Sequence stratigraphic interpretation of paralic successions is complicated by the complex interfingering of marine and continental strata. The successions may also include terrestrial extensions of marine parasequences and completely independent lacustrine parasequence analogues. Failure in recognizing the possible interbeddding of these two independent parasequence types may lead to construction of sequence stratigraphic schemes based on incompatible data sets. We have studied a Lower Jurassic paralic section from the Baltic island of Bornholm, situated in the Tornquist Zone, which demarcates the transition from the stable Precambrian Baltic Shield to the subsiding Danish Basin and Danish‐Polish Trough. The Hettangian‐Sinemurian Sose Bugt Member (Rønne Formation) of Bornholm includes lacustrine, fluvial and restricted marine, estuarine deposits reflecting the basin‐margin position. Biostatigraphic resolution is poor and a sequence stratigraphic interpretation of the paralic succession is far from straightforward. A multidisciplinary approach including facies analysis, recognition and lateral trading of key surfaces, palynostratigraphy, palynofacies, coal petrography, palaeopedology, clay mineralogy and source rock geochemistry is applied in order to obtain a high degree of precision in the interpretation of the paralic facies. In this way four sequences are recognized in the overall backstepping lacustrine to estuarine succession. Marine and marginal marine parasequences are distinguished from their purely lacustrine analogues, and an internally consistent sequence stratigraphic scheme is proposed. This is compared and tentatively correlated with fossiliferous marine sediments in the Danish Basin and with published eustatic cycle charts.

Structure and lithology of the infill sediments from 16 subglacial buried tunnel valleys of Pleistocene age in the North Sea were analyzed using 3D seismic data and geophysical log data from five hydrocarbon exploration wells. The infill sediments are characterized by three seismic facies: Facies I, the volumetrically most important and structurally most distinct, is composed of clinoform reflections downlapping axially up-valley (up-ice), Facies II is composed of near-horizontal, continuous and well layered reflections onlapping the clinoform reflections and the valley walls and Facies III is composed of clinoform reflections downlapping axially down-valley (down-ice). A model of formation of this sediment architecture is proposed, in which valley incision and infill are causally linked. It is proposed thatFacies I is related to glaciohydraulic supercooling of subglacial meltwater in the distal parts of tunnel valleys. The valleys formed time-transgressively during ice retreat, whereby sediment eroded further up-ice was re-deposited along adverse subglacial slopes of the valleys close to the ice margin. The formation of Facies II and III is related to the deposition in proglacial basins during final deglaciation. Figure 2. (A) TWT-structure map of the 16 buried valleys displayed without infill sediments. The depth scale in TWT is in ms b.s.l. (B) Perspective view of (A) projected onto a horizon map of the Near Base Quaternary (NBQ) surface. The seafloor is at 80 ms TWT (60 m b.s.l.). Modified from the work of Kristensen et al. (2007).Figure 3. Seismic time slice at 340 s TWT (290 m b.s.l.) illustrating the structure of the clinoform reflections inside the southern end of Tunnel Valley V02. The reflections extend across the full width of the valley.Figure 6. Six vertical seismic profiles along the valley axes and TWT-structure maps of the valleys. Seismic infill facies is marked. From crosscutting pattern between the valleys, shown in Figure 2, it can be seen how the valleys in this figure represent several different episodes of valley generation. This figure is available in colour online at www.interscience.wiley.com/journal/espl T. B. Kristensen et al.Figure 8. Two vertical seismic profiles between wells (A) Siri-5, Siri-3 and Sandra-1 and (B) Sandra-1, Sofie-1 and Nolde-1. The positions of profiles are given in Figure 2.The difference between the seismic infill facies in Valleys V01 and V02 correlates very clearly with the lithology logs from the two valleys ( Figure 8). Furthermore, the infill stratigraphy from lithology logs in the two valleys does not correlate with that of the surrounding strata, but the overall lithology of the infill from Valley V02 is quite similar to that of the uppermost 300 m in the reference well. Interpretation: Infill ProcessesThe variation in lithology and seismic structure of the three seismic infill facies found in the buried valleys indicates that they represent different depositional processes. The recognition of clinoform reflections dipping axially up-valley Time-transgress...

The PaleoceneSiriCanyon extendsfor morethan120 kmfrom the StavangerPlatform to the TailEnd Grabenalongthe Danish-NorwegianNorthSea boundary.Initialformation ofthe canyon systemtookplace in the Early Paleocene(Danian) andwasrelated to major,submarineslidinginthe uppermostchalksection caused byupliftofthe Scandinavianhinterlands. The trendofthe canyon partly follows salt structuresalongthe southern edge ofthe Norwegian-DanishBasin(part ofthe Northern ZechsteinBasin). The canyon fill consists ofdeepmarine, highly glauconitic sandstonesinterbeddedwithhemipelagic andturbiditemarls andmudstones. Asfor many Paleocened eep-marinesandstonesint he NorthS ea, the sandstoneso fthe SiriC anyon aremassivea nd blocky. Frequent occurrence ofi njected sandstonesills/dykes,i njection breccias,a sw ell aserosion and associated rip-down clasts alongthe upperboundariesof insitu sandstones,indicatethorough, post-depositional modification.Fluidization is,thus,likely to be the mainreason for the generalscarcity ofprimary sedimentary structuresandmassiveappearance ofthe sandstones. All sandstonesarebasically free ofdetritalclays andmost likely formed from non-cohesive, concentrated density flows probably developed asturbidity currents. The sand flows werec onfined byt he canyon andthe depositionalp attern indicatesac omplexinteraction ofturbidity currents,salt-induced seafloor topographyandd ifferentialcompaction. Releaseofsandyflows wasp robably caused byseismic shocksresultinginacollapseofunstableshelfsandsconcentrated on the StavangerPlatform. Transport distanceso fthe sandsw ereup to 120 kmandtherebycontrast withmany Paleocenesubmarine sandstonesint he NorthS ea.The deep-marineplayint he SiriC anyon relieso nl ongd istance migration of hydrocarbons,up to 75kmfrom matureJurassic source rocksinthe CentralGraben. Thiswasfacilitated bythe elongateandconfined geometry ofthe sandstonesformingawell-connected systemfor updipmigration.

As a result of a lithological, sedimentological and biostratigraphic study of well sections from the Danish sector of the North Sea, including some recently drilled exploration wells on the Ringkøbing–Fyn High, the lithostratigraphic framework for the siliciclastic Palaeogene to Lower Neogene sediments of the Danish sector of the North Sea is revised. The sediment package from the top of the Chalk Group to the base of the Nordland Group is subdivided into seven formations containing eleven new members. The existing Våle, Lista, Sele, Fur, Balder, Horda and Lark Formations of previously published lithostratigraphic schemes are adequate for a subdivision of the Danish sector at formation level. Bor is a new sandstone member of the Våle Formation. The Lista Formation is subdivided into three new mudstone members: Vile, Ve and Bue, and three new sandstone members: Tyr, Idun and Rind. Kolga is a new sandstone member of the Sele Formation. Hefring is a new sandstone member of the Horda Formation. Freja and Dufa are two new sandstone members of the Lark Formation. Danish reference sections are established for the formations, and the descriptions of their lithology, biostratigraphy, age and palaeoenvironmental setting are updated.

Intense drilling activity following the discovery of the Siri Field in 1995 has resulted in an improved understanding of the siliciclastic Palaeogene succession in the Danish North Sea sector (Fig. 1). Many of the new wells were drilled in the search for oil reservoirs in sand bodies of Paleocene–Eocene age. The existing lithostratigraphy was based on data from a generation of wells that were drilled with deeper stratigraphic targets, with little or no interest in the overlying Palaeogene sediments, and thus did not adequately consider the significance of the Palaeogene sandstone units in the Danish sector. In order to improve the understanding of the distribution, morphology and age of the Palaeogene sediments, in particular the economically important sandstone bodies, a detailed study of this succession in the Danish North Sea has recently been undertaken. An important aim of the project was to update the lithostratigraphic framework on the basis of the new data.The project was carried out at the Geological Survey of Denmark and Greenland (GEUS) with participants from the University of Aarhus, DONG E&P and Statoil Norway, and was supported by the Danish Energy Agency. Most scientific results cannot be released until September 2006, but a revised lithostratigraphic scheme may be published prior to that date. Formal definition of new units and revision of the lithostratigraphy are in preparation. All of the widespread Palaeogene mudstone units in the North Sea have previously been formally established in Norwegian or British wells, and no reference sections exist in the Danish sector. As the lithology of a stratigraphic unit may vary slightly from one area to another, Danish reference wells have been identified during the present project, and the lithological descriptions of the formations have been expanded to include the appearance of the units in the Danish sector. Many of the sandstone bodies recently discovered in the Danish sector have a limited spatial distribution and were sourced from other areas than their contemporaneous counterparts in the Norwegian and British sectors. These sandstone bodies are therefore defined as new lithostratigraphic units in the Danish sector, and are assigned Danish type and reference sections. There is a high degree of lithological similarity between the Palaeogene–Neogene mudstone succession from Danish offshore boreholes and that from onshore exposures and boreholes, and some of the mudstone units indeed seem identical. However, in order to acknowledge the traditional distinction between offshore and onshore stratigraphic nomenclature, the two sets of nomenclature are kept separate herein. In recent years oil companies operating in the North Sea have developed various in-house lithostratigraphic charts for the Paleocene–Eocene sand and mudstone successions in the Danish and Norwegian sectors. A number of informal lithostratigraphic units have been adopted and widely used. In the present project, these units have been formally defined and described, maintaining their original names whenever feasible, with the aim of providing an unequivocal nomenclature for the Palaeogene – lower Neogene succession in the Danish sector. It has not been the intention to establish a sequence stratigraphic model for this succession in the North Sea; the reader is referred to the comprehensive works of Michelsen (1993), Neal et al. (1994), Mudge & Bujak (1994, 1996a, b), Michelsen et al. (1995, 1998), Danielsen et al. (1997) and Rasmussen (2004).