Biotic recovery after the end-Triassic extinction event: evidence from marine bivalves of the Neuquén Basin, Argentina

DAMBORENEA, SUSANA E.; ECHEVARRÍA, JAVIER; ROS, SONIA

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 487 p. 93 - 104

0031-0182

Weanalyze the Late Triassic extinction and Early Jurassic recovery of bivalvefaunas within marine environments in the Atuel river area of the Neuquén Basin,Argentina. Data were collected from a hundred samples with invertebrates in awell-exposed latest Triassic to early Jurassic section in the Neuquén Basin(southern Mendoza Province, Argentina) and allow a high-resolutionreconstruction of the local diversity dynamics. The nearly continuous presenceof marine stenohaline major taxa such as cnidarians, rhynchonelliformbrachiopods, echinoderms and cephalopods indicates normal salinity throughout.All bivalve species were identified, and each occurrence was recorded in metersabove the base. To analyze the systematic diversity trends, diversity curveswere calculated on the basis of the first and last appearance data for eachbivalve species, and both total diversity and boundary crossers diversity wereused. As a result, four main phases were identified: a) Triassic equilibriumphase (Rhaetian), with relatively high origination and extinction rates; b)extinction phase (latest Rhaetian to earliest Hettangian), with high extinctionrates and low origination rates; c) recovery phase (late Early to early LateHettangian), with high origination rates and almost null extinction rates; and d)Jurassic equilibrium phase (Late Hettangian-Sinemurian), again with similar andrelatively high origination and extinction rates. The extinction and recoveryphases are separated by a gap of about 135 m without identifiable benthonicinvertebrates but with early Hettangian ammonites. On the other hand, bivalvepalaeoecologic diversity seems to have been more homogeneous along the section,being dominated by attached epifaunal species, though before the extinctionepifaunal habits were slightly surpassed by infaunal ones. Slight differencesobserved include a) shallow burrowers were more diverse during the Rhaetianthan during the earliest Jurassic and b) epifaunal free lying and semi-infaunalattached bivalves were more diverse after the Rhaetian extinction.