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A Jurassic Rift

7 February 2021
Geology

At www.geolsoc.org.uk/Geoscientist/Archive/July-2017/OLS-Jurassic-Brexit … actually, the  first sign of the rift began in the Triassic but it was accelerated in the mid Jurassic. At this time a  thermal dome rose up leading to upheaval as far west as the Hebrides, although the focus of the article is really about the geology of the North Sea basin. The dome was followed, in time, by an upwelling of lava, the Rattray Volcanic region. It was located at the point of a triple junction – between Norway and Scotland, to the east of the Shetlands. This was followed by a marine transgression event, flooding what is now a large part of western Europe.

However, the big issue in the article is that in the late Jurassic a rift came into being running down between Norway and Greenland, and between the British Isles and Newfoundland, Greenland and North America. A smaller rift opened along the North Sea basin. However, the British Isles remained connected to the European continent. It was, in effect, a muted rift, although it has remained in existence down into the modern world. It is thought this resulted in the Cretaceous being tectonically quiet. The chalk was laid down at this time, mostly the remains of the shells of algae and small marine creatures. The reason it was quiet, of course, in parlance, is that it is thought the chalk was laid down in a uniformitarian manner, at a very slow pace of acccummulation. A very long period of time. Hence, it would have been tectonically quiet otherwise the chalk would not be so pristine and perfectly white. Of course, if the chalk was laid down fairly quickly, a different view of tectonics would be relevant – but that is not mainstream way of thinking.

As such, all tectonic rumblings were confined to the Atlantic margins, and this is where the rift really became a very wide rift indeed, an emerging ocean basin. Having said that we are then told that it was not until the Eocene, roughly 50 million years ago, that new ocean crust arrived on the scene, as North America separated big time from Europe. Geology is certainly a strange subject. A geologist can rattle on about seismic rifts and the splitting apart of North America from EuroAsia whilst avoiding to mention that it was all part of a global event, the splitting up of Pangea, the super continent. The author's field of expertise in this instance is his own backyard. Early Cretaceous, it seems, also defines, or separates, late Triassic geology – which was an extinction event as well. So, the rift, t could be argued, as it opened up, coincides with catastrophic events – muted mostly in geological group think. The author uses the word 'imagineering' on several occasions, imagining or modelling what was going on back then.

At www.geolsoc.org.uk/Geoscientist/Archive/ May-2010/Pincer-movement/Frozon-on-the-beach … we have frozen on the beach. The meaning by the author is frozen in time – but the frozen object in this instance, is beach sand. The Jurassic Piper Sand reservoir represents an intrusion of sand in a catastrophist model but in the uniformitarian view of the past it was laid down inordinately slowly, each ripple in the sand stone representing a single stage of that process. The opposite view is that the sand was laid down quickly, or erupted out of the earth in a turbulent manner, interwoven with a wet and watery landscape, hence the ripples. In uniformitarian thinking, taken at its most extreme interpretation, each ripple in the  formation was formed slowly, as  what we observe in the past must be an ongoing process in the modern world today. The author of this piece points out some problems connected to this way of thinking, referring back to an earlier piece in the Geoscientist magazine of the Geological Society [in the UK]. A display of cross stratification and wave rippled layers was preserved over a long period of time. The author points out that a modern beach is subject to two daily tides and therefore a twice daily change in ripple formation, or even an outbreak of unpredictable weather, such as a storm, causing variation in wave direction and power. How could a series of ripples in the sand have survived over a long period of time in order to be preserved, or fossilised. In other words, it is patently obvious that we do not observe in the modern world the formation of anything comparable to the Piper Sand formation. It must have had a different kind of origin. Perhaps. However, the author is a mainstream geologist and  requires a uniformitarian explanation, of a sort. He suggests they are the random effect of a frozen [in time] accidental formation, or preservation. What caused the Piper Sand formation to freeze in time – and become fossilised? It could have been just the effects of a storm, or something a bit more powerful, frozen on the beach.

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