Mixed carbonate–siliciclastic tidal sedimentation in the Miocene to Pliocene Bouse Formation, palaeo‐Gulf of California

Mixed carbonate–siliciclastic deposits provide unique insights into hydrodynamic processes that control sedimentation in tidal systems. This study presents sedimentological and ichnological data from the upper Miocene to lower Pliocene Bouse Formation, which accumulated during regional transgression at margin of a strait near north end ancestral Gulf California. The basal carbonate member Formation records deposition tide-influenced, compositionally mixed system dominated by salt marsh, flat channel environments. is an overall deepening up succession facies associations comprising: Facies Association 1 – siliciclastic-rich heterolithic facies, lime mudstone with desiccation cracks, plant debris rich silt interpreted as flats; 2 well-sorted gravels, sandy strata, microbial micrite tidal-channel deposits; 3 carbonate-rich well-sorted, cross-bedded bioclastic grainstone intertidal shallow subtidal 4 deep low-energy record conditions basin. Trace fossils include marine forms Gyrolithes, Teichichnus Thalassinoides, non-diagnostic Arenicolites, Cochlichnus, Conichnus, Lockeia, Planolites, Skolithos Treptichnus (known marine, brackish freshwater environments). diminutive size trace reflects created mixing seawater. provides evidence for late early humid climate south-western North America, stark contrast modern hyperarid climate. Factors controlled relative percentage siliciclastic sediment input local rivers, situ production, current energy, degree sea level. Pronounced variability bedform, outcrop basin scale documented this appears be important characteristic depositional