On the application of alkenone- and GDGT-based temperature proxies in the south-eastern Brazilian continental margin

Branched GDGTs as Proxies in Surface Sediments From the South-Eastern Brazilian Continental Margin

“…In fact, the TOC-normalized crenarchaeol contents were higher at the shelf stations of both the transects influenced by upwelling (A and B) and by the Paraíba do Sul River flow (H and I). This process is favored by aggregation of the small cells of Thaumarchaeota with phytoplankton and other suspended matter (Wuchter et al, 2005;Huguet et al, 2006Huguet et al, , 2007Kim et al, 2008), which seems to also occur in our study region as discussed in a related previous paper (Ceccopieri et al, 2018).…”

“…The content of brGDGTs in the surface sediments showed a geographic distribution similar to the total isoGDGTs (Ceccopieri et al, 2018) and to other lipid biomarkers analyzed in the Campos Basin sediments (Oliveira et al, 2013;Cordeiro et al, 2018). Higher contents of total brGDGTs were found in the slope samples on all transects and in the middle shelf samples of the CFUS region, which are areas where preferential FIGURE 3 | Contents of (A) total brGDGTs (µg gTOC −1 ); (B) acyclic brGDGTs (µg gTOC −1 ); (C) crenarchaeol (µg gTOC −1 ), (D) BIT index; (E) #rings tetra index and (F) IR.…”

Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

“…Analytical precision was estimated as 12 % or better, based on triplicate analyses of a sediment sample. The U K 37 values were calculated according to Prahl and Wakeham (1987): U K 37 = C 37:2 /(C 37:2 + C 37:3 ) and were then converted to sea surface temperature (U K 37 -derived SST) using the Müller et al (1998) calibration, as follows: U K 37 = 0.033U K 37 -derived SST ( • C) +0.069; r 2 = 0.98; n = 149; SD = ±1.0 • C. This equation was chosen because it is derived from 149 tropical-to-subpolar eastern South Atlantic surface sediments and was already used in other studies from the same region (e.g., Ceccopieri et al, 2018).…”

“…Previous publications have used the combination of U K 37 -derived SST and foraminifera δ 18 O to estimate the δ 18 O IVF−SW . In these publications, it is generally assumed that the dominant alkenone producer Emiliania huxleyi and G. ruber have comparable water depth habitats (e.g., Rostek et al, 1993;Emeis et al, 2000;Carter et al, 2008;Sepulcre et al, 2011;Kasper et al, 2014), which is also the case in the subtropical western South Atlantic (Venancio et al, 2017;Ceccopieri et al, 2018). Seasonal corrections over the U K 37derived SST before application in δ 18 O IVF−SW have been considered in regions of extreme seasonal variations in temperature and salinity, as the Mediterranean Sea (e.g., Essallami et al, 2007), which is not the case for the subtropical western South Atlantic.…”

“…The paleoclimatic knowledge accessed through marine sediment cores from the extensive Brazilian continental margin has increased significantly through the last decades (e.g., Arz et al, 1999Arz et al, , 2001Chiessi et al, 2008;Govin et al, 2014;Jaeschke et al, 2007;Jennerjahn et al, 2004;Lessa et al, 2017;Portilho-Ramos et al, 2015;Rühlemann et al, 1999). The records distributed along the western South Atlantic display considerably het-L. G. Luz et al: Contrasting late-glacial record across the South Atlantic Slope erogeneous features in terms of sedimentation rate and response to the adjacent continental climate, which makes the scientific outputs extremely dependent on the core site location.…”