1 / 21

Geology 1023

Geology 1023. Shields and Precambrian fossils. Continental building-blocks (see map at side of lab). Shield : central core of Precambrian rocks Virtually all shield rocks are igneous or highly deformed metamorphic rocks

jaron
Download Presentation

Geology 1023

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Geology 1023 Shields and Precambrian fossils

  2. Continental building-blocks (see map at side of lab) • Shield: central core of Precambrian rocks • Virtually all shield rocks are igneous or highly deformed metamorphic rocks • Platform: a thin (a few hundred metres) skin of undeformed sedimentary Phanerozoic rocks • Divided into various sequences mentioned in class • Sauk, Tippecanoe, Kaskaskia, Absaroka, Zuni • Mobile (orogenic) belts: currently (or recently) active mountain chains, not yet fully worn down • Cordillera and Appalachians in North America.

  3. This week’s lab is in two parts • Rocks of the Shield • In the exercise you will look at maps and answer questions that pertain to the study of these ancient and mostly highly-deformed rocks • Precambrian life: • A first look at organisms that first arose in the Precambrian • Note that most of the specimens are of Phanerozoic fossils but they represent groups that first developed in the Precambrian

  4. Doing the lab. • Q. 1. Based on 3 maps (2543, 2586 & 900A). • (a) – (f) relate to reading information from map 2543 of Central Ontario • Mostly related to seeing the distribution of the rocks (shown on the map) and their ages (as shown on the legend) • (g) asks you to compare the geological map (2542) and the map showing the magnetic fields in the area (2586). • Magnetic fields are produced by the rocks and help us understand rock distribution even when the rocks are hidden from view.

  5. Doing the lab. • Canada’s wealth and status in the world today comes from our role as a resource-rich country. • A huge percentage of Canada’s wealth has come from mining. The Precambrian shield has provided a considerable amount of Canada’s mineral wealth. • Q. 1 (i). Asks you to look at map 900A, which shows the distribution of current (or recent) mining and oil and gas operations in Canada • At the side of the map is a legend for each Province • Determine the major minerals/elements mined in the the Precambrian shield areas of ON, QC, MB

  6. Precambrian life • Life arose in the Precambrian • Oldest known preserved life forms are colonial single-celled organisms of the Kingdom Monera which formed cabbage-shaped mounds called stromatolites • Oldest stromatolites are from 3.5 Ga (billion years ago) • Stromatolites are still found in parts of the world today.

  7. Modern stromatolites

  8. Ancient stromatolite

  9. Multi-cellular life • Multicellular organisms (like ourselves) first developed in the last part of the Precambrian • One famous group of multicellular organisms is known as the Ediacaran fauna, first found in Ediacara, Australia • Ediacaran fauna are now extinct • We do not have a collection of these bizarre-looking organisms which resemble primitive sea-pens, jelly-fish etc.

  10. Multi-cellular life • The two most primitive groups of multicellular organisms which are still living today are the Porifera, sponges, and the Cnidaria, which include jellyfish, sea anemones and corals. • Sponges and corals both have skeletal elements and thus are well-represented in the fossil record

  11. Sponges • Sponges are probably the most primitive multi-cellular organisms around today • Consist of a largely undifferentiated mass of gelatinous cells supported by a variably rigid structure (your modern bath-sponge is the skeleton of a modern sponge animal) • Sponges absorb water through their sides, extract food, and emit the water through their top – hence the chimney-type shape of most sponges.

  12. A modern funnel-shaped sponge

  13. Bath sponges, the skeletons of primitive animals

  14. A fossil sponge

  15. Cnidaria • Phylum that includes jellyfish, anemones, and corals • All are jelly-like organisms with “stinging” cells • Only corals produce a skeleton (a calcium carbonate structure attached to the bottom) • Most corals are colonial, but some Paleozoic (and probably Precambrian ones) were solitary. Many produced a conical cup-shaped skeleton (“cup corals”)

  16. Doing the lab. • Q. 2. Refresh your memory as to the Linnean classification scheme • Q. 3. Draw a representative portion of the stromatolite at the back of the lab. • Drawings do not have to be highly artistic, just show the relevant features • All drawings must have a scale, and label what you can (laminations in the case of the stromatolite)

  17. Doing the lab • Q. 4. Examine the examples of sponges at the back of the lab. • In the rock and fossils set (in drawer at the back of the lab) is a specimen of the calcareous sponge Girtyocoelia. Make a drawing of it with scale and labels. • At the back of the lab is a second handout “Diagrams showing simple body plans…”. Use it to determine features of interest.

  18. Various sponges showing inhalant pores and exhalant osculum.

  19. Doing the lab • Q. 5. Examine the specimens of corals at the back of the lab. There are both “solitary” and “colonial” forms. • Examine the set of fossils in the drawers at the back and identify the 4 that are corals. • Determine the genus and age range for two of the solitary forms. • Draw a solitary and a colonial form. Use the handout “Diagrams showing simple body plans…”to help you assign labels.

  20. Various coral diagrams showing, calice, tabula(e), septum(a), etc.

  21. Questions?

More Related