A facies analysis of Callovian-Oxfordian boundary beds has been carried out on numerous sections across western Europe, with the aim of constructing marine bathymetric curves for each geographic area. Onshore outcrops in northwest and northeast Scotland and borehole cores from the Beatrice Field in the Inner Moray Firth Basin were studied; virtually all the sediments are siliciclastic and often thick. An Early Callovian transgression is recorded from Skye and northeast Scotland, but the influence of local tectonics limits the lateral extent of distinctive lithological units. Within England the Callovian succession differs considerably from that found elsewhere. The most interesting unit is the Upper Callovian Hackness Rock, a condensed bed with chamositic ooids, which is thought to signify deposition at a time of rising relative sea level. The basal Oxfordian contains an organic-rich clay that may reflect a period of maximum flooding associated with anoxic conditions, and the clays above are likely to have been deposited during the ensuing regression. In central and southern England the Callovian-Oxfordian boundary occurs within the Oxford Clay. The change from the Lower to the Middle Oxford Clay (Middle-Upper Callovian boundary) marks a regional shallowing of the sea, signified by higher silt and kaolinite content, while the topmost Callovian, the Lamberti Limestone, is condensed and marks a time of relatively high sea level, with a fall in the proportion of kaolinite. Four regions in France were studied—Normandy, Poitou, Burgundy and Ardèche. The Normandy succession is very similar to that in Dorset, with the stage boundary occurring at the junction of two clay formations. A period of maximum flooding occurred at this boundary, before initial regression in the Early Oxfordian resulted in a renewed terrigenous input. The other regions generally have a very condensed, calcareous Callovian, often with a pelagic character. The condensed, iron ooidal limestones of the Spanish Iberian Chain were deposited in a relatively deep-water offshore setting. The majority of sections record a phase of severe sediment starvation during the latest Callovian and earliest Oxfordian zones, which are likely to reflect a period of maximum flooding. In the Swiss Jura the most significant period of negligible sedimentation rates occurred in the two zones across the stage boundary. Clear deepening or shallowing trends cannot readily be recognised in the offshore succession of the Swabian Alb. The comparison of a series of bathymetric curves has led to the recognition of regional sea-level events in western Europe during the Callovian-Early Oxfordian interval. A regional sea-level rise occurred during the Middle and Late Callovian, reaching its greatest extent in the latest Callovian (lamberti Zone) and highstand conditions and incipient sea-level fall characterised the Early Oxfordian. A literature review of boundary beds in seven further regions from five continents has shown that a Middle Callovian sea-level rise and late Callovian-Early Oxfordian phase of high sea level can be recognised on a global scale. The European regional sea-level changes are therefore considered to be eustatic in origin, and probably related to sea-floor spreading in the Atlantic. A eustatic curve has been constructed and compared with two other such curves. It differs from that of Hallam, also based on the facies analysis technique, but is quite similar to that of Exxon workers, based on sequence stratigraphic concepts.

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   |wiki=    Wicri/Terre
   |area=    NickelMaghrebV1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     ISTEX:D29585F6E046AA5477A8EDC23EF5CB4568C989D1
   |texte=   Facies variations across the Middle-Upper Jurassic boundary in Western Europe and the relationship to sea-level changes
}}