WHO DISSOLVES, WHO DIES, WHO TELLS YOUR STORY: DISENTANGLING SELECTIVE BIASES IN EXTRACTION METHODS FOR CAMBRIAN SMALL SHELLY FAUNAS

The study of small shelly fauna often requires destructive chemical extraction methods. Acid maceration is one such method, traditionally used to extract microfossils from host matrix, particularly those with insoluble hard parts or secondary replacement. However, this method also removes calcareous components, potentially introducing bias into the faunal assemblage recovered via acid residue. Quantifying that bias is therefore key to refining the accuracy of paleoecological interpretations. In this study, we examined eleven samples from a stratigraphic section in the Mernmerna Formation (Cambrian Series 2, Stage 3) in the Ikara-Flinders Ranges, South Australia. We employed petrographic thin sections in conjunction with acid-extracted components to analyze the small shelly fauna present before and after acid maceration. Using a combination of point counting, manual segmentation, particle analysis, and EDS analysis, small shelly fauna were differentiated by higher order taxonomic affinity and mineralogic composition, then compared to the abundance of taxa recovered from acid residue. By comparing the populations of taxa obtained from these different methods, we will bring to light the extent to which these extraction methods influence our perception of early biomineralized microfossil assemblages. This analysis will shed light on the biases inherent in extraction techniques and inform future paleoecological and biostratigraphic investigations. This approach can be extended to other geological settings, offering insights into methodological appropriateness across diverse faces and faunal assemblages.