Netherlands Journal of Geosciences — Geologie en Mijnbouw | 85 – 4 | 245 - 276 | 2006 Subsurface structure of the Netherlands – results of recent onshore and offshore mapping E.J.T. Duin, J.C. Doornenbal, R.H.B. Rijkers*, J.W. Verbeek & Th.E. Wong TNO Built Environment and Geosciences – Geological Survey of the Netherlands, P.O. Box 80015, 3508 TA Utrecht, the Netherlands. * Corresponding author. Email: [email protected] Manuscript received: September 2006; accepted November 2006 Abstract This paper presents depth maps for eight key horizons and seven thickness maps covering the onshore and offshore areas for the Late Permian to recent sedimentary section of the Netherlands. These maps, prepared in the context of a TNO regional mapping project, are supported by nine regional structural cross sections and a table summarizing the timing of tectonic activity from Carboniferous to recent. These new regional maps enable the delineation of various structural elements but also reveal the development of these elements through time with improved detail. Since the latest Carboniferous the tectonic setting of the Netherlands changed repeatedly. During successive tectonic phases several pre-existing structural elements were reactivated and new elements appeared. The various identified regional structural elements are grouped into six tectonically active periods: Late Carboniferous, Permian, Triassic, Late Jurassic, Late Cretaceous and Cenozoic. This study demonstrates that many structural elements and fault systems were repeatedly reactivated and that a clear distinction exists between long-lived elements, such as the Roer Valley Graben, and short-lived structural elements, such as the Terschelling Basin. Keywords: geological maps, structural elements, Permian, Triassic, Jurassic, Cretaceous, Cenozoic, Netherlands Introduction Depth and thickness maps have been created for the Zechstein Group (Late Permian), the Lower and Upper Germanic This paper presents the results of a regional geological Trias groups, the Altena Group (Early and Middle Jurassic), the mapping project of the Dutch onshore and offshore subsurface Schieland-Scruff-Niedersachsen groups (Late Jurassic), the at a scale of 1 : 2,500,000 that was carried out by TNO at the Rijnland Group (Early Cretaceous), the Chalk Group (Late request of the Ministry of Economical Affairs with the Cretaceous), the Lower and Middle North Sea groups (Paleogene) following objectives: and the Upper North Sea Group (Neogene) (Fig. 1). These maps – to promote exploration efforts in the Netherlands; provide an overview of the geological development of the deep – to obtain a regional framework for a detailed geological subsurface of the Netherlands since the Carboniferous. In this mapping program 2006 - 2010; paper the presented maps are discussed in two paragraphs for – to enhance research for the use of the subsurface for CO2 each lithostratigraphic group by describing (a) depth, thickness storage and geothermal energy production. and basin development and (b) structural development (faults, erosion and salt movements). The onshore part of the maps presented, was recently Figure 1 shows the geological time scale of Gradstein et al. published in the Geological Atlas of the Subsurface of the (2004) together with the mapped lithostratigraphic intervals Netherlands – onshore (TNO-NITG, 2004), while the offshore that are discussed in this paper. For detailed information on part is being published for the first time. In this paper we the lithostratigraphy of the mapped intervals and a discussion present these new integrated maps and cross sections and on regional structural elements readers are referred to earlier briefly discuss the main regional structural elements. publications by TNO-NITG (2004) and Van Adrichem Boogaert Netherlands Journal of Geosciences — Geologie en Mijnbouw | 85 – 4 | 2006 245 Time Era Period Epoch Age Lithostratigraphy according to Tectonic phase (Ma) Van Adrichem Boogaert & Kouwe (1993 - 1997) SNOrogeny 0 Pleistocene-Holocene Reuverian Brunssumian Pliocene Messinian Tortonian Neogene Serravallian Upper North Sea Group – NU Miocene Langhian Burdigalian Aquitanian 23 Savian Chattian Oligocene Middle North Sea Group – NM Rupelian 44 Priabonian Pyrenean CENOZOIC Bartonian Paleogene Eocene Lower North Sea Group – NL Lutetian Ypresian Thanetian 62 Paleocene Danian Laramide 65 Maastrichtian Campanian Late Cretaceous Chalk Group – CK Santonian Subhercynian Coniacian Turonian Cenomanian 100 Albian Cretaceous ALPINE Austrian Aptian Rijnland Group – KN Early Cretaceous Barremian Hauterivian 140 Valanginian Ryazanian 145 Portlandian Schieland, Scruff and Schieland Group Niedersachsen groups Late Kimmerian Malm Kimmeridgian SL SL, SG, SK Late Oxfordian 161 Callovian Bathonian Mid-Kimmerian MESOZOIC Dogger Bajocian Jurassic Middle Aalenian Toarcian Altena Group – AT Pliensbachian Lias Early Sinemurian Hettangian 200 203 Rhaetian Norian Early Kimmerian Keuper Late Upper Germanic Trias Group – RN Triassic Carnian Ladinian M Muschelkalk 245 Anisian E Buntsandstein Olenekian Lower Germanic Trias Group – RB Hardegsen 251 Induan Changhsingian Lopingian Zechstein Group – ZE Late Wuchiapingian 260 Capitanian M Guadalupian Wordian Upper Rotliegend Group – RO Roadian Kungurian Permian Artinskian Lower Rotliegend 285 Cisuralian Group – RV Saalian Early Sakmarian Asselian 299 Stephanian Asturian Westphalian Silesian Limburg Group – DC PALEOZOIC Sudetian Namurian VARISCAN 326 Carboniferous Visean 345 Dinantian Carboniferous Limestone Group – CL Early Late Tournaisian 359 Fig. 1. Geological time scale (after Gradstein et al, 2004) and lithostratigraphic column (after Van Adrichem Boogaert & Kouwe, 1993 - 1997) showing main tectonic deformation phases. 246 Netherlands Journal of Geosciences — Geologie en Mijnbouw | 85 – 4 | 2006 & Kouwe (1993 - 1997). Earlier structural geological models and of subsidence, faulting, uplift and erosion during a specific studies of basin evolution in the Netherlands have been time interval. The structural element maps have been published by Heybroek (1974), Van Wijhe (1987), Rijkers & reconstructed from the depth and thickness maps presented in Duin (1994), Racero-Baena & Drake (1996), Rijkers & Geluk this paper. In order to map these regional structural elements (1996), Dirkzwager (2002), Wórum (2004), Van Balen et al. systematically, the following structural types are used: basin, (2005) and De Jager (in press). All depth maps, thickness maps high, platform and fault (-zone). The boundaries of structural and figures that are presented in this paper can be downloaded elements, including basins, are delineated by subcrops, (major) from www.nlog.nl. faults or salt structures. In this study a high is defined as an area Further improvement of the structural reconstruction with significant erosion down into Carboniferous or Permian is necessary to explain geological distribution of aquifers, strata (Rotliegend and/or Zechstein). A platform is characterized reservoirs and hydrocarbon systems. In particular the by Late Jurassic erosion into the Triassic and the absence of reconstruction and timing of salt tectonics in the Netherlands Lower and Upper Jurassic strata. The term graben is used for can be improved strongly. Regional maps are also required for subsided structural elements that are clearly delineated by major analysis of paleo-stress fields and timing of salt movement linear faulting. Exceptions on this systematical methodology and contribute to an improved understanding of fault in nomenclature of structural elements are the Ems Low (EL), patterns, reservoir configuration and burial evolution on a Lauwerszee Trough (LT), Netherlands Swell (NS) and Zandvoort local scale. Ridge (ZR). These names are not changed because of their common use in literature. Data base and map reliability The regional structural elements have been reconstructed for six tectono-stratigraphic periods, namely Late Carboniferous - The data used for the construction of the maps were acquired Early Permian (Variscan phases), Middle and Late Permian, from various oil companies during their exploration and Triassic (Early Kimmerian phase), Late Jurassic (Late Kimmerian production activities since the beginning of the 20th century. phase), Late Cretaceous (Subhercynian phase) and Cenozoic For this project, only publicly released seismic and borehole (Laramide, Pyrenean and Savian phases) (Figs 4a - 4f). Improved data have been used (Fig. 2). The stratigraphic information of delineation of basin structures is obtained by using the 1756 boreholes has been incorporated in the interpretation of subcrops of the Lower and Upper Jurassic strata. Table 1a the seismic data. The interpreted seismic data were converted indicates the active geological period for each structural from time to depth using the seismic velocity model of Van element with regional significance that is recognized in these Dalfsen et al. (this volume). In contrast to the onshore area, new maps. Major fault zones that are indicated in the the offshore part shows a lower density of used seismic lines. deformation scheme in Table 1a are recognized both in the In the onshore area much more seismic data were available maps and the cross sections. In Table 1b the geological than in the offshore region resulting in a higher reliability of description and the used abbreviations of these main the map data in the onshore area. Offshore areas in which 3D structural elements are given. It is strongly recommended not seismic data have been