Tarim Crater

1) Why geologists do not recognize Tarim Basin as an impact crater?

Geologists who have studied the Tarim Basin limit themselves to investigate the basin up to its perimeter and the underground terrain within this area.

They do so because they consider it as a separate unit, a tectonic microplate originated from Proterozoic times.

The geological features of the Tarim Basin are analyzed in depth (literally) in book: The Early Permian Tarim Large Igneous Province in Northwest China: Tectonics, Petrology, Geochemistry, and Geophysics.[1]

As the book's title implies, the authors consider it a LIP, a large igneous province, a gigantic volcano of ellipsoidal rim from times before the formation of the super-continent of Pangeia – something unparalleled on the planet.

This remarkable detailed analysis presents the geological history of the entire length of the basin, highlighting the overlapping of terrains dating back to the Precambrian period.

The latter are found in the rocky substrate, but the accumulated sediments within the basin are all posterior to the Permian period.

This is as expected, since the basin’s substrate was not severely disturbed by the impact, but only the southernmost Tibetan Plateau, that is the real place to be surveyed for evidence of an impact.

By reading the analysis of the Tarim Basin, initially we have the impression that the data absolutely deny the possibility of the Tarim Basin to be an impact crater.

And based on those data, this conclusion is fully correct, because the geological analysis made within the basin does not correspond to the actual impact site that formed the crater.

In fact, the Tarim Basin is only the detached, deformed crater rim, and displaced up north.

The rim was dislodged from above the original crater by a process similar to that of deformation of volcanic arcs:

Not by a massive lava spill, but due to the Indian Plate drifting process which resulted in deformation in recent times.

Evidence of the actual impact crater will only be found in an investigation below the post-Permian sediments from the inner area of ​​the 750-kilometer karst lakes circle that correspond to the original position of the crater rim.

Investigating the substrate inside the Tarim Basin is the same as investigating the original composition of the Tibetan Plateau in the area that was not hit by the asteroid.

What clues do we have to estimate that the crater formation coincides with Permian Extinction?

A 750 km impact crater occurred after the Cambrian period certainly would have caused a mass extinction event, and the Permian Extinction remains as the strongest candidate for this title.

2) Tarim's underground tectonic microplate

A study of the Tibetan Plateau region indicates the mysterious existence of a 100 km thick underground tectonic microplate located at a 250 km depth.[2]

The existence of such a microplate at such a depth has no convincing explanation within classical Geology, just as the other underground tectonic microplate located in the Mediterranean Sea, Greater Adria.

Geologists propose that these microplates simply sank into the Earth's crust for hundreds of kilometers by means of spontaneous subduction.

To imagine that a tectonic plate could sink for hundreds of kilometers – even into the thicker section of the Earth's crust – is as unreliable as thinking that a magma pulse could arise from a convection process without the need for an external trigger.

But the creation of deep tectonic microplates can be fully explained in a rational and easy manner if we consider their creation by an impact event.

As the plate located at the depths of the Tibetan Plateau, the Greater Adria tectonic microplate can be associated with Viluy Crater, identified as causing the Devonian Extinction 360 million years ago (subject of another study).

3.3 South America

3.3.1 Araguainha Crater

Araguainha Dome or Araguainha Crater is an impact crater in Brazil with a diameter of 40 km and an estimated age of 254.7 ± 2.5 million years.

- Coordinates of the northernmost point of Araguainha Crater: 16° 47′ S, 52° 59′ W

3.4 Africa

3.4.1 Luizi Crater

Luizi Crater is an impact structure in Congo with a diameter of 12.6 km. Its estimated age is uncertain, only evaluated as more recent than 600 million years.

Despite such level of uncertainty do not allow us to associate it to the Permian Extinction, its perfect alignment in paleomaps with the Bedout and Araguainha Craters is sufficient to arouse a suspicion of synchronicity.

Coordinates of the northernmost point of Luizi Crater: 10° 10′ 00″ S, 28° 00′ 00″ E

3.5 Hypothesis of a double asteroid blast

Interestingly, the craters Arghanaty, Tarim and Wegener are arranged in an alignment that suggests a possible asteroid blast.

The huge gap between the impact points of Wegener Crater and their counterparts in Siberia suggests that one or more impacts may have occurred into the Proto-Pacific Ocean.

This possibility is hard to prove because any eventual craters would have been subducted below the Eurasian Plate long time ago.

Eventually, their hotspots – which remain relatively fixed compared to the tectonic plate drift – may still be present in the actual Pacific Ocean.

Hotspots will be able to pinpoint the locations of their impacts, but verification will be difficult without an isotopic identifier to associate each one to each other.

The analysis and dating of rocks is limited by the difficulty of access to the older lower layers of the rocky bed, especially at the oceanic bed.

However, given the hypothesis of a Wegener-Tarim-Arghanaty blast, would there be evidence of another blast in the alignment of the Wegener B and Bedout craters?

The impact of Araguainha Crater, diameter of 40 km in Brazil, is identified as occurred 254.7 ± 2.5 million years ago.

The possible impact of Luizi Crater, 16.2 km diameter in Congo, Africa, is of uncertain age, but more recent than 540 million years.

The impact of the Bedout Crater, 250 km diameter in Australia is identified as occurring 250.1 ± 4.5 million years ago.

Their alignment in paleomaps is perfect, and error margins for their dates are compatible with simultaneous impacts, if Luizi was confirmed as a Permian impact.

The impact of Wegener B certainly came after the impact of the Wegener Crater as evidenced by overlapping lava spills.

As said before, the actual position of Wegener Crater’s impact at the South Polar region has ruled out the possibility of Wegener B integrating this possible blast, unless it had occurred many millions of years after the major impact.

The supposed second blast needed to have occurred after the Wegener Crater’s Philippine Sea Plate/Mariana Plate fraction had drifted sufficiently up north to allow the alignment.

That would put at least the Araguainha impact out of this scope, if the estimated age is confirmed.

---

[1] Shufeng Yang Hanlin Chen Zilong Li, Yinqi Li, Xin Yu and published by Zhejiang University Press, 2018.

[2] Wenjin Zhao, Prakash Kumar, James Mechie, Rainer Kind, Rolf Meissner, Zhenhan Wu, Danian Shi, Heping Su, Guangqi Xue, Marianne Karplus, Frederik Tilmann:/“ Tibetan plate overriding the Asian plate in central and northern Tibet ” /, Nature Geosciences, DOI: 10.1038/NGEO1309, Franz Ossing, Helmholtz Center Potsdam, GFZ German Research Center for Geosciences, Deutsches GeoForschungsZentrum

ATTENTION: Blog in reverse order. To continue reading, go to the post below ("Postagem mais antiga").