Paleozoic: Lower   Mid Cambrian Rocks in Georgia

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Paleozoic: Lower Mid Cambrian Rocks in Georgia

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1. Paleozoic: Lower – Mid Cambrian Rocks in Georgia Ryan Perry

2. Paleogeography: N. America in the Paleozoic

3. Early Cambrian

4. Earliest Rox in GA The oldest rocks in Georgia are found in the Piedmont and Blue Ridge provinces and are Proterozoic in age (1 to 1.3 billion years old). Sediment -> SedRox- >Metamorphism. Early Cambrian:Grenville mountains eroded Streams stransport seds to sea, covering GA in sediments. Metamorphosed: gneiss, marble, metaconglomerate, phyllite, quartzite, schist, and slate found in the Blue Ridge and Piedmont.

5. Paleozoic: Cambrian Period (542 - 490 MA) Principle rock types:sandstones, dolostones, and shales. -Early beaches. Limestones and other carbonates were deposited later in the Cambrian in warm, shallow seas.

6. Early Cambrian The Valley and Ridge Physiographic Province is characterized by a sequence of folded and faulted, northeast-trending Paleozoic sedimentary rocks that form a series of alternating valleys and ridges that extend from Alabama and Georgia to New York.

7. Early Cambrian Weisner Quartzite/Chilhowee Formation Chilhowee comes from the Cherokee word, Tsu'lunwe'I, but noone remembers what it means! Maybe Kingfisher??

8. Origin of the Chilhowee Erosion of the proto-Appalachian Mountains during the Lower Cambrian Period. 1.2 billion years ago: Grenville orogeny; initial uplif of the proto-Appalachians. Erosion during this time created sediments. Eroded into Iapetus Ocean.

9. Chilhowee Quartzite Quartzite: derived from sandstone Sedimentary origin: orthoquartzite Percolating fluid; dissolved silica; silica cementation of quartz grains. High P and T = the silica grains recrystallize so that the original sedimentary structure is obliterated.

10. Chilhowee Quartzite

11. Chilhowee Quartzite

12. Chilhowee Formation Phyllite, Shale, Mudstone Shallow Marine Fossils: Skolithos ichnofacies Obvious evidence of metamorphism!

13. Where can we see the Chilhowee? Blue Ridge Province, NW Georgia -- earliest evidence of Pre- Cambrian life! Shenandoah Nat’l Park: Sky Line Drive, Brown Mountain

14. Cambrian Carbonates Shady Dolomite; first carbonate sequence in Georgia, Lower Cambrian Shallow, warm, aragonitic sea

15. Shady Dolomite Along the boundary between the Valley and Ridge province and Blue Ridge province from Alabama to Pennsylvania. 1,000 feet thick at most places and consist of gray to light-gray medium- to thick-bedded crystalline dolomite

16. Shady Dolomite local lenses of limestone and shale Andundant shallow marine fossils Biostratigraphic correlations with other units of same time period Maximum thickness at 1800 ft in SW. Virginia

17. Shady Dolomite

18. Shady Dolomite Mostly found in S. Tennessee Outcrops; contact between Chilhowee and Shady

19. Shady Dolomite

20. Shady Dolomite Manganese deposits Iron-oxides Rich in ochre, and ferruginous minerals Mined in pits

21. Middle Cambrian

22. Rome Formation fine-grained, interbedded sandstone, siltstone, and shale which are interbedded. Lower Formation: heavily bedded sandstones with interbedded fine-grained silt stones Upper Formation: thinly bedded, shaly siltstones, fine- grained sandstones, shales, and few dolomites

23. Rome Formation sandstone is its principle constituent and varies in color from red to green Similar beds of the same time of deposition and composition are observed in Alabama, Tennessee, and Virginia

24. Rome Formation

25. Rome Formation

26. Rome Formation

27. Rome Formation There are three belts of the formation which display out crops. The westernmost belt: extends from Villanow northeast to Tennessee Central belt: Resaca and Dalton. Cartersville to Crandall and passes beneath the rocks of Cohutta Mountain

28. Rome Formation thickness of the formation varies between 500 to 1,000 feet overall thickness, however, is difficult to estimate due to the abundant faulting and folding in the region.

29. Boundary Between Rome and Conasauga Difficult to distinguish lenticular lime stone and dolomite interbedded with thick deposits of shale, rust-colored sandstone within the uppermost portion of the Rome Formation fossil assemblages within shales of the Lower Conasauga Formation (Biostratigraphy).

30. Conasauga Formation named for the Conasauga River in Georgia by C.W. Hayes. consists of shales in varied states of weathering. yellow, grey, and pink coloration. The more stable, unweathered portions are typically pale green in color

31. Conasauga Formation Many outcrops of pale, highly fissile shale are visible at road cuts along the western portion of the formation

32. Conasauga Formation

33. Conasauga Formation

34. Honaker Formation northeastern Tennessee is about 2,000 feet thick thinbedded to massive dolomite and magnesian limestone and some interbedded limestone and shale. The lower part of the formation contains abundant chert

35. Honaker Formation Magnesian limestone beds of variable composition are most abundant; they generally contain 90 percent carbonate, of which the MgCO3 content ranges from 7 to 38 percent and averages slightly more than 10 percent

36. Rogersville Formation Earliest evidence of land plants Polynological analyses

37. Rogersville Formation

38. Rogersville Formation Estuarian environment Shallow Marine Fossil spores and pollen

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