Pollen in sediments matches low growth tree ring data

15 Jan 2013

There aren't a lot of posts under 'Dating' here but for a change we have one - go to http://smithsonianscience.org/2012/08/fossil-pollen-used-to-augment-clim... ... ancient pollen and charcoal preserved in sediments from the Nile delta have revealed a series of past super-droughts - accompanied by evidence of landscape fire. In dry periods the wetland zones is more prone to fire so this does not imply fire from an exotic source such as the sky. What they found was that during periods of lower wetland pollen the amount of charcoal increased. They were able to pin them down to the global super-drought of 4200 years ago (the end of Old Kingdom well documented drought episodes which appear to coincide with Moe Mandelkehr's 2300BC event as explored in a series of SIS articles). Another very similar event is dated from pollen analysis to between 5500 and 5000 years ago (the 3200BC event of tree rings) and lastly, at around 3000 years ago (the end of Late Bronze Age and the droughts recorded from dynasty 20). So, it seems that not only do low growth tree ring events, C14 data and ice cores, as well as the historical record, appear to largely stand together, with major events delineated from the end of Predynastic, end of Old Kingdom, and end of Late Bronze era, all fitted together in a rather snug fashion together with pollen in Nile sediments, lake sediments from different parts of the world, and as we saw yesterday, fossil raised beaches in Scotland. In fact, Steve Mitchell, in response to yesterdays post on the subject, replied by saying that Prof David Smith said that some features of sea level change are due to the land moving relative to the sea and not the sea moving relative to the land. Smith went on to write a critique of his article 'When the sea flooded Britain' (see articles page on this web site). He was at pains to point out the long time scale of the raised beaches of the Highland zone of Scotalnd (not just in the Forth Valley) but Steve has found evidence for more recent changes, in the Late Roman era, where the sea level appears to have peaked between 500 and 600AD. He spent a considerable amount of time in the field exploring a raised beach of not more than 5 to 7m high which ran along the coast for miles and which is now a few hundred metres inland, and another one a piece back to that, and these are even more recent than the raised beaches with stranded Early Christian ruins. In other words, two raised beaches have been created in the last 1000 years or so, probably as a result of isostatic tilting as Scotland bounces back from the compression the ice sheet imposed during the Ice Age.