belemnite biostratigraphy of the upper jurassic to lower cretaceous strata in the surghar range, nw pakistan: systematic and paleobiogeographic implications

Four belemnite genera and twelve age-diagnostic species were identified from the from upper jurassic–lower cretaceous sequence of the chichali formation, northwest pakistan. four local biozones were established based on the identified belemnites. these biozones are arranged from base to top as follows; hibolithes pilleti/hibolithes jaculoides/hibolithes hastatus zone of kimmeridgian age, hibolithes marwicki marwicki/hibolithes arkelli zone of tithonian age, belemnopsis malucana zone defines tithonian–berriasian boundary, and neohibolites ewaldi/hibolithes longior/belemnopsis jonkeri zone of velanginian age. the biostratigraphic and paleogeographic occurrences of belemnites in the tethyan and boreal realms were used to identify the migration pathways and distinctive paleobiogeographic provinces of belemnites. the paleoceanic settings closely linked the upper jurassic strata (~biozones 1–2, representing the kimmeridgian–tithonian range) in the tethyan and the boreal realms. the lower cretaceous (~biozone 3, representing the berriasian) strata also reveal a persistent oceanic connection between the indo-pacific and mediterranean provinces. however, the boreal and tethyan realms were also connected in the lower cretaceous (~biozone 4, representing the velanginian strata) by shallow-water routes.