| mhorn | Дата: Monday, 04.02.2013, 12:39 | Сообщение # 1 |
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| Bartolini A., Guex J., Spangenberg J. E., Schoene B., Taylor D. G., Schaltegger U., Atudorei V. (2012) Disentangling the Hettangian carbon isotope record: Implications for the aftermath of the end‐Triassic mass extinction // Geochemistry, Geophysics, Geosystems, Volume 13, Number 1, 11 pp. doi:10.1029/2011GC003807
pdf: http://www.princeton.edu/geoscie....312.pdf
This study provides an organic carbon stable isotope (d13Corg) record calibrated with detailed ammonite biostratigraphy, following the end‐Triassic biological crisis. Precise correlation between this crucial fossil group and the d 13Corg record is key to understanding feedbacks between biological and environmental events following mass extinction. The latest Triassic and Hettangi and 13Corg record shows several negative and positive excursions. The end‐Triassic negative shift coinciding with the mass extinction interval is followed by a positive excursion in the earliest Hettangian Psiloceras spelaebeds, which marks the onset of recovery in the
marine ecosystem. This positive trend is interrupted by a second negative 13Corg excursion in the P. pacificum beds related to a minor ammonite extinction event. This pattern of the d13Corg curve culminates in the uppermost Hettangian Angulata Zone major positive excursion. This indicates that both the ecosystem
and the carbon cycle remained in a state of perturbation for at least 2 Ma, although the recovery of some pelagic taxa already began at the base of Jurassic. The early and late Hettangian positived13Corgexcursions have been confused in several recent papers. Here, we show that during the Hettangian there are indeed two distinct positive d13Corg excursions. Phases of anoxia and further pulses of Central Atlantic Magmatic Province volcanism during the Hettangian might have inhibited the full recovery for that interval of time. The main Liasicus‐Angulata organic positive CIE (carbon isotope excursion) during the Late Hettangian might
be related to gradual decreasing of pCO2due to protracted high organic burial, and coincides with a second phase of recovery, as indicated by a pulse of ammonoid diversification.
Middle Jurassic - Lower Cretaceous ammonites & aptychi
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