A new midshelf record in the northern Bay of Biscay (NE Atlantic, CBT-CS11 core): Sedimentological, geochemical and palynological data over the last 7 kyrs

The high-time resolution (∼70 years in average) multi-proxy analysis conducted on the mid-shelf core CBT-CS11 (47°46.429′N; 4°25.308′W; 73 m depth; 3.96 m long; NW France, S Brittany) revealed the complexity of the palaeohydrological and palaeoclimatic signals recorded over the last 7 kyrs in the recently published paper: “Oceanic versus continental influences over the last 7 kyrs from a midshelf record in the northern Bay of Biscay (NE Atlantic)” [1]. This study presents the whole CBT-CS11 dataset discussed in [1] including sedimentological (XRF and grain-size (total from [1] and CaCO3-free from [2]) analyses), geochemical (oxygen and carbon stable isotopes on two different benthic foraminiferal species: Ammonia falsobeccarii from [1] and Cibicides refulgens from [2]) analyses) as well as palynological (dinoflagellate cyst and pollen assemblages from [1]) data. The present study also describes the different statistical tests from which ecological groups have been established from palynological indicators in [1].


Specifications
Global and Planetary Change Specific subject area Land-sea information on the northern Bay of Biscay over the last 7000 years are based on palynomorphs, sedimentology and stable isotopes and related to climate and human forcings. Type of data 1 Excel File 5 Figures How data were acquired -CABTEX cruise (Ifremer; PI: S. Toucanne) with CBT-CSx cores: [3], followed by core opening and XRF analysis (Ifremer GM, Plouzan e): J. Nizou and S. Toucanne / [2] for methodology -Sampling for AMS-14 C datations: A. Ganne and A. Penaud / 25 dates: 23 from ARTEMIS and 2 from Pozn an: Table 1 in Ref. [1] -First age model in Ref. [2] improved in Ref. [1] with 4 more radiocarbon dates: A. Penaud  Value of the Data Inedit high resolution (~70 years in average) multi-proxy analysis for hydrographical changes on the Bay of Biscay shelf together with vegetation changes in north-western France watersheds. These data can be used for regional/global synthesis regarding paleoceanographic and palaeoclimatic changes in the North Atlantic basin. Any researcher wishing to compare his data with those of this study will be able to retrieve the original work files.

Palynological data (refer supplementary data online)
All palynological (pollen and dinoflagellate cyst) data from [1] are available online (raw counts in the excel file, supplementary data), so as to be easily extracted and plotted in future studies in percentages/concentrations.

Canonical Correspondence Analysis (CCA)
CCA performed on XRF measurements show chemical elements co-occurrences regarding their environmental signature so as to select main useful data and ratios in [1,2]. On the studied area (silicoclastic margin), KeTieFe elements are related to a detrital terrigenous signature, while CaeSr elements are associated to a marine productivity signal [2]. This well-established source of XRF variation is reflected in our data by the second axis on the CCA (Fig. 1). The first axis refers to grain-size properties since Zr is mainly carried by zircon minerals in quartz-rich sands while AleSi elements are the main elementary components of phyllosilicates and thus potentially of the clayey fraction.
We have plotted the D50 from the total grain-size measurements with Sr-XRF counts (Fig. 2). Both are well correlated, reinforcing the idea that Sr can be used as a coarse biogenic tracer.
The Zr/Al ratio discussed in [1] allows deciphering generally coarser (Zr) versus finer (Al) sediment composition, while Ca/Fe and Sr/Ti ratios discussed in [2] allow discussing biogenic (Ca and Sr) versus terrigenous (Fe and Ti) fractions, with the biogenic component characterized by finer (Ca) or coarser (Sr) biogenic clasts. Subpolar North Atlantic dinocyst (Operculodinium centrocarpum and Spiniferites elongatus) percentages [1] show similar pattern with the terrigenous D50 CaCO 3 -free grain-size data from [2]. This dinocyst binome is addressed in [1] for tracing oceanic influence in the mid-shelf studied site.

DCA synthesis (Fig. 5)
Two natural modes (fluvial versus oceanic influences) can be distinguished while the third mode characterizes the strongest human impacts on the environment. Fluvial/proximal signature, with finer (Ca) or coarser (Sr) biogenic sediments, characterized by fine detritic sediments, is characteristic of the "L. machaerophorum -alluvial forest" pole (top right of Fig. 5). Marine/distal signature is characterized by coarse detritic sediments and is expressed by the "oceanic cysts e mixed oak forest" pole (bottom right of Fig. 5). The anthropic signature (top left of Fig. 5) is individualized by pollen indices of anthropisation combined with heterotrophic cysts and high total cyst (L. machaerophorum excluded) concentrations.

Sedimentological data [2]
Grain-size and XRF data are fully described in [2] and briefly described in Table 2 of [1]. [1,2] Ammonia falsobeccarii [1] (101 analyses) and Cibicides refulgens [2] (113 analyses) were hand-picked in the 150e250 mm fraction. Prior to isotopic analyses, foraminifera were cleaned in a methanol ultrasonic bath for a few seconds, and then roasted under vacuum at 380 C for 45 min to remove organic matter. The d 13 C and d 18 O (‰VPDB) were measured at the PSO (IUEM, Brest) using the IRMS platform (MAT253 mass spectrometer coupled with a KIEL IV preparation line for benthic species) for [1] and the Gas Bench platform for [2]. The external reproducibility (1s) on repeated measurements of NBS19 international standard is ±0.04‰ and 0.09‰ for d 13 C and d 18 O, respectively.

Palynological analyses [1]
Palynological treatments (EPOC laboratory, Bordeaux University) were conducted on the <150 mm fraction under the following protocol [5]: 3e5 cm 3 of dry sediments were first treated at room temperature by hydrochloric acids (cold HCl: 10-25-50% until the reaction is over and the effervescence disappears) and hydrofluoric acids (cold HF: 45% for 4 hours followed by 70% for 30h) to remove carbonates and silicates, respectively, then sieved through 10 mm nylon mesh screens.
Palynomorph (i.e. organic microfossils fossilized and observed on palynological slides) determinations were made using a Leica microscope DM2500 at X630 magnification. A minimum of 300 dinocysts and 200 pollen grains were counted per level. In case of over-representation of a taxon (here Lingulodinium machaerophorum for dinocyst assemblages), counts were prolonged until at least 100 other specimens were found.

Multivariate analyses
Multivariate analyses were performed on CBT-CS11 core: Canonical Correspondence Analysis (CCA) for XRF data and Detrended Correspondence Analysis (DCA) for palynological data (dinoflagellate cyst and pollen total and specific absolute concentrations, in parallel with environmental variables including grain-size, XRF, and stable isotopic data) thanks to the "Past version 1.75b" software [4].