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The date of the impact coincides precisely with the Cretaceous–Paleogene boundary (K–Pg boundary), slightly more than 66 million years ago. [7] The crater is estimated to be over 150 km (93 mi) in diameter [10] and 20 km (12 mi) in depth, well into the continental crust of the region of about 10–30 km (6.2–18.6 mi) depth.
Plant fossils are common in both the Late Cretaceous and early Paleocene portions of the Edmonton Group. [7] Remains of Triceratops and other dinosaurs are found in the Late Cretaceous portion, especially the Horseshoe Canyon Formation and the lower part of the Scollard Formation. Molluscs such as Ostrea and Unio are found in both portions. [1]
Because the Raton Formation is a well-preserved sequence of rocks spanning the Cretaceous-Paleogene boundary, it has been studied for evidence of a large meteor impact at the end of the Cretaceous that is thought to have caused the Cretaceous–Paleogene extinction event. The boundary is represented by a 1-cm thick tonstein clay layer which has ...
The Cretaceous-Paleogene boundary occurs in the lower part of the formation, and an exposure of the boundary layer has been identified and documented on South Table Mountain near the city of Golden. [12] Plant fossils [13] and remains of vertebrates, including turtles [14] and mammals, [15] are found throughout the Denver Formation. [6]
The Hell Creek Formation in Montana overlies the Fox Hills Formation and underlies the Fort Union Formation, and the boundary with the latter occurs near the Cretaceous–Paleogene boundary (K–Pg), which defines the end of the Cretaceous period and has been dated to 66 ± 0.07 Ma old. [6]
The date of the impact coincides with the Cretaceous–Paleogene boundary (commonly known as the K–Pg or K–T boundary). It is now widely accepted that the devastation and climate disruption resulting from the impact was the primary cause of the Cretaceous–Paleogene extinction event , a mass extinction of 75% of plant and animal species on ...
The "Defining markers" column lists the evidence in the rock used to define the boundary. (Ideally, these are applicable in rock sections worldwide.) Most of the boundaries rely on the fossil record (biologic), paleomagnetic data (magnetic), and/or climate data determined by carbon and oxygen isotopes.
The climate across the Cretaceous–Paleogene boundary (K–Pg or formerly the K–T boundary) is very important to geologic time as it marks a catastrophic global extinction event. Numerous theories have been proposed as to why this extinction event happened including an asteroid known as the Chicxulub asteroid, volcanism, or sea level changes.