The Linnean Society of New South Wales

Antarctica plays an important role in our climate and Prof Turney will discuss the realization of its scientific importance.  This year also marks the centenary of the departure of Dr. (later Sir) Douglas Mawson for Antarctica.

In this presentation, I review the latest research into the Ordovician System that provides insights into how the Ordovician world functioned and what it may have looked like. The past two decades has witnessed a major leap forward in our understanding of the life and times of the Ordovician Period, which extended between 491 and 443 million years ago. During this interval, the greatest expansion in biodiversity in Earth history occurred (known as the Great Ordovician Biodiversification Event, or GOBE). Towards the close of the Ordovician, one of the five big global extinction events took place, significantly depleting biodiversity. The disposition of continents and terranes was markedly different compared to the present, with pronounced faunal endemicity and provincialism the order of the day. It was a world inhabited in places by giant trilobites, with almost no land plants. Volcanoes were widely distributed, and a major meteorite shower impacted the planet. Evidence of icebergs and glaciers indicate that the southern polar icecap covered part of today’s Sahara Desert. Work continues to unravel the most likely distribution of land masses. The general position of NSW was facing (as it does today) a vast Palaeo-Pacific Ocean containing scattered tropical islands, but the coastline of the Australian craton was situated between Broken Hill and White Cliffs, offshore to which were deep ocean basins and volcanic island chains.
 
Biostratigraphic timescales, based on graptolites, conodonts and acritarchs, are now well-established for the entire Ordovician system, and provide a framework for correlation that is amongst the most precise in the Palaeozoic. Combined with SHRIMP high resolution age dating, and isotopic techniques enabling construction of seawater temperature curves that can be precisely matched globally, we now have the ability to reconstruct the Ordovician world, its climate and biota.