Abstract
The Jurassic succession of Denmark is largely confined to the subsurface with the exception of exposures on the island of Bornholm in the Baltic Sea. In East Greenland, in contrast, the Jurassic is extensively exposed. Comparison of basin evolution in the two regions, which now occur on two separate plates, thus relies on highly different datasets. It is possible nevertheless to construct an integrated picture allowing testing of hypotheses concerning basin evolution, regional uplift, onset and climax of rifting, relative versus eustatic sea-level changes and sequence stratigraphic subdivision and correlation. On a smaller scale, it is possible to compare the signatures of sequence stratigraphic surfaces as seen on well logs, in cores and at outcrop and of sequences recognised and defined on the basis of very different data types. Breakdown of the successions into tectonostratigraphic megasequences highlights the high degree of similarity in overall basin evolution and tectonic style. An important difference, however, lies in the timing. Major events such as late Early – Middle Jurassic uplift, followed by onset of rifting, basin reorganisation and rift climax were delayed in East Greenland relative to the Danish region. This has important implications both for regional reconstructions of the rift system and for the understanding and testing of classical sequence stratigraphic concepts involving eustatic versus tectonic controls of basin evolution and stratigraphy.
Highlights
The Jurassic succession of Denmark is largely confined to the subsurface with the exception of exposures on the island of Bornholm in the Baltic Sea
Exceptions to this include the island of Bornholm in the Baltic Sea and adjacent areas of Skåne, southern Sweden, where the Jurassic is exposed in many small outcrops
The basins of East Greenland and Denmark represent important pieces in this jigsaw puzzle and the studies reported in the following papers will help to further constrain regional models of rift development, and to better understand Jurassic stratigraphic development in general
Summary
From large parts of the area, the Central Graben, due to erosion following early Middle Jurassic uplift (e.g. Ziegler 1990; Underhill & Partington 1994; Andsbjerg et al 2001; Andsbjerg & Dybkjær 2003, this volume; Nielsen 2003, this volume). A comparable phase of basin restriction in East Greenland, albeit somewhat later (latest Toarcian – Aalenian), appears to be indicated by evidence of brackish water conditions in the lower part of the offshore marine Sortehat Formation (Dam & Surlyk 1998; Koppelhus & Hansen 2003, this volume) This event may be attributable to progressive tectonic isolation of the Jameson Land Basin due to regional uplift farther north. The uplift and especially the onset of rifting and the associated radical basin reorganisation appear to have occurred earlier in the Danish region than in East Greenland, the main onlap phase onto the regional unconformity was broadly coeval, from the Late Bajocian to the Early Oxfordian (Underhill & Partington 1993, 1994; Andsbjerg et al 2001; Andsbjerg & Dybkjær 2003, this volume; Nielsen 2003, this volume; Surlyk 2003, this volume). Rifting was not continuous but comprised phases of more intense rifting and block rotation
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