Editing Geography of Panama (section)

==Geology==
The Cocos and Nazca plates formed in the [[Miocene]]. The Panama microplate is made of [[oceanic crust]] [[basalt]], similar to the [[Caribbean large igneous province|basalt plateau]] at the bottom of the [[Caribbean Sea]]. The [[isthmus of Panama]] formed due to [[convergent boundary|convergent tectonics]] of the [[eastern Pacific]] [[subduction zone]], which created a [[volcanic arc|magmatic arc]] extending from southern [[North America]].

The center of the isthmus, from [[Arenal Volcano]] in [[Costa Rica]] to [[El Valle (volcano)|El Valle volcano]] in Panama was [[tectonic uplift|uplifted]] during the subduction of the unusually thick [[Cocos Ridge]] oceanic crust, which also produced the four kilometer high [[Talamanca Range]]. The western edge of the Caribbean Plate—the [[Central American Volcanic Arc]]—also collided in the [[Neogene]] and was compressed as the [[South American Plate]] moved northward. The El Valle volcano is the easternmost [[stratovolcano]] in [[Central America]]. [[Dacite]] and [[andesite]] flows from five to 10&nbsp;million years ago are the oldest rocks, followed by a period of quiet 3.4&nbsp;million years ago and newer dacite [[lava dome|dome]]s and [[pyroclastic flows]] between 900,000 and 200,000 years ago. The volcano was the result of crust subduction.<ref>{{cite journal|title=Andesite and dacite genesis via contrasting processes: the geology and geochemistry of El Valle Volcano, Panama|first1=Mare J.|last1=Defant|first2=Lee F.|last2=Clark|first3=Robert H.|last3=Stewart|first4=Mark S.|last4=Drummond|first5=Jelle Z.|last5=de Boer|first6=René C.|last6=Maury|first7=Hervé|last7=Bellon|first8=Thomas E.|last8=Jackson|first9=Juan F.|last9=Restrepo|date=1 January 1991|journal=Contributions to Mineralogy and Petrology|volume=106|issue=3|pages=309–324|doi=10.1007/bf00324560|bibcode=1991CoMP..106..309D |s2cid=130132647 }}</ref>

The combination of these forces produced the Isthmus of Panama and resulted in different [[sea surface]] [[salinity]] between the [[Pacific Ocean|Pacific]] and [[Atlantic Ocean|Atlantic]] since 4.2&nbsp;million years ago.<ref>{{cite journal|url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/29/3/207/191840|title=Role of Panama uplift on oceanic freshwater balance|first1=Gerald H.|last1=Haug|first2=Ralf|last2=Tiedemann|first3=Rainer|last3=Zahn|first4=A. Christina|last4=Ravelo|date=9 November 2018|journal=Geology|volume=29|issue=3|pages=207|doi=10.1130/0091-7613(2001)029<0207:ROPUOO>2.0.CO;2}}</ref> It also resulted in [[Great American Interchange|massive interchange of species]] between North and [[South America]] and brought global changes in [[paleoclimatology|climate]] and [[ocean current|ocean circulation]].
The [[Bocas del Toro Archipelago]] on the western Caribbean coast records local [[stratigraphy]] through this period, with [[Pliocene]] to [[Pleistocene]] [[coral reef]] [[carbonate]]s overlying Miocene basalt and [[siliclastic]] [[shale]].<ref name="si">{{cite journal |journal=Caribbean Journal of Science|volume=41|issue=3|pages=374–391|year=2005 |url=https://repository.si.edu/bitstream/handle/10088/3831/Coates_McNeill_Aubry_Beerggren_and_Collins_2005.pdf|title=An Introduction to the Geology of the Bocas del Toro Archipelago, Panama|author=A. G. Coates, D. F. McNeill, M-P. Aubry, W. A. Berggren, L. S. Collins |accessdate=2018-11-09}}</ref>

In the remote southeastern [[Darién Province]], [[crystal]]line [[basement rock]] of the [[San Blas Range|San Blas Complex]] forms [[massif]]s in the northeast and southwest, dating to the [[Cretaceous]], [[Paleocene]] and [[Eocene]]. These rocks and others in the north such as [[rhyolite]], [[dacite]], [[basaltic andesite]], [[granodiorite]] and [[quartz]] [[diorite]] indicate that the region was a separate magmatic arc until 20&nbsp;million years ago. In the south, pre-collision basement rocks include [[radiolaria]]n [[chert]], [[pillow lava|pillow basalt]] and [[diabase]]. Complex [[faulting]] and folding formed the {{anchor|Chucunaque-Tuira Basin}}[[Chucunaque River|Chucunaque]]-[[Tuira River|Tuira]] [[Sedimentary basin|Basin]] which includes three kilometers of [[sediment]]s from the Miocene deposited during the collision with South America.<ref>{{cite journal|url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/116/11-12/1327/125266|title=The Geology of the Darien, Panama, and the late Miocene-Pliocene collision of the Panama arc with northwestern South America|first1=A. G.|last1=Coates|first2=L. S.|last2=Collins|first3=M.-P.|last3=Aubry|first4=W. A.|last4=Berggren|date=1 November 2004|journal=Geological Society of America Bulletin|volume=116|issue=11–12|pages=1327–1344|doi=10.1130/B25275.1|bibcode=2004GSAB..116.1327C }}</ref>

Offshore of [[Colombia]] and western Panama, the Panama Basin formed between 27 and eight million years ago due to [[asymmetry|asymmetric]] [[seafloor spreading]] between the Nazca and Cocos plates. The Mapelo [[rift]] and the Yaquina [[graben]] in the eastern basin are remnants of [[aulacogen|old and now inactive spreading centers]]. Between 22 and 20&nbsp;million years ago, [[hotspot (geology)|hotspot]] [[volcanism]] generated the [[Carnegie Ridge|Carnegie]], Cocos and [[Malpelo Island|Malpelo]] ridges.<ref>{{cite journal|url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/89/7/981/187594|title=Structure and tectonic history of the eastern Panama Basin|first1=PETER|last1=LONSDALE|first2=KIM D.|last2=KLITGORD|date=9 November 1978|journal=Geological Society of America Bulletin|volume=89|issue=7|pages=981|doi=10.1130/0016-7606(1978)89<981:SATHOT>2.0.CO;2|bibcode=1978GSAB...89..981L }}</ref>