Middle Miocene nannofossil abundance and census counts (Atlantic deep-sea sites)


We present calcareous nannoplankton macroevolutionary patterns across the middle Miocene (~16.5-11 Ma) at 5 deep-sea sites on a North-South transect in the Atlantic Ocean (57°N to 28°S). We show that the major cooling step towards the modern “ice house” world impacted coccolithophore communities at all latitudes. Contrary to previous observations suggesting that tropical sites showed little change and that mid-latitudes were the most sensitive recorders of climate change across the MMCT, we show that all sites recorded a marked diversification and increase in abundance of reticulofenestrids. For each site, age models were based on compilations of available shipboard data, previous high-resolution nannofossil studies and geomagnetic reversal ages, using the Undatable MatLab age-depth modelling software Version 1.1 (Lougheed & Obrochta, 2019), which incorporates uncertainty in both depth and age. Undatable's deterministic routines (with a positive sedimentation rate prior and bootstrapping) result in median and mean age-depth models, with age error estimates (non-normally distributed 68% and 95% percentiles). Age-depth uncertainty in Undatable increases with increasing distance from age-depth determinations, thus including sedimentation rate uncertainty in the age-depth model, unlike linear age-depth models where sedimentation rate is assumed to be constant between age-depth determinations.A total of 233 samples were counted under a polarized light microscope (Olympus and Zeiss Axioskop 40) at 1000× magnification. Microscope slides were prepared from dried bulk sediments with the “drop technique” (Bordiga et al., 2015), which allows for calculation of the absolute number of coccoliths per gram of sediment (N/g), with a reproducibility of ±10-15%. Nannofossil assemblage compositions (in %) were quantified by counting at least 300 specimens. 50 morphospecies were recombined into 9 genus-level groups, and 19 other subordinate taxa were lumped as “others” in the genus-level multivariate analyses (see taxonomic list in Henderiks et al., 2020). The degree of calcification of the central area of the reticulofenestrids (ancestry of modern Emiliania huxleyi and Gephyrocapsa oceanica; Noelaerhabdaceae family) was distinguished in the genus-level groupings with a heavily calcified (Reticulofenestra closed) and less heavily calcified (Reticulofenestra open) category. The 95% confidence intervals (95% CI) for the relative abundance estimates were calculated in PAST version 3.20 freeware (Hammer et al., 2001; Suchéras-Marx et al., 2019).

DOI https://doi.org/10.1594/PANGAEA.921547
Related Identifier https://doi.org/10.1029/2020PA003915
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.921547
Creator Henderiks, Jorijntje ORCID logo; Bartol, Milos; Pige, Nicolas; Karatsolis, Boris Theofanis ORCID logo; Lougheed, Bryan C
Publisher PANGAEA
Publication Year 2020
Rights Creative Commons Attribution 4.0 International; https://creativecommons.org/licenses/by/4.0/
OpenAccess true
Resource Type Bundled Publication of Datasets; Collection
Format application/zip
Size 2 datasets
Discipline Earth System Research
Spatial Coverage (-43.489W, -28.533S, 2.846E, 57.517N)
Temporal Coverage Begin 1983-07-13T00:00:00Z
Temporal Coverage End 2003-04-08T03:50:00Z