5D: Crinoids & Blastoids
Of Northwest Georgia
By Thomas Thurman
02/March/2025
Experienced Georgia rockhounds will be familiar with the crinoid slabs of our northwestern counties. I rarely get to collect in Northwest Georgia. This slab was given to me by Jay Batcha, probably two decades ago. Jay is an old friend; he’s also an officer and often President of the Mid-GA Gem and Mineral Society. We’ve collected in the field together many times.
Below is a link to their website.
midgeorgiagemandmineral.com
Below is a link to their website.
midgeorgiagemandmineral.com
Jay reports that he collected this crinoid slab in Gore, Georgia, Chattooga County. “Right after they’d clear cut timber off some land just north of town on Highway 27.”
Crinoid and blastoid fossils are well published in our geologic literature from several locations in NW Georgia. Blastoids are probably more common on the literature.
Crinoids are echinoderns (meaning spiny skin) a group that includes echinoids, invertebrate animals related to sea urchins, sand dollars and sea stars. They are unusual animals when you think of it, they lack vision, a sense of smell (nostrils or antenna), and a sense of hearing. As far as I know, taste and touch are all they likely possess. Today there are stalked (sea lilies) and unstalked forms (feather stars). Stalked forms are prevalent in NW Georgia’s fossils record, their stalks are made up of stacked calcium discs, and it is these discs that are most frequently preserved, looking something like rolls of coins. (As seen in the slab above.)
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Blastoids are similar, but not very, and blastoids are extinct.
I asked Dr. Burt Carter, he’s a retired Professor of Paleontology from Georgia Southwestern, and an expert in echinoids, about the differences between crinoids & bastoids.
I asked Dr. Burt Carter, he’s a retired Professor of Paleontology from Georgia Southwestern, and an expert in echinoids, about the differences between crinoids & bastoids.
Burt Carter ( Text, 12/mar/2025)
“The most obvious simple difference is that crinoids are mostly arm with a small, usually simple calyx. Blastoids are mostly calyx, much more complex in the number of plates for example, and have stubby little arms (brachioles that don't branch at all). The respiratory system is drastically different. Crinoids are more like echinoids in this. The tube feet (which stock out of all the arm branches) are for both capturing food and gas transfer: external 'gills' if you will. In blastoids water is pulled into the calyx through the pores beside each of the multiple plates in the ambulacra and flushed out the top. Gas exchange is internal, but not deep, and tube feet on the brachioles capture food. Pinnules are the thin branches off those crinoid arms that are like feathers. Same idea.”
“The most obvious simple difference is that crinoids are mostly arm with a small, usually simple calyx. Blastoids are mostly calyx, much more complex in the number of plates for example, and have stubby little arms (brachioles that don't branch at all). The respiratory system is drastically different. Crinoids are more like echinoids in this. The tube feet (which stock out of all the arm branches) are for both capturing food and gas transfer: external 'gills' if you will. In blastoids water is pulled into the calyx through the pores beside each of the multiple plates in the ambulacra and flushed out the top. Gas exchange is internal, but not deep, and tube feet on the brachioles capture food. Pinnules are the thin branches off those crinoid arms that are like feathers. Same idea.”
Thanks Burt! Your explanations are always the best.
Paleontologists and geologists might retire, but they never stop exploring, learning, and researching. It’s just who they are.
Paleontologists and geologists might retire, but they never stop exploring, learning, and researching. It’s just who they are.
A special thanks also to the Paleontological Association of Georgia for posting the papers reviewed here as a free downloads on their website.
https://paleoassocga.wixsite.com/home/resources
https://paleoassocga.wixsite.com/home/resources
In 1972 Thomas W. Broadhead and Robert W. Bagby reported crinoids in the Floyd Shale of Floyd County, GA. They assigned these to Georgia’s Carboniferous strata, as Chesteran aged, which spans 333 to 318 million years ago. Broadhead and Bagby assigned them to Mississippian strata. Chesteran is an obscure term rarely used these days. By modern reckoning 333 to 318 million years ago would certainly be Carboniferous aged, but straddling the Mississippian and Pennsylvanian stages, the horizon between the two is at 323 million years ago.
Mississippian Period & Pennsylvanian Period transition is was very warm and sea levels were very high so that most continents were drowned. North America is deep in the southern hemisphere. The Mississippian Period saw the raising of the Appalachians. North America collided with Gondwana, buckling, compressing, and folding the terrain. This lifted the Appalachian Mountains which is shown, in the maps, as an island across North Georgia. By the Pennsylvanian the North America was moving northward and the Appalachian Mountains had pushed the shoreline a little further south.
Broadhead and Bagby were looking at particular crinoids, “inadunate” crinoids, this means “having arms completely free of the calyx”. The calyx is the “pod” at the top of the stems.
Their collection location is recorded the Floyd Shale near the east base of John's Mountain at 34°24'47"N & 85°10'8"W.
Their collection location is recorded the Floyd Shale near the east base of John's Mountain at 34°24'47"N & 85°10'8"W.
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The researchers explain that the Floyd Shale represented a shoreward deposit, a coastal environment along the southern flanks of the Appalachians.
They recognized 7 genre of inadunate crinoids and 10 species… Phanocrinus alexanderi Phanocrinus Formosus Pentaramincrinus fragosus Zeacrinites (sp?) Aphelecrinus bayensis Aphelecrinus popensis Aphelecrinus randolphensis Linocrinus (sp?) Tholocrinus wetherbi Ulrichicrinus cheterensis |
They reported “The circumstances involved in the destruction of the living fauna were probably catastrophic in nature…. The presence of such delicate structures as crinoid pinnules and blastoid brachioles indicates that sedimentation at the time of death was rapid…. Furthermore, among brachiopods, no disarticulated valves were found, and the predominant form of damage was crushing which occurred prior to preservation. … From the presence of delicate structures and evidence of compression, it is inferred that the biotope (a defined area of uniform conditions) was destroyed by the weight and volume of rapidly deposited clastic sediments.
This assembly stands as one of the largest and most varied crinoid populations yet described (1972) from the State of Georgia.”
This assembly stands as one of the largest and most varied crinoid populations yet described (1972) from the State of Georgia.”
Allen & Lester
In 1954 A. T. Allen & J. G. Lester from Emory University published the report Contributions to the Paleontology of Northwest Georgia and it is available as a free download from the State of Georgia at the link below, or as a download at the base of this page. This is the Georgia Geologic Survey Bulletin 62. If you hunt fossils in NW GA this is the Bulletin for you. It lists crinoids and blastoids, as well as many other fossils and a great wealth of maps. Bear in mind that this is a 1954 publication and things have changed since publication. There will be a future page on this website coving Bulletin 62 as a stand-alone topic.
Visit the GA DNR Environmental Protection Bulletin download page here, and look for Bulletin 62.
https://epd.georgia.gov/outreach/publications/georgia-geologic-survey-bulletins
In 1954 A. T. Allen & J. G. Lester from Emory University published the report Contributions to the Paleontology of Northwest Georgia and it is available as a free download from the State of Georgia at the link below, or as a download at the base of this page. This is the Georgia Geologic Survey Bulletin 62. If you hunt fossils in NW GA this is the Bulletin for you. It lists crinoids and blastoids, as well as many other fossils and a great wealth of maps. Bear in mind that this is a 1954 publication and things have changed since publication. There will be a future page on this website coving Bulletin 62 as a stand-alone topic.
Visit the GA DNR Environmental Protection Bulletin download page here, and look for Bulletin 62.
https://epd.georgia.gov/outreach/publications/georgia-geologic-survey-bulletins
Fort Payne Chert.
“The Fort Payne was named for its typical development at Fort Payne, Alabama. It is composed of limestone, argillaceous limestone, shales, and chert. In different areas it has a different appearance. In some localities it exhibits the characteristics of a typical limestone, massively bedded and containing geodes; in other areas the amount of chert has increased to about 50 percent and is in the form of nodules and thin beds intercalated with limestone; but perhaps the most typical and certainly the most easily recognized is the thin to massively bedded, black chert. (Authors list below locality on Highway 27 near Gore, on the flanks of Taylor Ridge, to observe the massive bedded black Fort Payne Chert) Although fossils are difficult to find in the fresh exposures of the Fort Payne, they are abundant in the chert residuum and soil derived from it. The specimens are silicified and the presence of abundant large crinoid stems can be relied on as marking the Fort Payne horizon”
“The Fort Payne was named for its typical development at Fort Payne, Alabama. It is composed of limestone, argillaceous limestone, shales, and chert. In different areas it has a different appearance. In some localities it exhibits the characteristics of a typical limestone, massively bedded and containing geodes; in other areas the amount of chert has increased to about 50 percent and is in the form of nodules and thin beds intercalated with limestone; but perhaps the most typical and certainly the most easily recognized is the thin to massively bedded, black chert. (Authors list below locality on Highway 27 near Gore, on the flanks of Taylor Ridge, to observe the massive bedded black Fort Payne Chert) Although fossils are difficult to find in the fresh exposures of the Fort Payne, they are abundant in the chert residuum and soil derived from it. The specimens are silicified and the presence of abundant large crinoid stems can be relied on as marking the Fort Payne horizon”
"The Floyd formation is a very fossiliferous, massively bedded, black, calcareous shale. It is restricted in occurrence to the southern part of the Paleozoic Province and seems to represent a magna facies equivalent to all the formations from the Fort Payne through the Gasper of the northern and western parts of the area. The exact stratigraphic relationships have not been worked out in detail. Although the fossils of this formation are grouped with those of the Fort Payne, it is not to be implied that they are exact age equivalents."
Allen & Lester assembled an illustrated guide for fossils from various localities. I’ve reproduced the Fort Payne Chert crinoid and blastoid fossils here. The researchers additionally provided field location maps for their fossils, as well as pics, and I have shared this information.
Fort Payne Chert Fossils
(Allen & Lester, 1954)
(Allen & Lester, 1954)
Figure #FPC1
Image 1-3.
Pentremites cava
Blastoid, stemmed echinoderm
Lateral, top, and basal views
Collected in Cherokee Valley one mile north of U. S. Highway 41,
Index Map 5, location C.
Image 4.
Allocatillocrinus rotundus
Crinoid
Basal plates
Collected in Cherokee Valley one mile north of U. S. Highway 41,
Index Map 5, location C.
Image 1-3.
Pentremites cava
Blastoid, stemmed echinoderm
Lateral, top, and basal views
Collected in Cherokee Valley one mile north of U. S. Highway 41,
Index Map 5, location C.
Image 4.
Allocatillocrinus rotundus
Crinoid
Basal plates
Collected in Cherokee Valley one mile north of U. S. Highway 41,
Index Map 5, location C.
Ste Genevieve and Gasper Limestones
(Mississippian Aged)
The lithology and faunal suites of the two formations are so similar that they are discussed together although the Gasper formation overlies the Ste. Genevieve. Both formations are notable for the massively bedded ooliths interbedded with coarsely crystalline limestones and the almost complete absence of chert.
Excellent exposures of all the Mississippian formations with the exceptions of the Floyd Shale can be seen on the roadcuts along Georgia highway 143 between Cooper Heights and Trenton on both the eastern and western flanks of Lookout Mountain. Although the outcrops are fresher in the Lookout-Pigeon Mountain area, weathering has been retarded by the overlying Pennsylvanian sandstones and the steep slopes of the Mountain and consequently fossil collecting is not too good. Fossil collecting is excellent in the Cherokee Ridge and the Little Sand Mountain areas because of the presence of the deep residual soil which encloses the silicified fossils.
(Mississippian Aged)
The lithology and faunal suites of the two formations are so similar that they are discussed together although the Gasper formation overlies the Ste. Genevieve. Both formations are notable for the massively bedded ooliths interbedded with coarsely crystalline limestones and the almost complete absence of chert.
Excellent exposures of all the Mississippian formations with the exceptions of the Floyd Shale can be seen on the roadcuts along Georgia highway 143 between Cooper Heights and Trenton on both the eastern and western flanks of Lookout Mountain. Although the outcrops are fresher in the Lookout-Pigeon Mountain area, weathering has been retarded by the overlying Pennsylvanian sandstones and the steep slopes of the Mountain and consequently fossil collecting is not too good. Fossil collecting is excellent in the Cherokee Ridge and the Little Sand Mountain areas because of the presence of the deep residual soil which encloses the silicified fossils.
Images 1-3.
Pentremites gemmiformis
Lateral, top, and basal views.
Image 4.
Pentremites cherokenzs
Lateral view
Image 5-7.
Pentremites princetonensis
Lateral, top, and basal view
Image 8.
Pentremites symmetricus
Lateral view
Image 9.
Pentremites welleri
Lateral view
Image 10.
Pentremites spicatus
Lateral view
Image 11.
Pentremites foshi
Lateral view
Image 12.
Pentremites pyriformis
Lateral view
Image 13.
Pentremites pulchellus
Lateral view
Image 14-15.
Pentremites conoideus
Lateral, top
Pentremites gemmiformis
Lateral, top, and basal views.
Image 4.
Pentremites cherokenzs
Lateral view
Image 5-7.
Pentremites princetonensis
Lateral, top, and basal view
Image 8.
Pentremites symmetricus
Lateral view
Image 9.
Pentremites welleri
Lateral view
Image 10.
Pentremites spicatus
Lateral view
Image 11.
Pentremites foshi
Lateral view
Image 12.
Pentremites pyriformis
Lateral view
Image 13.
Pentremites pulchellus
Lateral view
Image 14-15.
Pentremites conoideus
Lateral, top
Location
All the specimens figured of the Ste Genevieve and Gasper Limestones were collected on the north end of Cherokee Ridge, just south of the Tennessee/Georgia line. The locality is known as Cave Springs. See Index Map No. 5, location H.
All the specimens figured of the Ste Genevieve and Gasper Limestones were collected on the north end of Cherokee Ridge, just south of the Tennessee/Georgia line. The locality is known as Cave Springs. See Index Map No. 5, location H.
Image 16.
Pentremites conoideus
base views
Image 17-19.
Pentremites okawensis
Lateral, top, basal views
Image 20.
Pentremites buttsi
Lateral view
Image 21.
Pentremites canalis
Lateral view
Image 22.
Pentremites patei
Lateral view
Image 23.
Pentremites godoni
Lateral view
Image 24.
Pentremites pyramidatus
Lateral view
Image 25.
Pentremites pinguis
Lateral view
Image 26.
Talarocrinus inflatus
Basal plates
Images 27-29.
Pentremites gianteus
Basal, lateral, and top views.
Collected on the west flank of Little Sand Mountain, Salem Valley, 1 mile north of U.S. highway 41, Index Map 5, location E
Pentremites conoideus
base views
Image 17-19.
Pentremites okawensis
Lateral, top, basal views
Image 20.
Pentremites buttsi
Lateral view
Image 21.
Pentremites canalis
Lateral view
Image 22.
Pentremites patei
Lateral view
Image 23.
Pentremites godoni
Lateral view
Image 24.
Pentremites pyramidatus
Lateral view
Image 25.
Pentremites pinguis
Lateral view
Image 26.
Talarocrinus inflatus
Basal plates
Images 27-29.
Pentremites gianteus
Basal, lateral, and top views.
Collected on the west flank of Little Sand Mountain, Salem Valley, 1 mile north of U.S. highway 41, Index Map 5, location E
Bangor Limestone
"This formation is named for its development at Bangor, Blount County, Alabama. Charles Butts in his work in Alabama restricted the term "Bangor" to the limestone above the Hartselle sandstone and below the Pennington shale. This definition is used here. The Bangor limestone is composed of massively bedded gray limestones, thinly bedded brownish-gray limestones, and gray to buff calcareous shales. The limestone often is found as massive ledges or benches on the flanks of the mountains which are capped with Lookout sandstone. Fossils are plentiful but not nearly so abundant as in the Gasper and the Ste. Genevieve."
"This formation is named for its development at Bangor, Blount County, Alabama. Charles Butts in his work in Alabama restricted the term "Bangor" to the limestone above the Hartselle sandstone and below the Pennington shale. This definition is used here. The Bangor limestone is composed of massively bedded gray limestones, thinly bedded brownish-gray limestones, and gray to buff calcareous shales. The limestone often is found as massive ledges or benches on the flanks of the mountains which are capped with Lookout sandstone. Fossils are plentiful but not nearly so abundant as in the Gasper and the Ste. Genevieve."
Pennington Shale
"Overlying the Bangor limestone and underlying the Gizzard member of the Lookout Formation is approximately 100 feet of greenish gray, brown, yellow, thinly laminated shales. The top of the Pennington formation can be separated easily from the overlying Gizzard shale on Little Sand Mountain and on the east flank of Lookout Mountain because of a massive sandstone member at the base of the Gizzard. However, the problem is more difficult on the west side of Lookout Mountain because of the absence of the sandstone member. Here the top of the Pennington is placed above the highest invertebrate fossils and below the appearance of plant remains. The Pennington Shale carries abundant specimens of Fenestrellina and a few brachiopods which have been replaced by limonite."
"Overlying the Bangor limestone and underlying the Gizzard member of the Lookout Formation is approximately 100 feet of greenish gray, brown, yellow, thinly laminated shales. The top of the Pennington formation can be separated easily from the overlying Gizzard shale on Little Sand Mountain and on the east flank of Lookout Mountain because of a massive sandstone member at the base of the Gizzard. However, the problem is more difficult on the west side of Lookout Mountain because of the absence of the sandstone member. Here the top of the Pennington is placed above the highest invertebrate fossils and below the appearance of plant remains. The Pennington Shale carries abundant specimens of Fenestrellina and a few brachiopods which have been replaced by limonite."
Note; This author does not see where Allen & Lester state whether the Bangor Limestone or Pennington Shale produced these two blastoids, (below) several other fossils were shown on the original plate.
The above blastoids, and other fossils, were collected on Little Sand Mountain, east of Ringgold. See Index Map No. 5, location F below.
Image 8.
Pentremites sp.
Lateral view
Image 9 & 10.
Pentremites spicatus
Lateral and top view of calyx.
Image 8.
Pentremites sp.
Lateral view
Image 9 & 10.
Pentremites spicatus
Lateral and top view of calyx.
Download PDFs of the 1972 Broadhead & Bagby Paper and 1954 Allen & Lester papers below.
| broadhead_crinoids_floyd_shale_1972.pdf |
| b-62_allen_contributions_paleontology_nw_ga.pdf |
References
- Broadhead, Thomas Webb; Bagby, Robert W.; Chesteran Inadunate Crinoids from the Floyd Shale, Floyd County Georgia; Bulletin of the Georgia Academy of Science 30, pg 27-31, January 1972
- Allen. A. T.; Lester, J.G.; Contributions to the Paleontology of Northwest Georgia; Bulletin 62, Georgia Geological Survey, Department of Mines, Mining & Geology, 1954
