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quote:Originally posted by DinoI would be terribly grateful if anyone can tell me when South America separated from North America in the approximate period 135-140 million years ago. A separation based on the fossil record will do.Thanks.
quote:The Isthmus of Panama is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It was formed some 3 million years ago during the Pliocene epoch.
quote:Originally posted by ADD HAHAHAwats it matter?Drew Rody
quote:Originally posted by another_someonequote:Originally posted by DinoI would be terribly grateful if anyone can tell me when South America separated from North America in the approximate period 135-140 million years ago. A separation based on the fossil record will do.Thanks.What do you mean 'separated'?South America used to be joined to Africa, North America used to be joined up to Europe.North and South America connected about 3 million years ago.http://en.wikipedia.org/wiki/Isthmus_of_Panamaquote:The Isthmus of Panama is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It was formed some 3 million years ago during the Pliocene epoch. Or are you asking when Gondwana broke up, which was the supercontinent that connected all of the current land masses into one, including North and South America. That was around 160 million years ago, when Africa (with South America still attached) broke off from the remainder of Gondwana.
quote:The Jurassic period is a major unit of the geologic timescale that extends from about 200 Ma (million years ago) at the end of the Triassic to 146 Ma at the beginning of the Cretaceous. During the early Jurassic, the supercontinent Pangea broke up into North America, Eurasia and Gondwana. Still, the early Atlantic and Tethyan Oceans were relatively narrow. In the late Jurassic, the southern continent, Gondwana, started to break up and as the Tethys closed the Neotethys basin appeared. Climates were warm with no evidence of glaciation. As in the Triassic, apparently there was no land near either pole, and no extensive ice caps existed. The geological record of the Jurassic is well exposed in western Europe, where marine sequences are found along the coasts. A shallow sea (epicontinental sea) called the Sundance Sea was present in parts of the northern plains of the United States and Canada. Most Jurassic exposures in North America are continental. Important Jurassic exposures are also found in Russia, India, South America, Japan, Australasia, and the United Kingdom.
quote:The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65.5 Ma). The end of the Cretaceous also defines the boundary between the Mesozoic and Cenozoic eras. During the Cretaceous, the late Paleozoic - early Mesozoic supercontinent of Pangea completed its breakup into present day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened and South America drifted westwards, Gondwana itself broke up as Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached). Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide. To the north of Africa the Tethys Sea continued to narrow. Within the continents, a broad shallow sea advanced across central North America (the Western Interior Seaway) and then started to recede, leaving thick marine deposits sandwiched between coal beds.Other important Cretaceous exposures occur in Europe and China. In the area that is now India, massive lava beds called the Deccan Traps were laid down in the very late Cretaceous and early Paleocene. Climates were warm, and even polar regions had no permanent ice.
quote:The southern supercontinent Gondwana (originally Gondwanaland) included most of the landmasses which make up today's continents of the southern hemisphere, including Antarctica, South America, Africa, Madagascar, India, Arabia, Australia-New Guinea and New Zealand. It was formed in the early Jurassic about 200 million years ago by the break-up of Pangaea. The other continents at that time — North America and Eurasia — were still joined, forming the northern supercontinent, Laurasia.Although Gondwana was centered roughly where Antarctica is today (at the extreme south of the globe), the climate was generally mild. During the Mesozoic, average global temperatures were considerably warmer than they are today. Gondwana was then host to a huge variety of flora and fauna for many millions of years.The supercontinent began to break up in the late Jurassic (about 160 million years ago) when Africa became separated and began to drift slowly northwards. The next large block to break away was India, in the early Cretaceous (about 125 million years ago). New Zealand followed about 80 million years ago, only about 15 million years before the Cretaceous-Tertiary extinction event wiped out about 50% of all species on the planet, most notably the dinosaurs.As the age of mammals got underway, the continent of Australia-New Guinea began to gradually separate and move north (55 million years ago), rotating about its axis to begin with, and thus retaining some connection with the remainder of Gondwana for a considerable time.About 45 million years ago, the Indian subcontinent collided with Asia, forcing the crust to buckle and forming the Himalayas. At about the same time, the southern-most portion of Australia (modern Tasmania) finally separated from what is now Antarctica, allowing ocean currents to flow between the two continents for the first time. This in turn produced cooler and drier climates on the two landmasses.Far more significant as a world climatic event, however, was the separation of South America from Antarctica sometime during the Oligocene, perhaps 30 million years ago. With the opening of Drake Passage, there was now no barrier to force the cold waters of the Southern Ocean north, to be exchanged with warmer tropical water. Instead, a cold circumpolar current developed and Antarctica became what it is today: a frigid continent which locks up much of the world's fresh water as ice. Sea temperatures dropped by almost 10 degrees, and the global climate became much colder.About 15 million years ago, New Guinea began to collide with southern Asia, once again pushing up high mountains, and more recently still, South America became joined to North America via the Isthmus of Panama. This had the effect of cutting off circulation of warm water, creating the Arctic.The continent was named by Eduard Suess after Gondwana, a region of eastern India where some of the geology of the ancient continent was determined.
quote:Originally posted by DoctorBeaveranother_someone - that's almost exactly what it says in the link I posted.
quote:As the rift then extended further westwards and South America became separated from North and Central America the bodies of water on either side of Pangea finally met up with each other.
quote:As time went on the rift extended further west and south. It cut through that part of the US which is today the Gulf of Mexico and at the end separated South America from North America. It was only relatively late in the Jurassic that the enormous salt sediments of the Gulf of Mexico were deposited. Presumably the water, from which the evaporite originated, forced its way into the rift from the Pacific side of the continent..