Panama # 2
Monday, 11. August 2008, 12:46:05
In Gulf Stream born 3 million years ago? I wrote about what happened at the Panama isthmus about 3 million years ago.
But how was the situation in what is now Central America before then? Mainly based upon sedimentology Kirby et al. try to get a better grip on the last 30 million years in an open access article in PLoS ONE: Lower Miocene Stratigraphy along the Panama Canal and Its Bearing on the Central American Peninsula.
Here is the opening paragraph from their introduction:
The palaeogeographic nature of southern Central America before the isthmus has been much disputed. Much of the discussion relates to the relative and absolute timing of some of the sediment formations along the Panama Canal (see the paper for this discussion).
As part of the Central American volcanic arc, the Panama microplate formed through subduction of various oceanic plates during the Cretaceous (145 to 65 million years ago) and Cenozoic (65 million years ago to the present). This microplate lies between the Cocos and Nazca plates to the south, the Caribbean plate to the north and the South American plate to the east. See tectonic map below.
A short-lived strait - the Culebra Strait - may have existed across the Panama Canal Basin sometime between 21 and 19 million years ago (on the first map in this post light grey represents the outline of tectonic plates containing continental or volcanic-arc crust. Dark grey represents land above sea level). The earliest evidence for a terrestrial connection between Panama (but NOT South America) and North America is 19 million years ago. After that the authors found no evidence for the disruption of the southern Central America peninsula until 6 million years ago, when there is evidence for a short-lived strait across the Panama Canal Basin. The existence of a peninsula for much of the Miocene (about 23 to 5 million years ago) has implications for our understanding of the tectonic, climatic, oceanographic and biogeographic history related to the formation of the Isthmus of Panama.
* http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002791
* http://www.physorg.com/news136614198.html
* http://www.terradaily.com/reports/Isthmus_Of_Panama_Formed_As_Result_Of_Plate_Tectonics_999.html
But how was the situation in what is now Central America before then? Mainly based upon sedimentology Kirby et al. try to get a better grip on the last 30 million years in an open access article in PLoS ONE: Lower Miocene Stratigraphy along the Panama Canal and Its Bearing on the Central American Peninsula.Here is the opening paragraph from their introduction:
The palaeogeography of Central America has changed profoundly over the past 30 million years (m.y.), from a volcanic arc separated from South America by a wide seaway, to an isthmus that connected North and South America by 3 Ma. The formation of the Isthmus of Panama was important because it allowed the mixing of terrestrial faunas between the two continents, as well as physically separating a once continuous marine province into separate and distinct Pacific and Caribbean communities. The formation of the Isthmus of Panama also ultimately led to profound changes in global climate by strengthening the Gulf Stream and thermohaline downwelling in the North Atlantic.
The palaeogeographic nature of southern Central America before the isthmus has been much disputed. Much of the discussion relates to the relative and absolute timing of some of the sediment formations along the Panama Canal (see the paper for this discussion).
As part of the Central American volcanic arc, the Panama microplate formed through subduction of various oceanic plates during the Cretaceous (145 to 65 million years ago) and Cenozoic (65 million years ago to the present). This microplate lies between the Cocos and Nazca plates to the south, the Caribbean plate to the north and the South American plate to the east. See tectonic map below.
A short-lived strait - the Culebra Strait - may have existed across the Panama Canal Basin sometime between 21 and 19 million years ago (on the first map in this post light grey represents the outline of tectonic plates containing continental or volcanic-arc crust. Dark grey represents land above sea level). The earliest evidence for a terrestrial connection between Panama (but NOT South America) and North America is 19 million years ago. After that the authors found no evidence for the disruption of the southern Central America peninsula until 6 million years ago, when there is evidence for a short-lived strait across the Panama Canal Basin. The existence of a peninsula for much of the Miocene (about 23 to 5 million years ago) has implications for our understanding of the tectonic, climatic, oceanographic and biogeographic history related to the formation of the Isthmus of Panama.
* http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002791
* http://www.physorg.com/news136614198.html
* http://www.terradaily.com/reports/Isthmus_Of_Panama_Formed_As_Result_Of_Plate_Tectonics_999.html
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