a study by Schoene et al. (2010) involving ammonite-bearing strata in Peru. They used CA-ID-TIMS Uranium-Lead dating to date ash beds slightly below and slightly above the first appearance of Psiloceras in the Pucará Basin. The overlying ash bed was dated to 201.29 ±0.16 Ma while the underlying was 201.36 ±0.13 Ma. This allowed the first appearance of Psiloceras to be given a date of 201.31 ±0.18/0.43 Ma (assuming minimum/maximum uncertainty). Blackburn et al. (2013) instead estimated a slightly older end date. They used a combination of radiometric dates and astrochronology (via Triassic Milankovitch cycles) to constrain the end-Triassic extinction to 201.564 ±0.015/0.22 Ma. The biostratigraphically-defined Triassic-Jurassic (Rhaetian-Hettangian) boundary is considered to lie approximately 60-140 thousand years after the extinction by most sources, and therefore the Rhaetian ended in the range of 201.5 to 201.4 Ma under the methodology of Blackburn et al. (2013). Notable formations British fissure fills* (England and Wales, UK) Chinle Formation (Church Rock, Rock Point, and “siltstone” members)* (New Mexico, USA) Lower Elliot Formation (South Africa) Exter Formation (Norian – Rhaetian) (Germany) Penarth Group (England and Wales, UK) Redonda Formation* (New Mexico, USA) Trossingen Formation* (Norian – Rhaetian) (Switzerland and Germany) Wingate Sandstone* (SW USA) * Tentatively assigned to the Rhaetian; age estimated primarily via terrestrial tetrapod biostratigraphy (see Triassic land vertebrate faunachrons) See also Triassic-Jurassic extinction event Rhaetian sandstone References Literature ; 2005: The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale, Episodes 28(4), pp. 233–244. ; 2004: A Geologic Time Scale 2004, Cambridge University Press. External links GeoWhen Database - Rhaetian Upper Triassic timescale, at the website of the subcommission for stratigraphic information of the ICS Norges Network of offshore records of geology and stratigraphy: Stratigraphic charts for the Triassic, and 03 Geological ages Triassic geochronology