59th Annual Report on Research 2014

During this year the project has focused on laboratory work by undergraduates, in particular the preparation of serial sections (acetate peels) of the internal structures of fossil brachiopods and their conservation in glass slides. In addition, the analysis and writing up of results and their publication has been a priority during the final year of the project.

The focus in the laboratory has been on material from the Jurassic of Montenegro and the Jurassic-Cretaceous of Svalbard.

Jurassic of Montenegro.

The material from Montenegro is from the Lower Jurassic and has been referred to the dimerelloid brachiopod genus Rhynchonellina. This work has been in collaboration with Dr. Vladan Radulovic and Dr. Barbara Radulovic, Belgrade, Serbia. The genus Rhynchonellina has previously been considered to occur in shell-transported accumulations, derived from where they were living on the flanks of Tethyan seamounts, and subsequently transported basinward post-mortem. The Montenegrin occurrence is in blocks of limestone that are considered olistoliths. These transported blocks represent another mechanism whereby the brachiopods may be moved into deeper water settings – although in this case long after they lived – having become encased in lithified carbonates. However, it may be difficult to determine their original preferred habitat without the aid of stable isotopes. Rhynchonellina has been considered a candidate for inhabiting hydrocarbon seep-environments primarily on the basis of other closely-related dimerelloid brachiopods in such environments (Sandy 2010) – e.g., Sulcirostra from the Lower Jurassic of Oregon (Peckmann et al., 2013), and Cooperrhynchia from the Upper Jurassic of California (Sandy and Campbell 1994). In these cases stable isotope data have also supported these associations. Stable isotope analysis by my colleague Professor Jörn Peckmann from the University of Vienna indicates that the Montenegrin Rhynchonellina lived in “normal marine” waters prior to fossilization. Therefore at the moment there are no strong indicators for Rhynchonellina being associated with hydrocarbon seeps, unlike other members of the Dimerelloidea. However, other members of this rhynchonellide superfamily have been found to show a degree of plasticity in their ecological tolerances, for example, Dzieduszyckia from the Devonian (Peckmann et al. 2007), occurring in both normal marine and cold-seep environments. It may be that Rhynchonellina had a similar range of environmental tolerances.

Jurassic-Cretaceous of Svalbard.

Work continued on bringing the study of this fauna to publication. Students have been involved in all aspects of laboratory work on this fauna. The brachiopods were collected from a series of 15 cold-seep carbonate bodies that contain a high-diversity of invertebrate species. The brachiopods form part of a high-diversity, low abundance fauna that contrasts with many of the deeper-water brachiopod faunas known from Paleozoic-Mesozoic cold seeps where brachiopods may dominate and form monospecific shell accumulations (e.g., Sandy 2010). The brachiopod fauna comprises a dozen taxa typically represented by only a few specimens each. The paleobiogeographic signature of the fauna is strongly Boreal – with elements in common with parts of the Russian Platform and Siberia (e.g., Ptilorhynchia, Pseudomonticlarella, Rouillieria). The relatively high diversity in terms of numbers of species is seen as a reflection of the fauna being located in shallower-shelf waters compared to the aforementioned monospecific Paleozoic-Mesozoic brachiopod shell beds that are often found in basin-slope compressive-tectonic settings.

Important results during the period of the grant include:

• Investigation of Jurassic-Cretaceous brachiopods from Spitsbergen, Svalbard. This is the first description of a diverse brachiopod fauna from high-latitude hydrocarbon seeps (Sandy et al. 2014).
• The first confirmation of Sulcirhynchia (Jurassic) from hydrocarbon seep deposits (Peckmann et al. 2013).
• The first confirmation of Anarhynchia (Jurassic) from hydrocarbon seep deposits (Sandy and Peckmann 2012).
• The association of Anarhynchia with both hydrocarbon-seep (Sandy and Peckmann 2012) and hydrothermal-vent deposits (Jurassic of California, Little et al. 2004) make this taxon unique, being the only post-Paleozoic brachiopod currently identified from both of these environmental “end members”. The monospecific mass-occurrences of Anarhynchia from Oregon are reminiscent of other localities interpreted as hydrocarbon-seep deposits. The dark micritic limestones yielded negative δ¹³C values of -20.1‰ to -15.0‰ (Oregon samples) and -23.7‰ to -3.1‰ (California samples) reflecting hydrocarbon oxidation. The brachiopod-rich deposit formed at a hydrocarbon seep, but it is not possible to determine further the composition of the fluids.
• Confirmation of Peregrinella from a methane-seep environment in Romania (Sandy et al. 2012). Specimens of Peregrinella were transported down basin slopes in turbidites from hydrocarbon seep communities where the brachiopods had thrived. The association with hydrocarbon seeps had previously been reported for localities in California and the Crimea, Ukraine (Campbell et al. 1993, Campbell 2006, Kiel and Peckmann 2008). The Romanian record does strongly suggest a unique paleoecological association for Peregrinella.
• The first confirmation of a Cretaceous cold-seep brachiopod association from Tibet for Peregrinella (Sandy and Peckmann 2012) – with stable isotope work undertaken by Professor Jörn Peckmann (Vienna). The material investigated is from the Chebo section, northern Tibet. The rock contains petrographic seep indicators such as clotted micrite and banded botryoidal cement. These phases yielded negative δ¹³C values of -24.5‰ to -21.9‰. The brachiopod-rich deposit formed at a hydrocarbon seep, but it is not possible to determine further the composition of the fluids. For Peregrinella this marks the fourth record of the genus from hydrocarbon-seeps thereby supporting that this genus may be only associated with fossil hydrocarbon-seep environments, hinted at by its disjunct distribution and absence from contemporaneous marine shelf sediments.
• Following on from the above studies is a collaboration with Steffen Kiel and others on a compilation of information on the occurrences of the brachiopod Peregrinella (Kiel et al. 2014).

The research opportunities provided by the grant have been invaluable. Students have been fully involved in all aspects of the research and have consequently thoughtfully explored their planned vocation as scientists. Being able to facilitate this through ACS-PRF sponsored research is very rewarding for our students, as is the fact that they are involved with scientific advances in the field and the laboratory.