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.Vigla Formation at Paleobiodb.org
Description 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.
Fossil content Dinosaurs Saurischians
+GenusSpeciesLocalityMaterialNotesImagesTyrannosauridaeindet. Staton-LaPoint TKM001, dorsal vertebral centrumLozinsky et al. (1984) call it indeterminateTyrannosaurusT. mcraeensisElephant Butte (upper) NMMNH P-3698, a partial skull, lower jaw bones, teeth, and chevronsAlamosaurussp.upper TKM007, a damaged humerusTentative referral Sauropoda"McRae, Sierra County, New Mexico, USA" at mindat.orgPossibly from the Jose Creek MemberTheropoda
Ornithischians
TaxonLocalityMaterialNotesImagesTriceratops sp.2 miles south of Elephant Butte USNM 243, dorsal vertebral centrumThis genus, Torosaurus or a novel taxonSierraceratops turneriElephant Butte (lower) Partial skeleton with skullCeratopsidaeElephant Butte (upper) TKM002, a coranoid TKM020, crest fragmentA new genus similar to Torosaurus is said to exist above the base of the formationElephant Butte (lower)Indeterminate, in abundanceTorosaurus sp.Elephant Butte (upper)?Hadrosauridaecannot be determinedIndeterminate and of unknown origins due to faulting or Quaternary coverAnkylosauria TKM011, pyramidal bone fragmentPossibly from the Jose Creek Member, near identical from UNM-FKK-001P of the Kirtland Formation
Reptiles TaxonLocalityMaterialNotesTestudinataElephant Butte (upper)CrocodyliaCompsemysIndex fossils suggesting a Lancian ageBothremydidae
Plants GenusSpeciesLocalityMaterialNotesAraucaritesA. sp.CinnamomumC. sp.ExnelumbitesE. morphotype 2LeavesA member of NelumbonaceaeFicusF. sp.PhyllitesP. sp.SabalS. sp.SabalitesS. sp.SalixS. sp.SequoiaS. sp.TracheophytaIndeterminate2 miles south of Elephant ButteViburnumV. sp.
References