The Burgess Shale Fauna

Approximately 17 meters thick, Unit A defines the lowest third of the Juniata Formation. Fragments of marine fossils, including bryozoans, brachiopods, and gastropods, are commonly found in the bottom-most portion of this unit of structureless mudstone and quartz arenite. Quartz grains in the sandstone beds of Unit A are typically immature and fine-grained, though the sandstone packages tend to coarsen upwards. Though typically structureless, intermittent bedding of the sandstone and shale packages is observed in this unit, and some areas display

Explain why the author and his colleagues chose to focus on 375 million year old rocks in their search for fossils. Be sure to include the types of rocks and their location during their paleontology work in 2004.

The question of what caused the extinction of megafauna during the Late Pleistocene period is one that archaeologists have struggled to answer for decades, but why should it matter? Discovering with certainty the cause of megafaunal extinction would

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

During the Eocene epoch, 47,000,000 years ago, one of our ancestors lived in what is now Germany. She was still young, her baby teeth still intact and probably less than a year old. This little girl came to a lake’s edge for a drink of water; cupping the water with her hand she slowly drank the water while holding onto a branch with her other hand. Our ancestor died there when she was overcome by an underground gas bubble that erupted, the fumes leaving her unconscious; she fell into the water and drowned. Her body slowly drifted to the bottom of the lake with a myriad of other creatures. The lake where she was buried eventually filled with mud and algae that turned into oily shale

Analyses from 7,300 years ago at the Hawken site in northeast Wyoming do not match with the hypothesis of a dry Altithermal, though this may be limited to the site from which the data was collected, and not representative of the entire High Plains area (Lovvorn, Frison, and Teiszen 2001).

* Burgess Shale - One of the greatest fossil finds ever made is the Burgess fauna of British Columbia. Thousands of soft-bodied animal fossils paint us a picture of early marine life.

The 440 million year old Georgian Bay Formation is largely composed of fossiliferous grey-black shale (L1R). It also consists grey fine-grained limestone, sandstone and green/grey siltstone interbedded with green/grey and blue/grey shales (Bond et. al. 1976). The frequency of hard rock units increases toward the top of the formation. Recurrent tropical storms across the Ordovician seas caused the formation of shady, thin limestone with wave ripples on top. Numerous fossils can be found in the siltstones and limestone including molluscs, crinoids and gastropods

1. The author chose to focus on 375 million year old rock because the transition from fins to necks and limbs occurred then. The scientists knew that any time later than this and they would find lots of animals with limbs. But if they searched earlier than this time then there are only fish without necks. When the fish were evolving they evolved necks before they evolved limbs so this was a good sign in chronology. Sedimentary rocks are the best types of rocks for fossil due to their gradual pressure and low amounts of heat. Sedimentary rock is also found in lake beds and streams, where fish and aquatic wildlife are most likely to live.

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

The detractors of “Nonavian Feathers in a Late Triassic Archosaur” believe that the feather-like impressions in the fossil are not even feathers at all. Based on the angle and shape of the imprints, many paleontologists believe that they were left by ‘highly modified scales’, or possibly even ferns that had fallen on the animal’s body after death.4

Even though anoxia is in general reflected on as an essential pre-requisite, “anoxia alone is not sufficient enough to account for Burgess shale-type preservation,” (Garson 2012). Furthermore, the necessity of anoxia is not universally agreed upon (Garson 2012). Yet, while rare and commonly absent from today’s fossil record, this type of preservation is very common throughout most Burgess shale-type deposits of these ancient fossils (Gaines 2012). Localities of these types are somewhat confined to Series 2 and 3 of the Cambrian (Garson 2012).

: 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.