Abstract
Shatsky Plateau is probably the oldest extant oceanic plateau, and is of probable Late Jurassic or Early Cretaceous age. Like most such features, however, its origin is uncertain. The plateau has been thought to have been formed by a hotspot because it consists of large pile of volcanics. Bathymetric, magnetic, and gravity data were examined for clues to the origin of Shatsky Plateau. Bathymetric data were used to obtain morphology. Magnetic data were used to trace magnetic lineations as well as to examine the magnetic structure of the plateau. Gravity data were used to examine the density structure and to look at the flexure of associated seamounts. Shatsky Plateau consists of three isolated uplifts and each one has a symmetrical shape. The uplifts show an exponential decay in volume from south to north and age constraints also suggest an age progression from south to north. Magnetic lineations between uplifts imply undisturbed seafloor. The magnetic anomalies over the South High are positive and give a reversed magnetic polarity upon inversion. This result suggests that the edifice formed rapidly during a period of mostly reversed geomagnetic polarity. Age constraints suggest that M17 (about 144.2 Ma), which has a duration of about 1.2 Ma, has the highest probability of being the time of the edifice eruption. The length of this polarity epoch plus a volume estimation of 2.1 x 10^6 km^3 imply that the South High erupted at a minimum rate of 1.75 km^3/a. The other highs were poorly surveyed, but show normal polarity. The isostatic gravity anomaly indicates a density anomaly at the center of South High. This density anomaly can be modeled as intrusive complex and suggests a volcanic center. Thin elastic thickness values (less than 10 km) derived for adjacent seamounts are consistent with small volcanoes forming at about the same time as the plateau. These results suggest that Shatsky Plateau is formed of three main volcanoes of decreasing size, and the largest and oldest edifice formed rapidly at about M17 time. The High extrusion rate for the South High estimate is consistent with plume-head hypothesis of oceanic plateau formation. The other Shatsky volcanoes perhaps formed by the plume-tail and the volume progression also suggests tapering tail.
Han, Hyun-Chul (1993). Geophysical constraints on the origin of the Shatsky Plateau. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1526979.