1. Geology 1023 Platforms and Paleozoic life

2. Platform sequences Thin (mostly) Flat-lying “Layer-cake” stratigraphy Laps onto the shield Undeformed Rocks belong to the sequences mentioned in class (Sauk, Tippecanoe, etc.) Mostly Paleozoic rocks

3. Doing the lab. Q. 1 Two cross sections Change in sediment type Change in thickness How is that related to the position of the shield in each case?

4. Doing the lab. Q. 2. Detailed map showing the Grand Canyon area Map looks complicated But it is just a valley slicing into flat-lying Phanerozoic sediments

5. Important forms of Paleozoic life Trilobites (extinct) Brachiopods (a few living forms) Graptolites (extinct) Sponges (arose in the Precambrian but important in Paleozoic) Corals (arose in the Precambrian but important in Paleozoic)

6. Paleozoic Life Drawing (to get your “ eye ” in) No need to be detailed (artistic) Scales are MANDATORY, major features should be labeled. A few assemblage questions

7. Trilobites Arthropods (as are insects, spiders, scorpions, crustaceans…) Tri-lobe-ite: they have three lobes laterally (1 axial and 2 lateral or pleural) Also divided lengthwise into head (cephalon), thorax, and tail (pygidium). Cephalon usually recognizable due to eyes and central bulge called “ glabella ”

8. Trilobite (Phacops)

12. Brachiopods Look like bivalves (clams) BUT have different symmetry Bivalves (clams) have a plane of symmetry between the shells or are asymmetrical Brachiopods have plane of symmetry across the shells

13. Brachiopod features Two shells or “ valves ” Larger valve with a hole ( “ pedicle opening ” ) at “ beak ” = pedicle valve Other valve is the “ brachial ” valve Growth lines (are concentric away from beak) Costae (ribs) fan out from beak Sulcus and fold are deep (central) central furrows/ridges running from beak to edge

14. Brachiopod pedicle opening brachial valve costae (ribs) sulcus (furrow) growth lines (concentric) ~1 cm plane of symmetry plane of symmetry pedicle valve

15. Growth lines (concentric) Pedicles

16. Graptolites Colonial organism Fossils look like pencil markings, shaped like small sawblades The blade part called a “ stipe ” contained several individuals. Each “ tooth ” of the blade (where individual organism lived) called a “ theca ”.

17. Graptolite (Monograptus) thecae (sing. = theca) stipe ~1 cm

22. Questions?