Evaluating Algorithmic Approaches to Paleoenvironmental Interpretation in the Eocene of Kutch Basin, India

The Eocene of the Kutch Basin in western India comprises a highly fossiliferous rock sequence represented by three formations—Naredi, Harudi, and Fulra—arranged in stratigraphic succession. These formations record a transition from lagoonal to open marine depositional environments. This study integrates sedimentological, taphonomic, and palaeontological data with objective algorithmic tools to reconstruct the paleoenvironmental settings of 18 fossiliferous lithotypes identified through detailed fieldwork, petrography, and fossil assemblage analysis. A dataset of 23 binary and multistate litho-taphonomic, taxonomic, and geochemical characters was compiled into a comprehensive data matrix. Principal Coordinates Analysis (PCoA), performed using PAST 4.03, revealed two major environmental clusters—one representing restricted marginal marine and bar/shoal settings and the other associated with inner-to-outer carbonate ramp environments. To minimize interpretive bias, a tree analysis (using methods of cladistics) was conducted using TNT, with a coquina storm bed from the Harudi Formation as the outgroup. This approach successfully delineated environments such as lagoon, shoal/bar, inner ramp, and middle-to-outer ramp with a high Retention Index (0.714), supported by bootstrap values. However, given the ecological nature of the dataset, UPGMA cluster analysis using Hamming distance matrix was also performed in PAST 4.03, which proved to be the most appropriate method for this study, as it groups samples based on overall environmental similarity rather than evolutionary relationships. This analysis distinctly identified storm beds, lagoonal units, bars/shoals, and ramp environments, closely aligning with both field observations and previous sedimentological interpretations. The combined use of PCoA, tree analysis, and cluster analysis demonstrates the efficacy of objective, data-driven approaches in refining paleoenvironmental interpretations, offering a replicable model for analyzing fossiliferous strata in other sedimentary basins worldwide.