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Historical Geology�������������������������������������������������������������������������������������������������������������� R. Lopez

Study Questions 13: Evolution of Eastern Laurentia

1. During the Paleozoic Period, how many orogenic events did Eastern Laurentia experience and what are the names of these orogenies?

2. What are flysch and molasse deposits?

3. What do flysch and molasse deposits tell us about tectonic setting?

4. What is the name and age of the first orogenic event to occur along Eastern Laurentia?

5. What is the name of the second orogenic event to affect Eastern Laurentia?

6. What is the name and age of the youngest and last orogenic event to affect Eastern Laurentia?

7. What types of rocks were accreted to East Laurentia during the Late Orodovician Taconic Orogeny?

8. What was the tectonic setting of East Laurentia before the Taconic orogeny and what was the tectonic setting during the Taconic orogeny (ocean-ocean-arc accretion?, ocean-continent?, continent-continent?)

9. What event occurred during the Silurian-Devonian Acadian orogeny in northern East Laurentia (up around Greenland) and what continent resulted from this event?

10. The event in the question above was a ocean-ocean-arc accretion, ocean-continent convergence, continent-continent convergence?

11. At Sicar Point in Scotland, the Great Angular Unconformity occurs where Silurian marine sediments are steeply tilted and are overlain by nearly horizontal sediments.� What are these sediments, where did they come from, and what orogeny of part of an orogeny do they document?

12. What event occurred during the Silurian-Devonian Acadian orogney in northeast U.S. and Novia Scotia, what types of rocks were accreted, and what was the tectonic setting (ocean-ocean-arc accretion?, ocean-continent?, continent-continent?)?

13. What terrane was accreted to Laurentia south of the New York area and during the Acadian orogeny?

14. During the Alleghenian Orogeny, what part of Gondwanaland collided with East Laurentia?

15. What was the name of the terranes� that approached from the east before the Taconic Orogeny?

16. By the middle to end of the Silurian Period, northeast Laurentia had collided with Baltica to form Euramerica.� What was the name of this orogeny and where is the evidence for this continental collision?

17. Scottish geologists were puzzled as to the origin of the Devonian Old Red Sandstone found at Siccar Point.� What is the significance of the Old Red Sandstone?� What type of unconformity does it make with the underlying Silurian marine sediments?� What was the origin (provenance) of the Old Red Sandstone if it did not come from Europe?

18. Red sandstone beds (red beds) are typical of what sedimentary environment (terrestrial or marine)?

19. What is the origin of the micro-continent Avalonia?� Where is Avalonia now exposed?

20. What was the name of the Gondwanan Trilobite fossil that differed so much from North American type trilobite fossils?

21. During what orogeny was New York�s Castskill Wedge sediments deposited?

22. The Catskill Mountains records the westward advancement of the Acadian Orogeny and accretion of Avalonia.� Note that the base of the Catskills is formed of the Devonian Oriskany and Helderberg Formations (carbonate platform sediments).� What do these deposits tell us about the tectonic setting of the Catskills during the lower Devonian?

23. In the Catskills, the middle Devonian Hamilton Group marks a change in tecontic setting.� What type of sediments are found in the Hamilton Group?� What type of tecontic setting do they mark?

24. Finally, in the Catskills, the upper Devonian sediments are molasse deposits.� What do these molasse sediments tell us about the orogenic event?

25. Along the Carolina border, what type of tectonic setting occurred here during the Acadian orogeny?� What types of rocks were accreted?� What is the name of the Trilobite fossils common to the accreted terrane?

26. During what orogeny did the current structure of the Appalachian Mountains form?� What global tectonic event occurred at this time?

27. What is the fold and thrust belt in the Appalachians?� What does this fold and thrust belt represent?

28. What age and type of rocks are the Blue Ridge Mountains composed of and when were these rocks metamorphosed?

29. What was the name of the Late Paleozoic orogeny that affected the southern margin of Laurentia?

30. What was the tectonic setting of the late Paleozoic orogeny of the southern U.S. and what collided with Laurentia to cause the mountain-building event?