Brecht Ranch
Basic information
Sample name: Brecht Ranch
Reference: E. P. Gustafson. 1986. Preliminary biostratigraphy of the White River Group (Oligocene, Chadron and Brule formations) in the vicinity of Chadron, Nebraska. Transactions of the Nebraska Academy of Sciences 14:7-19 [ER 4137]
Geography
Country: United States
State: Nebraska
County: Dawes
Coordinate: 42.83° N, -103.07° W
Coordinate basis: estimated from map
Scale: local area
Formation: Chadron
Time interval: Late Eocene
Zone: Chadronian
Section: Chadron
Unit number: 1
Unit order: below to above
Max Ma: 35.102
Min Ma: 33.9
Age basis: other
Geography comments: coordinate based on a point west of the town of Chadron (see Fig. 1)
from six localities in the area's sections 1, 2, and 3 (see Fig. 1)
from chron C13r, just below the Eocene-Oligocene boundary (basis of age assignment using the C13r base of Ogg 2020 and the ICS 2023 boundary value)
the text misidentifies the normal zone in Fig. 3 as chron C11n instead of C13n
"Although fossils occur sparsely within much of the thickness of the Chadron Formation in the study area, the vast majority and the best specimens are concentrated in the uppermost part of the Chadron sediments, including some specimens found within the PWL" (Persistent White Layer, at the Chadron-Brule boundary)
from six localities in the area's sections 1, 2, and 3 (see Fig. 1)
from chron C13r, just below the Eocene-Oligocene boundary (basis of age assignment using the C13r base of Ogg 2020 and the ICS 2023 boundary value)
the text misidentifies the normal zone in Fig. 3 as chron C11n instead of C13n
"Although fossils occur sparsely within much of the thickness of the Chadron Formation in the study area, the vast majority and the best specimens are concentrated in the uppermost part of the Chadron sediments, including some specimens found within the PWL" (Persistent White Layer, at the Chadron-Brule boundary)
Environment
Lithology: siltstone
Taphonomic context: overbank deposit,paleosol
Habitat comments: "primarily siltstones, c1ay-siltstones, and silty-claystones... numerous superimposed green layers are seen" (indicating paleosols) and "Locality CSC-55 (Bartlett West # 1) which produced fossils from a coarse clay-siltstone conglomerate, heavily cemented with calcite and with very common root traces" indicating "flood in near-channel areas"
"the coarse texture of the sediment suggests relatively strong current-force and substantial hydraulic sorting. Such sorting is also indicated by the excessive abundance of skulls, jaws and teeth as opposed to postcranial skeletal elements"
"the coarse texture of the sediment suggests relatively strong current-force and substantial hydraulic sorting. Such sorting is also indicated by the excessive abundance of skulls, jaws and teeth as opposed to postcranial skeletal elements"
Methods
Life forms: carnivores,ungulates,other small mammals
Sample size: 72 specimens
Museum: Chadron State College
Sampling comments: "This paper is the result of three years of field work" (years not stated)
previous collections not enumerated here were made by the University of Nebraska State Museum and the AMNH
the Daphoenictis tedfordi specimen is in the F:AM collection
previous collections not enumerated here were made by the University of Nebraska State Museum and the AMNH
the Daphoenictis tedfordi specimen is in the F:AM collection
Metadata
Sample number: 4590
Contributor: John Alroy
Enterer: John Alroy
Created: 2024-12-09 11:04:45
Modified: 2024-12-09 11:04:45
Abundance distribution
18 species
9 singletons
total count 72
geometric series index: 48.4
Fisher's α: 7.703
geometric series k: 0.8360
Hurlbert's PIE: 0.8482
Shannon's H: 2.2973
Good's u: 0.8758
Each square represents a species. Square sizes are proportional to counts.
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