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CHAPTER 2.4
THE SOUTH AMERICAN
SURPRISE
India is the most recent continental tectonic
plate created at the antipode of a very large impact 65 MYA. The next youngest
is South America, created 132 MYA.
This chapter will explain the uplift
and movement of the South American continent, as well as the creation and
movement of its hotspot and the location of the impact that started it all.
The Standard Theory treats South America as an old continent that has
been around for a long, long time. All of the models of tectonic movement show
South America existing in one form or another going back 500 million years or
more.
Guess what? The models are wrong.
The actual continental
crust was old enough, but it was not separated from Africa. It was part of the
original African continent. The shape of South America did not exist as a
separate entity until it was created out of Africa and some oceanic sea floor
that was near it 132 MYA.
At first, I assumed that South America was an
old continent, similar to Australia, Africa and Europe. However, when
investigating the Large Igneous Provinces (LIP), I found that South America had
a LIP that was in the right place for an antipodal hotspot. Furthermore, this
LIP (the Parana and Etendeka traps) dated to a single big eruption 132 MYA. The
volcanism was extensive, rivaling that of India 65 MYA and Siberia 250 MYA. I
later realized that this LIP was the product of crack propagation going from
the interior antipode location to the continental uplift edge ... see "Crack
Propagation" later in this chapter.
Moreover, the magnetic anomalies
indicating the beginning of seafloor spreading did not begin until 132 MYA.
Therefore, the "real" breakup of Africa and South America didn't begin until
132 MYA. 60
PARANA & ETENDEKA TRAPS
The reason that the traps are called the Parana and Etendeka traps is because,
while most of them are in South America (Parana), there are some in Africa that
share the same characteristics … enough so that geologists generally
accept the idea that these traps were originally part of a single magmatic
province. 61
The Standard Theory says that Africa and South
America were rifting for a while (since 200 MYA?) and finally started
separating 132 MYA. The coastlines of the two continents meshed together while
they were part of Pangaea … I guess that was just a coincidence that the
two continents had such a close fit ... yeah, right.
GUESS AGAIN
All of the
factors for an impact causing a continental uplift are in place in this
situation (except for the impact, itself, and we will be getting to that). We
don't need a coincidental continental fit. To top it off, there was even a
worldwide anoxic event that occurred 132 MYA, causing a massive die off of
marine organisms.62 This result is not surprising, since the culprit
impact object was huge (bigger than the Permian object) and, this time, landed
in the Pacific Ocean.
SOUTH AMERICA'S SMOKING GUN
Let's look at the five characteristics needed for a fully formed smoking gun
for the creation of South America.
They are:
1. CRATER - Since the remains of the hotspot are
at about 20 degrees south latitude now and would have been at about 17 degrees
south latitude 132 MYA, we need to look on the opposite side of the world at
about 17 degrees north latitude 132 MYA. The longitudinal position of the
impact 132 MYA would have been directly antipodal to the western African coast
at 17 degrees south latitude. Since this section of Africa is at about zero
degrees longitude, this means that the impact would have been at about 180
degrees longitude.
Unfortunately, this impact location is in the middle
of the Pacific Ocean, which would have been subducting under the Filipino
plate. The subductive edge of the Filipino plate features a reverse arc at
around 146 degrees longitude. Given the normal rate of subduction, an impact
crater that started out at 180 degrees would have been completely subducted
long before now. So, we can assume that any evidence of a large crater would
have been subducted away … or can we? Let's take a closer look.
The subduction edge of the Filipino plate forms a strange reverse arc
at the Marianas Trench, the deepest trench in the world. The Mariana islands
and the seamounts near them are located just behind the Marianas Trench. They
are obviously volcanic structures formed by the subduction process.
The
really surprising feature is another row of seamounts located in more of a
straight line that are found behind the Mariana island reverse arc. Farther to
the north and to the south, these two lines of seamounts join back together,
into a single line. 64,65,66
It is as though the Mariana
island reverse arc pushed out and superceded the old seamount arc. How could
this happen?
Well, let's imagine a very large submarine crater with a
very deep annular trough. Let's imagine that this crater is being subducted
along the old, nearly straight line of seamounts in the Mariana island area
(and let's imagine that the Mariana island reverse arc does not exist yet). At
first, this subduction would not produce any unusual changes.
However,
as the back half of the crater approached the subduction zone, its deeper ring
might very well start to take over the subduction function.
As we will
see in Chapter 2.6 concerning the Tonga Trench, a trench is a powerful
subduction startup mechanism … even when the other helping factors are not
present.
This scenario would explain the strange double row of
seamounts and the unusual shape of the Mariana island arc.
Furthermore,
the timing is right. The island of Guam, located at the southern end of the
Mariana fore-arc, was the site of early arc magmatism between 43 MYA and 32
MYA, according to Mark K. Reagan and Arend Miejer. 63
If the
large impact occurred approximately 132 MYA and the earliest volcanic activity
at Guam was at about 43 MYA, this would give the crater about 90 million years
to travel from approximately 180 degrees longitude to approximately 145 degrees
longitude. In other words, the impact crater would have to move approximately
35 degrees (or about 2300 miles) in 90 million years. This works out to an
average of about 1.6 inches per year … a fairly normal subduction rate.
Therefore, even though we don't have an actual crater, we have what
looks like the remains of a huge crater subduction site with approximately the
right timing and approximately the right location.
The size of the
crater, judging from the subduction arc and the depth of the Mariana trench (a
stand in for the crater's annular ring), could have been huge … 500 miles
in diameter or more (even allowing for slumping and other crater enlargement
mechanisms). However, because the impact was in deep water, much of the energy
would have been absorbed by the water, leaving "only" a net Chicxulub-size
impact on land.
Granted, this Chicxulub-like impact effect was enough
to lift up a medium size continent. But it was not the absolutely apocalyptic
scenario that would have ensued if the impact object had hit on dry land. If it
had hit on dry land, it would have made the Permian extinction look small.
2. HOTSPOT - The hotspot is interior to the South American continent,
leading to a propagated crack which formed the huge Parana and Etendeka LIP.
There was a very large flow basalt eruption circa 132 MYA. There were also
other eruptions, some earlier and some later.
61,67
So, what are we to make of this? How could
there be lava flows more than five million years before the impact object
caused an antipodal hotspot?
The answer is that there were extensive
lava flows throughout the entire area (especially in the area that would become
the northern part of South America) as part of seafloor spreading. Prior to
continental uplift, the west coast of Africa experienced seafloor spreading in
the north and subduction of the Pacific plate (soon to break off as the Nazca
plate) underneath Africa to the south.
But wait a minute! Previously we
had found that magnetic anomalies associated with seafloor spreading in the
South America/Africa area didn't begin until approximately 132 MYA. How could
seafloor spreading have occurred before 132 MYA?
The answer is as
follows: Prior to 132 MYA, South America did not exist. There was seafloor
spreading in the north, but it was between the African plate and the Pacific
plate. The South American continent was uplifted from both seafloor (in its
western areas) and part of the African continent (in its eastern areas).
Therefore, the South American continent contained part of the African
continent's former west coast, as well as spread seafloor and lots of flow
basalt lava from the CAMP (especially the large Amazonia craton). All of the
previous magnetic anomalies of seafloor spreading (in the northern part of
South America) are now obscured, because it now part of the uplifted continent.
Therefore, new seafloor that can be analyzed begins at 132 MYA, at the
time of the South America uplift.
What about the Etendeka part of the
flow basalt lava? If the antipode was interior to the new South American
Continent, then how did the Etendeka area of Africa get involved?
First, let's notice that the Etendeka area is significantly smaller
than the Parana flow basalts. Second, let's remember that, even though the
antipodal hotspot was interior, it wasn't that far away. Also, the cleaving of
South America from Africa would have opened up the lithosphere relatively close
to the antipodal magma plume. It's not surprising that some of the magma
pressure escaped there.
CRACK PROPAGATION
But there
is an even bigger concept to explore here ... and that is the concept of crack
propagation. I have written about the uplift of continents that occurs at the
antipode when a really big impact occurs. However, I have not examined the
details of how this uplift occurs. Yes, it makes sense that the shear zone
would occur at the point where the uplifting power is just barely able to cause
both shear and uplift. But there is likely more to this situation than just a
stand-alone shearing uplift. I believe that the actual mechanism is crack
propagation.
At this point, I would like to harken back to another
example from the cold heading business. That example is the drywall screw.
Drywall screws need to have a very hard outer surface, so that the rolled point
(created during roll threading) will be sharp enough to pierce the drywall and
allow for an easy start, when screwing them in.
The cheap and easy
solution to this problem is to case harden the screws in a heat treat furnace
after the threads and points have been rolled. The case hardening process
infuses a layer of carbon into the surface of the screw (maybe .005 inch thick
) that becomes very hard because of the heat treatment. There is a drawback to
case hardening, however.
The drawback is that the case hardened area is
hard but much more brittle than the rest of the screw. If a crack occurs, it
will spread very easily. Drywall screws are not required to take much
punishment or to deliver much shear strength. Also, drywall screws are not used
in applications where shear failure is a big concern. Therefore, it doesn't
matter if drywall screws are a bit brittle and subject to crack propagation
under rough treatment. What matters is that they function in a normal
environment and that they are inexpensive.
The situation of crack
propagation can also be seen with aluminum foil and plastic wrap. Although both
aluminum foil and plastic wrap can be relatively strong when they are intact,
both can be easily torn when a small crack or tear has been started.
CRACKS FROM THE HOTSPOT
Now,
let's get back to hotspots and continental uplift.
When an impact is so
large that even a vigorous hotspot at the antipode is not enough to relieve the
pressure from deformation at the impact site, then something else must happen.
While my belief is that this type of large impact will result in the uplift of
a new continent, I also believe that the mechanism for this uplift will be
crack propagation.
In many important ways, the upper layers of the
Earth's surface are similar to the layers of a drywall screw. Both have a small
surface thickness that is hard and brittle. Both have a relatively weak
interior.
When the hotspot erupts at the antipode of a very large
impact, there is tremendous pressure at the edges of the hotspot. It is logical
that the pressure would cause crack propagation at the site of any
imperfections at the edges of the mostly circular hotspot.
I believe
that this crack propagation would continue until one of the cracks reaches the
inevitable continental perimeter, where the forces of uplift are only barely
able to overcome the weight of gravity on the surface rock. I believe that when
cracks propagate from the initial hotspot towards the eventual edge of the
soon-to-be continent, only one of these tentative propagation cracks is
actually used to propagate the circumferential shearing zone.
This
chosen path (mostly a result of highest degree of weakness, shortest journey to
the circumferential shearing zone and luck) receives by far the greatest
discharge of pressure, leaving a noticeable rift and lots of lava flows as the
pressure starts unzipping the circumference of the soon-to-be continent.
This situation is much like the slow motion pictures that are taken of
objects during a lightning storm. In slow motion, prior to a lightning strike,
we can see the small threading of an electrical charge weaving upwards from the
taller objects on the landscape. Then the lightning bolt begins (chooses?) its
path from the sky to one of these electrical tendrils and the entire electrical
discharge occurs along this one path.
Note that the lightning bolt does
not spread its energy among the several electrical tendrils that are reach up
towards it. Once a choice has been made, the entire force of the lightning bolt
heads down that chosen path.
I believe that the path of the primary
propagation crack from the initial hotspot to the edge of the soon-to-be
continent works in a similar way. Since molten lava is much thicker and slower
than electricity, the cut off of magma power to the secondary crack propagation
tendrils may be significantly slower than in the cases of lightning, so we may
actually see more than one track.
In actual practice, we have four
examples of antipodal continental tectonic plates that we can look at ... two
with interior hotspots and two with perimeter hotspots. In the cases of
perimeter hotspots (India and Siberia), the hotspots and their initial
propagation cracks are at the edge of the continental shearing zone already.
There is no path from the interior to the circumference that is needed ... and
none is found. In the cases of interior hotspots (Eastern North America and
South America), a primary pathway had to be established for the pressure to
reach the perimeter of these soon-to-be continents.
In Eastern North
America, a main pathway remnant is Lake Champlain and the Hudson River Valley,
with the massive lava outflows along the Hudson River Palisades, Newark and New
York City area, which are traceable to the same time period as the initial
separation of Eastern North America from Europe 202 MYA. There is also massive
lava flow down the St. Lawrence river area.
In South America, this
pathway remnant is the vast Rio La Plata, which separates Argentina, Brazil,
Uruguay and Paraguay. The Rio La Plata contains vast areas of ancient volcanism
that is traceable to the same time period as the initial separation of South
America and Africa 132 MYA.
3. BLOB WITH A TAIL - South America is the
classic example of a blob with a tail. Since its uplifting 132 MYA, the
continent has not run into anything that would change its shape. The only
factor that has modified its original shape is the subduction at the Nazca
plate that has compressed its entire western edge, making it appear slightly
lopsided to the east.
4. CONTINENTAL MOVEMENT - Since South America can
fit right into its original location as part of Africa, it is easy to see where
it started and where it has moved to in the past 132 million years.
5.
TANDEM MOVEMENT - The hotspot begins somewhere in the eastern interior of the
continent and gradually loses ground as the continent outpaces it. Both the
continent and the hotspot are moving mostly west, but the continent is moving
faster. Therefore, relative to the continent, the hotspot appears to be moving
to the east.
The logical candidate for the present location of this
hotspot is the Vitoria-Trindade seamount chain in the western Brazil basin of
the South Atlantic. Located at 20 degrees south latitude, this chain extends
almost due east. The currently active island at Trindade is at the far eastern
end of the chain. 72,73,74
An article entitled "New Data on
the Structure of the Vitoria-Trindade Seamount Chain" by S.G. Skolotnev, A.A
Peyve and N.N. Turko states:
"The origin of the chain is often attributed to
the activity of the Trindade hotspot, which was located below the
aforementioned islands and has lasted from the Late Cretaceous to present
times." 74 pg 435 If the hotspot started offshore in
the late Cretaceous (70 MYA?), then this would provide approximately 60 million
years for the hotspot to move from more in the interior of the continent to an
offshore position by approximately 70 MYA. The timing and direction all fit
nicely.
Furthermore, even though the eastward motion (relatively
speaking) is expected by the scenario that I have presented, this movement
pattern is currently a mystery of geology for those who view this hotspot
through the lens of the Standard Theory. Again, quoting Skolonev, Peyve and
Turko: "At the same time, no consistent explanations were reported so far for
the near E-W trend of this seamount chain." 74 pg435 (author's note:
E-W may sound like it means that the chain is moving from east to west, but
that is not what they mean … they are using a confusing old method which
always lists east first. As an additional note, the other seamount chains in
the area move in arcing directions or are associated with transform faults.
Transform faults do not apply in the case of the Trindade hotspot).
So,
now we have a solution to the mystery. It's always nice when a theory explains
phenomena beyond the normal things that are expected.
WHERE IS THE EXTINCTION?
We
now have a full picture of a huge deep ocean impact creating the South American
continent. The only thing missing is a major extinction.
There is no
major extinction at 132 MYA or even close to132 MYA. How come?
First,
even though the extinction charts do not show a major extinction event at 132
MYA, there was a significant marine extinction at that time. Called the
Valanginian Weissert Oceanic Anoxic Event (VWOAE), this disaster occurred at
the same time as the Parana and Etendeka volcanism.
68,69,70
David Thiede and Paolo Vasconcelos state that the
volume of magma eruption "is comparable with extrusion rates of CFBs (e.g.
Emesha Traps, Siberian Traps, Central Atlantic Magmatic Province [CAMP], Deccan
Traps) correlated with mass extinctions." 71pg750
They go on
to note that there may be circumstances which cause this huge magmatic eruption
not to create a mass extinction, or, "alternatively, the Valanginian Weissert
OAE may actually represent a mass extinction event, and its age must be revised
in light of the new results for Parana CFB volcanism." 71 pg
750
So, we have a minor extinction that may
actually be a major extinction, depending upon how it is analyzed. The core of
the extinction event was the anoxic effect in the world's oceans …
certainly this would be a likely result of the impact of a truly huge cosmic
object in the middle of the Pacific Ocean.
But why would the initial
hotspot be so tame? Why wouldn't it cause the same extinction situation as the
Siberian Traps or the Deccan Traps or the CAMP, or even the more modest
extinction results of the Manicouagan hotspot?
Perhaps the answer lies
in the explosive qualities of the eruptions. And the explosive qualities of the
eruptions may depend upon how much water was nearby and able to be subducted
(with other crust) as the continent and its hotspot moved by.
In the
cases of the Siberian Traps and the Deccan Traps, the initial hotspot was
located near the edge of the new continent, right near or even in the water,
itself. Crust that contained large amounts of water and was subducted into the
path of the upwelling magma would have created the opportunity for lots of
water to turn to steam, making for frequent, violent eruptions.
If the
initial hotspot were located more to the interior, then the flow of magma, even
though extensive, may not have been explosive. The Parana initial hotspot
appears to fit a more interior location. The crack propagated lava was located
at the following edge of the continent's movement, leading to a situation where
water-laden crust was not subducted into it.
SUMMARY
This chapter
presents a complete set of features demonstrating a cosmic impact in the deep
Pacific Ocean, with the consequent uplifting of the South American continent
approximately 132 MYA. In this case, due to the nature of the impact (deep
water) and the location of the hotspot within the interior of the continent,
there may have been a significant Oceanic Anoxic Event, rather than a full bore
major extinction. 60, 61, 62, 64, 65, 66, 63, 61, 67, 72, 73, 74, 74 pg
43, 74 pg435, 68, 69, 70, 71, pg 750, 71, pg
750
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