EVALUATING DIFFERENT METHODOLOGIES FOR SURFACTANT-BASED SHALE DISAGGREGATION FOR MICROFOSSIL RECOVERY: TOWARDS A STREAMLINED APPROACH

Surfactant-based methods for disaggregating shales have long been recognized as a potentially powerful tool for extracting calcareous and phosphatic microfossils from fine grained siliciclastic rocks. However, the literature on surfactant-based disaggregation includes significant variation in terms of the details of how the method is implemented. These differences include important details such as boiling versus non-boiling, duration of boiling, and procedures for sample pretreatment such as soaking in bleach. The relative efficacies of these different methodological variations have not previously been compared with one another, nor have their relative strengths in the face of different lithologies been evaluated. Further complicating this methodological variation are the facts that publications have varied in terms of how they define successful disaggregation and that much of the methodological literature focuses on Quaternary O, a commercial surfactant that is no longer produced. As part of developing a streamlined and updated procedure for surfactant-based disaggregation I subjected a suite of shales that vary in terms of age, mineralogy, and TOC to different surfactant-based disaggregation methodologies taken from the literature using the surfactant benzalkonium chloride. The results of the disaggregation treatments were then compared with the results achieved by submitting the same set of rocks to soaking in kerosene, the main alternative method of shale disaggregation. The results demonstrate that surfactant-based disaggregation using benzalkonium chloride can be used to disaggregate shales from low to high TOC, albeit with modified methodologies, a result that has previously been reported with Quaternary O.