Rapid formation of the Shatsky Rise oceanic plateau inferred from its magnetic anomaly

Formation and evolution of Shatsky Rise oceanic plateau: Insights from IODP Expedition 324 and recent geophysical cruises

“…A gap in radiometric ages and the occurrence of sediment layers between the two massive flows groups at Site U1347 indicate a significant hiatus at the end of shield formation lasting at least ~2-3 Myr (Heaton and Koppers, 2014;Tominaga et al, 2014;Geldmacher et al, 2014). Paleomagnetic data from Sites 1213 and U1347 have opposite inclination signs, suggesting that the Tamu Massif shield incorporates lava flows with opposite polarities , which also argues against rapid formation during a single polarity period (Sager and Han, 1993). The age span of Tamu Massif eruptions is further expanded by the radiometric date of ~129 Ma for Toronto Ridge, suggesting a gap of ~15 Myr from the end of shield building (Tejada et al, in press).…”

“…New radiometric ages and paleomagnetic data do show, however, that formation of Tamu Massif occurred over a longer time period than the brief (~0.5 Myr) span proposed by Sager and Han (1993). A gap in radiometric ages and the occurrence of sediment layers between the two massive flows groups at Site U1347 indicate a significant hiatus at the end of shield formation lasting at least ~2-3 Myr (Heaton and Koppers, 2014;Tominaga et al, 2014;Geldmacher et al, 2014).…”

“…As the crustal thickness of Shatsky Rise is several times thicker than that of normal oceanic plates, the presence of a thermal anomaly (i.e., a thermal plume head) beneath the plateau was proposed as a mechanism to produce a large amount of magma (Sager and Han, 1993). Whether such an anomaly existed beneath Shatsky Rise is thus an important facet of understanding the formation of the plateau.…”

“…10; Nakanishi et al, 1999;Huang and Sager, 2013). Although most of Tamu Massif is characterized by a broad anomaly that can be fit by a model of the volcano shape (Sager and Han, 1993), lineations likely traverse the north flank of the edifice ( Fig. 2) .…”

Seismic and gravitational studies of melting in the mantle's thermal boundary layers

“…The formation of Hess Rise, to the northeast of the bend in the Hawaii-Emperor chain, has been dated at 98-110 Ma [Pringle and Dalrymple, 1993] and is thought to have formed on or very near the Pacific-Farallon spreading center [Vallier et al, 1981;Kroenke and Nemoto, 1982;Mammerickx and Sharman, 1988]. Shatsky Rise, to the west of the bend in the hotspot track, has been dated at 138-145 Ma [Sager and Han, 1993;Party, 2002b] and magnetic lineations around the rise indicate that it formed along the trace of the Pacific-Farallon-Izanagi triple junction [Larson and Chase, 1972;Hilde et al, 1976;Sager et al, 1988;Nakanishi et al, 1989]. The bend in the hotspot track has been dated between 40 and 53 Ma [Sharp and Clague, 2002] and its origin is interpreted to be related to the cessation of southward motion of the Hawaii-Emperor hotspot that has been measured for the Emperor segment of the seamount chain [Tarduno and Cottrell , 1997;Party, 2002a;Cottrell and Tarduno, 2003;Tarduno et al, 2003].…”