color=}} | caption = Seafloor topographic map of area of Woodlark plate (W. P.) which is confined to the north of the Woodlark Basin's mid oceanic ridge.<ref name="Benyshek2021F2"/> The eastern part of the mid oceanic ridge boundary can be seen between the black label W.P, and the white label Woodlark Basin below it. }} The '''Woodlark plate''' is a small almost triangular shaped tectonic plate located east of the island of New Guinea and situated mainly within the northern half of the Woodlark Basin. It is located in a very complex tectonic environment, that because of associated features, has been extensively studied since it was first proposed to exist. It is now known to be much smaller than originally proposed, mainly because of information from GPS stations on islands and sea floor studies that have fully defined its margins.
==Tectonics== {{main|Woodlark Basin}} [[File:WoodlarkPlate.png|thumb|Woodlark plate as based on 2003 modelling<ref name="Bird2003"/> -it is now modelled as much smaller and essentially confined to the northern section of the Woodlark Basin.<ref name="Benyshek2021F2"/>]] The Woodlark plate was originally proposed to be somewhat larger than currently is believed to be the case.<ref name="Bird2003"/><ref name="Benyshek2021">{{Harvnb|Benyshek|Taylor|2021|loc=Abstract,9 Conclusions}}</ref> It is now suspected to have four active triple junctions, two of which are with the Australian plate to its south, based on areas of high seismic activity and other evidence.<ref name="Benyshek2021"/><ref name="USGS">{{cite web|url=https://earthquake.usgs.gov/earthquakes/eventpage/us6000kwy1/map?historic-seismicity=true&shakemap-intensity=false|title=USGS:Seismotectonics of the New Guinea Region and Vicinity:Historic Seismicity|access-date=6 August 2023}}</ref> As originally modelled it extended to the west along the east coast of New Guinea and was subducting beneath the Caroline plate along its northern border. This is no longer accepted to be the case, so that either the Solomon Sea plate,<ref name="Wallace2014">{{Harvnb|Wallace|Ellis|Little|Tregoning|2014|loc=Section:4 Interpretation of the GPS Results}}</ref><ref name="Boulart2022">{{Harvnb|Boulart|Rouxel|Scalabrin|Le Meur|2022|loc=Fig. 1: Regional map of the Woodlark Basin, Section:Introduction}}</ref> or a further plate called the Trobriand plate must assume this role based on new information such as that from GPS groundstations.<ref name="Benyshek2021F2">{{Harvnb|Benyshek|Taylor|2021||loc=Section:2.1 Geologic Background, Figure 2}}</ref> In this previous model, the Maoke plate had converged on its west, the Australian plate converges on the south,<ref name="Bird2003"/> and on the east there was an undefined compressive zone which might have been a transform fault that marked the boundary with the adjoining to the north Solomon Sea plate. When further oceanographic studies defined that there was a transform fault they also potentially enlarged the size of the Solomon Sea plate or created the need for a further current plate.<ref name="Benyshek2021I">{{Harvnb|Benyshek|Taylor|2021|loc=Introduction, Figure 1.Geology and tectonics of the Papuan Peninsula-Woodlark Basin region}}</ref> It was also in this model contacting the South Bismarck plate to the northeast.<ref name="Bird2003">{{cite journal |last1=Bird |first1=Peter |title=An updated digital model of plate boundaries |journal=Geochemistry, Geophysics, Geosystems |date=2003 |volume=4 |issue=3 |doi=10.1029/2001GC000252|bibcode=2003GGG.....4.1027B |doi-access=free}}</ref>
Most of its originally assigned area and boundary activity are now assigned to a combination of the Australian plate and other microplates. It is possible that if a still active Trobriand microplate exists, because active subduction is still taking place at the Trobriand Trough, all the western activity that some have assigned to an enlarged Solomon Sea plate will become assigned to the Trobriand microplate. The Trobriand microplate must have existed historically.<ref name="Benyshek2021"/><ref name="Benyshek2021F2"/> These assignments are partially informed by GNS studies where the Woodlark Basin region had distinctly different movements from a "Trobriand Block" and multiple eastern New Guinea land "Blocks" so that it was possible to define up to 5 distinct crustal blocks with possible independent movement that others later interpreted as components of differing microplates.<ref name="Wallace2014"/>
Subduction at the Trobriand Trough was originally assumed to be the case when the existence of the Woodlark plate was first modelled<ref name="Bird2003"/> but later went out of favour due to the relatively low seismic activity along some of the Trobriand Trough and measurement of movement across the trough.<ref name="USGS"/><ref name="Benyshek2021g"/> Today because the Woodlark Basin has been well characterised by deep sea ocean basin standards it is understood to have a northern boundary where the Woodlark Rise is associated with the Nubara Transform Fault.<ref name="Benyshek2021T">{{Harvnb|Benyshek|Taylor|2021|loc=6.3.1.Case 1: Three-Plate Solution}}</ref> This transform fault is definitely the boundary with the Solomon Sea plate,<ref name="Benyshek2021F"/> and will also be the northern boundary with the Trobriand plate if this currently independently exists.<ref name="Benyshek2021F">{{Harvnb|Benyshek|Taylor|2021|loc=6.3.1.Case 2: Four-Plate Solution, Figure 11}}</ref>
The Woodlark plate's eastern side is being subducted northeast beneath the New Georgia Islands on the Solomon Sea/Pacific plate but here the deformation front lacks a flexed outer rise and bathymetric trench, and is represented by the San Cristobal Trough extension to the north of the San Cristobal Trench.<ref name="Benyshek2021g">{{Harvnb|Benyshek|Taylor|2021|loc=2.2 Gravity, Figure 3.Seismicity and focal mechanisms of the Papua New Guinea-Solomon Islands region}}</ref> Where the Woodlark Basin is subducted northeast beneath the New Georgia Islands the relative light plate made of recent oceanic type basalt stays shallow and is presumably being melted on mantle contact and producing the many arc volcanoes of the western Solomon Islands.<ref name="Benyshek2021V">{{Harvnb|Benyshek|Taylor|2021|loc=2.3.Seismicity and Arc Volcanism}}</ref>
The southern boundary of the plate is defined by a mid oceanic ridge that is actively spreading tholeiitic basalt similar to mid-ocean ridge basalt (MORB) in a mostly north and south directions across its center in an east–west orientation with the Australian plate being to the south.<ref name="Boulart2022s">{{Harvnb|Boulart|Rouxel|Scalabrin|Le Meur|2022|loc=Section:Sulfide deposits and hydrothermal fluids}}</ref> The spreading centers are offset by transform faults, creating five segments,<ref name="Boulart2022"/> which causes the spreading center to be uneven across the basin. There are two larger transform faults called respectively the Moresby transform in the middle of the basin and the Simbo transform at the far eastern end of the spreading center.<ref name="Boulart2022"/>
The rate of spreading in the eastern section of the basin at {{convert|6.7|cm/year|abbr=on}} is significantly higher than the rate of spreading of {{convert|3.8|cm/year|abbr=on}} on the western side of the Woodlark Basin.<ref name="Boulart2022"/> As the eastern side of the basin has opened up much faster than the western side with the separation at the Moresby Transform Fault there is a shallower seafloor to the West, and an axial graben to the East,<ref name="Boulart2022"/> that is about {{convert|500|m|abbr=on}} deeper than the western basin.<ref name="Benyshek2021W">{{Harvnb|Benyshek|Taylor|2021|loc=3.1.Woodlark Basin Spreading Center}}</ref> The most recent major change in spreading direction of the Woodlark Basin spreading center and thus plate movement occurred about 450,000 years ago with a slowing in rate of divergence about 200,000 years ago.<ref name="Benyshek2021D">{{Harvnb|Benyshek|Taylor|2021|loc=8.Discussion}}</ref>
==See also == * {{annotated link|Woodlark Basin}}
==References== {{Reflist}}
===Sources=== {{Refbegin}} * {{cite journal|last1=Benyshek |first1=E. K. |last2= Taylor|first2= B. |year=2021 |title=Tectonics of the Papua-Woodlark region|journal=Geochemistry, Geophysics, Geosystems|volume= 22 |issue= e2020GC009209 | doi=10.1029/2020GC009209|doi-access=free }}<!-- {{Harvnb|Benyshek|Taylor|2021}} --> *{{cite journal|last1=Boulart|first1= Cédric |last2= Rouxel|first2= Olivier|last3= Scalabrin|first3= Carla|first4=Pierre |last4=Le Meur|first5= Ewan |last5=Pelleter|first6= Camille |last6=Poitrimol|first7= Eric |last7=Thiébaut|first8= Marjolaine |last8=Matabos|first9= Jade |last9=Castel|first10= Adrien |last10=Tran Lu Y|first11= Loic N. |last11=Michel|first12= Cécile |last12=Cathalot|first13=Sandrine |last13=Chéron|first14= Audrey |last14=Boissier|first15= Yoan |last15=Germain|first16= Vivien |last16=Guyader|first17= Sophie |last17=Arnaud-Haond|first18= François |last18=Bonhomme|first19=Thomas |last19=Broquet|first20= Valérie |last20=Cueff-Gauchard|first21= Victor |last21=Le Layec|first22= Stéphane |last22=L’Haridon|first23= Jean |last23=Mary|first24= Anne-Sophie |last24=Le Port|first25= Aurélie |last25=Tasiemski|first26= Darren C. |last26=Kuama|first27= Stéphane| last27=Hourdez |first28= Didier |last28=Jollivet |title=Active hydrothermal vents in the Woodlark Basin may act as dispersing centres for hydrothermal fauna|journal=Communications Earth and Environment|volume= 3 |issue=64 |year=2022| doi=10.1038/s43247-022-00387-9|doi-access=free|hdl=20.500.12210/63872|hdl-access=free}} *{{cite journal| last1=Wallace| first1=LM| last2=Ellis| first2=S| last3=Little| first3=T| last4=Tregoning| first4=P| last5=Palmer| first5=N| last6=Rosa| first6=R| last7=Stanaway| first7=R| last8=Oa |first8=J| last9=Nidkombu| first9=E|last10= Kwazi| first10=J| title=Continental breakup and UHP rock exhumation in action: GPS results from the Woodlark Rift, Papua New Guinea | journal=Geochemistry, Geophysics, Geosystems|year=2014| volume=15 |issue=11 |pages=4267–90| doi=10.1002/2014GC005458 | url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014GC005458# | hdl=1885/13228| hdl-access=free}}<!-- {{Harvnb|Wallace|Ellis|Little|Tregoning|2014}} --> {{Refend}} {{Tectonic plates}} {{SE Asia plates}}
Category:Tectonic plates Category:Geology of the Pacific Ocean