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Information found: http://home.att.net/~cochrans/brevrd01.htm
Brevard Fault Zone
Running southwest-northeast across Alabama, Georgia, and North Carolina, the Brevard Fault Zone (or the Brevard Zone of Cataclasis) is a prominent geologic feature of the Southeast United States.
Geologists continue to debate the Brevard's structure and significance, and the nature and direction of ancient movement on the fault. The Brevard has been interpreted as a left-lateral strike-slip fault, a right-lateral strike-slip fault, a normal fault, or a thrust fault. At one time, it was thought to represent the suture where Proto-Africa joined Proto-North America to form Pangea, although rocks on one side of the fault generally resemble those on the other side. Structural clues to movement are ambiguous; however, the "smeared" shapes of some granite bodies suggest right-lateral movement. The fault -- fortunately for us -- last moved about 185 million years ago, so the question is not of practical urgency.
Rocks in the Brevard zone are profoundly sheared and fractured; they include mylonites, button schists, and gneisses. In many segments, Brevard Zone topography features rhythmically-spaced parallel ridges, which control much of the Chattahoochee River's course.
Information is from this site: http://www.gly.uga.edu/default.php?PK=0&iPage=5
Geologic resources of the Blue Ridge presently include marble, much of which is mined by Georgia Marble Company. Talc has been mined in the western Blue Ridge just east of Chatsworth. Gold was mined at Dahlonega in the early 1800's, and in fact a U.S. mint produced gold coins there from 1830 to 1861. The North Georgia gold rush of the 1830's precipitated the eviction of the Cherokee and their forced migration on the Trail of Tears.
Georgia is the southwest end of the Blue Ridge, which extends northeast to Virginia through Great Smoky Mountain and Shenandoah National Parks. The southern boundary of the Blue Ridge in Georgia depends on one's perspective. A purely topographic approach would limit the Blue Ridge to just a few ridges extending southwestward from North Carolina, so that the Piedmont would extend all the way to the Georgia-Tennessee state line. Some geologists, in contrast, would extend the Blue Ridge region all the way to the Brevard Fault zone, which runs through northwest Atlanta and Gainesville. One of the most commonly accepted boundaries, which is based on changes in rock types, would run just southeast of Canton, Dawsonville, Dahlonega, and Helen.
The Piedmont is a region of moderate-to-high-grade metamorphic rocks , such as schists, amphibolites, gneisses and migmatites, and igneous rocks like granite. Topographically, the Piedmont mostly consists of rolling hills, although faulting has produced the impressive ridge of Pine Mountain near Warm Springs. Isolated granitic plutons also rise above the Piedmont landscape to give prominent features like Stone Mountain.
One major feature cutting across the Piedmont (as defined here) is the Brevard Fault zone. The Brevard Fault Zone runs from northeast to southwest and passes through Centralhatchee in Heard County, northwest Atlanta, Duluth, Buford, and Gainesville before leaving Georgia at the westernmost point on the Tugaloo River in northernmost Stephens County. The Chattahoochee River follows the Brevard Zone too. However, the regional extent of the Brevard Zone is reflected by the fact that it is named after the town of Brevard, North Carolina. The Brevard Zone has been interpreted as a variety of different kinds of faults or discontinuities, and its true nature remains enigmatic.
Information is from: http://csat.er.usgs.gov/statewide/layers/brevzone.html
Brevard Fault Zone
Information is from: http://quake.eas.gatech.edu/EMguide/Image6.gi
Information is from: http://ngeorgia.com/ang/Sweetwater_Creek_State_Park
Sweetwater Creek State Park
About North Georgia
The sun rises strong
most mornings on the Piedmont Plateau, and the skyscrapers of Atlanta cast
shadows westward toward Sweetwater Creek State Park. More than 2,000 acres of
land owned by the State of Georgia, adjacent to East Point's George H. Sparks
Reservoir, offer an excellent opportunity for historians, geologists and
environmentalists to study their crafts and catch a fish or two on the side.
Brevard Fault line, which bisects the park, was an excellent location for many
of the mills. Beginning in northeast Georgia(it is a major structural feature of
the entire southern Appalachians and defines the boundary between the Blue Ridge
and Piedmont belts) this line traverses the state near the high eastern ridge of
the Appalachian Mountains before turning south around Jasper and running through
Marietta. Moving to the southwest the line turns more westerly and crosses into
Alabama south of I-20. Local geologists believe the fault is more active than
the San Andreas, but less well known because the plate movement does not produce
INFORMATION IS FROM: http://www.sherpaguides.com/georgia/chattahoochee/natural_history/index.html
The Natural History of the Chattahoochee River
By Robert Montgomery. Photos by Richard T. Bryant.
Two hikers stop and stare in wonder as a black bear and her cub scramble across a tiny stream that shimmers in the morning light.
Signs of civilization are nonexistent here among the pine trees and hardwoods, but in just a few miles man's mark will appear as the trickle broadens and eventually feeds one of the most important U.S. Army Corps of Engineers impoundments in the nation, both for recreation and water supply.
Pouring out of Buford Dam, the river provides a trout fishery and rapids for canoeists and kayakers as it speeds toward one of the fastest growing metropolitan areas in the United States.
The city of Atlanta withdraws more than 300 million gallons a day and discharges more than 200 million gallons of wastewater while the river keeps flowing toward the sea.
A 70-mile stretch below the city is arguably among the most polluted stretches of river in the nation, but still the river endures. It fills up three more major reservoirs, as well as provides for hydroelectric power, commercial navigation, and flood control, before finally being set free to feed one of the world's most productive estuaries.
From its birth in the mountains to its surge into the sea more than 500 miles later, the Chattahoochee is the quintessential American river, complete with all the paradoxes that designation entails. It is used and abused, coveted and ignored, loved and cursed, as it provides drinking water for more than half of all Georgians and recreation for more than 25 million Americans.
"The importance of the Chattahoochee River is hard to overestimate," says Jerry McCollum, president of the Georgia Wildlife Federation (GWF). "We are water people. We can't live without it."
Since prehistory the Chattahoochee has been a working river. Cherokees, Creeks, and tribes long before them depended on it for drinking water, food, and transportation. Never, though, has it worked harder, as the river's basin today is the smallest in the nation serving as a primary source of drinking water for a large metropolitan area.
Demand will only increase, too, as development continues in and around Atlanta, as well as along the shores of the river that flows down the mountains, along the Georgia-Alabama border, into Florida, and ultimately into the Gulf of Mexico as a river renamed the Apalachicola.
Those three states have been waging "water wars" for nearly a decade, trying to decide how flow from the Apalachicola-Chattahoochee-Flint system will be apportioned during the next century. Many fear that the Chattahoochee is reaching critical mass and its rich, diverse ecosystems will collapse as politicians choose unbridled growth and development over conservation and preservation.
The Chattahoochee River begins as sparkling teardrops weeping out of the rocks on the southern edge of the Blue Ridge mountains, just below Brasstown Bald, Georgia's highest point at 4,784 feet. From its birthplace at Coon Den Ridge in Union County, it trickles through a lush forest of oaks and pines, ferns and rhododendrons, blackberries and buckberries, and, of course, pervasive poison ivy. Only a few inches wide at first, it soon is joined by other streams and widens to what some might call a mountain "creek." Eventually streams from Habersham, Lumpkin, Rabun, Towns, and White counties, as well as Union, broaden its shoulders.
If you are so inclined, you can climb to 3,600 feet or so, where Jack's Knob Trail dead-ends into the Appalachian Trail and see the origin of the river at Chattahoochee Gap. The spring lies about 200 feet south of the trail. Its only indication is a sign with a "W" (for "water") pointing downhill.
Or you can drive to Brasstown Bald for a panoramic view of the Upper Chattahoochee. On a clear day, Lake Lanier glistens on the horizon and the Atlanta skyline is visible. Rosebay rhododendron, mountain laurel, and mountain ash remind you that the city is farther away than it appears.
Much of the watershed along this upper stretch of the river is designated as the Chattahoochee Wildlife Management Area within the 750,000-acre Chattahoochee National Forest. More than 500 species of birds, mammals, fish, and reptiles live in this protected headwaters portion, with an estimated 1,000 miles of trout and warm-water streams dissecting the area.
This upper watershed is much healthier than it was in the 1920s, when the federal government began to buy the land that eventually was turned into national forest in 1936. For nearly a century poor farming practices, gold mining, and lumbering had degraded the land and water. The abuses began in the late 1830s, when the U.S. government forced out the Cherokees, who had lived there since at least the 1500s, and white settlers moved in. Today, though, you will see few signs of this earlier destruction as you hike the trails, canoe the streams, and camp in the recreation areas.
One of those trails will take you to Georgia's most visited waterfalls. The twin falls of Anna Ruby mark the junction of Curtis and York creeks, which begin on Tray Mountain. Curtis drops 153 feet and York 50 feet to form the falls that merge into Smith Creek, a tributary of the Chattahoochee.
By contrast, one of Georgia's best kept secrets is Horse Trough Falls, about 10 miles north of Helen. The flow from Little Horse Trough Creek spreads out across a massive rock face and plunges into a pool 75 feet below, just before the stream joins the river.
As it descends 1,580 feet in elevation and 14 miles in distance on its way to Helen, the first town along its journey to the ocean, the Chattahoochee picks up flow from creeks such as Smith, Low Gap, Henson, Dukes, and Sautee. Helen is a German-theme tourist town of festivals and businesses such as Alpine Village Outlets and Alpine Brew Package Store. A fast-food franchise now sits where the largest sawmill in the South used to slice timber from the mountains.
Degradation begins on the river above Helen, mostly from campers who destroy streamsides and don't care where they dispose of their wastes. But it is at this mountain town that the destruction first becomes truly visible. More and more development along the river is destroying the riparian buffer zone of plants that stabilizes the banks and keeps the water clear. The result is increased erosion that muddies up the river and contributes to the more than 200,000 tons of sediment that is filling up Lake Lanier, just downstream.
As the sediment load increases, the Upper Chattahoochee's value as a trout fishery correspondingly declines. The sediment smothers habitat, slows flow, and makes the water uncomfortably warm for cold-water fish.
From Helen, the river flows east through Nacoochee Valley, where humans are thought to have lived as far back as 14,000 years, the close of the last Ice Age. They buried their dead in mounds, still visible here.
Excavations suggest the Spanish searched for gold in the valley as long ago as the sixteenth century. The second gold search began in 1828, and once the stream beds were exhausted, miners began tunneling into the hills.
Just four years before the second gold rush, the first dam was built on the Chattahoochee to power a grist and lumber mill. In 1876, John Martin built the present Nora Mill, and he replaced the original dam in 1893. Today, this northernmost dam on the river is one of only 50 or so in the country still operating a water-powered mill. Nora Mill grinds cornmeal, grits, and whole wheat, rye, and buckwheat flours.
After it leaves this headwaters area, the Chattahoochee passes through at least 14 more dams on its way to the Gulf of Mexico.
Origin of the name "Chattahoochee" isn't nearly as certain as the birthplace of the river that carries the name. The most generally accepted story comes from the 1799 travel log of Benjamin Hawkins, an Indian agent:
"The name of the river derived from 'Chatto,' a stone, and 'hoche,' marked or flowered; there being rocks of that description in the river above Hoithletigua at an old town Chattahoochee."
Exact location of that old town remains a mystery, but most historians place it near the present town of Franklin in Heard County.
Living in the headwaters area, the Cherokee had named the river "Chota," which was also the name of a town in the Nacoochee Valley. When the river flowed into Creek territory, it became the "Chattahoochee."
When the Cherokees were forced out of their homeland, the name "Chota" disappeared with them.
The Chattahoochee, though, carried on, just as it had during the times of the mound builders hundreds of years before and just as it does today, when it helps grow peanuts and cotton in southwest Georgia, powers turbines, and flushes every toilet in Atlanta.
Over the centuries it served as possibly the most important route for connecting the Gulf of Mexico to the interior of the nation. It allowed for Indian tribes to travel and trade, and it provided entry for white explorers and settlers. The Spanish traveled up the river as early as 1639 and tried to establish exclusive trade with the Creeks.
By 1824, the federal government already had begun to "improve" the Apalachicola for commercial navigation. With the forced removal of the Indians, hundreds of steamboats began traveling the 262-mile waterway between the port town of Apalachicola and the Columbus wharf. Stopping at any number of the more than 200 landings along the way, the boats carried cotton bales downriver and brought back manufactured goods and food, including Apalachicola Bay oysters kept alive with cornmeal sprinkled in wooden barrels. The last steamboat to dock in Columbus was the George W. Miller in 1939.
In addition to the steamboat trade, grist, lumber, and textile mills flourished on the river, especially along the "fall line" between West Point and Columbus. During the 1830s, Columbus erected a dam to divert water to its business district, enabling it to become one of the South's most prominent industrial centers by the 1850s.
The fall line designates a dramatic change in character for the Chattahoochee, as it stops flowing from the mountains and starts running to the sea. Dropping more than 300 feet over 38 miles, the river historically raced over a long series of waterfalls and shoals created by the transition from Piedmont to Coastal Plain. The fall line provided the perfect setting for mills, as well as marked the end of navigable waters from the Gulf of Mexico. Millions of years before, the fall line had marked the edge of that same ocean body.
The richest land for farming along the river is just below the fall line. There the Chattahoochee drops its soil load across the bottomlands, and it was there that most of the Indian settlements occurred. The lower Chattahoochee, in fact, probably has the largest collection of archeological sites in Georgia, ranging from Paleo-Indian to Creek.
Farther upriver, the waterfalls and rocky creeks of the Brevard Fault also enabled mills to operate. The area around Hilly's Mill Creek and Red Bone Creek marks the point where the fault continues on into Alabama and the river turns south, forming the boundary between Georgia and Alabama. Since steamboats couldn't travel this far north, poled barges frequently moved cotton downstream to Columbus during the nineteenth century.
The Brevard Fault, which cuts diagonally from northeast Georgia to Alabama, probably is the Chattahoochee's most important geological feature and has contributed much to the scenic beauty of the river, both above and below Atlanta. A "fault" is the result of one part of the earth's crust moving or slipping in relation to another. In this case, the river flows through 100 miles of ridges, valleys, palisades, and waterfalls because of the fault.
Just as important to the character of the river is the fact that the Brevard Fault serves as the dividing line between the Appalachian Mountains and the Piedmont Plateau. The fault itself serves as a natural barrier to movement of flora and fauna between the two distinct geological regions. But plants and animals have migrated up and down the aquatic highway connecting the two, and thus have moved far outside of what might have been their natural range. Some species of salamanders and birds, for example, have made their way from the mountains to the Piedmont along the Chattahoochee, as have numerous species of trees. Beech, white oak, umbrella magnolia, tulip popular, black locust, and mountain laurel are but a few species that grow farther south than they might have if not for the Chattahoochee River and Brevard Fault.
Most all of the river along the fault lies exclusively in Georgia, but when the fault continues on past Heard County and into Alabama, the Chattahoochee turns more southerly, forming a 200-mile boundary with Alabama and a small portion of Florida.
On its way to flush 16 billion gallons of water a day into Apalachicola Bay, the Chattahoochee drains an estimated 8,770 square miles. The Flint drains another 8,460 square miles and the Apalachicola 2,370, so that the combined watershed of the system is an impressive 19,600 square miles. More than 70 percent of that lies in Georgia.
This information is from: http://home.att.net/~cochrans/brvsit01.htm
***GO TO THIS SITE TO SEE THE PICTURES IN ATLANTA!
Geologic Sites in the Brevard Fault Zone
Where the Brevard fault zone crosses northwest Atlanta, several sites expose crushed, distorted rock, including mylonite, button schist, fractured gneiss, and sheared granite. A few sites:
Felsic/intermediate gneiss that looks suspiciously like Clairmont formation.
Ga. Hwy 400 SB at Glenridge Connector entrance ramp
Schist and mylonite
I-285 EB near Ashford-Dunwoody Road
Long Island gneiss
Cumberland Parkway backroads
Gneiss, blastomylonite, etc.
Northside Drive approaching I-285
Seriously fractured roadcut
Rottenwood Creek (Chattahoochee tributary)
Creek-bed rock: garnet-kyanite mica schist, pegmatite, etc.
Palisades East and West -- Chattahoochee River National Recreation Area
Cliffs of gneiss and schist
Construction sites, e.g. Stillhouse Road Park and look!
I-285 near US 78 Mylonite and sheared Palmetto granite