Summary & Synthesis

Abstract

Carbonate sediment, generated by marine microbes, plants, and animals, covers many continental shelves of the world and has done so throughout much of geological history. Biofragments produced in the sea are unusually sensitive proxies that record the health of the oceans, their changing composition, and within their calcareous hard parts contain irrevocable evidence of global tectonic evolution. One of the ongoing quests of earth science is to ascertain how faithfully these calcareous particles encrypt environmental information. It has long been known, for example that modern tropical reefs, ooid shoals, and muddy tidal flats are powerful tools for unlocking past marine environments. Only recently has it become clear that carbonate sediments in temperate and polar oceans are widespread, distinctive, and important and thus can also be used to decipher the nature of ancient mid- and high-altitude oceans. The deposits that are documented herein, along the southern margin of Australia, are extremely important in this endeavour because they comprise the largest deposit of such carbonates in the modern world. Thus, this vast neritic realm contains information that can be used to unlock the nature of many Cenozoic and Mesozoic limestones, and to help formulate models that together can act as an intellectual bridge into the older world of ancient Paleozoic carbonates.