Field Trip #3: Paleozoic Rocks II

1. Field Trip #3: Paleozoic Rocks II Cretaceous Stratigraphy of Central Texas

3. Field Trip #3: Paleozoic Rocks II • Location • Geology • Assignment / Methods • Reminders Text: Manual, p. 267-278; Compton, p. 166-171; 182-184; 242-243.

4. Location Hamilton Creek Stop 1 (E. McBride) Stop 2 road cut near Max Starke Dam (E. McBride)

5. Location Creek near Stop 2 (Luis Garcia)

7. Geology

8. Geology Paleozoic Sedimentary Rocks Pennsylvanian – Smithwick Shale Ordovician – Honeycut Formation of Ellenburger Group Bastrop N 5 miles

9. (Manual, p. 272)

10. Geology Paleozoic Events • Flooding by Shallow Seas • Uplift Ouachita Mts (Penn) • Faulting (Penn) • Erosion of Ouachitas (P-J)

11. Geology Ellenburger Group • sabkha • evaporites • karst • natural gas - subsurface (nps.gov)

12. Geology Guidebook of the Geology of Travis County

13. Geology Smithwick Shale • marine • high sediment supply • turbidites (E. McBride)

14. Field Trip #3: Paleozoic Rocks II • Location • Geology • Assignment / Methods • Reminders Text: Manual, p. 267-278; Compton, p. 166-171; 182-184; 242-243.

15. Assignment / Methods 1) Smithwick Shale Paleocurrent and Deformation Features • measure and plot the orientation of: • 1) joints • 2) faults • 3) sandstone dikes • 4) fossil wood fragments • 5) current ripples and solemarks

16. sandstone feeder bed sandstone dike (416M) Assignment / Methods • water-saturated sediment • excess pore pressure

17. Assignment / Methods clastic dikes and joints (E. McBride) (E. McBride)

18. groove casts Assignment / Methods flute casts (416M) solemarks (416M) 416M

19. Assignment / Methods • plot features in 4 rings • show # of measurements • show bi-directional trends

20. Assignment / Methods 2) Honeycut Formation Checklist road cut near Max Starke Dam (E. McBride)

21. Assignment / Methods limestone vs dolomite Dolomite - Thin Section Dolomite - SEM (Soil Science Society of America) (Soil Science Society of America)

22. (Earth and Ocean Sciences at UBC) (Luis Garcia) Assignment / Methods stylolites vs stromatolites

23. (Compton, p. 183) Assignment / Methods fault breccia vs solution collapse breccia • solution collapse breccia – filled cave • fault breccia – repeated crushing / cementation

24. Assignment / Methods soft-sediment deformation vs brittle deformation (Compton, p. 243) • faults break more resistant layers only • mottled textures in shear zone

25. Assignment / Methods teepee structure and geopetal structure Geopetal – Thin Section (Matt Campbell)

26. Field Trip #3: Paleozoic Rocks II • Location • Geology • Assignment / Methods • Reminders Text: Manual, p. 267-278; Compton, p. 166-171; 182-184; 242-243.

27. Reminders • Brunton • Rock Hammer • HCl Acid • Hand Lens • Field Notebook • Lab Manual • Water • Lunch • Clipboard • Colored Pencils • Ruler & Protractor • Extra Paper

28. Field Trip #3: Paleozoic Rocks II Cretaceous Stratigraphy of Central Texas

29. Cretaceous Stratigraphy of Central Texas • Paleogeography and Sea Level • Stratigraphy

30. Paleogeography and Sea Level Late Cretaceous Paleogeography http://www4.nau.edu/geology/master.html?http://www4.nau.edu/geology/

31. Cretaceous Stratigraphy of Central Texas • Paleogeography and Sea Level • Stratigraphy

32. (Manual, p. 272)

33. Stratigraphy (Duex and Lock, Univ. LA) • relatively flat-lying • retreating escarpment

34. Stratigraphy • resistant and non-resistant limestone

35. (www.cretaceousfossils.com)

36. Stratigraphy • hard (pure) and soft (clay-rich) • shallow subtidal and supratidal (www.cretaceousfossils.com) Hensell Sand Badlands • sand, conglomerate, paleosols • terrestrial environment Glen Rose Limestone Stairsteps

37. Stratigraphy Edwards Limestone “Swiss Cheese” • pure limestone and dolomite • chert-rich Oyster-rich Del Rio Clay • carbonaceous clay • pyrite – anoxic lagoon