ALBERT

Description: Marine laminated sediments in dysoxic areas of the ocean floor are an excellent archive for high-resolution climate reconstructions. While the existence of discontinuities produced by natural events, such as underwater landslides (slumps), strong bottom currents, and/or bioturbation is usually acknowledged for long records, the extent of their influence on high-resolution sequences is usually not considered. In the present work we show strong evidence for multiple stratigraphic discontinuities in different gravity and box-cores retrieved off Pisco (Peru) covering the last 600 years. Chronostratigraphies are largely based on cross-correlation of distinct sedimentary structures (determined by X-ray image analysis) and validated using 210Pb, 241Am, and 14C profiles, as well as proxy records. The cross-correlation of distinct stratigraphic layers allows for chronostratigraphic tie points and clearly shows that some sedimentary sequences are continuous across scales of tens of kilometers, indicating that regional processes often determine laminae formation. Some differences in laminae thickness were found among cores, which could be explained by different sedimentation rates, spatially variable deposition of diatom blooms, changes in silica dissolution and partial deposition/erosion caused by bottom currents. Using multiple stratigraphic tie points provides clear evidence for laminated sequences present in some cores to be missing in other cores. Moreover, instantaneous depositions from upslope were identified in all the cores disrupting the continuity of the sediment records. These discontinuities (instantaneous deposits and missing sequences) may be due to slumps, possibly triggered by earthquakes and/or erosion by strong bottom currents. In spite of the missing sequences in some cores, a continuous composite record of the last six centuries was reconstructed from spliced sequences of the different cores, which provides a well-constrained temporal framework to develop further high-resolution proxies in this region. The present work shows that paleoreconstructions developed from single cores, particularly in areas with strong seismic activity and/or strong bottom currents, are subject to both temporal gaps and instantaneous depositions from upslope, both of which could be misinterpreted as abrupt climate changes or anomalous climate events. We stress the need for multiple cores to determine the stratigraphic continuity and chronologies for high-resolution records.

Description: Previously, carnosic acid and carnosol have demonstrated anti-proliferative activity against different types of cancer. To obtain extracts enriched in these two key phenolic compounds, two different processes have been developed in the present work based on the use of two-step sequential supercritical fluid extraction (SFE). By removing the interfering, less active fractions in a first step (150 or 300 bar, 40°C, neat CO2, 60 min), suitable enrichment is achieved in the second step (150 bar, 40°C, CO2 + 7% ethanol, 120 min), and this leads to carnosic acid concentrations in the extract as high as 40% of total dry weight, which are among the highest concentrations that have been described with this type of process. The enriched extracts were tested against the HT-29 human adenocarcinoma cell line, showing enhancement of their antiproliferative activity by approximately 3-fold compared to previously reported SFE rosemary extracts and higher inhibitory effects at lower concentrations (30 µg mL−1 of extract). Thus, the proposed two-step SFE process effectively improves the carnosic acid and carnosol recovery in shorter processing times (180 min vs. 300 min). Moreover, the obtained extracts possess higher anti-proliferative activity and consume less solvent.