5F: Pennsylvanian Plant Fossils
of Northwest Georgia
By
Thomas Thurman
17/May/2025
In 1989 William H. Gillespie, Thomas J. Crawford, and Johnny A. Waters published a paper which would act as a field trip guide to plant fossils of Georgia’s Pennsylvanian System. They were looking at southeastern coal belt.
Their original paper can be downloaded below.
Their original paper can be downloaded below.
The Pennsylvanian Period spanned 299 to 323 million years ago; Georgia was just south of the equator. Sea levels were high and the climate hot, but forests stood where the coal belt is today.
These illustrated plant fossils occur commonly enough to observed and collected.
These illustrated plant fossils occur commonly enough to observed and collected.
During Late Mississippian and Early Pennsylvanian time, the shallow slowly subsiding Appalachian basin extended from Alabama, through northwest Georgia, east central Tennessee, eastern Kentucky, southwestern Virginia, West Virginia, eastern Ohio, and western Pennsylvania.
The Pennsylvanian strata that developed during this time in what is now the State of Georgia are preserved in synclinal folds that cap roughly flat-topped mountains. These are the youngest Paleozoic strata in Georgia and are part of a belt, consisting almost entirely of clastic rocks, that extends from the northern end of Sand Mountain and Lookout Mountain near Chattanooga, Tennessee across northwest Georgia and on into Alabama. (Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock.)
In additional to Sand and Lookout Mountains, small outliers of Pennsylvanian strata occur on Sand Mountain in Catoosa County, Little Sand Mountain in Chattooga County, and Rocky Mountain in Floyd County. Fox Mountain in Dade County is an isolated remnant of Sand Mountain.
The contact in Georgia between the Pennsylvanian and the underlying Mississippian occurs in an interval of coarse clastics and it is not clearly identifiable. The oldest Pennsylvanian plant fossils occur in lithologies very similar to those in which the youngest Mississippian age fossils are found and, in some cases, only a few to several feet separate these fossiliferous horizons. The early Pennsylvanian age for the coal is based on plant compression floras, palynomorphs (microscopic organic material), and invertebrate marine assemblages. Most of the plant megafossils are found in shales and siltstones associated with the several coal beds. The palynomorphs were macerated from the coal.
The contact in Georgia between the Pennsylvanian and the underlying Mississippian occurs in an interval of coarse clastics and it is not clearly identifiable. The oldest Pennsylvanian plant fossils occur in lithologies very similar to those in which the youngest Mississippian age fossils are found and, in some cases, only a few to several feet separate these fossiliferous horizons. The early Pennsylvanian age for the coal is based on plant compression floras, palynomorphs (microscopic organic material), and invertebrate marine assemblages. Most of the plant megafossils are found in shales and siltstones associated with the several coal beds. The palynomorphs were macerated from the coal.
The researchers report that the historical boundary between Mississippian and Pennsylvanian plant fossils in Georgia was the contact of the Pennington Formation and the Raccoon Mountain Member of the Gizzard Formation. But after careful searches for either plant or animal fossils; Gillespie, Crawford, & Waters concluded that the boundary was not mappable in Georgia.
They additionally report that the most extensive flora assembly they found came from Upper Pennington strata near Hale Gap in Dade County. The presence of Archaeopteridium tschermacki and Sphenopteris elegans indicate that this flora is Upper Mississippian.
Pennsylvanian Plants
Pennsylvania plant fossils in NW Georgia occur in shales and siltstones associated with coal beds. The most extensive floras have been found in association with Number 3 coal bed of the Vandever Member and the Number 5 coal of the Whitmell Member of the Crab Orchard Mountains Formation.
Pennsylvania plant fossils in NW Georgia occur in shales and siltstones associated with coal beds. The most extensive floras have been found in association with Number 3 coal bed of the Vandever Member and the Number 5 coal of the Whitmell Member of the Crab Orchard Mountains Formation.
Common Pennsylvanian species
Lepidophloios laricinus
Lepidodendron aculeatum
Lepidodendron obovatum
Asterophyllites charaeformis
Calamites cistiiformis (Not Illustrated)
Asterophyllites charaeformis
Asterophyllites grandis (Not Illustrated)
Annularia asteris (Not Illustrated)
Sphenophyllum cunifolium (Not Illustrated)
Neuropteris Pocahontas
Neuropteris smithii
Neuropteris hollandica (Not Illustrated)
Neuropteris heterophylla (Not Illustrated)
Sphenopteris pottsvillea
Alethopteris lonchitica
Holcospermum (sp?) (Not Illustrated)
Eremopteris (sp?) (Not Illustrated)
Cordiates (sp?) (Not Illustrated)
Lepidophloios laricinus
Lepidodendron aculeatum
Lepidodendron obovatum
Asterophyllites charaeformis
Calamites cistiiformis (Not Illustrated)
Asterophyllites charaeformis
Asterophyllites grandis (Not Illustrated)
Annularia asteris (Not Illustrated)
Sphenophyllum cunifolium (Not Illustrated)
Neuropteris Pocahontas
Neuropteris smithii
Neuropteris hollandica (Not Illustrated)
Neuropteris heterophylla (Not Illustrated)
Sphenopteris pottsvillea
Alethopteris lonchitica
Holcospermum (sp?) (Not Illustrated)
Eremopteris (sp?) (Not Illustrated)
Cordiates (sp?) (Not Illustrated)
Other species commonly occurring at some horizons, but not throughout the column…
Neuralethopteris larishii
Alethopteris valida (Not Illustrated)
Zeilleria delicatula
Sphenophyllum tenue
Alethopteris decurrens (Not Illustrated)
Diplothmena cheathami (Not Illustrated)
Aneimites pottsvillensis (Not Illustrated)
Palmatopteris furcata
Eusphenopteris aldrichii (Not Illustrated)
Annularia radiata (Not Illustrated)
Asterophyllites equisetiformis (Not Illustrated)
Alloiopteris georgiana
Neuralethopteris larishii
Alethopteris valida (Not Illustrated)
Zeilleria delicatula
Sphenophyllum tenue
Alethopteris decurrens (Not Illustrated)
Diplothmena cheathami (Not Illustrated)
Aneimites pottsvillensis (Not Illustrated)
Palmatopteris furcata
Eusphenopteris aldrichii (Not Illustrated)
Annularia radiata (Not Illustrated)
Asterophyllites equisetiformis (Not Illustrated)
Alloiopteris georgiana
The researchers report that many of the floras are overall remarkably similar. Exceptions like Zeilleria delicatula, are usually associated with the Number 5 coal bed, and Shpenophyllum tenue, usually associated with the Number 3 coal bed, are present because it can be so abundant as to virtually exclude other plants.
Plant fossils have not been found in the Newton or Rockcastle Members of the Crab Orchard Mountains Formation.
Plant fossils have not been found in the Newton or Rockcastle Members of the Crab Orchard Mountains Formation.
| gillespie_pennsylvanian_plants.pdf |
Reference
Gillespie, William H.; Crawford, Thomas J.; Waters, Johnny A.; Plant Fossils of the Pennsylvanian System of Georgia, Guidebook Addendum, 38th Annual Meeting, Southeastern Section, The Geological Society of America, April 3-5, 1989
Gillespie, William H.; Crawford, Thomas J.; Waters, Johnny A.; Plant Fossils of the Pennsylvanian System of Georgia, Guidebook Addendum, 38th Annual Meeting, Southeastern Section, The Geological Society of America, April 3-5, 1989