Cape Johnson Guyot is a guyot in the Pacific Ocean, more precisely in the Mid-Pacific Mountains, and the type locality of guyots. It is of middle Cretaceous age and a number of fossils have been dredged from it.
Name
Cape Johnson Guyot is also known as Cape Johnson Seamount or Cape Johnson Tablemount.Marineregions 2019 The guyot was named by Harry Hammond Hess, after his ship the ; Hess had also named the kind of flat-topped seamount "guyot" and another seamount was named after Hess himself.BUDDINGTON, p.21 The seamount was first described in a 1946 publication.Hamilton 1956, p.18 Both Hess and Cape Johnson were discovered during the same cruiseHamilton 1953, p.213 and Cape Johnson Guyot is the type locality of guyots.Marineregions 2019
Geography and geology
The seamount lies in the Mid-Pacific MountainsHamilton and Rex 1959, p.787 on their southern side and is a submarine mountain with a flat top that risesHamilton 1953, p.213 over Hamilton 1956, p.19 to a depth of Hamilton 1953, p.213Hamilton 1956, p.20-.Hey and Grigg 1992, p.175 The flat top has an oval shape and a surface area of ;Hamilton 1956, p.20 it is characterized by a limestone dome on the summit, buried beneath sediments; in turn a volcanic hill is buried within the limestone dome.Winterer, Sager and Firth 1995, p.436 The top of the seamount has a hummocky appearance which has been interpreted as a sediment coverHamilton 1956, p.18 and its southeastern sector has a bank-like shape that resembles that of an atoll.Hamilton 1956, p.20 Cape Johnson Guyot is considered to be of Middle Cretaceous ageShields 1976, p.47 with an age of 120 million years reportedMorgan 1972, p.12 and shallow-water fossils were emplaced on it at that time.Winterer, Sager and Firth 1995, p.436
Apatite,El Wardani 1958, p.240 basaltic sandstone containing hypersthene,Heezen and MacGregor 1973, p.667 clay,Hamilton 1956, p.20 limestone, manganese crusts,Hamilton 1953, p.213 manganese oxide, phosphoriteHill 2005, p.682 and lithified carbonates have been found on Cape Johnson Guyot;Fischer and Garrison 1967, p.489 some carbonates of biogenic origin have been altered by apatite.Hamilton and Rex 1959, p.787 Globigerina ooze is also found on the seamountHamilton 1953, p.213 and can reach substantial thickness; such accumulations might be formed by ocean currents.Hamilton 1953, p.219 Similar rocks have been found at other guyots of the Mid-Pacific Mountains.Heezen and MacGregor 1973, p.655
Biology
During the Cretaceous, corals and rudists lived on Cape Johnson GuyotHamilton 1959, p.1409 and fossils have been dated to 91-112 million years ago;Hey and Grigg 1992, p.175 some coralsLöser 2010, p.158 and rudists are of Albian to Cenomanian age.Hamilton 1956, p.26 Fossils of anthozoa,Hamilton 1956, p.22 gastropods, reef-building hexacorals,Hamilton 1956, p.20 pelecypods, stromatoporoidsHamilton 1956, p.22 and Tridacna were also found.UNIVERSITY OF CALIFORNIA SCRIPPS INSTITUTION OF OCEANOGRAPHY. p.5 The Cretaceous fossilsCairns 1991, p.31 Actinostroma pacifica,Hamilton 1956, p.61 Astrocoenia dietzi,Cairns 1991, p.31 Brachyseris montemarina,Cairns 1991, p.42 the caprinid rudists Caprina mediopacifica, Caprina mulleriSano et al. 2012, p.849 - including a detailedly described holotype of the latterMasse, Sano and Skelton 2013, p.517 - and Cardita sp.,Cairns 1991, p.66 Lophosmilia fundimaritima,Cairns 1991, p.34 Montastrea menardii,Hamilton 1956, p.59 Nerinea sp.Cairns 1991, p.64 and Tiarasmilia casteri occur on Cape Johnson Guyot.Löser 2010, p.161 Caprina mulleri was also found on other Mid-Pacific Mountains.Masse, Sano and Skelton 2013, p.515 About 300 species of extant foraminifera have been found on the seamount as well,Hamilton 1953, p.207 with additional fossil foraminiferaHamilton 1953, p.213 including Paleocene-Eocene specimens that were redeposited by ocean currents.Hamilton 1953, p.219 Finally, a cetacean bone of undetermined age has also been found on Cape Johnson Guyot.Hamilton 1956, p.29
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