NEW SMEAR-SLIDE REFERENCE TOOL FOR FINE-GRAINED SEDIMENT DESCRIPTION

The smear-slide technique is critical to microscopic characterization of unlithified fine-grained sediments and the determination of lithologic names both in the laboratory and the classroom. Mastery of the technique requires that sedimentologists have training in optical mineralogy, sedimentary petrography, and micropaleontology sufficient to identify individual sediment components. Unfortunately, microscopy training in many academic programs is on the decline or has been dropped from the curriculum entirely. We have created a self-instructive module on smear-slide preparation, description, and interpretation for use by sedimentologists. Through funding by IODP-MI we have completed a first phase concentrating on siliciclastic and volcaniclastic components, and with additional funding from the Consortium for Ocean Leadership, are now creating a second phase concentrating on biogenic and other authigenic components. These modules are in the form of layered, interactive PDF files constructed with Adobe InDesign. Text includes rationale for where and when to do a smear slide in core description; techniques for how to make a smear slide; description of and data collection for smear slides, including strategies for estimating percentages; and basic caveats of smear vs. thin-section description of components. The atlas of high-resolution images of mainly mud fractions from Ocean Drilling Program core samples is searchable and includes multiple examples of smear slides of individual siliciclastic, volcaniclastic, and biogenic components as well as mixtures of these components. Images in plane-light and crossed-polar views have scale grids and detailed figure captions; they are organized and grouped with thumbnail summaries and hyperlinked for flexible browsing.