Old Earth Ministries Online Earth History Curriculum
Presented by Old Earth Ministries (We Believe in an Old Earth...and God!)
This curriculum is presented free of charge for use by homeschooling families.
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Chapter 10 - The Jurassic Period
Lesson 50: The Morrison Formation
Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United
States, which has been the most fertile source of dinosaur fossils in North
America. It is composed of mudstone, sandstone, siltstone and limestone and is light
grey, greenish gray, or red. Most of the fossils occur in the
green siltstone beds and lower sandstones, relics of the rivers and
floodplains of the Jurassic period.
Chapter 10 - The Jurassic Period
The distictive banding of the Morrison Formation, a group of rock layers that occur throughout Dinosaur National Monument. The formation originated as muds and sands laid down by ancient rivers, and some of its outcrops have been found to contain 150-million-year-old dinosaur fossils like those found at the monument's Dinosaur Quarry. (Picture Source)
It was named after Morrison, Colorado, where the first fossils were discovered by Arthur Lakes in 1877. That same year, it became the center of the Bone Wars, a fossil-collecting rivalry between early paleontologists Othniel Charles Marsh and Edward Drinker Cope.
According to radiometric dating, the Morrison Formation dates from 156.3 ± 2 million years old (Ma) at its base, to 146.8 ± 1 million years old at the top, which places it in the latest Oxfordian, Kimmeridgian, and early Tithonian stages of the late Jurassic. This is similar in age to the Solnhofen Limestone Formation in Germany and the Tendaguru Formation in Tanzania. Throughout the western USA, it variously overlies the Middle Jurassic Summerville, Sundance, Bell Ranch, Wanakah, and Stump Formations.
At the time, the supercontinent of Laurasia had recently split into the continents of North America and Eurasia, although they were still connected by land bridges. North America moved north and was passing through the subtropical regions.
The Morrison Basin, which stretched from New Mexico in the south to Saskatchewan in the north, was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west. The deposits from their east-facing drainage basins, carried by streams and rivers from the Elko Highlands (along the borders of present-day Nevada and Utah) and deposited in swampy lowlands, lakes, river channels and floodplains, became the Morrison Formation.
In the north, the Sundance Sea, an extension of the Arctic Ocean, stretched through Canada down to the United States. Coal is found in the Morrison Formation of Montana, which means that the northern part of the formation, along the shores of the sea, was wet and swampy, with more vegetation. Eolian, or wind-deposited sandstones are found in the southwestern part, which indicates it was much more arid — a desert, with sand dunes.
In the Colorado Plateau region, the Morrison Formation is further broken into four sub-divisions, or members. From the oldest to the most recent, they are:
Deposition in the Morrison Formation ended about 147 Ma. The latest Morrison strata
Though many of the Morrison Formation fossils are fragmentary, they are sufficient to provide a good picture of the flora and fauna in the Morrison Basin during the Kimmeridgian. Overall, the climate was dry, similar to a savanna but, since there were no angiosperms (grasses, flowers, and some trees), the flora was quite different. Conifers, the dominant plants of the time, were to be found with ginkgos, cycads, tree ferns, and horsetail rushes. Much of the fossilized vegetation was riparian, living along the river flood plains. Insects were very similar to modern species, with termites building 30 m (100 ft.) tall nests. Along the rivers, there were fish, frogs, salamanders, lizards, crocodiles, turtles, pterosaurs, crayfish, clams, and monotremes (prototherian mammals, the largest of which was about the size of a rat).
The dinosaurs were most likely riparian as well (dwelled by rivers). Hundreds of dinosaur fossils have been discovered, such as Allosaurus, Camptosaurus, Ornitholestes, several stegosaurs comprising at least two species of Stegosaurus and the slightly older Hesperosaurus, and the early ankylosaurs, Mymoorapelta and Gargoyleosaurus, most notably a very broad range of sauropods (the giants of the Mesozoic era). Since at least some of species are known to have nested in the area (Camptosaurus embryoes have been discovered), there are indications that it was a good environment for dinosaurs and not just home to migratory, seasonal populations.
Sauropods that have been discovered include the Diplodocus (most famously, the first nearly-complete specimen of D. carnegiei, which is now exhibited at the Carnegie Museum of Natural History, in Pittsburgh, Pennsylvania), Camarasaurus (the most commonly found sauropod), Brachiosaurus, Apatosaurus (also wrongly known as Brontosaurus), Barosaurus, the uncommon Haplocanthosaurus and the Seismosaurus. The very diversity of the sauropods has raised some questions about how they could all co-exist. While their body shapes are very similar (long neck, long tail, huge elephant-like body), they are assumed to have had very different feeding strategies, in order for all to have existed in the same time frame and similar environment.
There are numerous excavation sites within the Morrison, but the most famous is Como
Dinosaur National Monument in Utah is also a quarry site of the Morrison. For a list of quarry sites, see Morrison Formation on Wikipedia.
Dinosaur National Monument
Dinosaur National Monument is a National Monument located on the southeast flank of
The rock layer enclosing the fossils is a sandstone and conglomerate bed of alluvial or river bed origin. The dinosaurs and other ancient animals were washed into the area and buried presumably during flooding events. The pile of sediments were later buried and lithified into solid rock. The layers of rock were later uplifted and tilted to their present angle by the mountain building forces that formed the Uintas. The relentless forces of erosion exposed the layers at the surface to be found by paleontologists.
When dinosaurs are found in a mass graveyard, with many fossil specimens in one location such as Dinosaur National Monument, the remains are deposited in that location due to water, typically from a flood event, or several flood events. Young earth creationists often point to these mass graveyards as proof of the worldwide flood of Noah, and they claim it is proof that the earth is young. However, there are many reasons why this is not the case.
On the other hand, old earth creationism has no problems with accepting the theories of scientists, who view these graveyards as created by individual floods, or by a group of floods. (For additional reading - As an example of a young earth claim about a dinosaur graveyard, consider this young earth claim.)
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