| Hall Lake Formation | |
|---|---|
| Stratigraphic range: Late Cretaceous, Campanian–Maastrichtian ~ | |
| Type | Geological formation |
| Unit of | McRae Group |
| Underlies | Jose Creek Member |
| Overlies | "Quaternary-Tertiary basalt flows and alluvium" |
| Lithology | |
| Primary | Mudstone, "shale", sandstone |
| Location | |
| Coordinates | 33°12′N 107°06′W / 33.2°N 107.1°W |
| Approximate paleocoordinates | 40°30′N 81°06′W / 40.5°N 81.1°W |
| Region | New Mexico |
| Country | United States |
The Hall Lake Formation, formerly called the Hall Lake Member, is a geological formation in Sierra County, New Mexico preserving Lancian fauna, most notably dinosaurs. It is regarded as a member of the McRae Group, including the Elephant Butte and Staton-LaPoint locales.
While most estimates place it firmly within the Lancian fauna, specifically using taxa such as Compsemys as index fossils to recover a Campanian-Maastrichtian age, Lozinsky et al. (1984) note the presence of basalt flows and alluvium dating to the Quaternary-Tertiary.
It overlooks the Jose Creek Member and is composed of purple and maroon shales. When they meet, it is marked by a basal conglomerate or a color distinction where conglomerate is absent. Various Cenozoic units overly the formation. Where some choose to classify these layers as a member of the McRae Formation, others classify it as a distinct formation in a group of formations.
Color key
|
Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.
| Genus | Species | Locality | Material | Notes | Images |
|---|---|---|---|---|---|
| Tyrannosauridae | indet. | Staton-LaPoint |
|
Lozinsky et al. (1984) call it indeterminate | |
| Tyrannosaurus | T. mcraeensis | Elephant Butte (upper) |
|
||
| Alamosaurus | sp. | upper |
|
Tentative referral | |
| Sauropoda | Possibly from the Jose Creek Member | ||||
| Theropoda |
Color key
|
Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.
| Taxon | Locality | Material | Notes | Images |
|---|---|---|---|---|
| Triceratops sp. | 2 miles south of Elephant Butte |
|
This genus, Torosaurus or a novel taxon | |
| Sierraceratops turneri | Elephant Butte (lower) |
|
||
| Ceratopsidae | Elephant Butte (upper) |
|
A new genus similar to Torosaurus is said to exist above the base of the formation | |
| Elephant Butte (lower) | Indeterminate, in abundance | |||
| Torosaurus sp. | Elephant Butte (upper)? | |||
| Hadrosauridae | cannot be determined | Indeterminate and of unknown origins due to faulting or Quaternary cover | ||
| Ankylosauria |
|
Possibly from the Jose Creek Member, near identical from UNM-FKK-001P of the Kirtland Formation |
| Taxon | Locality | Material | Notes |
|---|---|---|---|
| Testudinata | Elephant Butte (upper) | ||
| Crocodylia | |||
| Compsemys | Index fossils suggesting a Lancian age | ||
| Bothremydidae |
| Genus | Species | Locality | Material | Notes |
|---|---|---|---|---|
| Araucarites | A. sp. | |||
| Cinnamomum | C. sp. | |||
| Exnelumbites | E. morphotype 2 | Leaves | A member of Nelumbonaceae | |
| Ficus | F. sp. | |||
| Phyllites | P. sp. | |||
| Sabal | S. sp. | |||
| Sabalites | S. sp. | |||
| Salix | S. sp. | |||
| Sequoia | S. sp. | |||
| Tracheophyta | Indeterminate | 2 miles south of Elephant Butte | ||
| Viburnum | V. sp. |
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