We try to unravel the relationship between the two largest sub-provinces of the Manihiki Plateau, the Western Plateaus and the High Plateau, which are separated by the Danger Islands Troughs. Did both sub-provinces experience the same magmatic history? The fragmentation of the Manihiki Plateau poses the question, whether distinct phases of magmatic or tectonic processes led to the deformation of the Manihiki Plateau and which role the Danger Islands Troughs played in this scenario. By processing, modeling and interpreting recently acquired seismic refraction/wide-angle reflection data; the deep crustal structure of both sub-provinces is revealed and interpreted for the first time.
In this paper, we use the term initial or first magmatic phase for the initial emplacement of the Manihiki Plateau (>120 Ma). The secondary magmatic stages comprise multiple episodic magmatic activities younger than 120 Ma, which occurred during and after the break-up.
It is important to note, that most of the publications have focused on the High Plateau along with the Danger Islands Troughs and the Manihiki Scarp. Other areas of the Manihiki Plateau, such as the basement of the Western Plateaus, are poorly sampled and therefore the evolution of the different sub-provinces and their magmatic and tectonic relationship to the other parts of the plateau is still poorly understood. Although satellite-derived gravity anomaly maps  indicate different crustal structures of the sub-provinces, plate tectonic reconstructions of the Cretaceous western Pacific  treat the Manihiki Plateau as a single tectonic block and disregard its different sub-provinces.
We present the first seismic refraction/wide-angle reflection P-wave and S-wave models of the two main sub-provinces – the Western Plateaus and the High Plateau – of the Manihiki Plateau. From the newly gained information on the crustal structure of the sub-provinces, the tectonic and magmatic evolution of this oceanic LIP can be further illuminated. Additionally we gain insight into the relationship between the sub-provinces, which have been treated as a single crustal block in previous studies.
The High Plateau shows key features of a LIP such as a HVZ in the lower crust and basaltic flow units in the upper crust. The crustal thickness presents a constant 20 km throughout the southern High Plateau. Eruptive centers of secondary magmatic phases are visible in the upper crust and major magmatic pathways can be traced in the middle and lower crust of the LIP throughout the High Plateau. The Western Plateaus, on the other hand show a gradual decrease in crustal thickness from 17.3 km in the east to 9.2 km in the west. The presence of the HVZ within the lower crust indicates a joined emplacement with the High Plateau during an initial magmatic stage. The upper crust of the Western Plateaus does not consist of major basaltic flow units and massive amounts of volcaniclastics such as the upper crust of the High Plateau. Therefore we propose an individual development of the two main sub-provinces of the Manihiki Plateau after the initial emplacement of the LIP. The two sub-provinces show a clear distinction between later magmatic stages, which has not been reported for any other oceanic LIP so far.

A detailed magmatic evolution history of the Manihiki Plateau is still lacking. Two volcanic periods have been distinguished. The main emplacement period occurred during the early Cretaceous (~ 125-110 Ma) and consisted of massive eruptions of basaltic, which resulted in an anomalously thick oceanic crust  up to 20 km [Hochmuth et al., in revision]. Based on dredge samples and borehole data of DSDP Leg 33 Site 317, those are considered to have formed in a shallow water environment. Around ~90-65 Ma, a second smaller volcanic period (secondary volcanism) emplaced alkalic volcaniclastics. This second period is discussed to have been triggered by the tectonic break-up processes.
We have further investigated the volcanic emplacement history of the High Plateau, part of the Manihiki Plateau using new high resolution seismic reflection data gathered during cruise So224. We could extend the existing seismostratigraphic model by incorporating new reflections R5a, R6a and IB1, which correspond to the onset of sedimentation after the secondary volcanic period (~65 Ma, R5a), represent the onset of the alkali late stage volcanic period (~90 Ma, R6a), and  likely represents an earlier volcanic flow period prior to R7 (>125 Ma, intrabasement reflection sequence IB1). The Intrabasement reflection sequence forms a high in the southern central part of the High Plateau and is interpreted to represent a shield volcano. We conclude that it represents the first volcanic emplacement phase within oceanic crust prior to the main emplacement phase.
The end of the major initial emplacement (Unit 4) is marked by the top of basalt (reflection R7) and characterized by a multitude of extrusion centers. We interpret those as a result of initial emplacement volcanism in the central part of the High Plateau (R7) and volcanism induced by tectonics at the eastern, western and southern flanks. For the late stage volcanic period, ending ~65 Ma the spatial distribution of the identified extrusion centers shows a relocation from the center of the High Plateau towards its eastern, southern and western flanks. We suggest two different source mechanisms have to be considered: sources either related to the initial emplacement of the HP and tectonic induced volcanism at the margins. This is in agreement with petrological data taken along the Suvarov and Danger Island Troughs.
At the eastern margin, the abrupt termination of the intrabasement reflection sequence IB1 across the Manihiki Scarp supports the hypothesis that a missing piece of the Manihiki Plateau rifted to the east before the formation of reflection R7. The south-western margin is characterized by a normal fault structure and a smooth appearance of reflection R7 and R6. This appearance supports the hypothesis of a stretched and rifted margin, which is associated with the break-up of the Hikurangi Plateau at the Osbourn Trough. The Western Plateaus in comparison to the High Plateau are characterized by a deficit of two distinguishable volcanic phases. Combining refraction and reflection data [Hochmuth et al., in revision], we conclude that this fragment was separated along the Danger Islands troughs at the end of the volcanic  main period. The graben structure along the Danger Islands troughs and fault structures gives evidence that the High Plateau has been tectonically active after the alkali late stage volcanic period (<65 Ma).