Cretaceous "Hell Creek Faunal Facies"; Late Maastrichtian
Phillip Bigelow
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The Hell Creek Formation is a layer of rock that was deposited at the very end of the "age of dinosaurs". This layer's deposition spanned a period of roughly 2 million years, from 67 million years ago to 65 million years ago. The formation1 (see shaded area on map) is found in Montana, North Dakota and South Dakota. A rock layer of the same age is found further south, and goes by another name (The Lance Formation). In Canada, correlative rock layers are the Frenchman Formation, the Willow Creek Formation, and the Scollard Formation. All of these these units were deposited by ancient rivers that flowed eastward into a large inland SEA that ran from north-central Canada to the Gulf of Mexico. The rock layer that underlies the Hell Creek Formation is called the Fox Hills Formation, and the overlying layer is called the Tullock Formation (Paleocene). In the Dakotas, the overlying formation is called the Ludlow Formation. The famous K-T boundary, which separates the Cretaceous and Cenozoic, occurs as a discontinuous but distinct thin marker bed within the Hell Creek Formation near its top, giving the rock unit added scientific importance. Some people wonder what types of plants and animals lived along with the dinosaurs. The following lists show you a life community at a particular point in time, and at a particular place on earth. As you will see, the species that were present in the Hell Creek Formation were rich and diverse. And this list shows only what has been found to date! What new species are yet to be discovered? 1 In this context, a "formation" does not mean a hill, cliff, peak, or knob, or any other landform. In geology, a "formation" is defined as a distinct layer of rock that is recognizable over a large geographic area, and which can be distinguished from other adjacent, underlying, or overlying rock formations by unique features, such as it's geologic age, color, composition, or grain size, to name but a few features. |
- Insect evidence Questions? Check out my FAQ
- Insect Ichnotaxa
- Aquatic Invertebrates
- Mammalia
- Lower Vertebrates
- Dinosauria
- Freshwater Algae
- Palynomorphs (fossil pollen and spores)
- Megaflora
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Insect Evidence From The Hell Creek Formation
[from Johnson et al. (2000)]
References: Johnson K. R., D. Nichols, C. Labandeira, and D. Pearson. 2000. Devastation of terrestrial ecosystems at the K-T boundary in North America: The first calibrated record of plant and animal response to the Chicxulub impact. In Catastrophic Events and Mass Extinctions: Impacts and Beyond, Vienna, pp. 85-86, LPI Contribution No. 1053, Lunar and Planetary Institute, Houston. Wilf, P., C. C. Labandeira, W. J. Kress, C. L. Staines, D. M. Windsor, A. L. Allen, and K. R. Johnson. 2000. Timing the radiations of leaf beetles: Hispines on gingers from latest Cretaceous to Recent. Science 289:291-294. | |||||
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Aquatic Invertebrates from the Hell Creek Formation
Comments: References:
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Lower Vertebrates from the Hell Creek Formation
Comments: The following may be Paleocene in age. Stratigraphic position highly dubious. Included for historical context. It is best to exclude the taxon from the "Hell Creek Faunal Facies": **Coriops amnicolus Estes 1969, fish. May be Paleocene in age. **Proamphiuma cretacea Estes 1969, eel-like salamander. May be Paleocene in age. **Colpodontosaurus crascens Estes 1964, Necrosaurid lizard. May be Paleocene in age. All "Bug Creek Faunal Facies" taxa excluded, due to an almost certain mixing of Cretaceous and Paleocene taxa (Lofgren et al., 1990; Lofgren, 1995). References:
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Dinosauria from the Hell Creek Formation
A paleo-population study is one of the most difficult of analyses to conduct in field paleontology. Here is the most recent estimate of the proportions of the eight most common dinosaurian families in the Hell Creek Formation, based on detailed field studies by White, Fastovsky and Sheehan (1998). •Ceratopsidae 61% •Hadrosauridae 23% •Ornithomimidae 5% •Tyrannosauridae 4% •Hypsilophodontidae 3% •Dromaeosauridae 2% (represented only by teeth) •Pachycephalosauridae 1% •Troodontidae 1% (represented only by teeth) Comments: References:
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Fresh Water Algae from the Hell Creek Formation
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Palynomorphs (fossil pollen and spores) from the Hell Creek Formation
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Mega Flora from the Hell Creek Formation Overview (from Johnson, 1997): 190 plant morphotypes, including: 1 bryophyte (mosses and liverworts) 6 "pteridophytes" (A paraphyletic group: modern examples are horsetails, club mosses and ferns.) 1 ginkgo (uncommon) •Ginkgo adiantoides 1 cycadophyte (cycads; uncommon) •Nilssonia yukonensis Hollick 9 conifers •Taxodiaceae (family that contains today's Bald Cypress) •Araucariaceae (family that contains today's Monkey Puzzle Tree and Norfolk Island Pine) •Cheirolepidiaceae (very widespread Mesozoic conifer group. All members are extinct) 172 angiosperms (90% of all specimens collected, as well as 90% of all taxa found) •Lauraceae (Laurel family) •Platanaceae (family includes today's American sycamore or plane tree) •Magnoliaceae (Magnolia family) •Berberidaceae (Barberry family) •Arecaceae (palms)
Comments: Dr. Kirk Johnson claims that there are no grasses, oaks, maples, or willows in the Hell Creek Formation. Ferns are uncommon in the majority of the formation, however there is a great increase in the abundance of fossil fern spores in the two centimeters of rock that directly overlies the impact fallout layer (the famous K-T boundary layer). This increase in fern spore abundance is commonly referred to as "the fern spike" (meaning that if the abundance of spores as a function of stratigraphic position were plotted out, the graph would show a spike just above the impact fallout layer). Johnson also found that the majority of the angiosperm genera in the Hell Creek Formation are now extinct. He also believes that, very roughly, 80% of the terrestrial plant taxa died out in what is now Montana and the Dakotas at the K/T boundary. Many of the modern plant affinities in the Hell Creek Formation (e.g., those with the prefix "aff." or with quotes around the genus name) may not in reality belong to these genera; instead they could be entirely different plants that resemble modern genera. Therefore, there is some question regarding whether the modern Populus or Juglans, as two examples, actually lived in the latest Cretaceous. Compared to the rich Hell Creek Formation fossil plant localities of the Dakotas, relatively few plant specimens have been collected from Montana. I added a few taxa that were collected at Brownie Butte Montana by Shoemaker, but most plants were collected from North Dakota (Slope County) and from South Dakota. "TYPE" after the binomial means that it is represented by a type specimen found in the Yale-Peabody Museum collections. "YPM" is the prefix for the Yale-Peabody Museum specimen number. The Araucariaceae may be the source plants for amber in the formation. Cretaceous amber from Lebonon (135 mya - 120 mya) comes from the flora Araucaria and Agathis. I have not found any specific references regarding the source flora for the North American Hell Creek amber, so if anyone has a reference on its source, please let me know! References:
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Hell Creek Life copyright © 1997-2010 by Phillip BigelowLast revised: July 21, 2010; First edition: November 3, 1997