Sequence Stratigraphy of the Jurassic-Lowermost Cretaceous of East Greenland

Abstract The Jurassic-lowermost Cretaceous succession of East Greenland was deposited in a seaway formed over a series of old extensional basins between Greenland and Norway. The succession is interpreted within a sequence stratigraphic framework with the main emphasis on the Middle and Upper Jurassic. The vertical and lateral dimensions of the stratigraphic units are measured in kilometers and hundreds of kilometers, respectively. The interpretation is comparable to seismic-scale sequence stratigraphy, and the results can be compared directly to those derived from conventional reflection-seismic studies of subsurface successions. Sequence boundaries, and thus sequences, are defined differently by various research groups. In contrast, systems tracts representing linkages of depositional systems are considered the basic building blocks in both genetic and sequence stratigraphy. In the present study, systems tracts are recognized as the unit of highest rank within the concept of sequence stratigraphy. Ten major systems tracts are recognized. A Pliensbachi-an-Toarcian transgressive systems tract consisting of a slightly retrogradational parasequence set is overlain by a thin uppermost Toarcian-Aalenian(?) highstand systems tract (290-420 m in total thickness). The 140-700 m thick upper Bajocian-middle Callovian interval is represented by a basal aggradational to slightly retrogradational parasequence set interpreted as a shelf margin systems tract transitional to a transgressive systems tract. This interval is overlain by a strongly onlap-ping retrogradational set formed under rapid sea level rise and high sediment input, and interpreted as a transgressive systems tract. The upper Callovian-mid-dle Oxfordian forms a composite progradational parasequence set that downlaps onto the top of the transgressive systems tract and represents a highstand systems tract. The transitional strata between the two systems tracts are highly condensed distally and contain the maximum flooding surface. Major regional deepening began in the late Oxfordian, and a thick succession of shales and turbiditic gully sandstones was deposited across the whole region. This succession represents another transgressive systems tract formed during a rapid sea level rise reaching highstand in the early Volgian when a sandy highstand systems tract prograded into the basin. The middle Volgian-Valan-ginian interval was characterized by rotational block faulting in northern East Greenland, in contrast to southern East Greenland, which continued its regular subsidence. A succession of a lowstand or shelf margin systems tract, a transgressive systems tract, and a highstand systems tract is recognized in both regions. This similarity may allow separation of sea level and tectonic signals in the two contemporaneous successions. The sequence stratigraphic analysis forms the basis for a coherent genetic model for the Jurassic-lowermost Cretaceous succession. The model may prove to be of value in interpreting deeply buried correlative hydrocarbon reservoirs in the northern North Sea and the Norwegian shelf.