ABSTRACT: An integrated, high sample-density biostratigraphic study of the Middle to Upper Jurassic Marrat, Dhruma, Sargelu, Najmah and Jubaila formations of Kuwait was completed on approximately 1600 core samples for palynology, calcareous nannofossils, and foraminifera (thin sections) in twenty wells. Five established Tethyan nannofossil zones are integrated with six recently recognized microfossil zones and two palynological zones, enabling chronostratigraphic correlations within Kuwait and to the equivalent units of Eastern Saudi Arabia. Paleoenvironmental and paleogeographic interpretation is carried out giving some insights to the timing of activation of the Rimthan Arch and formation of the Gotnia Basin, from the Bajocian to Kimmeridgian. The Dhruma Formation is assigned an early to late Bajocian age, nannofossil zone NJT 10 (upper part subzone NJT 10a) based on the co-occurrence of C. superbus and W. manivitae. The Sargelu-Dhruma Transition is of late Bajocian to early Bathonian age (NJT 10b nannofossil subzone to NJT 11 Zone) on the basis of the LO of C. magharensis and FO of W. barnesiae. Conoglobuligerina dagestanica defines the Bathonian upper boundary within the overlying Sargelu Limestone, which also shows G. calloviensis, suggesting an early Callovian age. This unit shows an increase in microfossils and the absence of nannofossils which enables the designation of the G. calloviensis / G. bathoniana planktic foraminifer zone. The overlying Najmah Formation is subdivided into the Najmah-Sargelu transition, the Lower Najmah and Upper Najmah members, of Callovian to Oxfordian age, with planktonic foraminiferal bioevents such as the LO of G. calloviensis, G. bathoniana, and G. oxfordiana. A sparse calcareous nannofossil assemblage which includes A. helvetica and C. deflandrei suggests the Callovian to Oxfordian NJT 11 to NJT 13 Zones for this formation. The topmost Upper Najmah Shale is dated as Kimmeridgian on the basis of the FO of the dinoflagellate Circulodinium spp. with the overlying peloid-skeletal wackstone and microbial-ooid-skeletal, grain-dominated packstones Najmah Limestone mainly characterized by benthic foraminifera assemblages. This unit unconformably underlies the laminated, organic-rich calcareous shales of the Kimmeridgian Jubaila Formation. The succession exhibits marine paleoenvironments ranging from inner to middle neritic for the Dhruma Formation and Sargelu-Dhruma Transition, middle to outer neritic for the Sargelu Limestone and Lower Najmah Shale, with predominantly outer neritic conditions for the Upper Najmah Shale. Shallower transitional to inner neritic has been interpreted for the Najmah Limestone whereas the Jubaila Formation was deposited in deeper middle to outer neritic conditions. The onset of tectonic activity that formed the Gotnia Basin started during the deposition of the Dhruma Formation, with down-faulting prevailing along the north edge of the Rimthan Arch. Accommodation space was never filled, up to the deposition of the Gotnia Formation.