Trobriand Plate | |
---|---|
Type | Microplates |
Movement1 | north-west (rotational) |
Speed1 | 10 mm/year |
Features | New Guinea, Pacific Ocean |
1Relative to the African Plate |
The Trobriand Plate was, and likely is, an independent microplate between New Guinea and the Solomon Islands. It has some unique geology, having the presence of the youngest metamorphic core complexes on earth. If there is presently active subduction between it and the Solomon Plate, at the Trobriand Trough, it continues to be an active microplate. Otherwise in the latest tectonic models it has merged with the Solomon Sea Plate, which becomes somewhat larger than predicted by Bird's 2003 model of Tectonic Plates. As a smaller Solomon Sea Plate is totally underwater, global positioning data can not resolve this issue. The area of the plate is associated with earthquake and volcanic activity as part of the Pacific Ring of Fire.
The Trobriand Plate underlies south-eastern parts of Papua New Guinea east of the Owen Stanley Range as it is separated in the range from the Australian Plate by the Owen Stanley Fault Zone [1] [2] This extends along the southern border of the Goodenough Basin and through the southern part of Normanby Island in the D'Entrecasteaux Islands. This fault zone then becomes the Nubara Transform Fault that strikes north-east towards the Solomon Islands but is only related to the Trobriand microplate until the Trobriand Trough is reached. The north eastern plate boundary is the Trobriand Trough. [3] Woodlark Island is on the area of the Trobriand Plate as the Nubara Transform Fault is to its south-east. [4] The western end of the New Britain Trench terminates at the Trobriand Plate.
Within the Trobriand Plate is the unigue to today's earth, the youngest (7–5 million year old) metamorphic core complexes formed of sedimentary rocks that have been subject to high and ultra–high–pressure, as well as gneissic domes that are being rapid emplaced at between 1–2 cm/year (0.39–0.79 in/year) vertically. [4] [2] The metamorphic core complexes include the Suckling–Dayman massif of south-eastern New Guinea and the Emo Metamorphics which have some characteristics shared with back-arc basin basalts. [5] The gneissic domes along the volcanic front include the D'Entrecasteaux Islands and Misima Island. [3]
The Trobriand Plate is located in a very complex tectonic environment between the current Australian Plate to the south and the South Bismarck Plate and Pacific Plate to the north. [6] This environment has been intensively studied in the last 20 years and these studies have contributed to the resolution of important tectonic theory issues. They have also created inconsistencies with observation as opposed to prediction from historic tectonic modelling. This for example means that the Woodlark Plate must be a small, almost triangular shaped oceanic tectonic plate, rather than one that included continental eastern portions of Papua New Guinea. [7] These portions must now be assigned to either the Trobriand Plate or if it is now fixed with respect to the Solomon Sea Plate, a larger Solomon Sea Plate. [7] GNS data can not resolve this issue as a smaller Solomon Sea Plate is all underwater. [8]
The Trobriand Plate must have been in the fairly recent past an independent microplate, and likely still is. [9] [10] The evidence for a separate Trobriand Plate includes:
Against a current separate Trobriant Plate is the evidence that:
Much of the historic academic tectonic plate literature up to 2016, in some cases, and later in popular literature, had the Woodlark Plate as originally proposed to be somewhat larger than current proposals, extending to the west along the east coast of New Guinea and subducting beneath the Caroline plate along its northern border. [20] This model had the Maoke Plate with a convergent boundary on its west, the Australian Plate converging on the south, and on the east an undefined compressive zone which that marked the boundary with the adjoining to the north Solomon Sea Plate. It was also in this model contacting the South Bismarck Plate to the north-east. [21] Interestingly subduction at the Trobriand Trough was originally assumed in this historic model, [21] but at a rate that proved to be quite incompatible with actual data.
Most of the Woodlark Plate's originally assigned area and boundary activity are now assigned to a combination of the Australian Plate and Solomon Sea minor plate. The northern Trobriand Plate will assume the subduction at the New Britain Trench that a larger Solomon Sea Plate has assigned. These assignments are partially informed by GNS studies over a decade after the original 2003 Bird model. This showed that 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, [22] that others later interpreted as components of the differing microplates. [7]
Trobriand Plate | |
---|---|
Type | Microplates |
Movement1 | north-west (rotational) |
Speed1 | 10 mm/year |
Features | New Guinea, Pacific Ocean |
1Relative to the African Plate |
The Trobriand Plate was, and likely is, an independent microplate between New Guinea and the Solomon Islands. It has some unique geology, having the presence of the youngest metamorphic core complexes on earth. If there is presently active subduction between it and the Solomon Plate, at the Trobriand Trough, it continues to be an active microplate. Otherwise in the latest tectonic models it has merged with the Solomon Sea Plate, which becomes somewhat larger than predicted by Bird's 2003 model of Tectonic Plates. As a smaller Solomon Sea Plate is totally underwater, global positioning data can not resolve this issue. The area of the plate is associated with earthquake and volcanic activity as part of the Pacific Ring of Fire.
The Trobriand Plate underlies south-eastern parts of Papua New Guinea east of the Owen Stanley Range as it is separated in the range from the Australian Plate by the Owen Stanley Fault Zone [1] [2] This extends along the southern border of the Goodenough Basin and through the southern part of Normanby Island in the D'Entrecasteaux Islands. This fault zone then becomes the Nubara Transform Fault that strikes north-east towards the Solomon Islands but is only related to the Trobriand microplate until the Trobriand Trough is reached. The north eastern plate boundary is the Trobriand Trough. [3] Woodlark Island is on the area of the Trobriand Plate as the Nubara Transform Fault is to its south-east. [4] The western end of the New Britain Trench terminates at the Trobriand Plate.
Within the Trobriand Plate is the unigue to today's earth, the youngest (7–5 million year old) metamorphic core complexes formed of sedimentary rocks that have been subject to high and ultra–high–pressure, as well as gneissic domes that are being rapid emplaced at between 1–2 cm/year (0.39–0.79 in/year) vertically. [4] [2] The metamorphic core complexes include the Suckling–Dayman massif of south-eastern New Guinea and the Emo Metamorphics which have some characteristics shared with back-arc basin basalts. [5] The gneissic domes along the volcanic front include the D'Entrecasteaux Islands and Misima Island. [3]
The Trobriand Plate is located in a very complex tectonic environment between the current Australian Plate to the south and the South Bismarck Plate and Pacific Plate to the north. [6] This environment has been intensively studied in the last 20 years and these studies have contributed to the resolution of important tectonic theory issues. They have also created inconsistencies with observation as opposed to prediction from historic tectonic modelling. This for example means that the Woodlark Plate must be a small, almost triangular shaped oceanic tectonic plate, rather than one that included continental eastern portions of Papua New Guinea. [7] These portions must now be assigned to either the Trobriand Plate or if it is now fixed with respect to the Solomon Sea Plate, a larger Solomon Sea Plate. [7] GNS data can not resolve this issue as a smaller Solomon Sea Plate is all underwater. [8]
The Trobriand Plate must have been in the fairly recent past an independent microplate, and likely still is. [9] [10] The evidence for a separate Trobriand Plate includes:
Against a current separate Trobriant Plate is the evidence that:
Much of the historic academic tectonic plate literature up to 2016, in some cases, and later in popular literature, had the Woodlark Plate as originally proposed to be somewhat larger than current proposals, extending to the west along the east coast of New Guinea and subducting beneath the Caroline plate along its northern border. [20] This model had the Maoke Plate with a convergent boundary on its west, the Australian Plate converging on the south, and on the east an undefined compressive zone which that marked the boundary with the adjoining to the north Solomon Sea Plate. It was also in this model contacting the South Bismarck Plate to the north-east. [21] Interestingly subduction at the Trobriand Trough was originally assumed in this historic model, [21] but at a rate that proved to be quite incompatible with actual data.
Most of the Woodlark Plate's originally assigned area and boundary activity are now assigned to a combination of the Australian Plate and Solomon Sea minor plate. The northern Trobriand Plate will assume the subduction at the New Britain Trench that a larger Solomon Sea Plate has assigned. These assignments are partially informed by GNS studies over a decade after the original 2003 Bird model. This showed that 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, [22] that others later interpreted as components of the differing microplates. [7]