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Nullarbor Reef Structure

9 September 2022

This news release is at https://phys.org/news/2022-09-unearths-ancient-reef-high-nullarbor.html … the Nullarbor Plain in southern Australia was once under the ocean. Just as in the Pleistocene a large area of the continental shelf system around Australia was above the water, there have been episodes where even areas of what are now land were under water. The evidence of course is the reet system. It is assumed this is due to rising or lowering water levels in the ocean. Equally, it could come about as a result of changes in the earth’s geoid, and redistribution of ocean waters. This occurred a long time ago, in the Miocene. The research however is interesting in a lot of different ways as the imprint of ancient rivers, or channels of water, have been found embedded in the limestone of the Nullarbor, as well as sand dunes, preserving it would seem, the ancient landscape. Isolated cave shafts preserve mummified remains of the Tasmanian Tiger and even complete skeletons of other animals, not necessarily confined to the Miocene but long vanished. On top of that, the icing on the cake perhaps, the Nullarbor Plain has preserved large numbers of meteorites. See https://doi.org/10.1002/esp.5459

On another track, it seems icy conditions may have existed on the Antarctic continent during the Late Cretaceous period, 66 million years ago. This may, it seems, be contemporary with the asteroid strike at the K/Pg boundary, which is also dated 66, or 65 million years ago. Because of that, it is interesting to read what they say about the rocks in Antarctica. Is there a connection? However, the authors of the research do not make such a connection, but they have other things on their minds. The idea of glaciation at the southern pole is contrary to current geological thinking, as it has become fashionable to think in terms of the Cretaceous as a very warm interlude in the earth’s history. It does of course require stationary poles – which is an assumption. It is geological fact that in the northern Atlantic the Jurassic and Cretaceous were a lot warmer than today. For example, trees were growing on what are now the frozen wastes of Ellesmere Island in northern Canada. Does continental drift account for this? Plate tectonics has succeeded drift and it is unclear if the land masses were distributed in different latitudes at any given time, although some geologists think Britain was once in the southern hemisphere and has progressed northwards over millions of years. In the dinosaur era, it is thought Britain had a climate similar to modern Florida, with a semi-tropical profile. At other times it was a desert, and so forth. So, you can shift the continents around in one scheme but you need a lot of C02 to get the dinosaur era at a high temperature, in the other. One can see that modern global warming theory plays a role in the idea of the warmer dinosaur world. Of course, there was a lot of biomass at that time, but it was warmer and plants grow abundantly in a warm environment.

The whole planet was hotter than it is today according to modern ideas. This is derived from evidence accumulated in the northern hemisphere, which presumably includes Russia and China as well as Europe and northern America – but does it? This new piece of research seems to upset the idea of a hotter globe as their findings come from field research rather than modeling. The rocks in question are along the Transantarctic Mountain chain, adjacent to the Ross Ice Shelf. It is an igneous complex which means it was formed by magma. However, it contains a large quantity of glass and layered alteration. This indicates significant physical, chemical, or environmental events have occurred, they say, changing the composition. The rocks also contain a lot of water – after analysis. It is incorporated into the glass. Of course, it may have been carried up with the magma, moving through groundwater sources. In addition, it may have included water from deeper inside the earth. Whatever, it would have involved an event of some kind, and this is where the K/Pg boundary event may come into focus – but is not laboured. Did the oceans expand at this time and if so did water from inside the earth play a role? This is where laboratory analysis comes in. They determined most of the water originated externally and its oxygen and nitrogen isotopic composition clearly match ice and snow. This indicates, they say, polar glaciation. Interesting information. The K/Pg boundary event may have caused a sharp drop in temperatures – but was it enough to cause glaciation? What this research has done is throw into question some of the assumptions about the climate in the Jurassic and Cretaceous. They are now looking to visit other parts of Antarctica in order to find confirmation in different rocks.

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