A remarkable series of comments by Jim Coyle describes The Drake Passage as a massive “impact trench”.
Jim Coyle says: December 21, 2013 at 21:35
This is phenomenal and answers a lot of my questions about geologic and geographic entities.
You should try looking at The Drake passage between South America and Antartica.
On Google earth you will see a definite crater and impact trench, also possibly 3 smaller craters in a small cluster just to the north of it.
The main crater has a classic double wall rim but the smaller hits appear to have filled in the west side of the crater so no rebound cone or ridge is visible.
The smaller craters do have central cone features.
On one of your maps showing impacts around the globe I noticed one on about the same latitude but further west of what I’m proposing.
Could be a 5th related hit kind of daisy chaining?
Jim Coyle says: December 22, 2013 at 14:44
You need to move to the east to see the double ring leading edge of the main crater.
Also pull back a little bit more for a larger view.
You will se how the 2 landmasses are pulled to the east with the impact and you’ll also see the 2, possibly 3 craters to the north and just behind the main one.
Jim Coyle says: December 26, 2013 at 17:09
As I was checking things out I looked for any climate changes in the 33 million yr range and found that was when Antartica started to glaciate.
At that same time there was a down turn in atmospheric CO2. Coincidence?
The mainstream Age of the Ocean Floor suggests The Drake Passage Impact Event occurred around 33 million years ago.
This dating places The Drake Passage Impact Event at the start of the Oligocene.
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present (33.9±0.1 to 23.03±0.05 Ma).
As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly uncertain.
Therefore, it is unsurprising that the mainstream associates the start of the Oligocene with “a notable extinction event called the Grande Coupure”.
The start of the Oligocene is marked by a notable extinction event called the Grande Coupure; it featured the replacement of European fauna with Asian fauna, except for the endemic rodent and marsupial families. By contrast, the Oligocene-Miocene boundary is not set at an easily identified worldwide event but rather at regional boundaries between the warmer late Oligocene and the relatively cooler Miocene.
The Grande Coupure, or “great break” in continuity, with a major European turnover in mammalian fauna about 33.5 Ma, marks the end of the last phase of Eocene assemblages, the Priabonian, and the arrival in Europe of Asian immigrants. The Grande Coupure is characterized by widespread extinctions and allopatric speciation in small isolated relict populations
The mainstream failure to recognise The Drake Passage Impact Event has resulted in considerable debate over when The Drake Passage actually opened and confusion regarding the dramatic changes in ocean circulation [and heat distribution] that were triggered by this impact event.
The Oligocene sees the beginnings of modern ocean circulation, with tectonic shifts causing the opening and closing of ocean gateways.
Cooling of the oceans had already commenced by the Eocene/Oligocene boundary, and they continued to cool as the Oligocene progressed.
The formation of permanent Antarctic ice sheets during the early Oligocene and possible glacial activity in the Arctic may have influenced this oceanic cooling, though the extent of this influence is still a matter of some significant dispute.
The effects of oceanic gateways on circulation
The opening and closing of ocean gateways: the opening of the Drake Passage; the opening of the Tasmanian Gateway and the closing of the Tethys seaway; along with the final formation of the Greenland-Iceland-Faroes sill; played vital parts in reshaping oceanic currents during the Oligocene.
As the continents shifted to a more modern configuration, so too did ocean circulation.
The Drake Passage
The Drake Passage is located between South America and Antarctica.
Once the Tasmanian Gateway between Australia and Antarctica opened, all that kept Antarctica from being completely isolated by the Southern Ocean was its connection to South America.
As the South American continent moved north, the Drake Passage opened and enabled the formation of the Antarctic Circumpolar Current (ACC), which would have kept the cold waters of Antarctica circulating around that continent and strengthened the formation of Antarctic Bottom Water (ABW).
With the cold water concentrated around Antarctica, sea surface temperatures and, consequently, continental temperatures would have dropped.
The onset of Antarctic glaciation occurred during the early Oligocene, and the effect of the Drake Passage opening on this glaciation has been the subject of much research.
However, some controversy still exists as to the exact timing of the passage opening, whether it occurred at the start of the Oligocene or nearer the end.
Even so, many theories agree that at the Eocene/Oligocene (E/O) boundary, a yet shallow flow existed between South America and Antarctica, permitting the start of an Antarctic Circumpolar Current.
Stemming from the issue of when the opening of the Drake Passage took place, is the dispute over how great of an influence the opening of the Drake Passage had on the global climate.
While early researchers concluded that the advent of the ACC was highly important, perhaps even the trigger, for Antarctic glaciation and subsequent global cooling, other studies have suggested that the δ18O signature is too strong for glaciation to be the main trigger for cooling.
Through study of Pacific ocean sediments, other researchers have shown that the transition from warm Eocene ocean temperatures to cool Oligocene ocean temperatures took only 300,000 years, which strongly implies that feedbacks and factors other than the ACC were integral to the rapid cooling.
The Late Oligocene opening of the Drake Passage
The latest-hypothesized time for the opening of the Drake Passage is during the early Miocene.
Despite the shallow flow between South America and Antarctica, there was not enough of a deep water opening to allow for significant flow to create a true Antarctic Circumpolar Current.
If the opening occurred as late as hypothesized, then the Antarctic Circumpolar Current could not have had much of an effect on early Oligocene cooling, as it would not have existed.
The Early Oligocene Opening of the Drake Passage
The earliest-hypothesized time for the opening of the Drake Passage is around 30 Ma.
One of the possible issues with this timing was the continental debris, as it were, cluttering up the seaway between the two plates in question.
This debris, along with what is known as the Shackleton Fracture Zone, has been shown in a recent study to be fairly young, only about 8 million years old.
The aforementioned study concludes that the Drake Passage would be free to allow significant deep water flow by around 31 Ma.
This would have facilitated an earlier onset of the Antarctic Circumpolar Current.
Currently, an opening of the Drake Passage during the early Oligocene is favored.
The Opening of the Tasman Gateway
The other major oceanic gateway opening during this time was the Tasman, or Tasmanian, depending on the paper, gateway between Australia and Antarctica.
The time frame for this opening is less disputed than the Drake Passage and is largely considered to have occurred around 34 Ma.
As the gateway widened, the Antarctic Circumpolar Current strengthened.
The Tethys Seaway Closing
Though the Tethys was not a gateway, but rather a sea in its own right.
Its closing during the Oligocene had significant impact on both ocean circulation and climate.
The collisions of the African plate with the European plate and of the Indian subcontinent with the Asian plate, cut off the Tethys seaway that had provided a low-latitude ocean circulation.
The closure of Tethys built some new mountains (the Zagros range) and drew down more carbon dioxide from the atmosphere, contributing to global cooling.
The gradual separation of the clump of continental crust and the deepening of tectonic sill in the North Atlantic that would become Greenland, Iceland, and the Faroe Islands helped to increase the deep water flow in that area.
Evidence for ocean-wide cooling during the Oligocene exists mostly in isotopic proxies.
Patterns of extinction and patterns of species migration can also be studied to gain insight into ocean conditions.
For a while, it was thought that the glaciation of Antarctica may have significantly contributed to the cooling of the ocean, however, recent evidence tends to deny this.
Isotopic evidence suggests that during the early Oligocene, the main source of deep water was the North Pacific and the Southern Ocean.
As the Greenland-Iceland-Faroe sill deepened and thereby connected the Norwegian-Greenland sea with the Atlantic Ocean, the deep water of the North Atlantic began to come into play as well.
Computer models suggest that once this occurred, a more modern in appearance thermo-haline circulation started.
North Atlantic Deep Water
Evidence for the early Oligocene onset of chilled North Atlantic Deep Water lies in the beginnings of sediment drift deposition in the North Atlantic, such as the Feni and Southeast Faroe drifts
South Ocean Deep Water
The chilling of the South Ocean Deep Water began in earnest once the Tasmanian Gateway and the Drake Passage opened fully.
Regardless of the time at which the opening of the Drake Passage occurred, the effect on the cooling of the Southern Ocean would have been the same.
The Drake Passage Impact Event provides intriguing insights into the Ice Age Paradox where additional oceanic heat is required to drive precipitation and ice accumulation in Polar Regions.
Firstly, the establishment of the Antarctic Circumpolar Current and the Thermo-Haline Circulation cooled the tropical oceans and warmed the polar oceans.
Secondly, the heat released via seafloor spreading helped drive the global Thermo-Haline Circulation and increased precipitation over Greenland, Norway and around Antarctica.
Thirdly, the establishment of the Antarctic Circumpolar Current and Thermo-Haline Circulation ensured that the climate changed on a global scale.
Whether this abrupt change was caused by climate change associated with the earliest polar glaciations and a major fall in sea levels, or by competition with taxa dispersing from Asia, few argue for an isolated single cause.
More spectacular possible causes are related to the impact of one or more large bolides in northern hemisphere at Popigai, Toms Canyon and Chesapeake Bay.
Improved correlation of northwest European successions to global events confirms the Grande Coupure as occurring in the earliest Oligocene, with a hiatus of about 350 millennia prior to the first record of post-Grande Coupure Asian immigrant taxa.
Intriguingly, the relationship between sea floor spreading and global temperatures appear to have been closely correlated for the last 180 million years.
Unsurprisingly, the rate of seafloor spreading is also closely correlated with sea level for the last 180 million years.
Unsurprisingly, the Drake Passage Impact Event [at the start of Oligocene] provides further support for the Inflating Earth and Increasing Terrestrial Gravity theories.
An element of the paradigm of the Grande Coupure was the apparent extinction of all European primates at the Coupure: the recent discovery of a mouse-sized early Oligocene omomyid, reflecting the better survival chances of small mammals, further undercut the Grand Coupure paradigm.