Sequence Stratigraphy and Graben Tectonics: Fennoscandian Border Zone and Central Graben, NW Europe
The Jurassic of NW Europe is a period of active graben tectonics during the break-up of Pangea. The interrelationship between sequence stratigraphy and tectonics is illustrated by two case studies.
The Fennoscandian Border Zone separates the Fennoscandian Shield from the Mesozoic basins. The border zone is characterized by block faulting and graben development. During the Lower-Middle Jurassic two progradational shelf sequences were building out from the shield. The sequences are both characterized by low stand, transgressive and high stand systems tracts. The structural development of the basin floor show that the lower shelf sequence developed in response to inversion tectonics while the upper sequence postdates the graben inversion phase.
In the Central Graben, North Sea, the peak activity took place in the Late Jurassic. The Upper Jurassic can be divided into three units or megasequences: 1) a lower aggradational unit of stacked sequences dominated by transgressive and high stand systems tracts, 2) an intermediate prograding unit composed of stacked sequences building up and out into the basin and 3) an upper unit consisting of sequences dominated by transgressive systems tracts in the lower part turning into aggradational conditions at the top of this unit. Mapping of the megasequence boundaries into the graben border fault reveal that the megasequences correlate with tectonic phases of the graben subsidence.
The described examples show that the tectonic basin subsidence was a major factor in both areas during relative sea-level change and creation of new accommodation space.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California