Foraminifera source details
Hjálmarsdóttir, H. R.; Nakrem, H. A.; Nagy, J. (2018). Environmental significance and taxonomy of well preserved foraminifera from Upper Jurassic – Lower Cretaceous hydrocarbon seep carbonates, central Spitsbergen. Micropaleontology. 64(5-6). 435-480.
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Hjálmarsdóttir, H. R.; Nakrem, H. A.; Nagy, J.
2018
Environmental significance and taxonomy of well preserved foraminifera from Upper Jurassic – Lower Cretaceous hydrocarbon seep carbonates, central Spitsbergen
Micropaleontology
64(5-6). 435-480
Publication
Available for editors [request]
Five hydrocarbon seep carbonate structures in the upper part of the Slottsmøya Member (Agardhfjellet Formation) in central
Spitsbergen have been sampled and processed for foraminifera. The carbonates have been found to contain excellently preserved agglutinated assemblages, in contrast to the diagenetically deformed assemblages in the adjacent shales. In total 15 genera and 35 agglutinated species are recognised in the palaeoseeps. The pristine condition of the foraminiferal tests allows for detailedmorphological
documentation of 21 species, ofwhich the following six are proposed as new: Reophax pyriloculus n. sp., Haplophragmoides perlobatus n. sp., Labrospira lenticulata n. sp., Ammobaculites deflectus n. sp., Ammobaculites knorringensis n. sp. and Textularia pernana n. sp.. Depositional environment of the carbonate palaeoseeps is interpreted to be similar to that of a normalmarine shelf, as opposed to the previously documented restricted (hypoxic) environment of the adjacent shales. Morphogroup analysis of assemblages in the palaeoseeps reveals that over 89% of genera in the seep carbonate bodies are categorised as surficial/shallow infaunal to deep infaunal. The same morphogroup component in the shale succession onlymakes up 31.5% of the total genera. Agradual shift can be seen in the shale assemblages
from almost exclusively epifaunalmorphogroups in the lower part to a dominating surficial to infaunal component in the samples closest to the palaeoseep stratigraphic levels, which translates to an upwards decreasing oxygen level trend. The foraminifera date the palaeoseeps as late Volgian – late Ryazanian, and the ages for each seep structure are constrained by previously reported associated ammonite occurrences. Some species of foraminifera occurring in the palaeoseeps are possible candidates for extended stratigraphic ranges.
Spitsbergen
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Ammobaculites deflectus Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Ammobaculites knorringensis Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Haplophragmoides perlobatus Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Labrospira lenticulata Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Recurvoides paucus Dubrovskaya, 1962 † (basis of record)
Reophax pyriloculus Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Schleiferella emeljanzevi (Sharovskaya, 1966) † accepted as Evolutinella emeljanzevi (Sharovskaya, 1966) † (new combination reference)
Schleiferella vallata (Nagy & Basov, 1998) † accepted as Evolutinella vallata Nagy & Basov, 1998 † (new combination reference)
Textularia pernana Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Ammobaculites knorringensis Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Haplophragmoides perlobatus Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Labrospira lenticulata Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Recurvoides paucus Dubrovskaya, 1962 † (basis of record)
Reophax pyriloculus Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)
Schleiferella emeljanzevi (Sharovskaya, 1966) † accepted as Evolutinella emeljanzevi (Sharovskaya, 1966) † (new combination reference)
Schleiferella vallata (Nagy & Basov, 1998) † accepted as Evolutinella vallata Nagy & Basov, 1998 † (new combination reference)
Textularia pernana Hjálmarsdóttir, Nakrem & Nagy, 2018 † (original description)