Ectasian

Ectasian is a geochronological period within the Mesoproterozoic Era of the Proterozoic Eon. It follows the Calymmian Period and precedes the Stenian Period. The International Chronostratigraphic Chart places the Ectasian at roughly 1,400 to 1,200 million years ago, though exact boundary dates can vary slightly among sources. As a middle subdivision of the Mesoproterozoic, it helps divide a time of continental stabilization and crustal development into more precise intervals.

Stratigraphic context and geography: The Ectasian is identified primarily through radiometric dating and lithostratigraphic correlations of sedimentary and volcanic rock sequences. Rock records from cratons such as Laurentia and Baltica, among others, contribute to understanding the period, though globally continuous marker beds are scarce. The interval is characterized by ongoing tectonic reworking and basin development in various cratonic regions, reflecting broader plate tectonic activity of the Mesoproterozoic.

Paleobiology: Fossil evidence from the Ectasian is sparse and dominated by microorganisms. Fossil microfossils and isotopic signatures provide limited insight into early life during this time, with more definitive biological indicators appearing in later Mesoproterozoic and Neoproterozoic rocks. Overall, the biological record for Ectasian remains interpretive and debated among researchers.

Etymology and naming: The term Ectasian derives from the conventional Greek-based naming scheme used for Mesoproterozoic subdivisions, situated between Calymmian and Stenian. The period’s exact boundaries and correlations continue to be refined with ongoing geochronological work.