Abstract:
The Ordovician Period was one of the most important in the history of life on our planet. But the system remained obscured by the conflict between Adam Sedgwick and Roderick Murchison, hidden within the Silurian until the early years of the 20th Century. Key to its recognition were the Ordovician rocks of the Southern Upland of Scotland and the strata around Bala Lake in North Wales. I will review its turbulent early history and outline the importance of the period for the diversification of marine life, the early colonization of the land and the establishment of more modern climates.

The speaker:

David Harper is a leading international expert on palaeontology and the fossil record. He was formerly Professor in Palaeontology and a head of department in the Natural History Museum of Denmark, University of Copenhagen. He is now Emeritus Professor and a former Principal of Van Mildert College at Durham University. Harper was President of the International Palaeontological Association and the Palaeontological Association and is currently Chair of the International Commission for Stratigraphy. His research has addressed some of the most fundamental developments in the history of life, for example the Cambrian Explosion, Great Ordovician Biodiversification Event and the End Ordovician mass extinction. These events occurred over 440 million years ago, yet their impact had profound consequences for the evolution of the modern marine realm. His research has been recognised by foreign memberships of the Royal Danish Academy of Sciences and Letters, the Royal Swedish Physiographic Society and an Einstein Professorship in the Chinese Academy of Sciences together with two honorary doctorates and the Jean Baptiste Lamarck Medal from the European Geosciences Union.

Logistics:

The talk will commence at 18:30. The venue (upstairs at the Royal Cambrian Academy, behind Plas Mawr, Conwy, LL32 8AN) will be open from 18:00 for seasonal drinks and snacks.

The Late Triassic – Early Jurassic evaporites of the Berkine Basin will be described. Time series analysis of gamma logs shows that astronomical forcing played a key role in their deposition. Long eccentricity cycles (~405kyr, ~50m) reflect lacustrine expansion and contraction, whereas precessional cycles (~20kyr, ~3m) reflect desiccation and halite deposition. These Saharan Platform basins bear much in common with other western Mediterranean evaporite basins. Many show the same overall pattern of sedimentation with increased sulphate deposition near the Tr-J boundary, possibly linked to the CAMP. In late Triassic times they formed a contiguous low-lying zone flanked by cratonic highlands. This zone spanned the Gondwana-Laurussia boundary immediately prior to the break-up of Pangea and Greater Adria formed the barrier between the basins and developing Neotethys to the east.