What is the fine-grained topic of the following text: retrieved two sediment cores from the deepest part of the lake in June of 2007 that they analyzed via what they describe as "a novel methodological approach that combines microfacies analyses, high-resolution element scanning (µ-XRF), stable isotope data from bulk carbonate samples (δ13Ccarb, δ18Ocarb), and X-ray diffraction (XRD) analyses (Brauer et al., 2009)." Only return the topic.
Analysis of lake sediment cores using various scientific methods