Netherlands Journal of Geosciences / Geologie en Mijnbouw 81 (2): 149-158 (2002) Rifting processes in NW-Germany and the German North Sea Sector F. Kockel Eiermarkt 12 B, D-30938 Burgwedel, Germany Manuscript received: September 2000; accepted: January 2002 Abstract Since the beginning of the development of the North German Basin in Stephanian to Early Rotliegend times, rifting played a major role. Nearly all structures in NW-Germany and the German North Sea - (more than 800) - salt diapirs, grabens, in­ verted grabens and inversion structures - are genetically related to rifting. Today, the rifting periods are well dated. We find signs of dilatation at all times except from the Late Aptian to the end of the Turonian. To the contrary, the period of the Co- niacian and Santonian, lasting only five million years was a time of compression, transpression, crustal shortening and inver­ sion. Rifting activities decreased notably after inversion in Late Cretaceous times. Tertiary movements concentrated on a lim­ ited number of major, long existing lineaments. Seismically today NW-Germany and the German North Sea sector is one of the quietest regions in Central Europe. Key words: Rifting, NW Germany, North Sea, Permian, Mesozoic, Tertiary Introduction Zechstein structures (salt and inversion structures) straddling and triggered by these basement faults. The area considered here forms part of the mobile epi-Variscan platform on which the Polish-North Pre-Variscan German and southern North Sea basin developed since the beginning of the Late Permian. This basin The rifted passive northern margin of the Late Pre- with its filling of partly more than 10.000 m of sedi­ cambrian to Silurian Tornquist Ocean is the oldest ments is by no means the result of a mere subsidence well-documented trace of rifting and can be observed caused by the cooling of an early Permian mantle in seismic sections off Riigen in the Baltic Sea. The plume. It represents a complex system of deep rifts southern margin of Baltica, covered with thin Cam­ and rift basins which had been active in different peri­ brian sediments, is step-faulted towards the Tornquist ods of the Mesozoic (Table l).The pattern of base­ Ocean in the SSW.This ocean closed in Early Silurian ment block boundary faults (Fig.l) underlying these times and its passive continental margin was thrusted rifts originated in Permian and Triassic times and be­ from the south by an internally imbricated accre- came frequently reactivated later. Modern reflection tionary wedge of Ordovician and Early Silurian sedi­ seismic measurements by the German oil industry ments called the 'Caledonian front' (Pieske & Neu­ permit the exact dating of the fault movements and mann, 1991; Schluter et al., 1997). reveal a highly complex genetic history of the post- Netherlands Journal of Geosciences / Geologie en Mijnbouw 81 (2) 2002 149 Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.139, on 30 Sep 2021 at 04:47:14, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0016774600022381 symbol floodinga H (DOM) •ra epoch stratigraphic unit in main tectonic and volcanic events regressions (Ma) section erosional periods 1.8 Quaternary Pleistocene, Holocane (q) 1,8 further uplift of the Central Oacman hile Neogene Pliocene 3.5 upNtt and erosion of NW-Germany, HHng toward* N and W S.3 c CW 23.8 Miocene (tmi) 18,5 strong rifling (Upper + Lower Rhine rM), baaaka mid-Miocene flooding 33,7 OHgocena (tol) 9,9 (Hassan), several moderate movements of basement faults 54,8 Palaogana Eocene (too) 21,1 in NW Germany and the German Morth Sea 8,1 Cenozoi (tpo) Saaiandlan/Thanetian flpa) Midway foodlng 85 Oanian, Monttan W 4,0 several regreaelona and MaastrichBan (krma) 6,3 apoalonal periods L. Cretaceous Campanian (krca) 12.2 Campanian flooding Santonian (krsa) 2,3 compression ana inversion in Lower Saxony Basin and erosion in LSB Coniacien (krcc) 3,2 locally at lineaments in the Pompeckj block (P B i (kro) Turortan (krt) 4,5 98.9 Cenomanian (krc) 5,4 Albian (krt) 13,3 P. B. completely flooded E. Cretaceous Aptian (krp) 8,8 end of rifting activities in the Lower Saxony basin Barremian (krb) 6,0 continuous rifting and dieptrtsm Haute rrvlan (krh) Sfl In the Lower Saxony Basin (LSB) ueuaMiisj or nooning (kru) Valanginian (krv) 4,5 of PompeekJ block 142,0 Ryazanian (Wd) 5,4 SerpuM Fm. (loS) emeraien and erosion L. Jurassic Munder Margal Fm. (joM) 8,8 paroxysmal rifting and subsidence of the LSB of Pompeckj block Eimbeekhausen Fm. OoE) LSB isolated from oceans (Malm) GigasFm. floG) rifling and dlapirism in the Lower Saxony Basin Kimmaridge Fm. OoKi) 3,4 and locally on the Pompeckj block M. Klmmaridgian flooding flo) Korallenoolith Fm. floK) 5,3 c 159,4 Heersum Fm. floH) i Callovian QmcO 5,0 progadation of deka'j o M. Jurassic Bathonian (jmbt) 4,8 continuous rifting, dlapirism fiom the N z <jm) Bajocian dmbj) 7,3 formation of the Lower Saxony rift basin flmal) 3.6 180.1 o Aalsnian Toarcian (Jute) 9,5 s E.Jurassic Pliensbechian (jupl) 5,7 e (M Slnemurian flush 6,6 Beginning of rifting in the Lower Saxony Basin M 206.7 Hettangian (June) 3,8 beginning of the Jurassic Exter Fm. (to) 6,0 flooding hi NW Germany Amstadt Fm. (km4) 6,0 Keupar WeserFm. (km3) 4,8 strong rifling (Ems-, Horn-, Gtuckstadt-Graben, (k) Stuttgart Fm. (km2) 1,0 Brunewick-Gifhorn zona and other), main phase of Grabfeld Fm. (km1) 5.5 dlapirism in NW Germany and southern North Sea 231.5 Erfurt Fm. <ku) 2,5 Muschalkalk U. Muschalkalk (mo) marina Ingfasslon from W (m) M. Muschalkalk (mm) 9,5 241 L. Muschalkalk (mu) rifting (Ems-, Horn-, Giuckstadt-Graben and others) marina Ingresston from E U. Buntsandst. Rot Fm. 1-4 (so) Soling Fm. (smS) M. Hardegsen Fm. (smH) strong rifling (Ems-. Horn-, Giuckstadt-Graben ate.) Buntsandstein DetfurthFm. (smD) 11.0 (sm) Volpriahausen Fm (smV) Quickbom Fm. (smQ) local rifling L. Bunt- Catvorde Fm. (suC) 251 sandstain (su) BernburgFm. (suB) Mdlln Fm. (E7) local rifling Friesland Fm. <z6) c OhreFm. <*5) Zachstein Alter Fm. (24) 7,0 (*> LeineFm. (z3) marina ingressun StaBfurt Fm. (z2) local rifting (southern Oldenburg) marina Ingrasslon 258 WerraFm. (Z1) local rifting (Lower Rhine embayment) Copper shale Ingresston RotHegend Upper RotHegend (K>) 38.0 rifling between Elba and Weser 296 (ro+ru) Lower Rotliegend (ru) rifling, strong acid to basic voleanism, intrusions Staphanlan (est) erosion of variaoan L. Carboniferous Westphalian (cwD-A) 24,0 and of Variscan folding In Westphalian D chain Paleozoi 320 Namurian <enC-A) 1 354 E. Carboniferous Dtnantian (ed) 34,0 beginning of Variaoan folding in Rheno-hercynian zona Table 1. Stratigraphic column for NW Germany and major tectonic events.Time scale from Menning (1997) (Carboniferous toTriassic) and Gradsteinetal. (1999). 150 Netherlands Journal of Geosciences / Geologie en Mijnbouw 81 (2) 2002 Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.139, on 30 Sep 2021 at 04:47:14, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0016774600022381 Variscan reservoir rocks. Rifting was caused by the Altmark I- III pulses. The rift boundary faults are covered by The central part of the Rheno-Hercynian zone of the sediments of the Dethlingen Formation (Upper Rot­ Variscan chain was also part of a rift. In Siegenian, liegend). Some of the faults became reactivated in Emsian and Eifelian times the Aachen-Midi Thrust post-Zechstein times. near Aachen formed a prominent rift edge south of There are indications in the German North Sea the Eurasian platform. This was revealed by the bal­ Sector and in Schleswig-Holstein of rifting continu­ anced reconstruction of a deep seismic DEKORP ing into the late Upper Rotliegend times. The halite section (vonWinterfeld &Walter, 1993). deposits intercalated in the Dethlingen and Hannover Grabens and half-grabens are cut into the Car­ Formations in the Horn Graben and in the Gliick- boniferous limestone platform of Dinantian age in stadt Graben are much thicker than on the graben Central UK and it is possible that they extend to­ shoulders (Flensburg Z 1 borehole without salt and wards the east into the North Sea and into Dutch and Schleswig Z 1 in the graben with undisturbed and German waters. thick Dethlingen and Hannover salts). Dinantian rifting has also been assumed for paleo- The next period of rifting is well documented in geographic reasons in the Rheno-Hercynian zone of the Lower Rhine Graben and in the Netherlands. the Variscides to explain the different facies units in Half-graben structures there have been encountered the Harz Mountains (Wachendorf et al., 1995). Later containing thick Zechstein 1 (Werra) halite, which in compressional overprinting during the Variscan the vicinity is lacking. The graben structures are cov­ orogeny, however, reshaped these rifts and horst ered by basal Zechstein 2 sediments and rifting had blocks into imbricated thrust zones. stopped at the onset of the Stassfurt cycle (Geluk, Nevertheless, these early rifting processes had no 1999; Wolf, 1985). influence on the genesis of the Mesozoic structures in Rifting has also been assumed for the Zechstein 2 the North German basin. (Stassfurt) cycle to explain thickness variations (Ziegler, 1989). This should be investigated in more Permian detail. A further pulse of rifting can be observed in Late Block faulting older than Upper Rotliegend is ob­ Zechstein times. In the Dutch-German border zone served in Norwegian and Danish waters north of the (Best, 1989) and in the Netherlands (Geluk, 1999) Duck's Beak.