Unterpermische Bryozoen des East Gondwana Rift Systems: Blick aus der globalen Perspektive
Zusammenfassung der Projektergebnisse
The project comprises a comprehensive investigation of bryozoan faunas from the Lower Permian of Western Australia. The study mainly concentrated on bryozoans from the Callytharra Formation (upper Sakmarian-lower Artinskian) and Noonkanbah Formation (upper Artinskian-Kungurian), accompanied by contemporary faunas from Timor and Tibet. The material for study has been collected by own as well as provided by collaborating scientists. The identified bryozoan fauna from the Callytharra Fm. includes 54 species, and in the material from the Noonkanbah Fm. 27 bryozoan species were found. Bryozoans of the Callytharra Formation (late Sakmarian-early Artinskian) characterize coolwater conditions and show closest relations to Sakmarian-Artinskian faunas of Eastern Australia followed by Thailand, Timor, and Iran. In contrast, the warm-water fauna from the Noonkanbah Fm. showed connections to the warm-water faunas from Tibet, Oman, Indonesia, Malaysia and Thailand. The genus Timanotrypa from the Noonkanbah Fm. indicates connection to the bryozoan faunas of the Northern Hemisphere. The both faunas demonstrate distinct vertical and horizontal faunal transition in the Southern Hemisphere during the Lower Permian. The cool-water faunas are restricted by latitudes of 45-55° S, whereas the faunas within 45-35° S indicate warm water conditions. Two distinct and indicative faunal assemblages of Sakmarian-Artinskian and Artinskian-Kungurian age can be constituted in the Lower Permian of Western Australia. The deglaciation event during the mid-Sakmarian enabled distribution of bryozoan faunas inside of the East Gondwana rift system. This fauna (Callytharra Fm.) was rather adapted to the cool-water conditions and suffered considerably under the warming event at the late Artinskian–early Kungurian transition. Together with few holdovers the new bryozoan assemblage (Noonkanbah Fm.) was formed under a strong influence of the bryozoan faunas from the higher latitudes. The general structure of the fauna (individual size and set of growth forms) remained without significant changes, only the taxonomic content changed. This observation allows the conclusion that the change of the climatic conditions does not affected the structure of the fauna adapted to such conditions as depth, water energy and sediment influx. The performed ecological an geochemical analyses within the present study showed that the Permian bryozoans can be used as proxies for ecological reconstructions. Distribution of elements (e.g., Mg, Fe, Sr) in bryozoan skeletons showed annual fluctuations assuming strong seasonality in the basins where the Callytharra Fm. was deposited. The bryozoans from the Callytharra Fm showed similar growth rates as bryozoans in modern cool- to cold-water environments. Morphologically, bryozoans from colder environments had larger zooecia (apertures and distances between them) than those occurred at warmer conditions. This trend has been also observed on modern bryozoans. Analyses of studied bryozoan assemblages showed that distribution of bryozoan growth forms in depends on such environmental conditions as depth, water energy, and sediment impact. Assemblages with delicate forms were adapted to deeper and quieter biotopes with insignificant sediment impact, whereas those with predominantly robust erect forms, corresponded to the shallow shelf environment. Furthermore, the study of bryozoan skeletons revealed presence of two distinct sets of microborings which reliably characterize colder and warmer conditions in the Lower Permian basins of East Gondwana.
Projektbezogene Publikationen (Auswahl)
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(2014): Postglacial Early Permian (Sakmarian–Artinskian) shallow-marine carbonate deposition along a 2000 km transect from Timor-Leste to northern Perth Basin, Western Australia. – Palaeogeography, Palaeoclimatology, Palaeoecology, 409: 180–204
Haig, D. W., Mccartain, E., Mory, A. J., Borges, G., Davydov, V., Dixon, M., Ernst, A., Groflin, S., Håkansson, E., Keep, M., Dos Santos, Z., Shi, G., & Soares, J.
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(2016): Bryozoan fauna from the Permian (Artinskian-Kungurian) Zhongba Formation of southwestern Tibet. – Palaeontologia Electronica, 19.2.15A: 1-59
Ernst, A.
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(2017): Late Artinskian–Early Kungurian (Early Permian) warming and maximum marine flooding in the East Gondwana interior rift, Timor and Western Australia, and comparisons across East Gondwana. – Palaeogeography, Palaeoclimatology, Palaeoecology, 468: 88–121
Haig, D.W., Mory, A. J., Mccartain, E., Backhouse, J., Håkansson, E., Ernst, A.,Nicoll, R. S., Shi, G. R., Bevan, J. C., Davydov, V. I., Hunter, A., Keep, M., Martin, S. K., Peyrot, D., Kossavaya, O., & Dos Santos, Z.
