Seawater signatures of Ordovician climate and environment

Tracking climatic changes throughout the Ordovician is crucial to a better understanding of the coevolution of life and environment on Earth. Ordovician climate fluctuations have been the subject of a vigorous and productive body of work over the past two decades. Here we present a synthesis of studies that have focused on reconstructing Ordovician climate and environment via direct geochemical proxy datasets and/or numerical modelling approaches. Many new insights have been gained on potential causes of events: the timing and potential causes of the major radiation of Ordovician marine life, changes in weathering and the transition from a greenhouse-to-icehouse state, and cooling and (de)oxygenation during the end-Ordovician Glaciation. Marked improvements in sample resolution/distribution of traditional palaeotemperature (oxygen isotopes), palaeoredox (sulfur isotopes) and weathering proxy records (strontium and neodymium isotopes), as well as the development of new palaeoenvironmental proxies (e.g. clumped, uranium, molybdenum and thallium isotopes; iodine, iron, trace metal geochemistry), have led to better constraints on Ordovician climate and environment. These recent works have led to a more nuanced understanding of the Ordovician Earth System, which allows the global community to focus future efforts on answering remaining questions regarding palaeoclimate and environment, as well as embark upon new investigations.