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TitleThe Carnian/Norian boundary succession at Berlin-Ichthyosaur State Park (Upper Triassic, central Nevada, USA)
AuthorBalini, M; Jenks, J F; Martin, R; McRoberts, C A; Orchard, M J; Silberling, N J
SourcePaläontologische Zeitschrift vol. 89, issue 3, 2014 p. 399-433,
Alt SeriesEarth Sciences Sector, Contribution Series 20140177
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia
AreaBerlin-Ichthyosaur State Park; Nevada; Black Bear Ridge; Juvavites Cove; California; Pizzo Mondello; United States; Canada; Italy
Lat/Long WENS-118.5000 -117.2500 39.5000 38.7500
Subjectspaleontology; stratigraphy; Carnian; Norian; biostratigraphy; taxonomy; fossil assemblages; fossils; fossil distribution; stratigraphic correlations; correlations; Luning Formation; Ammonoids; bivalves; Conodonts; Mesozoic; Triassic
Illustrationslocation maps; stratigraphic columns; photographs
ProgramWestern Arctic Sverdrup Basin, GEM2: Geo-mapping for Energy and Minerals
AbstractThe Upper Carnian-Lower Norian (Upper Triassic) Luning Formation at Berlin-Ichthyosaur State Park (BISP) in central NV (USA) has been sampled using for the first time the bed-by-bed approach for ammonoids, pelagic bivalves, and conodonts, more than 60 years after its first description by Silberling (U.S. Geological Survey Professional Paper 322: 1-63, 1959). BISP is historically important for the definition of the uppermost Carnian of the North American Triassic chronostratigraphic scale and is known worldwide as one of the most important ichthyosaur Fossil-Lagerstätte because of its extraordinary record of 37 articulated, large-sized specimens of Shonisaurus popularis. Nearly 190 ammonoids were collected from two stratigraphic sections, documenting all the latest Carnian to Early Norian ammonoid faunas previously described by Silberling. Halobiids were collected from five levels, and the first report of conodonts from BISP includes faunas from 13 levels. The ~340-m thick Brick Pile section, the most complete in the study area, includes the uppermost Carnian Macrolobatus Zone, which provides conodont faunas of the lower primitia zone and Halobia septentrionalis. The 200-m thick lowermost Norian Kerri Zone, which begins 52 m above the Macrolobatus Zone, yields conodonts of the upper primitia zone in its lower part, together with H. cf. beyrichi and H. cf. selwyni. The ichthyosaur-bearing interval, whose stratigraphic position has been interpreted quite differently by previous authors, is documented in the uppermost Carnian Macrolobatus Zone and is characterized by rich Tropites-dominated ammonoid faunas and by the onset of Halobia. All models proposed by various workers to explain the unusual ichthyosaur record are discussed and an additional explanation for the main ichthyosaur-bearing bed is proposed. The new hypothesis is that a harmful algal bloom (HAB) may have been the trigger for the mass mortality recorded in this level. Although the C/N boundary in the Brick Pile section lies within a 52 m interval that presently lacks paleontologic data, this succession is included in a small group of sections that are expected to contribute to the definition of the GSSP of the Norian stage. Correlation of the Brick Pile section with the best Carnian/Norian sections in northeastern British Columbia is discussed. Compared to the British Columbia Juvavites Cove and the GSSP candidate Black Bear Ridge sections, the Brick Pile section exhibits an ammonoid and Halobia record that is slightly more similar to that of the Tethyan sections. Correlation of the Brick Pile section with the second GSSP candidate Pizzo Mondello (Sicily, Italy) well demonstrates the significant problems encountered in calibration of the Tethyan and North American scales.
Summary(Plain Language Summary, not published)
A study of the Upper Triassic Luning Formation at Berlin-Ichthyosaur State Park in Nevada has been undertaken by an international team of paleontologists as a contribution to the development of the International Time Scale. Ammonoids, bivalves, and conodonts occur in a section that has yielded a world-famous fauna of articulated ichthyosaur specimens. The association of different fossil species provides a comparative yardstick for resolution of the boundary between the Carnian and Norian stages of the Triassic, and is important as an aid in the global correlation of standard reference sections in British Columbia and Sicily.