Paper No. 111-1
Presentation Time: 9:00 AM-6:30 PM
MODIFIED ACID-MACERATION METHOD FOR EXTRACTING PALYNOMORPHS FROM NEOPROTEROZOIC GLACIOGENIC DIAMICTITES
AGIĆ, Heda, Department of Earth Science, University of California Santa Barbara, 1006 Webb Hall, Santa Barbara, CA 93106, HÖGSTRÖM, Anette E.S., Tromsø University Museum, UiT, the Arctic University of Norway, Tromsø, N-9036, Norway, MATTHEWS, Jack J., Department of Earth Sciences, Memorial University of Newfoundland, St. John's, NF A1B 3X5, Canada, LIU, Alexander G., Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom; Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom and PORTER, Susannah M., Earth Science, University of California, Santa Barbara, 1006 Webb Hall, Santa Barbara, CA 93106
Glaciations can have a calamitous effect on the biosphere, yet assessing their direct impact is often challenging. They are usually represented in the fossil record by poorly sorted sediments (diamictites). Due to their heterogeneous composition, however, diamictites are not an ideal archive for preserving evidence of the ancient biosphere. The mixed, coarse-grained material is generally ill-suited for preservation of delicate fossils (e.g. many Precambrian organic-walled microfossils, OWM), but some diamictites may contain fine-grained matrix. During the palynological maceration procedure, the larger grains presumably mechanically destroy any microfossils that may have gotten preserved in the finer sediment.
Here we present a modified acid-maceration extraction method for recovering OWM from diamictites. The new method was applied to recover a microfossil assemblage from the fine-grained matrix of the late Neoproterozoic glaciogenic diamictites of the Mortensnes Formation exposed on the Digermulen Peninsula in Arctic Norway, and the Trinity Diamictite on the Bonavista Peninsula of Newfoundland.
The novel approach yielded more abundant and larger-sized microfossils from the Mortensnes diamictite compared to standard maceration, such as long-chained and toroidal cellular aggregates and large acritarchs. A twofold increase was observed in the max. number of microfossil taxa per level extracted using the new method (11 taxa) as opposed to standard palynological processing (6 taxa). Additionally, the new method allowed the recovery of large-sized taxa (>100 μm) comprising 33% of the assemblage, that were underrepresented in standard macerate (7%). No microfossils were recovered from the Gaskiers diamictite via standard processing, while the novel method yielded a depauperate assemblage of leiosphaerids. This modified method may help unearth palaeontological material from understudied facies and intervals in Earth’s history.
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