Chapter 24 Late Ordovician zooplankton maps and the climate of the Early Palaeozoic Icehouse

Abstract

Chitinozoans and graptolites are the main components of preserved Ordovician zooplankton. As with much of the modern plankton, the ‘first-order’ species distributions of Ordovician plankton reflect water masses defined on the basis of sea surface temperatures. For ‘time slices’ of less than a few million years, zooplankton distribution patterns can be used to infer latitudinal sea surface temperature gradients, key palaeoceanographical boundaries and the position of Ordovician climate belts. Here, using two Late Ordovician time intervals – the early Sandbian and Hirnantian – we review how zooplankton distribution patterns identify Late Ordovician cooling and reflect the development of severe icehouse conditions.Supplementary material:Additional information on methods and material is available at:http://www.geolsoc.org.uk/SUP18670

Middle Ordovician acritarchs and problematic organic-walled microfossils from the Saq-Hanadir transitional beds in the QSIM-801 well, Saudi Arabia

“…darriwilense, Dicrodiacrodium ancoriforme and Tyrannus proteus, display extreme polymorphism, leading, in some cases, to aberrant (teratological) morphotypes. Previous studies have correlated the occurrence of aberrant acritarch morphotypes to changes in paleoenvironmental parameters such as changes in salinity of oceanic waters (Ellegaard, 2000), ␦ 13 C excursions linked to glacial events (Munnecke et al, 2012), or high levels of heavy metals in the sediments (Vandenbroucke et al, 2013). Any of these parameters, alone or in combination, could be at play in the present material from the Hanadir Member in QSIM-801.…”