Come Explore Georgia's Natural History
  • Home: Georgias Fossils
  • 1: Georgia's Oldest Fossils; Archaeocyathids, At 513 Million Years Old
  • 2: Trilobites; 500 Million Years Ago
    • 2A; Murray County Stromatolites
    • 2B; A Trilobite Nest in Georgia
  • 3: Geologic Time
  • 4: Georgia's Oldest Vertebrate?
  • 5: Georgia Before the Dinosaurs
    • 5A; Georgia’s Pennsylvanian Plant Fossils
    • 5B: Carpentertypus durhami, Georgia’s Giant Insect, 315 Million Years Ago
    • 5C: Mississippian Trilobites in Northwest Georgia Describing the New Species Australosutura georgiana
    • 5D: Crinoids & Blastoids Of Northwest Georgia
  • *NEW* 5E; Fossils of Northwest Georgia
  • 6: 200 Million Years Ago
  • 6A: Birth of the Atlantic Ocean
  • 7: Cretaceous Georgia, Dinosaurs & more
    • 7A: Georgias Pterosaur
    • 7B: So Many Sharks
    • 7C: Coelecanths
    • 7D: Xiphactinus vetus
    • 7E: Side-necked turtles
    • 7F: Marine Reptiles
    • 7G: Dinosaurs in Georgia
    • 7H: Deinosuchus schwimmeri in Recognition of Dr. David Schwimmer
    • 7I; The Blufftown Formation
    • 7J: New Species of Cretaceous Flowers Reported From Crawford County
    • 7K: Field Trip, Chattahoochee River Valley 1980
    • 7L: The Eutaw Formation
    • 7M: The Pio Nono Formation
    • 7N: Plant Fossils of Crawford County, GA
    • 7O; 1914 Report Georgia Plant Fossils From the Upper Cretaceous
    • 7P: Bill Montante's Mega "Gator" Tooth Discovery
  • 8: Suwannee Current, Gulf Trough, & Bridgeboro Limestone
  • 9: 60 million years ago, The Paleocene's Clayton Formation, A Report; By Hank Josey
    • 9A: The Georgia Turtle
    • 9B; Sassafras Hill Quarry Huber Formation Plant Fossils in Kaolin
  • 10: The Eocene; Georgia's Oldest Mammals
    • 10A: The Origins of Whales
  • 11: A Whale For Georgia
  • 12: Basilosaurids; The First Modern Whales
    • 12A: Basilosaurus cetoides
    • 12B: Basilotritus
    • 12C: Cynthiacetus (Revised)
    • 12D: Chrysocetus
    • 12E: The Redmond Mandible of Albany Ga
    • 12F: Houston County's Famous Great Whale Goes to the Smithsonian
  • 13: Ziggy and The Museum of Arts & Sciences, Macon, GA
  • 14: Late Eocene
    • 14A: Eocene Fossils & Stratigraphy
    • 14B; Fossils, Impacts, & Tektites Dating the Clinchfield Formation
    • 14C: The Tivola Limestone
    • 14C1: Oldest Oreodont in the Southeast & Georgia's first!
    • 14D: Twiggs Clay Vertebrates
    • 14E: Ocmulgee Formation Vertebrates
    • 14F; Sandersville Limestone, By Hank Josey
    • 14I: Dating Late Eocene Sediments
    • 14J: Georgia's Tektites; Georgiaites
    • 14K; Shell Bluff; Georgia's Most Historic Paleontology Site
    • 14L; Taylors Bluff, Paleo Paddling the Ocmulgee River
    • 14M; Eocene Terrestrial Mammals From Gordon, GA
    • 14N: Fossil Ridge, A Stratigraphic Study in Oaky Woods Wildlife Management Area
    • 14O; Georgia's First Entelodont
    • 14P: Historic Rich Hill
    • 14Q; Bibb County's Christy Hill, Clinchfield Formation Hilltop
    • 14R: Browns Mount, The Fall Line, Elevations, Uplifts, & Native Middle Georgians
  • 15: Early Oligocene
    • 15A: The Marianna Limestone
    • 15B; The Glendon Limestone
    • 15C: Undiffereniated Oligocene Residuum
    • 15D; Brissus bridgeboroensis; A New Echinoid Species From Georgia’s Bridgeboro Limestone
    • 15E: The Curious Steinkern Sea Biscuits of Red Dog Farm Road
    • 15F: Early Oligocene Gordian Knot
  • 16: Bonaire GA Entelodont
  • 17: The Whale Eating Shark
  • 18: Miocene Epoch; 23.3 to 5.3 Million Years Ago
    • 18A; Miocene Terrestrial Vertebrates
    • 18B; Paul Fell, Rockhouse Cave
    • 18C: The Marks Head Formation
    • 18D: Miocene Terrestrial Vertebrates of the Marks Head Formation
    • 18E: The Statenville Formation
    • 18F: Georgia’s 13 Million Year Old Dugong Metaxytherium calvertense
    • 18G: Gastropod Gulch, Julia Gardner, & Miocene Invertebrates In Decatur County
    • 18H; Bony Bluff, Rocky Ford, Echols County In Southernmost Georgia
  • 19: Pliocene Epoch; 5.3 to 2.5 Million years Ago
    • 19A: Two Small Primitive Horses from Taylor County Advance the Science of Georgia Geology
  • 20: The Pleistocene & Holocene Epochs, The Ice Ages
    • 20A; Clark Quarry's Mammoths & Bison
    • 20B: Pleistocene Vertebrate List
    • 20C: Georgia’s Eolian Dunes
    • 20D: Georgia’s Carolina Bays
    • 20E: Late Pleistocene Significant Events
    • 20F: Southeastern Thermal Enclave
    • 20G; Diamond Back Terrapins
    • 20H; A Kaolin Mine Beaver Dam
    • 20I; Pleistocene Vertebrate Fossils On Georgia’s Piedmont
    • 20J; Watkins Quarry Pleistocene Vertebrates, Glynn County, GA
    • 20K: Pleistocene Vertebrates from Coastal Georgia
    • 20L; Sandy Run Creek Core, Warner Robins, Houston County, GA
    • 20M: Bone Bed, Pleistocene, Coastal Georgia
    • 20N: Caribou & Elk Fossils from Georgia & Alabama
    • 20O; Tapir Veroensis, Walker County, Late Pleistocene
    • 20P; Ladds Pleistocene Vertebrates, Bartow County, GA
  • 21: Humans in Georgia
  • 22: Geology of the Coastal Plain, 1911
    • 22A: 1911 Cretaceous Fossil Locations
    • 22B: 1911 Eocene Fossil Locations
  • 23: GA County Localities, Houston County
  • 24: Science: Natural History & Geology
    • 24A; Podcast; The Tivola Whale of Houston County
    • 24B: Coastal Plain Correlation Chart
    • 24C: Presentation; Oaky Woods Stratigraphy
    • 24D: Physiographic Map of Georgia
    • 24E: Fossils of Oaky Woods
    • 24F: Collections & Stewardship of Georgia’s Fossils
    • 24G: I, Periarchus (A Fossil's Tale)
    • 24H: The Tivola Whales (April 2023 talk to the Mid-Georgia Gem & Mineral Society)
    • 24L: Needed; The Georgia Geologic Survey
    • 24M: Georgiacetus Presentation; A Whale for Georgia
    • 24N: Paul F. Huddlestun PhD, Georgia Coastal Plain Field Investigator >
      • 24N1: Late Eocene & Older... Coastal Plain Stratigraphy
      • 24N2: Gulf Trough Cores, Colquitt County, by Paul Huddlestun
      • 24N3; Washington County Core Logs By Paul Huddlestun
      • 24N4: Coastal Plain Core Logs by Paul F. Huddlestun
      • 24N5: Colquitt Core #6 By Paul Huddlestun
      • 24N6: Colquitt 10 & 7 Core
      • 24N7: Wayne County Core, Manningtown
      • 24N8: Gulf Trough Cores >
        • 24N8-1: Chatham County, Tybee Island Core
        • 24N8-2: Gulf Trough, USGS, Claxton, Evans County Core
        • 24N8-3: Blue Springs Landing Core, Screven County
        • 24N8-4: Toombs County Core, Baxley
    • 24O: Echinoids of Georgia, Cenozoic Era (Sand Dollars & Urchins) >
      • 24O1: Echinoids of Georgia, Cenozoic, By County
    • 24P; Exploring the Paleontology of Southernmost Georgia >
      • 24P1; Seminole County
      • 24P2: Decatur County Fossils & Natural History
      • 24P3: Grady County Blowing Caves, Forest Falls, Fossils & Natural History
  • 25: Education Material
    • 25A: My Field Kit; What You Need In The Field
    • 25B: Meet Crassostrea gigantissima, Georgia's Historic Giant Oyster
    • 25C: The Natural History & Fossils Record of Houston County, GA
    • 25D: Evidence for Evolution in Georgia's Fossil Record... A look at Teeth
    • 25E: Georgia's State Fossil; Shark Teeth
    • 25F: Georgia's Paleontology For Georgia's Classrooms
    • 25G: Library & School Presentations
    • 25H; An Introduction To Fossils; Presentation
  • 26: Georgia's Meteorites
    • 26A: Did I Find A Meteorite?
    • 26B: Georgia's Lost Meteorite
    • 26C: Georgia's Witnessed Meteorite Falls
    • 26D: The Sardis Iron, Georgia's Largest Meteorite
15C: Oligocene Undifferentiated Residuum

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The power of solution….
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The Oligocene undifferentiated residuum is essentially fossil rich chert dornicks and boulders typically suspended in sandy red clay. A dornick is a throwing sized rock, or a hand sample. The fossils and suspending clay matrix are probably of different ages, with the chert being older.

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​Okay, what is chert?
Chert is a hard, enduring, often opaque, fine grained sedimentary rock composed of microscopic silica, it can come in many colors depending on what other minerals are present at formation; jasper, agate, flint, chalcedony and onyx are all forms of chert. Even a single dornick can even be highly variable in color.
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American Indians of the Coastal Plain knapped chert for their tools. Most commonly the chert of the residuum is brick red (stained by oxidized iron), thought this varies dramatically.

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Our Oligocene residuum chert began 23 to 33 million years ago as rather pure beds of calcium carbonate limestone on the seabed, some of which were dense with shelly fossils and some of which completely lacked fossils. The sea levels retreated and the limestone beds were left behind and buried by later terrestrial sediments. Once underground they then became charged with fresh ground water; porous limestone makes a good aquifer. These aquifers held silica rich, acidic groundwater.

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Where the microscopic silica was richest, it was absorbed by the porous limestone. Other minerals were also absorbed, and in time these stained the limestone to assorted colors.
 
The silica slowly replaced and changed the limestone into dense, hard chert. The limestone which didn’t chertify was gradually dissolved by the solution of acidic freshwater, forming caves which continued to grow subsurface until their rooves collapsed forming sinkholes.
 
Weathering also played its part, the softer limestone weathers quickly compared to the rugged chert. In most cases the heavier chert simply dropped vertically in place when the limestone was dissolved or weathered away.

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Great for education
This material abundantly produces wonderfully preserved shell fossils and has a deep story to tell over geological processes. The chert is rugged and tolerant of rough handling by small hands. It’s hard to imagine a better source of educational fossils. In parts of Georgia it is abundant and often a nuisance to farmers and construction.

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​In the past it was referred to as the Flint River Formation by many authors but in 1993 Huddlestun recognized its history and reassigned these sediments as Oligocene undifferentiated residuum (1).


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​Is it undifferentiated?
The name Oligocene undifferentiated residuum suggests mixed Oligocene residual sediments possessing both Early and Late Oligocene fossils in a tough chert matrix; but it’s not so simple (things on the Coastal Plain rarely are). Huddlestun questioned if Late Oligocene fossils were even present in the residuum (1).

​Definitions:
​     Early Oligocene 
​          Rupelian Stage (regionally; Vicksburgian Stage)
               Dated from 33.9-28.4 million years ago.
​    Late Oligocene
​          Chattian Stage (regionally; Chickasawhayan Stage)
​                Dated from 28.4 to 23.03 million years ago


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​Huddlestun confirms that researchers in 1916, 1923, 1937, 1940 and 1943 reported mixed Rupelian (Early) and Chickasawhayan (Late) Oligocene fossils in the sediments. Some boulders or dornicks held Early, some held Late Oligocene fossils. But M. E. Hunter, working in southwest Georgia, Alabama and the Florida Panhandle in 1992 failed to identify any Late Oligocene species in the residuum.


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In 1995 Dr. Burt Carter at Georgia Southwestern prepared a field trip in southwest Georgia for the Georgia Geological Society (3). The focus of his guide was the Dougherty Plain which rests between Georgia’s Pelham Escarpment and the Fall Line hills. He concurred with Huddlestun that the residuum on southwest Georgia was Early Oligocene.​
​
“Based on the conclusions of Huddlestun (1993) concerning the age of Oligocene deposits in Georgia, all of the Oligocene residuum is considered here to be Early Oliogocene, Vicksburgian Age.”

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It would be worthwhile to compare the material Huddlestun mapped in the northern extent of the residuum to see if it is indeed restricted to the Early Oligocene.

Oligocene Sea Levels
During the roughly 10-million-year span of the Oligocene (33.9 to 23.03 mya) climates changed dramatically. There were two high stands where sea levels reached roughly 46 meters (150 feet) above current sea levels.
The first happened at about 33 million years ago (Early Oligocene).
The second at about 26 million years ago (Late Oligocene).

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These high stands are separated by a glacial event and sea level retreat to low stands where coastlines retreated 42 meters (138 feet) below modern sea levels, this happened roughly 28 million years ago.
That’s a 90 meter (295 foot) shift in sea levels.

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So, the Oligocene fossils contained in the undifferentiated residuum could easily represent two distinct seas separated by 6 million years and a global glaciation event.
The fossils;
In 1970 Sam Pickering, who went on to become Sate Geologist, referred to this residuum as the Flint River Formation (nomenclature overturned) and recorded the following species (2). Bear in mind that Huddlestun also divided Pickering’s (& others) Flint River Formation into multiple distinct sediments, though the bulk of the material would fall into Undifferentiated Oligocene Residuum.      

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Vertebrates:
None reported by Pickering

Echinoids (sand dollars & sea urchins):
Gagaria mossomi                Rare
Clypeaster cotteaui             Rare
Rhyncolampus gouldii       Common

Bivalves:
Glycymeris cookie               Common
Glycymeris suwaneensis    Rare
Pecten suwaneensis             Rare
Ostrea mauricensis              Rare
​Lima halensis                        Rare
Crassatellites paramesus   Very Abundant
Phacoides wacissanus         Common
Chione bainbridgensis        Common
 
Corals:
Trochocyathus sp.               Rare
 
Foraminifera:
Quinqueloculina vicksburgensis   Common
Pyrgo byramensis                            Rare
Pararotalia mexicana var              Abundant
Lepidocyclina undosa                     Abundant
Reusella byramensis                       Abundant

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References:
(1)   A Revision of the Lithostratigraphic Units of the Coastal Plain of Georgia, T
HE OLIGOCENE, Paul F. Huddlestun, Georgia Department of Natural Resources, Georgia Geologic Survey, Bulletin 105, 1993


(2)  Stratigraphy, Paleontology, and Economic Geology of Portions of Perry and Cochran Quadrangles, Georgia; Sam M. Pickering Jr., Bulletin 81, The Geological Survey of Georgia, Dept of Mines, Mining & Geology 1970.

(3)  Paleogene Carbonate Facies and Paleogeography of the Dougherty Plain Region; Burchard D. Carter, Department of Geology & Physics, Georgia Southwestern State University, 30th Annual Field Trip, Georgia Geological Society, Georgia Geological Society Guidebooks, Vol15, Number 1; October 1995

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