Thalassinoides Ichnofabric Architecture as Complementary Evidence for Sequence‐Stratigraphic Interpretation in Carbonate Ramp Systems: Insights From the Mississippian Mobarak Formation (Alborz, Iran)

ABSTRACT This study integrates ichnological, sedimentological, and sequence‐stratigraphic observations to investigate depositional and substrate changes within the Mississippian Mobarak Formation carbonate ramp in the Alborz Basin, Iran. Four stratigraphic sections were examined, and seven facies associations were recognised, documenting spatial and stratigraphic variations across the ramp. Five recurring ichnofabric associations, Thalassinoides – Planolites – Ophiomorpha , Thalassinoides – Phycodes – Chondrites , Thalassinoides – Sinusichnus , Thalassinoides – Rhizocorallium , and Thalassinoides ‐dominated firmground assemblages, record variations in substrate consistency, colonisation history, depositional energy, sedimentation, and benthic conditions. Thalassinoides ‐rich associations commonly occur in bioclastic and open‐marine deposits, whereas lower‐bioturbation assemblages containing deeper‐tier Chondrites and Zoophycos occur in finer‐grained intervals. Firmground Thalassinoides assemblages locally coincide with erosional contacts, shell‐rich lags, and condensed intervals, providing ichnological evidence for substrate stabilisation and omission. Integration of these ichnofabric patterns with facies stacking, sedimentary structures, and stratigraphic contacts provides additional evidence for identifying and correlating stratigraphic discontinuities within five depositional sequences. The results indicate that ichnofabric architecture can provide complementary evidence for sequence‐stratigraphic interpretation by constraining substrate evolution, colonisation history, and intervals of reduced net sediment accumulation. However, ichnofabrics are not considered uniquely diagnostic or direct proxies for relative sea‐level change; their stratigraphic significance is strongest when integrated with independent sedimentological and stratal criteria. This integrated approach provides a framework for evaluating the sequence‐stratigraphic significance of ichnofabrics in carbonate‐ramp successions while emphasising the need for integration with independent sedimentological and stratal criteria.