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The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk.
The Maastrichtian (/ m ɑː ˈ s t r ɪ k t i ə n / mahss-TRIK-tee-ən) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from .
Paleontological camp of Museum of the Rockies in eastern Montana – Hell Creek Formation (summer dig season 2009). The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana.
Lance Formation – stratigraphy. The Lance (Creek) Formation is a division of Late Cretaceous (dating to about 69–66 Ma) rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas.
Despite the western upheaval, the eastern US had achieved geological stability by the Late Cretaceous. [72] The weather was uniformly warm and rainy throughout the year. [85] Flowering plants were now common and fossil of broadleaf trees and shrubs were preserved in Late Cretaceous rocks. [85] The Cretaceous ended with another mass extinction.
Paleomagnetic data from late Jurassic-early Cretaceous rocks in the southern portion of the North Patagonian Massif indicate that clockwise rotation of up to 30 degrees occurred in that area during the Early Cretaceous, affecting a crustal block at least tens of kilometers in size. [6]
The middle–late Campanian formations show a greater diversity of dinosaurs than any other single group of rocks. The late Maastrichtian rocks contain the largest members of several major clades: Tyrannosaurus, Ankylosaurus, Pachycephalosaurus, Triceratops, and Torosaurus, which suggests food was plentiful immediately prior to the extinction ...
These widespread carbonates and other sedimentary deposits make the Cretaceous rock record especially fine. Famous formations from North America include the rich marine fossils of Kansas's Smoky Hill Chalk Member and the terrestrial fauna of the late Cretaceous Hell Creek Formation.