tag:blogger.com,1999:blog-3005668431384229268.post9089172126515613523..comments2024-03-11T18:46:56.863+11:00Comments on New England's History: Understanding the impact of sea level change in Aboriginal New England - a noteJim Belshawhttp://www.blogger.com/profile/10075614280789984767noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-3005668431384229268.post-75751990429642130422017-12-20T16:58:36.551+11:002017-12-20T16:58:36.551+11:00Very interesting. I will have to look at those map...Very interesting. I will have to look at those maps properly over Xmas, John. Probably of more importance than the tsunami question, is what the maps tell us about possible changing environments.<br /><br />Without bogging down, if the Aborigines arrived in the North say 30,000 years ago with a sea level 50 metres below present. That level had been in existence for a while, so a coastal/estuarine environment would have formed somewhat to the east of the current coast. Then came the LGM. The sea level retreated a further 70-80 metres. As it did so, the previous coastal environment would have degraded to be replaced with a new once the seal level fall stopped. The new environment took time to form.<br /><br />Its been suggested that the limited size of the continental shelf in many place and its rugged slope meant, ignoring climatic variations, that it was inherently less attractive than that it replaced. So the pattern along the coast is important. The only relevant site we have is Wallen Wallen Creek on North Stradbroke island. From memory, that was cc22,000 years ago. The view is that this was a camping site for people moving onto a coast that was then 12-20k further east. <br /><br />The rising seas created a new western moving coastline. At highstand, sea levels would have been perhaps a metre above present levels. With the Holocene warmer weather and higher rainfall, the rivers carried greater volumes of sand and silt. At hightstand and then the subsequent slight fall in sealevels, the rivers created deltas. Kempsey which have been on the coast now becomes inland as the Macleay delta was formed.<br /><br />The pattern is going to vary along the coast depending on local conditions such river size and the size and configuration of the coastal shelf. Jim Belshawhttps://www.blogger.com/profile/10075614280789984767noreply@blogger.comtag:blogger.com,1999:blog-3005668431384229268.post-41312204471294543182017-12-18T09:25:46.780+11:002017-12-18T09:25:46.780+11:00I used your link to check the mapping for the area...I used your link to check the mapping for the area South of Yamba Jim to find an abundance of rocky reefs overlain at times by shallow silts and muds. Such geology I would imagine as unlikely to produce slides sufficiently significant to generate tsunami, but then I may be misreading the information. Offshore Macleay may be a better prospect as the reef structures became associated with particular features such as Fish Rock and Black Rock. Moving further South and continuous rocky reefs once again became the norm. Given the variation in sealeavels the majority of these rocky reefs must have been exposed at some point. The evidence suggests that these reefs extend to the edge of the Continental Shelf so we might have to look further afield for tsunami sources affecting the Mid North Coast’s coastal plains. The Macleay seems to be the critical link whereby the Coastal impacted the Tablelands.Johnbhttps://www.blogger.com/profile/09694479587834247002noreply@blogger.comtag:blogger.com,1999:blog-3005668431384229268.post-19481656251167128592017-12-16T16:52:44.944+11:002017-12-16T16:52:44.944+11:00Hi John. I think that the link should be https://e...Hi John. I think that the link should be https://en.wikipedia.org/wiki/Storegga_Slide, although that's almost the same. <br /><br />I had forgotten those huge slides. I think that the effects of the local slides off New England would have been far smaller, but a geologist might be able to estimate. I don't know what oral history survived. Jim Belshawhttps://www.blogger.com/profile/10075614280789984767noreply@blogger.comtag:blogger.com,1999:blog-3005668431384229268.post-67440863171878478772017-12-16T10:08:58.077+11:002017-12-16T10:08:58.077+11:00The Storeega slides are possibly the best document...The Storeega slides are possibly the best documented Jim and also link into changing sea levels and the last glacial BP.<br />https://en.m.wikipedia.org/wiki/Storegga_Slide.<br /> For Australia, it is as ever, find the evidence, if tsunami’s have arrived they will have left their mark. Oral tradition may also be there.Johnbhttps://www.blogger.com/profile/09694479587834247002noreply@blogger.com