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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 Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group.It dates to the Late Cretaceous, between 79 and 75.3 million years ago, [4] corresponding to the "Judithian" land vertebrate age.
Paleogeography of the Late Cretaceous with La Colonia Formation indicated. It is divided up into three distinct facies, the first is up to 16 metres (52 ft) thick and consists of conglomerate, the second is by far the thickest at over 100 metres (330 ft), consists of siltstone and claystone, with interbeds of claystone/shale and sandstone, the third is less than 10 metres (33 ft) thick and ...
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.
The Cretaceous is characterized by warm global temperatures caused by the high amounts of carbon dioxide and possibly methane greenhouse gases in the atmosphere. This caused a lack of permanent ice coverage in the polar regions, though the carbon dioxide level dropped between 115 and 66 million years ago (mya), possibly allowing some permanent ice cover.
Baculites from the Pierre Shale showing sutures and remnant aragonite; western South Dakota, Late Cretaceous. The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains , from Pembina Valley in Canada [ 2 ] to New Mexico .
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 .
A broken concretion with fossils inside; late Cretaceous Pierre Shale near Ekalaka, Montana. Monument Rocks (Kansas), located 25 miles south of Oakley. By the late Cretaceous, Eurasia and the Americas had separated along the south Atlantic, and subduction on the west coast of the Americas had commenced, resulting in the Laramide orogeny, the early phase of growth of the modern Rocky Mountains.