Hall Lake Formation | |
---|---|
Stratigraphic range: Late Cretaceous, Campanian–Maastrichtian ~ | |
Type | Geological formation |
Unit of | McRae Group |
Underlies | Jose Creek Member [1] |
Overlies | "Quaternary-Tertiary basalt flows and alluvium" |
Lithology | |
Primary | Mudstone, "shale", sandstone |
Location | |
Coordinates | 33°12′N107°06′W / 33.2°N 107.1°W |
Approximate paleocoordinates | 40°30′N81°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. [2]
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, [3] 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, [4] others classify it as a distinct formation in a group of formations. [5]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Genus | Species | Locality | Material | Notes | Images |
---|---|---|---|---|---|
Tyrannosauridae [4] | indet. | Staton-LaPoint |
| Lozinsky et al. (1984) call it indeterminate | |
Tyrannosaurus [6] | T. mcraeensis | Elephant Butte (upper) |
| ![]() | |
Alamosaurus [4] [5] | sp. | upper |
| Tentative referral | |
Sauropoda [7] | Possibly from the Jose Creek Member | ||||
Theropoda [7] |
Color key
| Notes Uncertain or tentative taxa are in small text; |
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Triceratops sp. [2] [4] | 2 miles south of Elephant Butte |
| This genus, Torosaurus or a novel taxon | ![]() |
Sierraceratops turneri [5] | Elephant Butte (lower) |
| ![]() | |
Ceratopsidae [3] | 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. [3] | Elephant Butte (upper)? | |||
Hadrosauridae [3] | cannot be determined | Indeterminate and of unknown origins due to faulting or Quaternary cover | ||
Ankylosauria [4] [7] |
| Possibly from the Jose Creek Member, near identical from UNM-FKK-001P of the Kirtland Formation |
Taxon | Locality | Material | Notes |
---|---|---|---|
Testudinata [2] | Elephant Butte (upper) | ||
Crocodylia [2] | |||
Compsemys [3] | Index fossils suggesting a Lancian age | ||
Bothremydidae [3] |
Genus | Species | Locality | Material | Notes |
---|---|---|---|---|
Araucarites [7] | A. sp. | |||
Cinnamomum [7] | C. sp. | |||
Exnelumbites [8] | E. morphotype 2 | Leaves | A member of Nelumbonaceae | |
Ficus [7] | F. sp. | |||
Phyllites [7] | P. sp. | |||
Sabal [7] | S. sp. | |||
Sabalites [7] | S. sp. | |||
Salix [7] | S. sp. | |||
Sequoia [7] | S. sp. | |||
Tracheophyta [2] | Indeterminate | 2 miles south of Elephant Butte | ||
Viburnum [7] | V. sp. |