Massive Early Cretaceous volcanic activity in the Nauru Basin related to emplacement of the Ontong Java Plateau

Abstract

[1] The Mesozoic Nauru Basin in the western Pacific was created by seafloor spreading in Late Jurassic and Early Cretaceous time and was subsequently affected by Early Cretaceous flood volcanism approximately contemporaneous with emplacement of the nearby $120 Ma Ontong Java Plateau (OJP). To investigate structure and stratigraphy of the basin, we completed a coincident multichannel seismic reflection (MCS) and refraction (sonobuoy) transect from the center of the Nauru Basin to the eastern flank of the OJP in 1998 aboard R/V Hakuho Maru. Along the transect we identify four segments of distinct crustal structure: C1, a thick igneous complex with no observable refractions; C2, basaltic sills and flows, C3, faulted sediment and rock near the flank of the OJP; and C4, the OJP. On data from seven sonobuoys we observe P-wave refraction arrivals with apparent velocities of $6.0 km/s in each segment except C1. Sonobuoy data from segment C1 show no refractions, a common phenomenon in the northern Nauru Basin. We consider that the structure in segment C1 is most representative of typical Nauru Basin crust, and we estimate the volume of the thick igneous complex from discrepancies between actual seafloor depths and those predicted by an agedepth model, which commonly exceed 1000 m. We selected an appropriate model by comparing observed seafloor depths at drill holes in the Mesozoic Pigafetta and East Mariana basins where Cretaceous igneous complexes are thin or absent. From an empirical density-velocity relation, we calculated a basalt loading factor of 780 m/s for subsidence of the Late Jurassic-Early Cretaceous oceanic crust. We then applied the factor to estimate the thickness of the younger Early Cretaceous igneous complex, using previous seismic reflection (Charcot 2), drilling (DSDP Site 462), and wide-angle seismic data from DSDP Site 462 as controls. We estimate that the igneous complex is thickest, $5500 m, in the center of the basin and that the total volume of the Early Cretaceous igneous complex is 3.3 Â 10 6 km 3 .

Large igneous provinces and silicic large igneous provinces: Progress in our understanding over the last 25 years

“…Within 10 m.y., another major large igneous province cluster had developed, by ca. 120 Ma, with (1) the emplacement of the megaoceanic plateau of Ontong Java, Manihiki, and Hikurangi, (2) Pigafetta-East Marianas ocean basin fl ood basalts (Tarduno et al, 1991;Pringle, 1992) and probably the onset of Nauru Basin fl ood basaltic volcanism (e.g., Saunders, 1989;Mochizuki et al, 2005); (3) Kerguelen-Rajmahal Traps ± Wallaby Plateau (Kent et al, 2002); (4) the onset of the peak of volcanism in the Whitsunday silicic large igneous province (Bryan et al, 1997(Bryan et al, , 2012, (5) formation of the Mozambique Ridge (Gohl et al, 2011); and (6) continued tholeiitic volcanism in the High…”

Nonlinear 40Ar/39Ar age systematics along the Gilbert Ridge and Tokelau Seamount Trail and the timing of the Hawaii‐Emperor Bend

“…The Gilbert Ridge also rides on the edge of a region of “anomalously” shallow seafloor (Figure 1) that may have been thermally reactivated as part of the Darwin Rise [ Menard , 1964, 1984; McNutt and Menard , 1978; Hillier and Watts , 2005]. More likely this basement has been thickened because of the emplacement of volcanic sills during the formation of the Ontong Java and Manihiki Plateaus around 125 Ma [ Tarduno et al , 1991; Castillo et al , 1994; Larson , 1997; Mochizuki et al , 2005; Taylor , 2006]. As a result, the intrusion of Ontong Java Plateau basalts in the Nauru Basin may have weakened or preconditioned the Pacific lithosphere for later seamount emplacements.…”

“…As a result, the intrusion of Ontong Java Plateau basalts in the Nauru Basin may have weakened or preconditioned the Pacific lithosphere for later seamount emplacements. Multichannel seismic reflection and refraction data from the Nauru Basin [ Mochizuki et al , 2005] shows the presence of a 2,200–5,500 m thick volcanic complex (of sills in between the sediment layers) that explains the anomalous shallow seafloor underneath the Gilbert Ridge.…”

Collision of Manihiki Plateau fragments to accretional margins of northern Andes and Antarctic Peninsula

“…Intrabasement reflections of the eastern part of the High Plateau of the Manihiki Plateau show no decrease in the initial crustal thickness toward the eastern fragment [ Pietsch and Uenzelmann‐Neben , ]. If a steady decrease of basaltic volume similar to the northern Ontong Java Plateau is assumed [ Mochizuki et al ., ], the eastern fragment extends at least 500 km to the east with decreasing crustal thickness. The size estimation of the fragments of the Manihiki Plateau is comparable to that of other parts of Ontong Java Nui such as the Hikurangi Plateau.…”

“…If a steady decrease of basaltic volume similar to the northern Ontong Java Plateau is assumed [Mochizuki et al, 2005], the eastern fragment extends at least 500 km to the east with decreasing crustal thickness. The size estimation of the fragments of the Manihiki Plateau is comparable to that of other parts of Ontong Java Nui such as the Hikurangi Plateau.…”