When dinosaurs roamed the Western Isles
Quite a challenge, I expect, to the local Free Presbyterians.
My friend Kim Johnson commented on the strange appearance of the footprints, Steve Drury (author of the blog of which this is just an annotated repost) referred me to Paige Depolo, senior author of the paper on which Steve’s post is based, and Paige replied as follows:
When it comes to the depositional environment, the tracks were formed in a low-energy lagoon and are generally preserved today as impressions into shaley limestone. Later, additional limestone layers were laid down at the site and in-filled the impressions. Those layers form the casts that we can still observe for some of the tracks today. In some cases at this site, the cast remains while the surrounding impression which it was originally infilling has been almost completely eroded. These rocks were deposited during the Middle Jurassic. Later, likely during the Paleogene, a sill was intruded immediately below the track bearing layer and the surrounding rocks were baked. The low-level contact metamorphism of the track-bearing layers definitely makes for some interesting looking exposures!
h/t Kim and Steve, and many thanks to Paige
Cuillin Hills, Isle of Skye, Scotland, UK (credit: Wikipedia)
The Isle of Skye off the northwest coast of Scotland is known largely as a prime tourist destination, such as Dunvegan Castle with a real clan chief (The MacLeod of MacLeod) and its Faerie Flag; Britain’s only truly challenging mountains of the Black Cuillin; and, of course, the romantic connection with the Young Pretender, Charles Edward Stuart and his escape, in drag, from the clutches of the Duke ‘Butcher’ Cumberland, hence the Skye Boat Song. Geologists know it best for its flood basalts with classic stepped topography and the exhumed guts of a massive central volcano (the Cuillin), relics of the Palaeocene-Eocene (62 to 54 Ma) North Atlantic Large Igneous Province. The spectacular Loch Coruisk, a glacial corrie drowned by the sea, exposes the deepest part of the main magma chamber. It is also the lair of Scotland’s lesser…
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Posted on April 3, 2018, in Evolution, Fossil record, Geology, Science, Scotland and tagged Bathonian, Dinosaur tracks, dinosaurs, Jurassic, Paige Depolo, sauropods, Skye, Theropods. Bookmark the permalink. 3 Comments.
Time is not easy to visualise, our lives are so short and everything seems so constant in spite of climate change. Even continents are not constant over millions of years as this article demonstrates. Is it true that the earth was changing faster in the days of the dinosaurs ? I have read that the time of rotation of the earth was a few hours quicker and from pictures painted of the early planet it was a place of tremendous upheaval. As a layman I have been led to believe that the move from four legs to two was a sign of intelligence the example being our own early human ancestors, yet these dinosaurs were bipedal did they start this way ? Is this in any way linked to the way a human baby crawls before it walks ? I wonder just how extensive was the area we call the tropics today ,was the earth much warmer?
Much of our idea of turmoil in earlier eras is simply the result of perspective. Not my speciality, but at the time we are discussing here I don’t think tectonic change was more rapid than it is right now. If I recall correctly, throughout most of the Mesozoic the Earth was indeed warmer than it is today.
Bipedalism and intelligence? Interesting question. We now know that bipedalism developed in hominins before the expansion in cranial capacity. Having hands free makes manipulations possible, and I think it quite possible that if it weren’t for that unfortunate piece of rock, bipedal dinosaurs would have developed intelligence. On the other hand, crows lack hands, and they are pretty smart.
‘Answers made up by us that are loosely based upon the book of Genesis’ (otherwise known as Answers in Genesis) are scoffing – from 13 minutes in: https://www.youtube.com/watch?v=KjJc8OF-XAo How could these prints (of huge creatures that are not obviously mentioned in Genesis 1) possibly be 170 million years old if “the footprints were difficult to study owing to tidal conditions, the impact of weathering [another report said erosion] and changes to the landscape”? But as this post (quoting one author of the Scottish Journal of Geology research paper) explains “the tracks were formed in a low-energy lagoon” and “later, additional limestone layers were laid down at the site and in-filled the impressions; those layers form the casts that we can still observe for some of the tracks today” and “in some cases the cast remains while the surrounding impression which it was originally infilling has been almost completely eroded”. Presumably casts can be preserved almost indefinitely barring something like a volcanic eruption. But Ken Ham does not want scientific answers. He wants to give religious ‘answers’ instead. (Incidentally I see comments under the BBC article managed to discuss both religion and Brexit as well as dinosaur footprints.)