krétapaléogén

Krétapaléogén refers to the geological period marking the boundary between the Cretaceous and Paleogene periods. This boundary is famously defined by the Cretaceous-Paleogene (K-Pg) extinction event, which occurred approximately 66 million years ago. The K-Pg extinction event is characterized by the abrupt disappearance of a vast number of species, including non-avian dinosaurs, ammonites, and many marine reptiles. Evidence suggests this mass extinction was triggered by a catastrophic asteroid impact, with the Chicxulub crater in the Yucatán Peninsula being the primary site of impact. Volcanic activity, particularly the Deccan Traps eruptions in India, may have also played a contributing role.

The transition from the Cretaceous to the Paleogene saw profound changes in Earth's ecosystems. The extinction of dominant groups paved the way for the diversification and rise of new life forms. Mammals, which were relatively small and nocturnal during the Cretaceous, began to evolve into a wide array of forms, eventually dominating terrestrial ecosystems. Birds, the avian descendants of dinosaurs, also underwent significant diversification. Marine environments, devastated by the extinction, saw the rise of new plankton groups and the eventual dominance of teleost fish and marine mammals. The geological record from this period is crucial for understanding the long-term impacts of mass extinction events on the evolutionary trajectory of life on Earth.