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LITHOSTRATIGRAPHY Kaibab Limestone Toroweap Formation Coconino Sandstone Hermit Shale Redwall Limestone Muav Limestone Bright Angel Shale Tapeats Limestone Brahma Schist These are the Paleogene rocks that occur along the Flint River between Montezuma and the dam at Lake Blackshear. Eocene Oligocene Youngest L Bridgeboro Limestone U Ocala Limestone Clinchfield Sandstone M Lisbon Formation Tallahatta Sandstone Paleocene Hatchetigbee Formation L Tuscahoma Sandstone U Nanafalia Formation L Clayton Formation Oldest The Bridgeboro Limestone was first recognized and described from a quarry near Bridgeboro, GA (southeast of Albany). It can be traced from Dublin, GA (near Macon) to the western part of Florida. Eocene Oligocene The Ocala Limestone was first recognized at Ocala, FL (central part of the state). It can be traced from central Florida to near Macon, GA and westward to southeastern Mississippi. L U Bridgeboro Limestone Ocala Limestone Clinchfield Sandstone M Lisbon Formation Tallahatta Sandstone Paleocene Hatchetigbee Formation L Tuscahoma Sandstone U Nanafalia Formation L Clayton Formation The Clinchfield Sandstone was described at Clinchfield, GA (near Perry). It can be traced southwestward to near Albany, GA. The Lisbon Formation was described at Lisbon Bluff, AL and can be traced eastward to near Americus and westward to Louisiana. In the Americus area it contains Sands, mudstones, and limestone. The limestone is less common west of here. The Tallahatta Sandstone was described in the Tallahatta Hills in western Alabama, and can be traced from the Flint River westward to Mississippi. The Hatchetigbee Formation was described from Hatchetigbee Bluff on the Tombigbee River in western Alabama. It comprises sand and clay, some of the clay a bit limy. It thins into both Mississippi and Georgia and is difficult to find near Americus. At Andersonville it is apparently missing (because of a disconformity). The Tuscahoma Sandstone was described near Tuscahoma, Alabama and stretches from western Georgia to Mississippi. The Nanafalia was described at Nanafalia Bluff on the Tombigbee, and can be traced from Georgia to Mississippi. It comprises mudstone and sandy mudstone. The kaolin mined at Andersonville is from the Nanafalia. The Clayton Formation (named for Clayton, AL) is a complex mix of sandstones, mudstones, and limestones. Near the Flint it is mostly mudstone with oyster reefs. Near Cuthbert, GA and on the Chattahoochee it is almost all limestone, westward it becomes less lime. It extends from near here to western Tennessee and Arkansas. All the “units“ of rock on the preceding page are “formations”. This is the basic unit of lithostratigraphy. A formation is defined as a package of sedimentary rocks of a certain minimum thickness, and of an easily recognized character, and that can be easily distinguished from the formations above and below, and that can be traced or correlated over a considerable distance. The locations on the preceding page are the type sections. The rocks were first described there and their top and bottom contacts characterized. They are found (mostly) from Mississippi to Georgia with similar characteristics and always in the same vertical order. The type section is always the first part of the name of a formation. The second part may be descriptive of the rock (Bridgeboro Limestone, for example) or just the word “Formation” if the rock type is variable (Clayton Formation, for example). This is a picture of the Bridgeboro Limestone at the “type section” (at Bridgeboro, GA). The people are standing on mining rubble. In-place rock starts at the girl’s feet. The formation is at least twice as thick as what you see. Notice that it contains thinner beds than itself. Some are cherty (the blackish ones) some have very course algal fossils (behind the girl and near the top) and some are finer grained (above the chert). All are limestone (or silicified limestone). Look carefully near where the girl is and you’ll see even thinner layers inside these. The Bridgeboro is a layer of limestone that contains even thinner layers. All formations are like this. Oligocene Eocene L Bridgeboro Limestone U Ocala Limestone Clinchfield Sandstone M Lisbon Formation Tallahatta Sandstone Paleocene Hatchetigbee Formation L Tuscahoma Sandstone U Nanafalia Formation L Clayton Formation Oligocene All the formations (except the Hatchetigbee) can be seen on a float trip down the Flint River from just north of Montezuma to the Dam, or in nearby quarries. (Some are covered by the waters of Lake Blackshear and can only be seen at exceptionally low water levels.) L Bridgeboro Limestone U Ocala Limestone Eocene Clinchfield Sandstone M Paleocene ? Lisbon Formation Tallahatta Sandstone Hatchetigbee Formation L Tuscahoma Sandstone U Nanafalia Formation L Clayton Formation Notice that they are encountered in superpositional order as you go downstream – older farther north and progressively younger southward. (North is not “up”. When you look at the map you are looking straight “down”). Why is this? All the rocks dip generally southward at a very low angle – roughly the angle of the continental shelf they were deposited on. (Most have marine organisms in them). The older ones dip beneath the younger ones southward. 1 - 2° N (land surface) Bridgeboro S Ocala Clinchfield Lisbon Tallahatta Dips are greatly exaggerated! Hatchetigbee Tuscahoma Nanafalia Clayton Dam GA Vet. St. Pk. N. Spring Cr. Cir. Ocala Danville Bluff Lisbon Powerline Crossing Reeves Landing Hatch.?? Tallahatta Andersonville Quarries Tallahatta Tuscahoma Montezuma Bluffs Clayton Nanafalia Tallahatta Clinchfield Ocala Bridgeboro Ocala WF George Dam Nanafalia Clayton The same pattern holds along the Chattahoochee River, but the sandstone between the Lisbon and Ocala looks different – more like a sand at Moodys Branch, near Jackson, MS. They are in the same position, but look different. Roaring Creek Tuscahoma Nanafalia Abbie Creek area Tallahatta Hatchetigbee Tuscahoma Columbia, AL Lisbon Tallahatta Andrews Dam Moodys Br. Lisbon US 84 Bridge Ocala Moodys Br. Lake Seminole Bridgeboro Ocala OLDER TO NORTH 1 - 2° 1 - 2° YOUNGER TO SOUTH U Ocala Limestone Moodys Br. Sandstone M Lisbon Formation Tallahatta Sandstone Oligocene Bridgeboro Limestone Eocene Oligocene Eocene L L Bridgeboro Limestone U Ocala Limestone Clinchfield Sandstone M L Tuscahoma Sandstone U Nanafalia Formation L Clayton Formation Tallahatta Sandstone Hatchetigbee Formation Paleocene Paleocene Hatchetigbee Formation Lisbon Formation L Tuscahoma Sandstone U Nanafalia Formation L Clayton Formation Oligocene Eocene Paleocene L Bridgeboro Limestone Bridgeboro Limestone U Ocala Limestone Ocala Limestone Moodys Br. Sandstone Clinchfield Sandstone Lisbon Formation Lisbon Formation Tallahatta Sandstone Tallahatta Sandstone Hatchetigbee Formation Hatchetigbee Formation L Tuscahoma Sandstone Tuscahoma Sandstone U Nanafalia Formation Nanafalia Formation L Clayton Formation Clayton Formation M
