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Jurassic Forum » JURASSIC references & paper reviews » Jurassic around the world » Two papers concerning Jurassic crinoids (published in new issue of Acta Paleontologica Polonica)
Two papers concerning Jurassic crinoids
mhornДата: Sunday, 15.03.2009, 18:29 | Сообщение # 1
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Stolarski J., Gorzelak P., Mazur M., Marrocchi Y., Meibom A. (2009) Nanostructural and geochemical features of the Jurassic isocrinid columnal ossicles // Acta Palaeontologica Polonica. V.54. no.1. P.69–75.

Pdf: http://www.app.pan.pl/archive/published/app54/app54-069.pdf

Calcite isocrinid ossicles from the Middle Jurassic (Bathonian) clays in Gnaszyn (central Poland) show perfectly preserved micro− and nanostructural details typical of diagenetically unaltered echinoderm skeleton. Stereom pores are filled with ferroan calcite cements that sealed off the skeleton from diagenetic fluids and prevented structural and geochemical alteration. In contrast with high−Mg calcite skeleton of modern, tropical echinoderms, the fossil crinoid ossicles from Gnaszyn contain only 5.0–5.3 mole% of MgCO3. This low Mg content can be a result of either a low temperature environment (ca. 10 C) and/or low Mg/Ca seawater ratio. Both conditions have been proposed for the Middle Jurassic marine environment. Occurrence of Mg−enriched central region of stereom bars of Jurassic columnal ossicle of Chariocrinus andreae is consistent with the concept of magnesium ions involvement in earliest growth phases of calcium carbonate biominerals

Hunter A.W., Underwood C.J. (2009) Palaeoenvironmental control on distribution of crinoids in the Bathonian (Middle Jurassic) of England and France // Acta Palaeontologica Polonica. V.54. no.1. P.77–98.

Pdf: http://www.app.pan.pl/archive/published/app54/app54-077.pdf

Bulk sampling of a number of different marine andmarginalmarine lithofacies in theBritish Bathonian has allowed us to assess the palaeoenvironmental distribution of crinoids for the first time.Although remains are largely fragmentary, any species have been identified by comparison with articulated specimens from elsewhere, whilst the large and unbiased sample sizes allowed assessment of relative proportions of different taxa. Results indicate that distribution of crinoids well corresponds to particular facies. Ossicles of Chariocrinus and Balanocrinus dominate in deeper−water and lower−energy facies, with the former extending further into shallower−water facies than the latter. Isocrinus dominates in shallower water carbonate facies, accompanied by rarer comatulids, and was also present in the more marine parts of lagoons. Pentacrinites remains are abundant in very high−energy oolite shoal lithofacies. The presence of millericrinids within one, partly allochthonous lithofacies suggests the presence of an otherwise unknown hard substrate from which they have been transported. These results are compared to crinoid assemblages from other Mesozoic localities, and it is evident that the same morphological adaptations are present within crinoids from similar lithofacies throughout the Jurassic and Early Cretaceous.


Middle Jurassic - Lower Cretaceous ammonites & aptychi
 
Jurassic Forum » JURASSIC references & paper reviews » Jurassic around the world » Two papers concerning Jurassic crinoids (published in new issue of Acta Paleontologica Polonica)
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