16.0 Dating; 2020 Ma, 2055 Ma and 2575 Ma or 214 Ma – to summarise.

The sciences progress not so much by the discovery of new truth as they do by the correction of old error (Robert Dietz August 1961b).

16.1 Vredefort - Dating on the rebound

The Vredefort Dome has a remnant rebound central core made up of target rock thrown up from the transient cavity floor. This took place seconds after the explosion that created the chamber following the impacts. This floor was part of the 20 km thick, deeply buried Transvaal Supergroup which has strata aged from about 3000 Ma at the bottom to 1800 Ma at the top of the Rooiberg Group. Most of the rebound and collar rock fell back into the crater with the balance being eroded to the present ground level.

Depending on which layer of the floor strata is at this present dome ground level, an age determination dating of 2020 Ma for the Vredefort Impact Structure would be of the local rock and not the meteorite.

Graham Ryder of the Lunar and Planetary Institute in Houston said, after examining lunar rock from the Apollo mission, that ages of rocks are not easily reset. Most are broken up but not substantially heated (Taylor 1994). This theory is borne out in the Vredefort Dome where experienced geophysicists concluded that there was no evidence for shock melting, nor do the geological settings favour this. They only found melting of local country rocks and no impact melt with local material (Reimold, Hoffmann, Hauser, Schmitt, Zaag & Mohr-Westerheide 2016).

If the rocks within the Vredefort Dome were not heated sufficiently to reset their age at the time of impact then the radiometric dating would show the age of the local rocks and not the age of impact. These target rocks are aged between 3000 Ma and 1800 Ma which would fit in with an age of 2020 Ma for that particular layer being dated of the uplifted rocks. This would have nothing to do with the age of the impact, which could be 214 Ma.

16.2 Bushveld Complex - dating between strata layers

Scientists cannot date fossils themselves but they can accurately date the strata layers above and below to get precise dates of when the fossils were laid down. In 1980, Luis and Walter Alvarez, Frank Asaro and Helen Michels could date the mass extinction by measuring the age of strata above and below iridium from a meteorite that rained down worldwide. This was shortly after the great meteorite impact which caused the Cretaceous-Paleogene (K-Pg) mass extinction which wiped out the dinosaurs 65.5 Ma. Fern spores below but not above the iridium layer confirmed this mass extinction marker.

These examples of dating are possible because the fossils or iridium were laid down on top of a layer of strata of measurable age and then covered by another layer of measurable age. One can then assume that the fossils or iridium is of an age between the two.

However, if you have many kilometres of sediment laid down between 3000 and 1800 Ma and can measure how old every layer is from bottom to top, you cannot know the age of minerals that were intruded later from the side. Imagine shooting a bullet today into the side of a cliff where the strata is 2055 Ma. This does not make the bullet 2055 million years old.

In our case, the meteorite’s minerals and magma in the Bushveld Complex were intruded horizontally, forcing the floor down and the roof up, between layers of strata in the Transvaal Supergroup that are same age as claimed for the formation of the Bushveld Complex.

If 2055 Ma is the age of the target rock layer there is nothing to prevent the horizontal intrusion of the Bushveld Large Igneous Complex from taking place in 214 Ma.

16.3 The Great Dyke in Zimbabwe-dating the strata.

This straight, 550 km long, chrome and platinum mineral-rich, penetrative crater across the Zimbabwe Craton is obviously part of the meteor shower that caused the Vredefort Structure.

The Vredefort Structure and Bushveld Complex are probably related, being unique, contemporary, and close (Elston & Twist 1986), within 500 km of each other. The Merensky Reef in the Bushveld Complex and the Great Dyke contain similar minerals and the Great Dyke is also close, within 500 km. It is exactly in line and has the same approach angle, allowing for about 5-8 degrees of longitude, as Vredefort and Bushveld.

Accepting that the three sites are from the same meteor cluster then there is a problem with the current event formation age determination of 2020 Ma (Vredefort), 2055 Ma (Bushveld) and 2575 Ma (Great Dyke), a spread of 555 million years. If, however you look at the age of target rock you will see that, in each case, this would fit in with 2020 Ma, 2055 Ma and 2575 Ma respectively. If, incorrectly, the target rock has been dated instead of the meteorite fragments this means that the common impact age could be 214 Ma for all three events.

16.4 Glaciation

We know from Chapter 5 that four kilometre thick ice followed by glaciation from 302 Ma to 288 Ma would have levelled any protrusions. This would mean that any signs of the impact and the resulting ripples would have been eroded if they were older than this glaciation era.

The string of shock-sheared caves parallel to the Witwatersrand Ridge is certain to be connected to the Vredefort Impact but not at 2020 Ma. These caves had to have been formed after the Dwyka Glaciation period which ended 288 Ma as they definitely could not support 4 km thick ice followed by a serious glaciation event. As the oldest other cave system known is dated at 340 Ma this makes 214 Ma far more likely.

16.5 Multiple meteorite impacts 214 Ma

From Chapter 3.0 we know that it is unlikely that Vredefort, Bushveld and Great Dyke were three separate events, and that the combined event would have been a once in a solar lifetime occurrence. The window of opportunity for this combined multi-particle event to take place in the same direction, west to east, the same longitude and angle of approach would have to be at the same time and date as that of the Manicouagan cluster of 214 Ma.

16.6 Events after 214 Ma

The following major events took place after 214 Ma that would require an enormous amount of energy to occur:

16.7 Comments about the age of the Vredefort Structure and Bushveld Complex

In the early 1960s, before the radiometric 2020/2060 Ma dates were arrived at, geophysicists and astrophysicists of the time believed that the Vredefort Structure’s age was in the order of at least 250 Ma (Dietz 1961) or that it was comparatively young looking for the ages given to them.

Unless a crater is unusually large all traces of its presence will be eroded away in less than 600 million years’ (Wetherill 1979).

Old craters are less abundant simply because they have been destroyed by erosion, sedimentation and other geologic processes’ (Grieve 1990).

The Bushveld magmatic province is an unusual LIP. In spite of its Palaeoproterozoic age [2055 Ma] it is undeformed’ (Kinnaird 2005).




Rev 20180907 Copyright (c) 2018 dave (at) howcroft.co.za