Resolution Guyot
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.
[2] Resolution Guyot is one of the western Mid-Pacific Mountains, located west of Hawaii, north-northeast of the Marshall Islands.
[11] Other guyots in the Mid-Pacific Mountains are Sio South, Darwin, Thomas, Heezen, Allen, Caprina, Jacqueline and Allison.
[23][24] The Pacific Ocean seafloor contains many guyots formed during the Mesozoic era (251.902 ± 0.3 – 66 million years ago[21]) in unusually shallow seas.
[12] 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.
[30] Continued subsidence balanced by upward growth of the reefs led to the formation of thick carbonate platforms.
[31] 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[c] developed.
Alteration has produced analcime, ankerite, calcite, clay, hematite, iddingsite, pyrite, quartz, saponite, serpentine and zeolite.
[50] Dolomite alteration is particularly widespread in modern atolls and several processes have been invoked to explain it, such as geothermally driven convection of seawater.
[45] Barite needles,[50] calcretes,[53] cementation forms[d] that developed under the influence of freshwater,[45] desiccation cracks[14] and ferromanganese occurrences as dendrites have also been found.
[14] Clays found on Resolution Guyot are characterized as chlorite, glauconite, hydromica,[61] illite,[62] kaolinite, saponite and smectite.
[68] Eruptions in the area built a pile of volcanic rocks, including stacks of lava flows, each of which is about 10 metres (33 ft) thick, but there are also breccias,[f] intrusions and sills.
[71] Volcanic activity took place in a tropical or subtropical environment and between eruptions weathering, soil formation and potentially mass wasting generated layers of clay, rock debris and alteration products[1] such as laterite.
113 – 100.5 million years ago[21]), about 1,619 metres (5,312 ft) of carbonate was deposited on the volcanic structure,[47] eventually completely burying it during the Albian.
[79] During this time, Resolution Guyot underwent little latitudinal plate motion; from the magnetization it appears that it was stably located at about 13° southern latitude between the Hauterivian and Aptian.
[82][83] Analysis of the carbonate layers has identified that several environments existed on the platform, including swash beaches, lagoons, marshes, mudflats,[84] sabkhas,[85] sand bars and washover fans from storms;[52][78] at times there were also open-marine conditions.
[85] Some environments on Resolution Guyot were hypersaline at times,[65] probably implying that they had only limited water exchange with the surrounding ocean.
[90] The platform was exposed to southeasterly trade winds which left its northern side sheltered from waves, except from storm-generated ones.
[95] The Selli event left a black shale layer and may have caused a temporary interruption in carbonate accumulation before the platform recovered.
[97] Life on Resolution Guyot included algae – both green and red algae[52] and species forming microbial mats –,[98] bivalves[52] including rudists,[99] bryozoans, corals, echinoderms, echinoids, foraminifera, gastropods, ostracods,[100] oysters, serpulid worms,[45] sponges[47] and stromatoliths.
This tectonic event has been explained by a major change in mantle convection in the middle Cretaceous pushing the ocean floor upward and sideward.
[111] The platform became irregular[112] and part of it was eroded away;[109] calcrete crusts,[113] carbonate pinnacles,[18] cavities, caverns containing speleothems and sinkholes formed[114] and exist to this day.
[92] There is disagreement about whether Resolution Guyot was close enough to the equator and nutrient rich equatorial waters to drown at the time when carbonate sedimentation ceased.
[124][125] After the drowning, crusts formed by ferromanganese and by phosphate-modified rocks developed on exposed surfaces at Resolution Guyot.
