Fossil Lagerstätten

“A minority disputes this theory, arguing that other events-such as volcanic eruptions, sea-level changes or a series of impacts-were to blame for the spectacular loss of species that occurred at the transition between the Cretaceous and Tertiary periods…”

Although the Ediacaran period was well before the first appearance of dinosaurs it shows that there were fossils many years ago. When dinosaurs first appeared things had changed there was still shallow water which meant that bones could be fossilized.

During the Late Kaskaskia (Cratonic Sequence 3), what type of deposition predominated on the craton?

In the following space, explain the role of fossils in developing the Geologic column. Your explanation must be between 200 and 300 words.

Sedimentary rocks interpret dinosaur habitats through encased environmental structures of the past. Through sedimentary rocks, paleoecologists’ can examine the arranged formation of sedimentary structures to specify what type of environment the dinosaurs’ lived in. An example of a specific sedimentary rock structure can be seen through formed weathering and ripple marks by how wind and sand formed distinct patterns in the past layered sediment. These arrangements provide interpretations on the structure of the sediment and the habitat of encased fossils, through modern day comparisons

They chose the time period of 375 million year old rocks because they thought that it was an ideal age to check the transition. They were only able to find fish found in 380 million year old rock and the animals with limbs in 365 million year old rocks. Sedimentary rocks are ideal because they are made due to the turns of the river, ocean and lakes. This is the place where fishes and animals are ideal to live and survive upon. Also the environment, in which they are made, doesn’t destroy the fossils and they preserve them. In 2004, the fossils were found on Ellesmere Island in Northern Canada. This location was chosen because this is the place where there are no humans or roads or any disturbance that would forbid them to dig anywhere they want.

Hildebrand, (2009, 2003) attempts to integrate both observed geologic features (hinterland high grade metamorphism, Laramide basement uplifts, Cordilleran batholiths, regional-scale Neogene extension) and the lack of observed features (large scale strike/slip faults), while matching paleomagnetic data (large amounts of northward motion in the oceanic realm exist with no evidence on land) (Fern Esperanza beetle-Moorcroft, MS Thesis, 2014).

One piece of this history is the subsurface Paleozoic rocks. Paleozoic rocks are for the most part hidden in the Park despite being in the Colorado Plateau, which is likely due to both erosion, and it being buried in other various rocks. Next is the deposition of the Moenkopi Formation during the early Triassic time period. When North America was still apart of Pangea, the area that was the Colorado Plateau was located within close range of the Equator. 300-600 feet of sand and mud were accumulated during this time, with marine life being included which tells Geologists that the sea sometimes was in the area. The climate at the time was warm, with varying times of humid and dry spells. There is very few beds of the Moenkopi Formation left in the area once again due to erosion. Third is the deposition of the Shinarump Member of the Chinle Formation. This basal conglomerate was deposited on top of the Moenkopi Formation. It is made up of gravel and sand, which indicates that there was water depositing it. The Shinarump Member also averages between 35-50 feet thick. Next in the geological history is the deposition of Chinle beds later in the Triassic time period. When the sea regressed to the west of the area, a large plain was left behind. As the climate changed, so did the environment. Soon grasslands and marshes began to form in the area. During this time hundreds of feet of shaly material accumulated which formed both the Lower Petrified Forest Member and the Upper Petrified Forest Member. In some parts, these two members are separated by the Sonsela Sandstone Member, composed of the most petrified wood compared to all other rock units featured in the Park. The Owl Rock Member is at the top of the Chinle Formation, and completes it. Near the end of the Triassic time period, tectonic activity was occurring heavily in the Arizona basin. In the western sea at this time a chain of volcanoes erupted,

The Sangre de Cristo Mountains are a structurally complex block having a Precambrian igneous core that is bounded by major, high-angle reverse faults and highly contorted, steeply dipping to overturned sedimentary beds of Paleozoic and Mesozoic age. The range resulted from uplift and eastward thrusting during the Laramide orogeny commencing in Late Cretaceous time and continuing intermittently to possibly late Tertiary time (Wanek and Read, 1956).

These Paleozoic rocks are steeply plunging sandstones and siltstones, with a little event of limestone at Lilydale - the Early Devonian Lilydale Limestone. The Silurian rocks were stored in profound water, while the Devonian rocks, which are exceptionally fossiliferous, appear to have been stored in shallower water. These Silurian and Devonian rocks were folded into a progression of anticlines

At the beginning of the Tertiary, there is a layer of andesite breccia -a fast cooling extrusive rock that has not traveled far from its original deposition. This indicates a volcanic depositional environment. This formation was then intruded by intrusive slower cooling rocks that create a noncomformity between it and the Walker formation. The tuff breccia in the Walker formation is consistent with the same depositional environment as the andesite breccia formation as they are both extrusive rocks. It is possible that there was an eruption from a volcano that deposited the highly viscous andesite rocks followed by slower falling ash, which was then

The author and his colleagues chose to focus on 375 million year old rocks in their search for fossils because amphibians that look dissimilar to fish were discovered in 365 million year old rocks, while fish without amphibian characteristics were discovered in 385 million year old rocks. Thus, it is possible that the evolutionary intermediary, or the “missing link” between fish and amphibians, would be discovered in 375 million year old rocks, between the two time periods. The rocks examined were sedimentary in composition, as the gradual and relatively gentle formation of sedimentary rock under conditions of mild pressure and low heat are conducive to the fossilization of animal remains. Sedimentary rock is also often formed in rivers and seas, where animals are likely to live. This site provides a resource that describes means by which fossils are formed and how the fossil record may be interpreted, and shows some examples of fossils demonstrating evolution through geological periods: http://www.fossilmuseum.net/fossilrecord.htm. In 2004, Shubin and his colleagues were looking for fossils on Ellesmere Island, in northern Canada. This location was chosen because of its lack of human development, as well as of obstructing natural formations and life forms such as trees, which

: Fossils are the remains or traces of ancient organisms which have been preserved. For example, a fossil can exist as skeletal remains or even as a footprint. Such organisms are subjected to a slow rate of decaying since they have been rapidly buried under conditions that facilitate this. It is common for fossils to occur as hard-bodied organisms as these are more resistant to environmental influences. Fossils are usually found embedded in rock. The layers of rock are of different age and makeup. Hence fossils found in one layer would vary in characteristics from those found in another layer. They can be observed and analyzed through visual as well as radiometric means so that the age and morphology can be determined. These features indicate

My outside source for questions 3 and 4 is a journal by Pat Shipman titled Fossils. This journal was published in The New Scientist Vol. 215, Issue 2876, p. 8-16.

These techniques led to the discovery of the boundary between the two eras. A single thin layer of clay found within predominantly limestone rocks established this. By comparing the marine life found in, above, and below the clay, the marine life, like the dinosaurs, had been terribly affected by the extinction event. The percentage of life in the upper layers was dramatically lower than that in the lower. This was far more compelling than what was suggested by dinosaur’s fossils.