Resolution Guyot (formerly known as Huevo) is a guyot in the underwater Mid-Pacific Mountains in the Pacific Ocean. It is a circular flat mountain, rising above the seafloor to a depth of about , with a summit platform. The Mid-Pacific Mountains lie west of Hawaii and northeast of the Marshall Islands, but at the time of its formation, the guyot was located in the Southern Hemisphere.
The guyot was probably formed by a hotspot in today's French Polynesia before plate tectonics shifted it to its present-day location. The Easter, Marquesas, Pitcairn and Society hotspots, among others, may have been involved in the formation of Resolution Guyot. Volcanic activity has been dated to have occurred 107–129 million years ago and formed a volcanic island that was subsequently flattened by erosion. Carbonate deposition commenced, forming an atoll-like structure and a carbonate platform.
The platform emerged above sea level at some time between the Albian and Turonian ages before eventually drowning for reasons unknown between the Albian and the Maastrichtian. Thermal subsidence lowered the drowned seamount to its present depth. After a hiatus, sedimentation commenced on the seamount and led to the deposition of manganese crusts and pelagic sediments, some of which were later modified by phosphate.
Name and research history
Resolution Guyot was informally known as Huevo Guyot before it was renamed after the drilling ship JOIDES Resolution during Leg 143 of the Ocean Drilling Program in 1992. During that Leg, JOIDES Resolution took drill cores from Resolution Guyot called 866A, 867A and 867B; 866A was drilled on its summit, 867B (and the unsuccessful drilling attempt 867A) on its platform margin, and 868A on a terrace outside of the platform.
Geography and geology
Local setting
Resolution Guyot is one of the western Mid-Pacific Mountains, located west of Hawaii, north-northeast of the Marshall Islands. Unlike conventional Pacific Ocean island chains, the Mid-Pacific Mountains are a group of oceanic plateaus with guyots (also known as tablemounts)) that become progressively younger towards the east. Other guyots in the Mid-Pacific Mountains are Sio South, Darwin, Thomas, Heezen, Allen, Caprina, Jacqueline and Allison.
The seamount is about high and rises from a raised seafloor to a depth of about . At a depth of it is capped off by a wide rather flat and roughly circular summit platform with a high rim and a moat inside of this rim. At the margin of the platform, structures interpreted as sea cliffs or wave cut terraces have been found; at one site there is a terrace about wide, surmounted by a high cliff. Pinnacles and depressions dot the surface platform. The surface of the platform consists of limestone that is partially covered by pelagic sediments; underwater cameras have shown the presence of rock slabs covered by ferromanganese crusts.
The guyot rises from a seafloor of Jurassic age (201.3 ± 0.2 – ca. 145 million years ago) that might be as much as 154 million years old. Terrestrial organic material on the seafloor around Resolution Guyot originated from when it was still an island, and carbonate sediments swept away from the guyot collected on the surrounding seafloor.
Regional setting
The Pacific Ocean seafloor contains many guyots formed during the Mesozoic era (251.902 ± 0.3 – 66 million years ago) in unusually shallow seas. These submarine mountains are characterized by a flat top and usually the presence of carbonate platforms that rose above the sea surface during the middle Cretaceous (ca. 145 – 66 million years ago). While there are some differences to present-day reef systems, many of these seamounts were formerly atolls, which still exist. These structures formed as volcanoes in the Mesozoic ocean. Fringing reefs may have developed on the volcanoes, which then became barrier reefs as the volcano subsided and turned into an atoll, and which surround a lagoon or a tidal flat. The crust underneath these seamounts tends to subside as it cools, and thus the islands and seamounts sink. Continued subsidence balanced by upward growth of the reefs led to the formation of thick carbonate platforms. Sometimes volcanic activity continued even after the formation of the atoll or atoll-like structure, and during episodes where the platforms rose above sea level erosional features such as channels and blue holes developed.