The upper Bajocian (Middle Jurassic) vegetation and paleoenvironment dynamics in the eastern Binalud mountains (NE Iran)

The lower part of the Dalichai Formation was analyzed to reconstruct the vegetation, paleoenvironment, and paleoclimate dynamics of these deposits in the Binalud Mountains. The shale and marlstone deposits of the studied section contain abundant and diverse terrestrial and marine palynomorphs. The consistent presence of the dinoflagellate cyst genus Cribroperidinium crispum throughout the section and the absence of early Bajocian index taxa support an upper Bajocian age for this interval. Palynofacies indicates a highly proximal to marginal marine depositional setting. The vegetation reconstruction reveals an expanded lowland environment dominated by ferns and Cycadales in the lower part of the section. The overlying interval is characterized by a sea-level rise, which correlates with an increased abundance and diversity of upland SEG conifers and seed ferns. The coastal environment expanded during this phase, leading to the proliferation of coastal SEG such as Cheirolepidiaceae and Araucariaceae, which persisted until the end of the section. The sporomorph assemblages suggest a generally warm and dry climate throughout the studied interval. However, the increase in cool-dependent Araucariaceae toward the uppermost Bajocian is interpreted as evidence of a cooling phase, which aligns with global records of similar climatic shifts during this period.

کلیدواژه ها:

Dalichai Formation ، Northeastern Iran ، Palynofacies ، Palynostratigraphy ، Sporomorph ecogroups