The Cretaceous-Period is a geological period and system that spans from approximately 145 to 66 million years ago. It is the last period of the Mesozoic Era and is known for significant evolutionary events, climatic changes, and the eventual mass extinction event that marked its end.
Geological Timescale and Stratigraphy
- The Cretaceous-Period is subdivided into two epochs: the Early Cretaceous (145-100.5 million years ago) and the Late Cretaceous (100.5-66 million years ago).
- Its name comes from the Latin "creta," meaning chalk, due to the extensive chalk deposits found in many parts of the world, notably in the White Cliffs of Dover in England.
Climate and Environment
- During the Cretaceous-Period, the Earth experienced a greenhouse climate with high levels of atmospheric CO2, leading to warm temperatures and high sea levels.
- Sea levels were significantly higher than today, flooding continental margins, creating shallow seas, and contributing to the formation of extensive limestone deposits.
- The period saw the breakup of the supercontinent Pangaea, with continents moving towards their current positions, which influenced global climate patterns.
Flora and Fauna
Mass Extinction
- The Cretaceous-Paleogene Extinction Event at the end of the Cretaceous period resulted in the extinction of approximately 75% of Earth's species, including non-avian dinosaurs.
- The most accepted theory for this event involves a massive asteroid impact, evidenced by the Chicxulub Crater in Mexico, along with volcanic activity, climate change, and possibly other factors.
Notable Fossil Sites
Sources