midCretaceous

The mid-Cretaceous is an informal term used by geologists to describe the middle portion of the Cretaceous period. Its exact span varies among authors, but it commonly falls roughly between 125 and 90 million years ago. Because it is not a formal stage, the term is used to discuss broad climatic, tectonic, and biotic patterns of that interval.

During the mid-Cretaceous, the climate was generally warm and largely ice-free, with high atmospheric CO2 levels. Global sea levels were high, producing extensive shallow epicontinental seas that covered large parts of continents. The configuration of continents and oceans was actively reshaping the planet as the major tectonic plates continued to fragment the supercontinent Pangaea and create new ocean basins, including the early stages of the Atlantic Ocean and various seaways such as the Tethys.

Biologically, the mid-Cretaceous saw significant evolutionary activity. Marine life included abundant ammonites, belemnites, and calcareous plankton, with thriving reef and carbonate platform ecosystems. On land, dinosaurs continued to dominate, while early angiosperms (flowering plants) began to diversify and spread, contributing to shifts in terrestrial ecosystems. Birds and small mammals were present, and various groups of reptiles and freshwater organisms inhabited both marine and continental settings.

The interval also includes notable oceanographic events, such as oceanic anoxic events around the Aptian and Cenomanian-Turonian boundaries, which are studied for their carbon-cycle dynamics and sedimentary signatures. The mid-Cretaceous thus provides key insights into a greenhouse world with dynamic tectonics, high biodiversity, and evolving terrestrial flora.