STRATIGRAPHY AND PALEOGEOGRAPHY OF THE HAUPTROGENSTEIN AND KLINGNAU FORMATIONS (MIDDLE BAJOCIAN TO LATE BATHONIAN), NORTHERN SWITZERLAND

The middle Bajocian to middle Bathonian epicontinental sediments of no rthern Switzerland consist of shallow-marine oolitic carbonates (Haupt rogenstein Formation, Celtic realm) and marly basinal deposits (Klingn au Formation, Swabian realm). Detailed biostratigraphic data based on ammonites and dinoflagellates provide a time frame for a sedimentologi c analysis. The carbonate series of the Celtic realm is composed of th ree shallowing-upward successions, each capped by a hardground. In the basinal domain east of the Aare River, marls persist in a monotonous facies throughout the same lime period. The first shallowing-upward su ccession within the Hauptogenstein Formation, started during the Blagd eni Subzone with marry beds and intercalated tempestites (Rothenfluh B eds), covered in the western Jura by fine-grained, bioclastic tempesti tes (Grenchenberg Beds). Simultaneously, the Gislifluh Reef developed in the southeastern Jura, probably on a morphologic high. Oolitic sedi mentation started in the central Jura during the Niortense/Subfurcatum Zone (Lower Oolitic Series). The units of 0.5-2 m thick, cross-bedded oolites are attributed to a tidal, shallow-marine, high-energy settin g. At the same time, the oolitic beds in the eastern Jura contain up t o 35% of mud, and a low-energy setting is inferred (Lower Acuminata Be ds). During the Garantiana Zone oolite-belts prograded eastwards reach ing the area of the Aare River. An up to 70 m thick oolitic succession was deposited during a period of moderate sea-level rise and a steady subsidence. The second shallowing-upward succession started in the ea rly Parkinsoni Zone. The production of ooids ceased during a sea-level highstand and marls and bioclastic limestones accumulated in northern Switzerland: the Homomya Marls in the western and the Upper Acuminata Beds in the central and eastern Jura. Later, a drop in relative sea-l evel during the late Parkinsoni Zone re-established ooid production (U pper Oolitic Series). The third shallowing-upward succession started d uring the latest Bajocian and earliest Bathonian (Zigzag Zone). Marry sediments rich in coarse bioclasts (Movelier Beds) are again interpret ed as formed during a relative sea-level highstand. They are overlain by micritic oncolites in the western Jura; to the east, sparry bioclas tic, locally cross-bedded limestones occur (''Spatkalk''), probably de posited by storms and tides. The deposition of the ''Spatkalk'' lasted until early Middle Bathonian, prograding eastward and covering the to p of the basinal KLingnau Formation. The facies belts within the Haupt rogenstein and Klingnau Formations suggest the evolution of a middle J urassic, north-south trending oolitic barrier dominated by tides. Back barrier facies belts formed to the west and off-barrier assemblages to the east of this barrier. A decrease in the production of sediments, as evidenced by platformwide facies changes and in the thickness of sh allowing-upward successions, was probably caused by changes in water c irculation and local climate. On the other hand, more or less abrupt l ateral changes in thickness and facies within the successions suggest local and regional patterns of differential subsidence.