Editing Atlantic Ocean (section)

=== South Atlantic ===
{{Multiple image
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 | image1 = Gondwana115Ma hg.png
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 | footer = The opening of the South Atlantic
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West Gondwana (South America and Africa) broke up in the Early Cretaceous to form the South Atlantic. The apparent fit between the coastlines of the two continents was noted on the first maps that included the South Atlantic and it was also the subject of the first computer-assisted plate tectonic reconstructions in 1965.<ref name="Eagles-intro">{{Harvnb|Eagles|2007|loc=Introduction, p. 353}}</ref><ref>{{Harvnb|Bullard|Everett|Smith|1965}}</ref> This magnificent fit, however, has since then proven problematic and later reconstructions have introduced various deformation zones along the shorelines to accommodate the northward-propagating break-up.<ref name="Eagles-intro" /> Intra-continental rifts and deformations have also been introduced to subdivide both continental plates into sub-plates.<ref name="Seton-2012-p217">{{Harvnb|Seton|Müller|Zahirovic|Gaina|2012|loc=South Atlantic, pp. 217–218}}</ref>

Geologically, the South Atlantic can be divided into four segments: equatorial segment, from 10°N to the Romanche fracture zone (RFZ); central segment, from RFZ to Florianopolis fracture zone (FFZ, north of Walvis Ridge and Rio Grande Rise); southern segment, from FFZ to the Agulhas–Falkland fracture zone (AFFZ); and Falkland segment, south of AFFZ.<ref name="Torsvik2009-p1316">{{Harvnb|Torsvik|Rousse|Labails|Smethurst|2009|loc=General setting and magmatism, pp. 1316–1318}}</ref>

In the southern segment the Early Cretaceous (133–130&nbsp;Ma) intensive [[magmatism]] of the [[Paraná and Etendeka traps|Paraná–Etendeka Large Igneous Province]] produced by the [[Tristan hotspot]] resulted in an estimated volume of {{cvt|1.5e6|to|2.0e6|km3}}. It covered an area of {{cvt|1.2e6|to|1.6e6|km2}} in Brazil, Paraguay, and Uruguay and {{cvt|0.8e5|km2}} in Africa. [[Dyke swarm]]s in Brazil, Angola, eastern Paraguay, and Namibia, however, suggest the LIP originally covered a much larger area and also indicate failed rifts in all these areas. Associated offshore basaltic flows reach as far south as the Falkland Islands and South Africa. Traces of magmatism in both offshore and onshore basins in the central and southern segments have been dated to 147–49&nbsp;Ma with two peaks between 143 and 121&nbsp;Ma and 90–60&nbsp;Ma.<ref name="Torsvik2009-p1316" />

In the Falkland segment rifting began with dextral movements between the Patagonia and Colorado sub-plates between the Early Jurassic (190&nbsp;Ma) and the Early Cretaceous (126.7&nbsp;Ma). Around 150&nbsp;Ma sea-floor spreading propagated northward into the southern segment. No later than 130&nbsp;Ma rifting had reached the Walvis Ridge–Rio Grande Rise.<ref name="Seton-2012-p217" />

In the central segment, rifting started to break Africa in two by opening the [[Benue Trough]] around 118&nbsp;Ma. Rifting in the central segment, however, coincided with the [[Geomagnetic reversal#Superchrons|Cretaceous Normal Superchron]] (also known as the Cretaceous quiet period), a 40&nbsp;Ma period without magnetic reversals, which makes it difficult to date sea-floor spreading in this segment.<ref name="Seton-2012-p217" />

The equatorial segment is the last phase of the break-up, but, because it is located on the Equator, magnetic anomalies cannot be used for dating. Various estimates date the propagation of seafloor spreading in this segment and consequent opening of the Equatorial Atlantic Gateway (EAG) to the period 120–96&nbsp;Ma.<ref name="GiorgioniEtAl2015">{{cite journal|last1=Giorgioni|first1=Martino|last2=Weissert|first2=Helmut|last3=Bernasconi|first3=Stefano M.|last4=Hochuli|first4=Peter A.|last5=Keller|first5=Christina E.|last6=Coccioni|first6=Rodolfo|last7=Petrizzo|first7=Maria Rose|last8=Lukeneder|first8=Alexander|last9=Garcia|first9=Therese I.|date=March 2015|title=Paleoceanographic changes during the Albian–Cenomanian in the Tethys and North Atlantic and the onset of the Cretaceous chalk|url=https://www.sciencedirect.com/science/article/abs/pii/S0921818115000211|journal=[[Global and Planetary Change]]|volume=126|pages=46–61|doi=10.1016/j.gloplacha.2015.01.005|bibcode=2015GPC...126...46G|access-date=2 December 2022|issn=0921-8181|archive-date=10 October 2023|archive-url=https://web.archive.org/web/20231010112024/https://www.sciencedirect.com/science/article/abs/pii/S0921818115000211|url-status=live}}</ref><ref name="LateAptianPalaeoceanography">{{cite journal|last1=De A. Carvalho|first1=Marcelo|last2=Bengtson|first2=Peter|last3=Lana|first3=Cecília C.|date=23 November 2015|title=Late Aptian (Cretaceous) paleoceanography of the South Atlantic Ocean inferred from dinocyst communities of the Sergipe Basin, Brazil|journal=[[Paleoceanography and Paleoclimatology]]|volume=31|issue=1|pages=2–26|doi=10.1002/2014PA002772|doi-access=free}}</ref> This final stage, nevertheless, coincided with or resulted in the end of continental extension in Africa.<ref name="Seton-2012-p217" />

About 50&nbsp;Ma the opening of the [[Drake Passage]] resulted from a change in the motions and separation rate of the South American and Antarctic plates. First, small ocean basins opened and a shallow gateway appeared during the Middle Eocene. 34–30&nbsp;Ma a deeper seaway developed, followed by an [[Eocene–Oligocene extinction event|Eocene–Oligocene climatic deterioration]] and the growth of the [[Antarctic ice sheet]].<ref>{{Harvnb|Livermore|Nankivell|Eagles|Morris|2005|loc=Abstract}}</ref>