PALEONTOLOGY - the study of the history of life as reflected in the fossil record

Transcription

1 Paleontology

2 PALEONTOLOGY - the study of the history of life as reflected in the fossil record FOSSIL - remains or traces of organisms that lived in the geologic past and are preserved in the crust of the Earth.

3 Fossilization Step 1: death The animal dies and bacteria destroy the soft parts of the organism and the hard shell or bones remain

4 Step 2 sediments bury the remains. The faster this happens the more likely fossilization will occur. Very fine grained particles, like clays, allow more detail in the future fossil. Course sediments, like sand, allow less detail to show.

5 Step 3 Preservation of unaltered remains in amber, ice, mummification, tar Preservation of altered remains by replacement by minerals (petrified wood, etc)

6

7

8 Step 4: Uplift and exposure tectonic motion and mountain building lift the sedimentary rocks up

9 Step 5 Erosion erosion of the sedimentary rock allows the remains to become visible

10 Modern example of same species 50 Million year old fish, note the faint black stripes

11 complete skeletons of the rhino Teleoceras preserved in ash.

12 Preservation Molds and casts: Animals with shells or hard exoskeletons buried in sediments are often acted upon by acid-rich ground water which may dissolve away shells or other organic structures. The void created by this action is called a mold.

13 Carbonization: the organic compounds are removed by pressure and heat Usually covered by fine mud a thin carbon film is left behind

14 Petrification: Fossils in which the entire cellular structure of the organism is replaced by mineral matter are considered petrified.

15 Permineralization: Porous organic structures, like bone, certain shells and woody tissue are replaced by minerals ammonite in pyrite (fools gold)

16 ammolite

17 Mummified: in ice or desert In amber

18

19 Footprints, burrows, etc. Trace fossils

20 Fossils can give us much useful scientific data Community Structure: other organisms in the ecosystem, social nature (herds, nesting behaviour) Paleogeography: location of the continents, sea depth Paleoclimatology

21 Relative Dating Techniques Fossil Succession uses index fossils to age rocks

22 Index Fossils

23 Correlation index fossils can help determine the relative ages of rocks in different locations. Index fossils should be: common, easily recognizable, occurred over a large area, lasted for a relatively short time

24 Each layer with the same index fossil is the same age

25 William Smith supervised the digging of the Somerset Canal in southwestern England, a job that lasted six years. The job of surveying canal routes required detailed knowledge of the rocks through which the canal was to be dug.

26 This led Smith to examine the local rocks very carefully. Smith observed that the fossils in a section of sedimentary rock were always in a certain order from the bottom to the top of the section. This order of appearance could also be seen in other rock sections, even those on the other side of England.

27 He developed the "principle of faunal succession." The layers of sedimentary rocks in any given location contain fossils in a definite sequence; the same sequence can be found in rocks elsewhere, and so strata can be correlated between locations.

28 Cambrian Explosion At the beginning of the Cambrian, there appeared a whole range of complex animals Many of them are the earliest known representatives of modern animals. In addition to the sudden increase in numbers of different animals, many seemed to have acquired hard skeletal parts also, for the first time in Earth s history.

29 Burgess Shale in BC's Yoho National Park The Burgess Shale contains the best record of Cambrian animal fossils. The rock contains many fossils of soft bodied animals as well as those with hard parts.

30 They were buried in an underwater avalanche of fine mud that preserved exceptionally fine details of the structure of their soft parts

31 It s the single most significant evolutionary transition period seen in the fossil record. Waptia fieldensis, was a small shrimp-like creature from the Middle Cambrian

32

33 Pikaia, has the beginning of a backbone

34