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Spencer G. Lucas - One of the best experts on this subject based on the ideXlab platform.
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Late Paleozoic–early Mesozoic continental biostratigraphy — Links to the Standard Global Chronostratigraphic Scale
Palaeoworld, 2020Co-Authors: Joerg W. Schneider, Spencer G. Lucas, Hendrik Klein, Frank Scholze, Sebastian Voigt, Lorenzo Marchetti, Stanislav Opluštil, Ralf Werneburg, V. K. Golubev, James E. BarrickAbstract:Abstract Nonmarine biostratigraphic/biochronologic schemes have been created for all or parts of the late Carboniferous–Middle Triassic using palynomorphs, megafossil plants, conchostracans, blattoid insects, tetrapod footprints and tetrapod body fossils, and these provide varied temporal resolution. Cross correlation of the nonmarine biochronologies to the Standard Global Chronostratigraphic Scale has been achieved in some parts of the late Carboniferous–Middle Triassic in locations where nonmarine and marine strata are intercalated, the nonmarine strata produce biochronologically significant fossils and the marine strata yield fusulinids, conodonts and/or ammonoids. Other cross correlations have been aided by magnetostratigraphy, chemostratigraphy and a growing database of radioisotopic ages. A synthetic nonmarine Biochronology for the late Carboniferous–Middle Triassic based on all available nonmarine index fossils, integrated with the Standard Global Chronostratigraphic Scale, is presented here. The focus is on the nonmarine biostratigraphy/Biochronology of blattoid insects, conchostracans, branchiosaurid amphibians, tetrapod footprints and tetrapod body fossils within the biochronological framework of land-vertebrate faunachrons. Correlation to the Standard Global Chronostratigraphic Scale presented here is divided into seven time intervals: Pennsylvanian, Carboniferous–Permian boundary, Cisuralian, Guadalupian, Lopingian, Permian–Triassic boundary and Early to Middle Triassic. The insects, conchostracans and branchiosaurs provide robust nonmarine correlations in the Pennsylvanian–Cisuralian, and the footprints and tetrapod body fossils provide robust correlations of varied precision within the entire Pennsylvanian–Middle Triassic. Radioisotopic ages are currently the strongest basis for cross correlation of the nonmarine biostratigraphy/Biochronology to the Standard Global Chronostratigraphic Scale, particularly for the Pennsylvanian–Cisuralian. Chemostratigraphy and magnetostratigraphy thus far provide only limited links of nomarine and marine chronologies. Improvements in the nonmarine-marine correlations of late Paleozoic–Triassic Pangea require better alpha taxonomy and stratigraphic precision for the nonmarine fossil record integrated with more reliable radioisotopic ages and more extensive chemostratigraphic and magnetostratigraphic datasets.
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late triassic terrestrial tetrapods biostratigraphy Biochronology and biotic events
2018Co-Authors: Spencer G. LucasAbstract:The fossil record of Late Triassic tetrapods can be organized biostratigraphically and biochronologically into five, temporally successive land-vertebrate faunachrons (LVFs) that encompass Late Triassic time (in ascending order): Berdyankian, Otischalkian, Adamanian, Revueltian and Apachean. An up-to-date review of the age constraints on Late Triassic tetrapod fossil assemblages and correlation within the framework of the LVFs is presented. This makes possible a much more accurate evaluation of the timing of biotic events of Late Triassic tetrapod evolution, including: (1) Otischalkian, HO (highest occurrence) of almasaurids and chroniosuchians?, LOs (lowest occurrences) of crocodylomorphs and dinosaurs; (2) Adamanian, HO of mastodonsaurids and trematosaurids, LO of mammals; (3) Revueltian, HOs of capitosaurids, rhynchosaurs and dicynodonts; and (4) Apachean, HOs of metoposaurids, plagiosaurids and aetosaurs. The LO of turtles is Early Triassic or older, and the HO of phytosaurs is an Early Jurassic record. There is no compelling evidence of tetrapod mass extinctions at either the Carnian-Norian or the Triassic-Jurassic boundaries.
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Age and correlation of Late Triassic tetrapods from southern Poland
Annales Societatis Geologorum Poloniae, 2015Co-Authors: Spencer G. LucasAbstract:Age assignments of Triassic tetrapod fossils can be achieved by direct reference to a scheme of Triassic land-vertebrate faunachrons (LVFs) that correlates Triassic tetrapod fossil assemblages to each other based solely on the tetrapod fossils. Correlation of Triassic tetrapod assemblages to the standard global chronostratigraphic scale (SGCS, the “marine timescale”) is a separate cross correlation between the vertebrate Biochronology and marine Biochronology that usually relies on other data (e. g., palynostratigraphy, magnetostratigraphy, radioisoto- pic ages) to be completed. Late Triassic tetrapod fossils in southern Poland are found at two stratigraphic positions, the Krasiejow and Lisowice levels. The tetrapod assemblage of the Krasiejow level is assigned to the early Adamanian LVF based primarily on the stratigraphic overlap of the phytosaur Parasuchus with the Adamanian index aetosaur Stagonolepis . The amphibians Cyclotosaurus and Gerrothorax , a Proterochersis -like turtle and the aetosaur Paratypothorax from the Lisowice level indicate it is assignable to the Revueltian LVF. Cross correla- tions to the SGCS are less definitive, but suggest that the Krasiejow level is late Carnian and the Lisowice level is early/middle Norian. However, this correlation of the Krasiejow level is confounded by disagreements over correlation of the marine Carnian–Norian boundary to nonmarine strata. Indeed, the possibility that the Krasiejow tetrapods fill a gap in the early Norian record of tetrapods merits consideration. Such difficulties emphasize the value of correlating tetrapod assemblages to each other using a land-vertebrate biostratigraphy/Biochronology, instead of immediately attempting the more problematic correlation to the SGCS.
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Triassic Timescale Based on Tetrapod Biostratigraphy and Biochronology
Springer Geology, 2014Co-Authors: Spencer G. Lucas, Lawrence H. TannerAbstract:The Biochronology based on the global biostratigraphy of tetrapod fossils allows the Triassic System to be divided into eight land-vertebrate faunachrons based mainly on the first appearance datums of tetrapod genera. Temporal resolution may be improved by subdivision of these faunachrons. We note, however, that this Biochronology is undermined by the use of cladotaxonomy. The Triassic tetrapod footprint Biochronology has lower resolution, dividing the entire system into five footprint-based biochrons. The temporal resolution of this Biochronology also may be improved through subdivision based on ichnotaxon range zones.
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vertebrate biostratigraphy and Biochronology of the upper paleozoic dunkard group pennsylvania west virginia ohio usa
International Journal of Coal Geology, 2013Co-Authors: Spencer G. LucasAbstract:Abstract The Dunkard Group is ~ 343 m of mostly clastic rocks exposed in Pennsylvania, Ohio and West Virginia, USA. Correlation of the Dunkard Group to the Pennsylvanian–Permian boundary has long been debated. Fossil vertebrates from the Dunkard Group include paleoniscoids, dipnoans, a rhipidistian crossopterygian, selachians, lepospondyl and temnospondyl amphibians, diadectomorphs, primitive amniotes, eureptiles and eupelycosaurs. These vertebrates represent two biostratigraphically distinct assemblages, one from the Waynesburg and Washington formations and the other from the overlying Greene Formation. Comparison of the Dunkard vertebrate biostratigraphy to a vertebrate biostratigraphy and Biochronology developed in New Mexico–Texas allows correlation to the Coyotean (= latest Virgilian–middle Wolfcampian) and Seymouran (late Wolfcampian–early Leonardian) land-vertebrate faunachrons. Tetrapod taxa from the Waynesburg and Washington formations include Edops and Protorothyris , Coyotean index taxa, as well as the characteristic Coyotean taxa Trimerorhachis , Diadectes , Edaphosaurus and Dimetrodon . Significantly, these Dunkard taxa are best known from the Archer City Formation in Texas, which is late Coyotean (= middle Wolfcampian). The Greene Formation contains the eupelycosaur Ctenospondylus , an index taxon of the Seymouran land-vertebrate faunachron. Dunkard xenacanth selachians support the tetrapod-based correlations. Vertebrate Biochronology thus indicates that the Waynesburg and Washington formations are late Coyotean, whereas the Greene Formation is Seymouran. Therefore, vertebrate biostratigraphy and Biochronology indicate that the entire Dunkard Group is Early Permian and likely straddles the Wolfcampian–Leonardian boundary.
Joerg W. Schneider - One of the best experts on this subject based on the ideXlab platform.
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Late Paleozoic–early Mesozoic continental biostratigraphy — Links to the Standard Global Chronostratigraphic Scale
Palaeoworld, 2020Co-Authors: Joerg W. Schneider, Spencer G. Lucas, Hendrik Klein, Frank Scholze, Sebastian Voigt, Lorenzo Marchetti, Stanislav Opluštil, Ralf Werneburg, V. K. Golubev, James E. BarrickAbstract:Abstract Nonmarine biostratigraphic/biochronologic schemes have been created for all or parts of the late Carboniferous–Middle Triassic using palynomorphs, megafossil plants, conchostracans, blattoid insects, tetrapod footprints and tetrapod body fossils, and these provide varied temporal resolution. Cross correlation of the nonmarine biochronologies to the Standard Global Chronostratigraphic Scale has been achieved in some parts of the late Carboniferous–Middle Triassic in locations where nonmarine and marine strata are intercalated, the nonmarine strata produce biochronologically significant fossils and the marine strata yield fusulinids, conodonts and/or ammonoids. Other cross correlations have been aided by magnetostratigraphy, chemostratigraphy and a growing database of radioisotopic ages. A synthetic nonmarine Biochronology for the late Carboniferous–Middle Triassic based on all available nonmarine index fossils, integrated with the Standard Global Chronostratigraphic Scale, is presented here. The focus is on the nonmarine biostratigraphy/Biochronology of blattoid insects, conchostracans, branchiosaurid amphibians, tetrapod footprints and tetrapod body fossils within the biochronological framework of land-vertebrate faunachrons. Correlation to the Standard Global Chronostratigraphic Scale presented here is divided into seven time intervals: Pennsylvanian, Carboniferous–Permian boundary, Cisuralian, Guadalupian, Lopingian, Permian–Triassic boundary and Early to Middle Triassic. The insects, conchostracans and branchiosaurs provide robust nonmarine correlations in the Pennsylvanian–Cisuralian, and the footprints and tetrapod body fossils provide robust correlations of varied precision within the entire Pennsylvanian–Middle Triassic. Radioisotopic ages are currently the strongest basis for cross correlation of the nonmarine biostratigraphy/Biochronology to the Standard Global Chronostratigraphic Scale, particularly for the Pennsylvanian–Cisuralian. Chemostratigraphy and magnetostratigraphy thus far provide only limited links of nomarine and marine chronologies. Improvements in the nonmarine-marine correlations of late Paleozoic–Triassic Pangea require better alpha taxonomy and stratigraphic precision for the nonmarine fossil record integrated with more reliable radioisotopic ages and more extensive chemostratigraphic and magnetostratigraphic datasets.
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non marine permian biostratigraphy and Biochronology
Geological Society London Special Publications, 2006Co-Authors: Spencer G. Lucas, Giuseppe Cassinis, Joerg W. SchneiderAbstract:During the Permian, the single supercontinent Pangaea stretched from pole to pole. Early Permian glacial deposits are found in southern Gondwana. Along the sutures of Pangaea, mountain ranges towered over vast tropical lowlands. Interior areas included dry deserts where dune sands accumulated. Gypsum and halite beds document the evaporation of hot, shallow seas that formed the most extensive salt deposits in the geological record. The Permian period (251 to 299 Ma) encompasses nine ages (stages) arranged into three epochs (series). Most of the Permian marine timescale has been defined by global stratotype sections and points for the stage boundaries. This volume presents new data regarding the biostratigraphy and Biochronology of the non-marine Permian and provides a basis for temporally ordering Permian geological and biotic history on land, and correlating that history to events in the marine realm.
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non marine permian biostratigraphy and Biochronology an introduction
Geological Society London Special Publications, 2006Co-Authors: Spencer G. Lucas, Joerg W. Schneider, Giuseppe CassinisAbstract:The Permian time scale based on marine rocks and fossils is well defined and of global utility, but non-marine Permian biostratigraphy and chronology is in an early phase of development. Non-marine Permian strata are best known from western Europe and the western United States, but significant records are also known from Russia, South Africa, China and Brazil. Global time terms based on non-marine Permian strata, such as Rotliegend, Zechstein, Autunian, Saxonian and Thuringian, are either inadequately defined or poorly characterized and should only be used as lithostratigraphic terms. Macro- and microfloras have long been important in non-marine Permian correlations, but are subject to limitations based on palaeoprovinciality and facies/climatic controls. Charophytes, conchostracans, ostracodes and freshwater bivalves have a potential use in non-marine Permian biostrati- graphy but are limited by their over-split taxonomy and lack of well-established stratigraphic distributions of low-level taxa. Tetrapod footprints provide poor biostratigraphic resolution during the Permian, but tetrapod body fossils and insects provide more detailed biostrati- graphic zonations, especially in the Lower Permian. Numerous radioisotopic ages are available from non-marine Permian sections and need to be more precisely correlated to the global time scale. The Middle Permian Illawarra reversal and subsequent magnetic polarity shifts are also of value to correlation. There needs to be a concerted effort to develop non- marine Permian biostratigraphy, to correlate it to radio-isotopic and magnetostratigraphic data, and to cross-correlate it to the marine time scale.
Manuela Aiglstorfer - One of the best experts on this subject based on the ideXlab platform.
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The late Middle Miocene (Sarmatian s.str.) fossil site Gratkorn – the first decade of research, geology, stratigraphy and vertebrate fauna
Palaeobiodiversity and Palaeoenvironments, 2014Co-Authors: Martin Gross, Madelaine Böhme, Philipe Havlik, Manuela AiglstorferAbstract:This article summarises the history of research, the geological background and the stratigraphy of the Gratkorn locality (SE Austria). Since its discovery in 2005, 65 vertebrate taxa, comprising fishes, amphibians, reptiles, birds, and small and large mammals have been documented, as well as a variety of plant and invertebrate fossils. Due to its origin from a rapidly accumulated floodplain paleosol, time-averaging is low and the taphocoenose reflects well the original vertebrate community. The Gratkorn site is dated by integrated stratigraphy, but independent from vertebrate Biochronology, to about 12.2–12.0 Ma (late Middle Miocene). Thus, it probably yields the most diverse, systematically excavated vertebrate fauna of that age in Europe and is an extremely important benchmark for a vertebrate-based, continental biostratigraphy of the Central Paratethyan realm and beyond.
Lawrence H. Tanner - One of the best experts on this subject based on the ideXlab platform.
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Triassic Timescale Based on Tetrapod Biostratigraphy and Biochronology
Springer Geology, 2014Co-Authors: Spencer G. Lucas, Lawrence H. TannerAbstract:The Biochronology based on the global biostratigraphy of tetrapod fossils allows the Triassic System to be divided into eight land-vertebrate faunachrons based mainly on the first appearance datums of tetrapod genera. Temporal resolution may be improved by subdivision of these faunachrons. We note, however, that this Biochronology is undermined by the use of cladotaxonomy. The Triassic tetrapod footprint Biochronology has lower resolution, dividing the entire system into five footprint-based biochrons. The temporal resolution of this Biochronology also may be improved through subdivision based on ichnotaxon range zones.
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Tetrapod biostratigraphy and Biochronology of the Triassic-Jurassic transition on the southern Colorado Plateau, USA
Palaeogeography Palaeoclimatology Palaeoecology, 2006Co-Authors: Spencer G. Lucas, Lawrence H. TannerAbstract:Abstract Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups on the southern Colorado Plateau preserve tetrapod body fossils and footprints that are one of the world's most extensive tetrapod fossil records across the Triassic–Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean–Wassonian boundary approximates the Triassic–Jurassic boundary. This tetrapod biostratigraphy and Biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau confirms that crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic.
Andrew B. Heckert - One of the best experts on this subject based on the ideXlab platform.
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Global Triassic tetrapod biostratigraphy and Biochronology: 2007 status
2010Co-Authors: Andrew B. HeckertAbstract:The global Triassic timescale based on tetrapod Biochronology remains a robust tool for both global and regional age assignment and correlation. The Lootsbergian and Nonesian land-vertebrate faunachrons (LVFs) are of Early Triassic age; cross correlation of part of the Lootsbergian to the Olenekian and all or part of the Nonesian to the Anisian lacks support. In the South African Karoo basin, both the Lootsbergian and the Nonesian can and should be subdivided into sub-LVFs. The upper part of the South African Cynognathus zone, previously considered Nonesian in age, is younger, of Perovkan age. We redefine the beginning of the Perovkan as the first appearance datum of the temnospondyl Eocyclotosaurus, which resolves uncertainties in the correlation of Eocyclotosaurus assemblages and shansiodont assemblages. The Berdyankian LVF equates to parts of Ladinian and Carnian time. Rejection of recent cladotaxonomy of phytosaurs and an incorrect claim of a Revueltian record of the temnospondyl Metoposaurus, as well as newly established stratigraphic ranges and new taxonomy of aetosaurs, have improved correlation and temporal resolution within the interval Otischalkian-Apachean. This further supports separation of the Otischalkian and Adamanian and runs contrary to suggestions to merge the two LVFs as a single Ischigualastian LVF. Though readily recognized and correlated in western North America, the Apachean LVF remains the most problematic LVF for global correlation. A recent purported test of the Triassic LVFS based on GIS is rejected as invalid because it is replete with internal inconsistencies, factual errors and questionable interpretations. Continued careful biostratigraphy in the field and improved alpha taxonomies that are not cladotaxonomies will further develop, elaborate and test the Triassic timescale based on tetrapod evolution.
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Tetrapod biostratigraphy and Biochronology across the Triassic- Jurassic boundary in northeastern Arizona
2010Co-Authors: Andrew B. HeckertAbstract:Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups in northeastern Arizona and adjacent areas preserve tetrapod body fossils and footprints that are one of the world’s most extensive tetrapod fossil records across the Triassic-Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean-Wassonian boundary approximates the Triassic-Jurassic boundary. This tetrapod biostratigraphy and Biochronology of the Triassic-Jurassic transition on the southern Colorado Plateau confirms that non-crocodilian crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic.