The Black Peaks Formation is a geological formation in Texas whose strata date back to the Late Cretaceous (Maastrichtian) and Paleocene. It is exposed in and around Big Bend National Park in Brewster County, where it overlies the Late Cretaceous Javelina Formation and underlies the Eocene Hannold Hill Formation.
The Black Peaks Formation is one of the best sources of Paleocene vertebrate fossils in Texas, including many species of mammals (multituberculates, "condylarths", plesiadapiforms, etc.), as well as alligatorids like Bottosaurus. Turtle fossils have also been unearthed here too.
Geology The Black Peaks Formation has a higher proportion of mudstone compared to the Javelina and Hannold Hill formations. Though this makes it more easily eroded (and thus less widely preserved), in areas with sandstone caprock it can form colorful badlands. The mudstone represents ancient floodplain deposits, though the formation also preserves bands of black-white-red "candy-striped" layers representing ancient lakes. The Black Peaks Formation is named after a trio of volcanic plugs on Tornillo Flat, a small plain in Big Bend National Park where the formation is most extensively exposed.
The K-Pg boundary is estimated to be shortly above base of the Black Peaks Formation, in a narrow contact zone where the sandstone-dominated Javelina Formation grades into the mudstone-dominated Black Peaks Formation. In the Dawson Creek area, a 63-million-year-old conglomerate bed divides the youngest dinosaur fossils of the Javelina Formation from the oldest mammal fossils of the Black Peaks Formation.
Paleobiota Most fossils from the Black Peaks Formation are Paleocene in age, from the Torrejonian and Tiffanian North American Land Mammal Ages (NALMAs). Some major fossil-bearing sites include:
Dogie Mountain (TMM 42327), from the Torrejonian 2 NALMA. Tom's Top (TMM 41400), from the Torrejonian 2 NALMA. T2 (TMM 40147), from the Torrejonian 3 or Tiffanian 1 NALMA. C-Con (TMM 41274), from the Tiffanian NALMA. Ray's Bonebed (TMM 40535-40537, 41367) and vicinities, from the Tiffanian 3 NALMA. Joe's Bonebed (TMM 41365-41366), from the Tiffanian 5 NALMA.
Mammals
Condylarthra "Condylarths" of the Blacks Peak FormationGenus / TaxonSpeciesSite(s)NALMANotesImagesArctocyonA. cf. A. feroxJoe's BonebedTiffanianAn arctocyonidChriacusC. baldwiniDogie MountainTorrejonian 2An arctocyonidC. cf. pelvidensTom's Top, Dogie MountainTorrejonian 2DeuterogonodonD. noletilJuniper Canyon, Robber's RoostTorrejonianAn arctocyonidEctocionE. cf. E. montanensisRay's Bonebed, Joe's BonebedTiffanianA phenacodontidEllipsodonE. cf. E. inaequidensDogie MountainTorrejonian 2A mioclaenid, originally identified as Ellipsodon priscus.cf. Goniacodoncf. G. levisanusDogie MountainTorrejonian 2A triisodontid, originally identified as Eoconodon sp.HaplaletesH. disceptatrixJoe's BonebedTiffanianA mioclaenid or apheliscidHaploconusH. sp.Dogie MountainTorrejonian 2A periptychid, originally identified as Haploconus inopinatus.LambertocyonL. eximiusJoe's Bonebed, near New Taeniodont siteTiffanianAn arctocyonidMimotricentesM. sp.Dogie Mountain, Cobb's KnobTorrejonianAn arctocyonidMioclaenusM. sp.Tom's Top, Dogie MountainTorrejonian 2A mioclaenid. A new species, previously mentioned under the nomen nudum Nexus plexus.M. turgidusTom's Top, Dogie MountainTorrejonian 2A mioclaenidPeriptychusP. carinidensDogie Mountain, T2, C-Con, Ray's BonebedTorrejonian - TiffanianA periptychid. Some fossils were originally identified as Carsioptychus coarctatus or Periptychus superstes.PhenacodusP. bisonensisC-ConTiffanianA phenacodontid, originally identified as Phenacodus matthewi.P. grangeriRay's Bonebed vicinities, Green Hill, Joe's Bonebed, Rock CrusherTiffanianA phenacodontidP. matthewiRay's Bonebed vicinities, Joe's BonebedTiffanianA phenacodontidP. primaevusC-ConTiffanianA phenacodontid, originally identified as Phenacodus grangeri.PromioclaenusP. acolytusC-ConTiffanianA mioclaenidP. cf. P. lemuroidesTom's TopTorrejonian 2A mioclaenid, originally identified as Ellipsodon priscus.ProthryptacodonP. sp.T2TorrejonianAn arctocyonidProtoseleneP. cf. griphusYellow HillTorrejonianA mioclaenidP. opisthacusRay's BonebedTiffanianTetraclaenodonT. puercensisTom's Top, Dogie Mountain, T2TorrejonianA phenacodontid, originally identified as Phenacodus matthewi.TricentesT. truncatusRay's Bonebed, Joe's BonebedTiffanianAn arctocyonid, possibly a synonym of Chriacus baldwini.TriisodonT. quivirensisTorrejonian 2A triisodontid, originally identified as Eoconodon coryphaeus.
Euarchonta Euarchontans of the Blacks Peak FormationGenus / TaxonSpeciesSite(s)NALMANotesImagesChiromyoidesC. sp.Ray's Bonebed, Joe's BonebedTiffanianA plesiadapid plesiadapiform (primate relative), previously identified as Chiromyoides caesor or Plesiadapis gidleyi.IgnaciusI. frugivorusJoe's BonebedTiffanianA paromomyid plesiadapiform (primate relative), previously considered a species of Phenacolemur.MixodectesM. malarisTom's Top, T2TorrejonianA mixodectid (primate and colugo relative)NannodectesN. gidleyiJoe's BonebedTiffanianA plesiadapid plesiadapiform (primate relative), originally identified as Plesiadapis gidleyi.NavajoviusN. kohlhaasaeRay's Bonebed, Joe's BonebedTiffanianA microsyopid plesiadapiform (primate relative)PalaechthonP. cf. P. woodiT2TorrejonianA "palaechthonid" plesiadapiform (primate relative), originally identified as Navajovius kohlhaasae.PlesiolestesP. nacimientiTom's TopTorrejonian 2A "palaechthonid" plesiadapiform (primate relative), originally identified as Palaechthon nacimienti.Zanycteris?Z.? sp.Joe's BonebedTiffanianA picrodontid plesiadapiform. Identification doubtful.
Multutuberculata Multituberculates of the Blacks Peak FormationGenus / TaxonSpeciesSite(s)NALMANotesImagesBaiotomeusB. douglassiT2TorrejonianA ptilodontid, previously considered a species of Neoplagiaulax or Ptilodus.MesodmaM. cf. pygmaeaT2TorrejonianA neoplagiaulacidM. thompsaniDogie MountainTorrejonian 2MimetodonM. silberlingiT2, Joe's BonebedTorrejonian - TiffanianA neoplagiaulacidParectypodusP. sinclairiT2TorrejonianA neoplagiaulacid, originally identified as Ectypodus musculus or Parectypodus sloani.P. sloaniJoe's BonebedTiffanianA neoplagiaulacidPtilodusP. mediaevusTom's Top, T2TorrejonianA ptilodontidP. sp.C-ConTiffanianP. torridusDogie MountainTorrejonian 2StygimysS. gratusSnail's PlaceTorrejonian?A eucosmodontidS. vastusTom's TopTorrejonian 2ViridomysV. bovorbatusDogie MountainTorrejonian 2A multituberculate of uncertain affinities.
Other mammals Other mammals of the Blacks Peak FormationGenus / TaxonSpeciesSite(s)NALMANotesImages"Barylambda"?"B." jackwilsoniRay's BonebedTiffanianA pantodont, potentially synonymous with Caenolambda jepseni and unrelated to other species of Barylambda.BryanictisB. sp.Tom's TopTorrejonian 2A viverravid (carnivoran relative), originally identified as Protictis terlinguae.CaenolambdaC. sp.Schiebout-Reeves QuarryLate Torrejonian or early TiffanianA pantolambdid pantodontCimolestidaeindet.Dogie MountainTorrejonian 2An indeterminate cimolestid, originally identified as Gelastops sp.JepsenellaJ. sp.Joe's BonebedTiffanianAn apatemyid (aye-aye-like insectivore)Palaeictops?P.? sp.Joe's BonebedTiffanianA leptictid (hopping insectivore)PaleotomusP. seniorC-ConTiffanianA pantolestid (otter-like carnivore)PeradectesP. sp.Dogie MountainTorrejonian 2A peradectid metatherian (marsupial relative), originally identified as Peratherium.PsittacotheriumP. multifragumDogie Mountain, Cobb's Knob, CT2, Ray's Bonebed and vicinities, Joe's Bonebed, New Taeniodont SiteTorrejonian - TiffanianA stylinodontid taeniodontSwaindelphysS. solastellaRay's BonebedTiffanianA "herpetotheriid" metatherian (marsupial relative). The largest metatherian known from Paleocene North America.TitanoidesT. zeuxisRay's Bonebed, Joe's BonebedTiffanianA titanoideid pantodont, probably a synonym of T. gidleyi.
Reptiles Indeterminate turtle, crocodylian, and lizard fossils are known throughout the formation. Rare fossils of dinosaurs (Alamosaurus and a tyrannosaurid tooth)Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. . and the giant pterosaur Quetzalcoatlus have been reported from the base of the Black Peaks Formation, though further investigation revealed that these are actually from the Javelina Formation, in layers displaced upwards by faulting. Reptiles of the Blacks Peak FormationGenus / TaxonSpeciesSite(s)NALMANotesImagesBorealosuchusB. sp.Ray's Bonebed and vicinities, West Tornillo FlatTiffanianA close relative of crocodyliansBottosaurusB. fustidensRay's Bonebed vicinities, Joe's BonebedTiffanianA broad-snouted early caimancf. BrachychampsaDogie Mountain, Tom's TopTorrejonianAn alligatorid (alligator or caiman relative) with broad crushing teethChampsosaurusC. sp.Moon ValleyTorrejonian?A large choristodereDunnophisD. cf. D. microechinisDogie Mountain, Tom's TopTorrejonian 2A constrictor snakeGlyptosaurusG. cf. G. sylvestrisDogie Mountain, Tom's TopTorrejonian 2A glyptosaurine (armored lizard)HoplochelysH. sp.Moon ValleyTorrejonian?A musk turtleScolecophidiaDogie MountainTorrejonian 2A new species of blind snake, also known as the nomen nudum Suffosio praedatrix.Trionychidaeindet.Torrejonian - TiffanianIndeterminate softshell turtle fossils
Amphibians Indeterminate frog fossils are also known from Dogie Mountain. Amphibians of the Blacks Peak FormationGenus / TaxonSpeciesSite(s)NALMANotesImagesHabrosaurusH. dilatusTom's TopTorrejonian 2A siren (sirenid salamander)OpisthotritonO. kayiTom's TopTorrejonian 2A batrachosauroidid salamander
Fish Indeterminate teleost and gar fossils are known throughout the formation.Hunt, ReBecca K., Vincent L. Santucci and Jason Kenworthy. 2006. "A preliminary inventory of fossil fish from National Park Service units." in S.G. Lucas, J.A. Spielmann, P.M. Hester, J.P. Kenworthy, and V.L. Santucci (ed.s), Fossils from Federal Lands. New Mexico Museum of Natural History and Science Bulletin 34, pp. 63-69. Fish of the Blacks Peak FormationGenus / TaxonSpeciesSite(s)NALMANotesImagesAmiaA. sp.Dogie MountainTorrejonian 2A bowfinAtractosteusA. sp.Dogie MountainTorrejonian 2A garDasyatisD. matrixDogie Mountain, Tom's TopTorrejonian 2A stingrayRhombodusR. tortusC-ConTiffanianA stingray
See also List of dinosaur-bearing rock formations List of pterosaur-bearing stratigraphic units
References
Further reading J. A. Fronimos and T. M. Lehman. 2014. New specimens of a titanosaur sauropod from the Maastrichtian of Big Bend National Park, Texas. Journal of Vertebrate Paleontology 34(4):883-899 T. M. Lehman and K. Barnes. 2010. Champsosaurus (Diapsida: Choristodera) from the Paleocene of West Texas: Paleoclimatic Implications. Journal of Paleontology 84(2):341-345 J. A. Schiebout. 1974. Vertebrate paleontology and paleoecology of Paleocene Black Peaks Formation, Big Bend National Park, Texas. Texas Memorial Museum Bulletin 24:1-88 J. A. Wilson. 1967. Early Tertiary mammals. In R. A. Maxwell, J. T. Lonsdale, R. T. Hazzard, & J. A. Wilson (eds.), Geology of Big Bend National Park, Brewster County, Texas. The University of Texas Publication 6711:157-169