Palynofacies analysis: a review of principles, applications and future directions

Palynofacies analysis examines acid-resistant organic matter (phytoclasts, amorphous organic matter (AOM), and palynomorphs) from sedimentary rocks to interpret depositional environments, organic matter provenance, thermal maturity, and hydrocarbon potential. This review synthesizes the application of palynofacies in three core domains: source rock evaluation, paleoenvironmental reconstruction, and sequence stratigraphy. In source rock evaluation, palynofacies complements Rock-Eval pyrolysis, offering a particular advantage where vitrinite is absent. In paleoenvironmental reconstruction, different organic matter components serve as sensitive indicators of depositional conditions, including redox status, water depth, hydrodynamic energy, transport distance, and marine versus terrestrial influence. In sequence stratigraphy, palynofacies parameters help identify systems tracts and maximum flooding surfaces, especially in marginal-marine and non-marine settings lacking traditional marine indicators. This review also clarifies fundamental differences between palynofacies and coal petrological classifications, cautioning against uncritical use of terminology from other disciplines. Through case studies, the versatility and limitations of palynofacies analysis are demonstrated. Future directions include standardized classification, artificial intelligence (AI)-assisted identification, application to unconventional reservoirs, and integration with stable isotopes and event stratigraphy.