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This study presents subdaily resolved chemical records through fossil mollusk shell calcite. Trace element profiles resolve periodic variability across similar to 40-mu m-thin daily growth laminae in a Campanian Torreites sanchezi rudist bivalve. These high-resolution records are combined with seasonally resolved stable isotope and trace element records that allow shell-chemical variability to be discussed on both seasonal and daily scale. A combination of layer counting, spectral analysis of chemical cyclicity and chemical layer counting shows that the rudist precipitated 372 daily laminae per year, demonstrating that length of day has increased since the Late Cretaceous, as predicted by astronomical models. This new approach to determine the length of a solar day in geologic history through multiproxy chemical records at subdaily resolution yields considerably more control on the uncertainty of this estimate. Daily chemical variability exceeds seasonal variability in our records, and cannot be explained by diurnal temperature changes. Instead, we postulate that rudist shell chemistry is driven on a daily scale by changes in light intensity. These results together with those of stable isotope analyses provide strong evidence that Torreites rudists had photosymbionts. Bivalve shell calcite generally preserves well. Therefore, this study paves the way for daily-scale reconstructions of paleoenvironment and sunlight intensity on geologic time scales from bivalve shells, potentially allowing researchers to bridge the gap between climate and weather reconstructions. Such reconstructions improve shell chronologies, document environmental change in warm ecosystems, and widen our understanding of the magnitude of short-term changes during greenhouse climates.

Consumers' interest in organic foods is increasing and so is the need for robust analytical tools for their authentication. This review focuses on the most promising biomarkers/analytical approaches that are available for the authentication of organic produce. Food products have been subdivided into two groups: foods of plant origin (crops) and foods of animal origin (meat, milk and dairy products, eggs and fish). For each food category the most suitable biomarkers are presented and their potential for authentication is discussed. In the light of current knowledge, it is unlikely that the authentication of organic food products can be attained by the measurement of a single marker. Analytical approaches based on the measurement of multiple markers and/or complex chemical or physical profiles/fingerprints supported by multivariate statistical analysis seem considerably more promising in this respect. For the development of robust classification models, well-designed experimental studies must be performed that rely on data sets that are both well balanced and of sufficient size to ensure that all relevant sources of variation for the target biomarkers are included in the reference database. © 2012 Society of Chemical Industry.

Consumers' interest in organic foods is increasing and so is the need for robust analytical tools for their authentication. This review focuses on the most promising biomarkers/analytical approaches that are available for the authentication of organic produce. Food products have been subdivided into two groups: foods of plant origin (crops) and foods of animal origin (meat, milk and dairy products, eggs and fish). For each food category the most suitable biomarkers are presented and their potential for authentication is discussed. In the light of current knowledge, it is unlikely that the authentication of organic food products can be attained by the measurement of a single marker. Analytical approaches based on the measurement of multiple markers and/or complex chemical or physical profiles/fingerprints supported by multivariate statistical analysis seem considerably more promising in this respect. For the development of robust classification models, well-designed experimental studies must be performed that rely on data sets that are both well balanced and of sufficient size to ensure that all relevant sources of variation for the target biomarkers are included in the reference database. © 2012 Society of Chemical Industry.