Document Type

Article

Abstract

Ita Mai Tai is a large, locally uncompensated seamount on the eastern edge of the East Mariana Basin. A large positive gravity anomaly of 254 mgal characterizes the summit and a low of -69 mgal, the surrounding moat. Using polygonal prisms to approximate the bathymetry, the observed gravity was inverted to calculate an average density of 2.59 g/ems for the seamount. Observed-calculated gravity residuals are reduced by including the flanking sedimentary basins and a dense volcanic conduit. The drill sites from DSDP Legs 20 and 89 describe a volcanic edifice formed in the Aptian!Albian on Jmassic/Cretaceous crust. The volcanism is recorded in volcanoclastic and epiclastic deposits in the basins nearby. The guyot was covered initially by a succession of reefal and lagoonal sediments followed by a thick mantling of pelagic sediments after it subsided. Gravity models that adequately match the calculated and observed data sets for Ita Mai Tai show little crustal thickening, suggesting that Ita Mai Tai is almost completely locally uncompensated.

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