The Panama Uplift and the Closing of the Central American Seaway – Part I

As discussed in the last post, most scientists, historians and scholars are conditioned by their training and the strict criteria of their profession. When that training insists that the world is 4.55 billion years old and it takes eons of time for the features of the Earth to change, then these professionals interpret all matters based on that single, and to them, unquestionable fact.
    As an example, most geologists agree that there was once a flow-through waterway between what is now Central America and South America—it was called the Central American Seaway, also known as the Panamanic Inter-American and Proto-Caribbean Seaway, or just plain Panama Seaway, was a body of water that once separated North America from South America.

The Great Panamanian Seaway, a single tropical ocean between North and South America 

At that point in time, what is now Panama and much of Central America, was then under water or, more accurately, much of this land mass was yet to form, and water flowed freely between these two climatically important ocean basins—the Pacific and Caribbean Basins.
    Naturally, the position of continents or large land masses, drifting around the Earth’s surface would have a major impact on the climate. The positioning of continents naturally affects the shape and size of the oceans, and crucially, the currents that flow within them that transport energy (in the form of heat) to different parts of the globe. It also effects the direction and manner in which wind currents flow over the lands and the oceans.
    Thus, in the shoaling (shallowing) of the flow-through ocean, or the Panama Seaway, any closure of that “gateway” that would connect the two land masses of North and South America, would obviously affect in some ways the ocean currents, winds, and climate those waters bring. In the case of the forming of the Isthmus of Panama, a warm (or tropical) current from the Caribbean flowing northeastward was established, without mixture with the colder Pacific currents, creating the Gulf Stream (North American Drift) that warmed the eastern seaboard of North America as well as western Europe.

Closing the “gate” of the Panamanian Seaway diverted Pacific Currents to flow back into the Pacific, and the Gulf Currents to flow northward

The emerging of the Central American landmass, as a result of the volcanic Isthmus of Panama rising up from the sea floor and bridging the formerly separated continents and the closing of the Central American Seaway can be divided into four categories.
1. Direct geologic observation of crustal thickening and submarine deposits in Central America.
2. The Great American Interchange, which is the interchange of vertebrates between North and South America which required a continuous land bridge across the two areas for the organisms to travel along with a climate that was very different than the climate today.
3. Different histories of the oceans on either side of the isthmus, with formation of the Isthmus of Panama is recorded by changes in the chemistry, composition, and structure of sediments and fossils in deep sea and coastal rock records across the Caribbean and eastern Pacific.
4. Development of differences in marine assemblages and their isotopic signatures in the Caribbean from those in the Pacific.
    In this last issue, the interchange is visible from observation of both biostratigraphy and nature, with its most dramatic effect seen in the zoogeography of mammals, including marsupials, but also provided opportunity for reptiles, amphibians, arthropods (insects, arachnids, myriapods and crustaceans), weak-flying or flightless birds and even freshwater fish to migrate. In fact, in the deep ocean, divergences in neodymium isotopes and benthic foraminifera (taxa) between Caribbean and Pacific sites, as well as an abrupt increase in the Pacific carbonate compensation depth, provide strong evidence that deepwater connection was shut off with the deepest part of the sill of the Panama Arc must shoaled to around  have shoaled to less than 4,000 feet.

After the Isthmus of Panama formed, animals and plants could move back and forth between continents, the Great American Biological Interchange. Smithsonian scientists are debating when this happened.                                    Image: Smithsonian Tropical Research Institute 

According to geologists and palaeoceanographic scientists, an ocean once covered the area where Panama is today. There was a gap between the continents of North and South America through which the waters of the Atlantic and Pacific Oceans flowed freely. Beneath the surface, two plates of the Earth’s crust were colliding into one another, forcing the Pacific Plate to slide under the Caribbean Plate. The pressure and heat caused by this collision led to the formation of underwater volcanoes, some of which grew tall enough to break the surface of the ocean and form islands which became filled in between.
    As more volcanic islands rose to fill in the area as the movement of the two tectonic plates pushed up the sea floor, eventually forcing some areas above sea level. This created the current Panama Isthmus, enabling an interchange to occur.
    This interchange was first discussed in 1876 by the "father of biogeography,” Alfred Russel Wallace, British naturalist, explorer, geographer, anthropologist and biologist, who spent 1848-1852 exploring and collecting specimens in the amazon Basin. In addition, the fossil discoveries of Florentino Ameghino, an Argentine naturalist, paleontologist, anthropologist and zoologist, and the most important founding figure in South American paleontology also played an important role in the ancient Seaway discovery. William D. Matthew, with his work in mammal fossils; William B. Scott, a vertebrate paleontologist and professor of geology and paleontology at Princeton; Bryan Patterson, an American paleontologist at the Field Museum of Natural History in Chicago; and George Gaylord Simpson, the most influential paleontologist of the 20^th century, also contributed to the studies and finding of the ancient Seaway.
    It should be noted that while almost all geologists, anthropologists and paleontologists agree that the Seaway once subsisted, the controversy today is based on not whether it existed, but when it took place. Typically, it is proposed by those who have developed this theory, that the Seaway closed between 3.5 to 2.8 million years ago.

The major tectonic plates involved in the closing of the Seaway were the Cocos, Nazca, Panama, and North Andean; in addition, the microplates of Galapagos and Caribbean were also part of this tectonic activity

As for the tectonic aspect of the closing, the Southern Caribbean geology is a very complex product of three colliding tectonic plates and their interactions. These geological processes drive both the generation and movement of terrestrial landmasses of this area, which in turn control the distribution, migration and ultimately, the evolution of terrestrial biotas. The colliding and moving of these three plates resulted in the rising of the area now known as the Panama Isthmus and lower Central America.
    Even though the geological build-up of Panama occurred over a small spatial scale, it produced major palaeoceanographic, climatic, biogeographic and evolutionary changes that have attracted the attention of researchers for a long time. Before the closure, the separation of North and South America provided a tropical seaway between the Atlantic and Pacific that remained open until the Isthmus of Panama formed “in the relatively recent past.”
(See the next post, “The Panama Uplift and the Closing of the Central American Seaway – Part II,” for additional information and effect of the uplift of the Isthmus of Panama and the closing of the Panama Seaway to see the reality of this event, as well as that of other effects of land mass uplift in South America)