The North Horn Formation is a widespread non-marine sedimentary unit with extensive outcrops exposed in central and eastern Utah. The formation locally exceeds 3,600 feet (1,100 m) in thickness and is characterized by fluvial , lacustrine , and floodplain dominated systems, representing a terrestrial, high energy, depositional environment. The sediments date from Late Cretaceous ( Maastrichtian ) to early Paleocene in age and include the K-Pg extinction event boundary; however, this boundary is extremely difficult to locate and there is no strong stratigraphic evidence available that indicates a specific marker bed such as an iridium rich clay layer. Thus far, the only visible evidence is represented in the form of faunal turnover from dinosaur to mammal-dominated fossil assemblages. Taxa from the Cretaceous part of the formation include squamates , testudines , choristoderes , crocodyliforms, sharks, bony fishes, amphibians, mammals, dinosaurs, eggshell fragments, trace fossils, mollusks, plant macrofossils , such as wood fragments, and palynomorphs .
13-779: The North Horn Formation is a non-marine, stratigraphic unit located in east and central Utah which unconformably overlies the Late Cretaceous Price River Formation west of the San Rafael Swell , and the Tuscher Formation east of the swell. The formation is overlain by the late Paleocene-early Eocene Flagstaff Formation , also called the Flagstaff Limestone. The North Horn type section is located on North Horn Mountain in Emery County, Utah. Laterally,
26-446: A 200 ft (60 m) thick set of strata composed of sandstone, pebbly sandstone, and conglomerates which make up the coal canyon unit. The uppermost unit is the upper redbed unit, which is nearly a 390 ft (120 m) thick and is composed of red brown mottled siltstone and sandy siltstone. Characteristic dinosaur taxa include the ceratopsian Torosaurus utahensis , the titanosaurid sauropod Alamosaurus sanjuanensis , and
39-526: A 330 ft (100 m) thick basal conglomerate unit that consists of an upward fining conglomerates and sandstone and lacks any interbedded shale , followed by the lower redbed unit, a 790 ft (240 m) thick sequence dominated by red sandy siltstone , conglomerate, and pebbly sandstone. The third unit is the sheet sandstone unit and is composed of sheetlike sandstone beds that are interbedded with gray and carbonaceous siltstones. Some limestone beds are present but are uncommon. The fourth unit
52-517: Is a family of Cretaceous - Paleocene placental mammals , known definitively only from North America . The family is part of a radiation of early herbivorous and omnivorous mammals formerly classified in the extinct order " Condylarthra ", which may be related to some or all living ungulates (hoofed mammals). Periptychids are distinguished from other "condylarths" by their teeth, which have swollen premolars and unusual vertical enamel ridges. The family includes both large and small genera, with
65-649: Is approximately 200 metres (660 ft) thick at its type locality ( Price River Canyon ) and consists of cliff-forming sandstone and siltstone visible in the Book Cliffs . Irregularly bedded light-gray to gray, and grayish-brown to dark-gray beds of sheet sandstone, plus some beds of conglomerate and conglomeratic sandstone; sparse mudstone beds as well. The crossbedded sandstones are generally thin bedded to massive, and commonly thick bedded. Beds alternate irregularly to form steep, steplike slopes. Ranges in thickness from 9 to 75 m (30–250 ft). Fluvial in origin. This unit
78-449: Is characterized by 131 to 374 ft (40 to 114 m) thick coal beds and coal-streaked siltstone deposits and are referred to as the coal-bearing unit. This unit is overlain by a 833 ft (254 m) thick sequence of primarily calcareous siltstone beds, called the calcareous siltstone unit. The big mountain unit consists of nearly 750 feet (230 m) of interbedded conglomerates and trough cross bedded sandstones, followed by
91-683: Is equivalent, in part, to the Tuscher and Farrer Formations of the eastern Book Cliffs. Fossil pollen (palynomorphs) indicate a late Campanian (Late Cretaceous) age . This article about a specific stratigraphic formation in Utah is a stub . You can help Misplaced Pages by expanding it . This article related to the Cretaceous period is a stub . You can help Misplaced Pages by expanding it . Periptychidae † Anisonchinae † Conacodontinae † Periptychinae incertae sedis Periptychidae
104-576: The Dinosaur Tracks Museum, of the University of Colorado at Denver . Bird and dinosaur eggs have also been found at the site, along with unidentified hadrosaur fossils (possibly from Edmontosaurus or Kritosaurus ). Price River Formation The Price River Formation is a geologic formation in Utah . It preserves fossils dating back to the Cretaceous period . The Price River Formation
117-579: The North Horn Formation nearly spans an 87-mile (140 km) long east–west transect that extends from the Wasatch Plateau on the west and the Book Cliffs , near Green River , on the east, separated in the middle by the San Rafael Swell. The North Horn Formation varies greatly in thickness and lithology , representing a time transgressive stratigraphic sequence, which means that the age of
130-431: The base and top of the formation changes as one moves laterally. West of the San Rafael Swell, near Price Canyon , Utah , the basal contact for the North Horn Formation is Maastrichtian (latest Cretaceous ) in age, whereas its base is Paleocene in age on the eastern side of the swell. Some of the most complete sections of the North Horn Formation are exposed west of the San Rafael Swell at North Horn Mountain in which
143-431: The local stratigraphy sometimes exceeds 3,600 ft (1,100 m) in thickness. Further to the east, towards Green River, Utah, stratigraphic sections are significantly thinner compared to sections in the west with thicknesses varying between as little as 50 to 130 ft (15 to 40 m). The formation is divided into three informal units based on broad but distinct lithological characteristics. These units include
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#1733086211210156-460: The lower variegated unit at the base, a middle coal unit (in which the K-Pg boundary is located), and the upper variegated unit at the top. The units themselves are further divided into a total of eight sub-units, or lithofacies, based on facies scale lithological features. A detailed sedimentary study of the North Horn Formation was conducted by Lawton et al. These units, from oldest to youngest, include
169-804: The theropod Tyrannosaurus ; however, the most frequently occurring taxon in the Cretaceous strata of the North Horn Formation is the Polyglyphanodont squamate Polyglyphanodon . Fauna recorded from Paleocene strata within the formation appear to be far more diverse and over 70 different taxa have been identified, including frogs, numerous multituberculate , protoeutherians , periptychids , arctocyonids and phenacodontid mammals, crocodyliforms , choristoderes , trace fossils, and palynomorphs . Marsupial remains similar to Alphadon and Eodelphis have also been found here as well. Pterodactyloid tracks present at an unnamed site. The specimens are kept at
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