Cretaceous Ecological catastrophe of the Tertiary extinction event

Between the Cretaceous and Tertiary strata, there is a layer of iridium-rich clay called the K-T boundary. K is the German abbreviation for Cretaceous (Kreidezeit), and T is an abbreviation for Tertiary. Since the International Commission on Stratigraphy no longer recognizes the Tertiary as the official name of geological time, it was replaced by Paleogene and Neogene.

Therefore, the Cretaceous-Tertiary extinction event can also be called the Cretaceous-Paleogene extinction event.

Fossils of dinosaurs (excluding birds) have only been found in the lower layer of the K-T line, suggesting that they became extinct rapidly at (or before) the time of this extinction event. A small number of dinosaur fossils have been found above the K-T boundary, but these fossils are thought to have been removed from their original locations due to erosion and other effects, and then deposited in younger sedimentary layers. In addition to dinosaurs, the family Sauridae, plesiosaurs, pterosaurs, and a variety of plants and invertebrates were also extinct during this event.

Mammals and birds survived and radiated to become dominant animals in the Cenozoic.

Li Yang, a paleontologist and physicist from China, published at Yale University in 2009, said that according to the accurate determination of the iridium content around the Gulf of Mexico, it was an asteroid-like material that not only hit the earth's Central American region, but also broke through the earth's crust, causing the earth's internal magma to erupt, and the supervolcanic eruption caused by the impact. This time, the diameter of the hole was more than 148 kilometers. The whole earth is covered with thick volcanic ash and poisonous gases, the life on the earth does not see the sun and the moon for a long time, plants cannot photosynthesize, and the oxygen content in the atmosphere is extremely low, all of which caused the mass extinction of organisms. Most scientists speculate that the extinction event was caused by one or more causes, such as:

Impact events caused by asteroids or comets, or prolonged volcanic eruptions. Craters such as Chicxulub Crater and volcanic eruptions at the Deccan Dark Rocks, which are close to the K-T boundary, are thought to be the most likely cause of this extinction event. Impact events or volcanic eruptions can impact ecosystems around the globe by sending large amounts of dust into the atmosphere, blocking sunlight and reducing photosynthesis in plants.

However, a few scientists believe that the extinction event occurred slowly, and that the cause of the extinction was gradually changing sea level and climate [6].

Cretaceous period (Cretaceous) The last epoch of the Mesozoic Era. The Cretaceous period is the last epoch of the Mesozoic Era, beginning 100 million years ago and ending 65 million years ago, with 70 million years in between. Both the inorganic and organic worlds underwent important changes during the Cretaceous period.

Located above the Jurassic and below the Cenozoic. The Cretaceous period was the most submerged period of the earth's surface during the Mesozoic Era, during which the northern hemisphere was extensively deposited with the Cretaceous layer, which was named the Cretaceous in 1822 by the Belgian scholar Omali Daruwa. The chalk is an extremely fine and pure silty limestone, a biogenetic marine sediment composed mainly of calcareous ultrafine fossils called lithophyllum and pelagic foraminifera fossils.

8 Ecological environment during the Cretaceous period.

The duration of the Cretaceous-Tertiary extinction event has long been debated, as some theories suggest that the extinction event was short (between years and thousands of years), while others believe that the extinction lasted for a long time. Since it is not possible to find a complete fossil record of a species, the true extinction of an extinct species may be later than the last fossil record. As a result, it is difficult to determine the time of the extinction event.

Scientists have found a small number of fossilized strata that span the K-T line, dating from millions of years before the K-T line to nearly 2 million years after the K-T line.

The Cretaceous-Tertiary extinction event (Artistic Depiction of Asteroidal Impact) is a large-scale species extinction event in the history of the earth, which occurred between the Cretaceous period of the Mesozoic Era and the Tertiary era of the Cenozoic Era, about 65.5 million years ago, and wiped out most of the animals and plants (including dinosaurs) on the earth at that time. The Cretaceous-Tertiary extinction event is famous for causing the extinction of dinosaurs and the rise of mammals, but it should be pointed out that the Permian-Triassic extinction event wiped out about 95% of the earth's living things at that time, and was the most serious collective extinction event in geological time.