18. Structural geology exercise.
This figure is the basis for a small structural geology exercise. If you were logging this ‘image’ underground, in core or under a microscope slide you would describe;
The top of the image as having crenulation cleavage, the centre as orthogonal shearing and jointing, and running up the centre is a slightly deformed set of horizons which could be earliest stratigraphy or bedding.
The reason for looking at this, and determining that we are viewing brittle structures, will become clear in the following seismic tomography cross sections.
19. South America seismic tomography sections 26°S, 18°S and 5°S
South America seismic tomography sections 26°S
This is seismic tomography at section 26°S cutting across South America just below Rio de Janeiro (Lee 2019). The surface is a Landsat image draped over the globe.
Tomographic image of South America across section 26°S shows the main structures under South America. The image has been enhanced mainly to retain the different lithology colours. However, the Landsat plan looks exactly like the Landsat plan that I enhanced, with ring structures and linear structures traversing the continent. This shows the veracity of my enhancement methods as used on databases from difference sources.
Most noticeable about this image is the four or five sets of linear structures (blue ticks) traversing right from the north South America across to central South America in plan and then continue as linear structures, exactly in line, right down to the core-mantle boundary.
The tomographic section shows ring structures and convoluted, contorted structures on the left-hand west side and is more horizontally structured on the east side.
There are a set of flat structures (blue) outcropping in the Pacific Ocean and extending deeper to the east under South America.
Some of the linear structures in plan are associated with mines dating back to 3.4 billion years old and this suggests that the Earth locked up back in the Archaean and that only certain areas such as the spreading mid-ocean ridge areas have moved since that time.
20. Watchorn Hypothesis of the South American mineralisation system.
This figure shows the tomography of South America at 26°S. Structural geology in broad detail shows much less contorted structures on the right-hand east side than on the west side. The west side of the section shows contorted brown lithology in the far west of the Pacific plate subducting under the Andes.
The central area in the bottom half of the lithosphere shows circular structures, upward facing arch (red) and large flat east dipping structures.
The bowl-shaped structures under the continent (yellow) correlate with the Hadean impact structures observed on the Seismic tomography plans earlier in this paper. The arcuate white line from the Andes in the west and under the continent to the core separates the totally different east/west morphologies and is where I believe the 4 billion-year-old immovable barrier lies.
The broad structural geology of South America is a pop-up structure. South America is getting pushed by the Asia-African plate to the west at 25 mm per year and it is getting pushed eastward by the Pacific plate which moves at about 40 mm a year (see top right inset). That’s a total compression of about 65 mm a year, or about a metre every 15 years. The only way this pressure can release itself is upwards. Hence there are large orthogonal flat fractures under South America. This lower pressure under South America to the core allows for heat and fluid release.
These release pathways can be seen as the dotted yellow lines under the mines of South America. These are similar, but on a much larger scale, to those seen in Australia, North America and Africa.
The red arches give the direction of the heat flow. They are fronts of the original cratonic rock altered by the heat flow coming up from the core.
21. South America seismic tomography sections 18°S.
We now go about 1500 km further north to South America section 18 S (Braz et al., 2018).
This section shows exactly the same structural geology as section 26° south.
The 4 billion year old immovable barrier is still present. It has relatively horizontally stratified lithosphere and crust on the east side and a contorted appearance on the west side of the boundary.
As in section 26°S the contorted area is cut through by flat structures and orthogonal steep brittle structures suggesting early freeze-up.
22. South America seismic tomography sections 5°S.
The seismic tomography section 5° S (Lee 2019) is about 3,200 km north of section 26° south. It still shows exactly the same pattern as the previous two sections.
The sharp immovable boundary separating the horizontally stratified eastern lithosphere and the turbulence flow western lithosphere is very clear. In the turbulent flow lithosphere huge 500 km diameter circular structures are seen overlapping each other. The section deep under South America has the appearance of turbulent flow in water.
Under the core of the South American continent large bending linear structures can be seen. They are vertical through the upper lithosphere down to 1000 km and gradually flatten to the east nearer the core.
This is the expected structure expected from a rigid lithosphere undergoing brittle deformation by sinistral movement.
There is a strong set of orthogonal flat joints about 5000 km in length. The pattern of the heat affected (browner) rock from the core shows that much heat terminates on these flat joints. This suggests that they may be strong mechanical impermeable structures similar in effect to shale on top of an oil field.
The section shows exactly the same pattern as the two previous sections 26° south and 18° south. Compression from either side lifts the South American continent and forms compression vertical structures, up which the heat for mineralisation and intrusive can flow, and extensional orthogonal flat structures.
The crust (top few mm on this section – see bottom inset) in this section of North America looks similar to the crust under Australia with ramp structures showing east block over west movement. This implies strong sinistral movement under the crust.
As this ramp appearance is consistent right across from the Pacific to the Atlantic it suggests that the crust did not accrete in South America just as the crust did not accrete in Australia.
By accretion I mean in the terms used in Plate Tectonics theory where large slabs of continent are supposedly added (accreted) to a pre-existing continent.
The lithosphere is the original continent and did not accrete but has split up over the eons. The ramping seen in the crust would be as a result of the continental east movement (sinistral) ramping surface material over existing crust and lithosphere.
Hence the younging of most continental crust to the general east in Australia, Africa, North America and now South America. This suggests these continents have stayed in the same general orientation since the Hadean.
If this is correct then the current Plate Tectonics concept of randomly moving seed continents accreting and growing larger through time is incorrect Fast forward the Algol 2018 video to see this in action. If it was correct the crust would be a jumble of differently oriented thrust stacks. It is not, in any of the major continents!
Now that we can use structural geology in ultra-detail from the surface to 2,850 km depth we can interpret Plate Tectonics movement much more accurately than the current situation of just using surface data and geophysical subsurface data that does not show structural geology.
In the next post we will look at an oblique section through South America and Africa (Ballmer et al., 2015). The section extends from about Fiji, south of the equator, through to the central Sahara in Africa north of the equator.
This section ties in all of the new discoveries we have made in this detailed look at the two continents.
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Cheers
Bob