Blackford 'sinkhole', Douglas Lake: Llanvirn, Tennessee

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
unclassified
Cestites mirabilis
Douglasocaris collinsi
Chasmataspidida - Chasmataspididae
Chasmataspis laurencii Caster and Brooks 1956
see common names

Geography
Country:United States State/province:Tennessee
Coordinates: 36.0° North, 83.5° West (view map)
Paleocoordinates:30.0° South, 69.7° West
Basis of coordinate:estimated from map
Geographic resolution:outcrop
Time
Period:Ordovician Epoch:Middle Ordovician
10 m.y. bin:Ordovician 2-3
Key time interval:Llanvirn
Age range of interval:468.40000 - 458.40000 m.y. ago
Stratigraphy
Formation:Blackford
Stratigraphic resolution:formation
Stratigraphy comments: Whiterockian; All from Unit B; most from upper 8 feet of this unit
Lithology and environment
Primary lithology:planar lamination,deformed bedding lithified dolomite
Secondary lithology:volcaniclastic lithified conglomerate
Includes fossils?Y
Lithology description: ... is a sequence of laminated, massive deposits. Concentrations of organic material at the top of the varvelike graded beds emphasize the laminated appearance. There are 1 to 20 laminations per inch. This lithologic member, designated as Unit B, does not have shale partings. IT is massive when fresh but weathers rapidly. The weathered material splits readily at the carbonaceous plane at the top of each "varve". Layers and lenses of conglomerate and breccia are recurrent throughout this unit. These beds and lenses, usually 1/8 to 2 inches in thickness, contain angular to subrounded pebbles up to 2 1/2 inches in diameter. Most of the graded beds have a basal zone of angular pyroclastic granules. The breccia fragments are predominantly of volcanic origin whereas the subrounded pebbles are of a wide variety of lithologic types, some unknown in this vicinity. In many places the laminations of this unit have been contorted by the soft rock deformational processes of sediment flowage and slumping. Laurence (1944, fig. 6A and 6B) figured contorted laminations between undisturbed beds and an angular unconformity within a sequence of conglomeratic beds.
Environment:peritidal Tectonic setting:foreland basin
Taphonomy
Modes of preservation:mold/impression
Size of fossils:macrofossils
Collection methods and comments
Reason for describing collection:taxonomic analysis
Museum repositories:USNM
Metadata
Database number:37450
Authorizer:S. Holland Enterer:S. Holland
Modifier:J. Alroy Research group:marine invertebrate
Created:2004-03-15 11:21:51 Last modified:2024-03-31 19:20:44
Access level:the public Released:2004-03-15 11:21:51
Creative Commons license:CC BY
Reference information

Primary reference:
10030.1% K.E. Caster and H.K. Brooks. 1956. New fossils from the Canadian-Chazyan (Ordovician) hiatus in Tennessee. Bulletins of American Paleontology 36(157):157-199 [S. Holland/S. Holland/S. Holland]