De Lira Mota, Marcelo Augusto; Dunkley Jones, Tom; Sulaiman, Nursufiah; Edgar, Kirsty M; Yamaguchi, Tatsuhiko; Leng, Melanie J; Adloff, Markus; Greene, Sarah E; Norris, Richard D; Warren, Bridget; Duffy, Grace; Farrant, Jennifer; Murayama, Masafumi; Hall, Jonathan; Bendle, James A (2023): Selected palynomorph-based indicators for the Mossy Grove sediment core [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.960400,

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In: De Lira Mota, MA et al. (2023): Micropaleontological and geochemical dataset of shallow-marine deposits in central Mississippi, US Gulf Coastal Plain [dataset bundled publication]. PANGAEA, https://doi.org/10.1594/PANGAEA.960394

Palynology: Altogether, 112 samples collected at ~1.2 m intervals from the Mossy Grove borehole between ~17.0 and 152.0 m were treated with 40% HCl for 30 minutes and 60% HF for 24 hours to dissolve carbonates and disaggregate the rock matrix, and sieved over a 10 µm nylon mesh to retain the HF effluent from the material. A second HCl treatment was applied to remove any precipitate, followed by a final sieving over a 10 µm mesh. The remaining sample material (>10 µm) was subjected to oxidation (70% HNO3 for exactly two minutes) to remove pyrite, debris and any unstructured organic material from the palynomorphs, followed by another sieving over a 10 µm mesh to remove any HNO3 effluent. A final cleaning treatment was undertaken with a combination of domestic and industrial detergents. Using swirling techniques, palynomorphs in each sample were then concentrated and Bismark brown was added to make them more visible with light microscopy. Finally, the samples were sieved into two size fractions, 10-30 μm (concentrating spores and pollen) and 30 μm+ (concentrating dinocysts), and then mounted on separate 22x22 mm coverslips, which were glued to a glass slide using Norland optical adhesive. In this work, only the coarse-fraction content of each slide was analyzed. A pilot survey of these slides revealed that the acid and oxidizing technique yielded higher diversity than their non-acid and non-oxidizing counterparts61. The coarse/fine-fraction sorting follows the premise that pollen and spores size mostly ranges between 11 and 44 µm, whereas dinocysts range between 20 and 150 µm62. All slides are stored in the collection of the School of Geography, Earth and Environmental Sciences, University of Birmingham, and are available upon request from Tom Dunkley Jones.

Palynomorph components: In this work, the coarse-fraction content of each slide was analyzed with a Zeiss transmitted light microscope (400x magnification). Two hundred dinocyst specimens were counted in each sample, along with any spores, pollen, algae (prasinophyceae and chlorophyceae), zoomorphs/zooclasts, phytoclasts and amorphous organic matter. Only palynomorphs that were more than 50% complete and not obscured either by air bubbles or organic debris were considered 63. Reworked acritarchs and amorphous organic matter were excluded from the final sum of palynomorphs and thereby from the percentage calculations. Palynomorph-based paleoenvironmental indicators include the peridinioid/gonyaulacoid dinocyst (P/G) ratio 64–70, and salinity reconstructions based on the relative abundance of the high-salinity favoring Homotryblium spp. 43,71–73 and in the ratio of short-to-long process of dinocyst genus Spiniferites 74–78.