The Upper Cretaceous Succession (Cenomanian- Santonian) of the Staffhorst Shaft, Lower Saxony, Northern Germany: Integrated Bios
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Acta Geologica Polonica, Vol. 49 (1999), No.3, pp. 175-213 The Upper Cretaceous succession (Cenomanian Santonian) of the Staffhorst Shaft, Lower Saxony, northern Germany: integrated biostratigraphic, lithostratigraphic and downhole geophysical log data BIRGIT NIEBUHR 1, REINHARD BALDSCHUHN2, GUNDOLF ERNST3, IRENEUSZ WALASZCZYK4, WOLFGANG WEISS5 & CHRISTOPHER J. WOOD6 I Institut fiir Palaontologie, Bayerische lulills-Maximilians-Universitat, Pleicherwall I, D-97070 Wiirzburg, Germany. E-mail: [email protected] 2 Ernst-Pfliiger-Str. 7, D-30938 Burgdorf-Wettmar, Germany 3 Institutfiir Paliiontologie, Freie Universitat Berlin, Malteser Str. 74-100, D-12249 Berlin, Germany. E-mail: [email protected] 4 Institute of Geology, University of Warsaw, AI. Zwirki i Wigury 93, PL-02-089 Warszawa, Poland. E-mail: [email protected] 5 Bundesanstalt fur Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover, Germany. E-mail: [email protected] 6 Scops Geological Services Ltd., 20 Temple Road, Croydon, Surrey CRO I HT, United Kingdom. ABSTRACT: NIEBUHR, B., BALDSCHUHN, R., ERNST,G., WALASZCZYK, 1., WEISS, W. & WOOD, C.J. 1999. The Upper Cretaceous succession (Cenomanian ~ Santonian) of the Staffhorst Shaft, Lower Saxony, northern Germany: integrated biostratigraphic, lithostratigraphic and downhole geophysical log data. Acta Geologica Polonica, 49 (3),175-213. Warszawa. The Cenomanian to Santonian succession of the Staffhorst shaft, ca. 50 km south of Bremen, because of its struc tural position in the northel11 Gelman Upper Cretaceous basin, is intermediate in character and fossil content between the pelagic sediments characterizing the Pompeckj Block in the north and the proximal sediments of the Lower Saxony Block in the south. The biostratigraphic subdivision of the shaft is based on inoceramids, echi noids, belemnites and foraminifera. The vm10us biozonations and zonal boundm'ies used in the Boreal Realm are compared and applied to the zonation of the shaft succession, and the biostratigrapy of the individual fossil groups is described. A new inoceramid zone, that of Inoceramus gibbosus, is proposed for the topmost Lower Coniacian; and an echinoid assemblage zonation is introduced. The existing benthic foraminiferal zonation of the Middle Turonian to Santonian has been modified, with changed age assignments based on the macrofossil zona tion. The proposed basal stage boundary criteria of the "Second International Symposium on Cretaceous Stage Boundaries" (Brussels, 1995) could be applied only in some cases. The proximity of the Staffhorst shaft to the trial borehole, situated only 39 m away, has permitted the Self Potential (SP) and Resistivity (R) logs to be uniquely directly calibrated against the lithostratigraphical and biostratigraphic succession of the shaft. The pre vious identification of some stage and substage boundaries on the logs of northel11 Gel111an boreholes based on foraminiferal zonation will need to be shifted by several tens of metres as a result of this calibration. Key words: Upper Cretaceous, Northern Germany, structural geology, electric borehole logs, stratigraphy, inoceramids, belemnites, echinoids, foraminifers. 176 BIRGIT NIEBUHR & al. Contents 1. History (B. NIEBUHR) ....................... 82 6. Echinoid stratigraphy (G. ERNST) . .. 97 2. Objectives (B. NIEBUHR) .................... 82 7. Belemnite stratigraphy (G. ERNST) ......... 102 3. Structural development in the Staffuorst 8. Supplementary faunal records (C.J. WOOD) .. 104 area (R. BALDSCHUHN) ....................... 83 9. Foraminiferal stratigraphy (W. WEISS) . .. 106 4. Borehole log peak stratigraphy and lithostratigraphy (B. NIEBUHR) .......... 85 10. Multistratigraphic correlation and conclusions. .. 110 5. Inoceramid stratigraphy (1. WALASZCZYK & c.J. WOOD) ............. 91 References ................................... 1 J 6 1. HISTORY (B. NIEBUHR) sponges) is incorporated into the collection of the University of Hamburg. The echinoids and belem The Staffuorst shaft is situated at the boundary of nites also belong to the collection of the University the Lower Saxony and Pompeckj blocks ca. 50 km of Hamburg, but are temporarily on loan to G. south of Bremen on the ordnance survey map sheet ERNST, Berlin, for further investigation. 3219 (Affinghausen). Boreholes drilled by the Part of the Staffuorst shaft Upper Cretaceous German oil/gas companies (Staffuorst 2 and 3 bore succession (Middle Turonian to Lower Coniacian) holes) prov'ed the Staffuorst Dogger iron ore deposit was already illustrated by WOOD & al. (1984). in 1954. In order to investigate this deposit in detail, Stratigraphic data were published by ERNST & al. the Staffuorst trial borehole was drilled in September (1983). FRIEG & al. (1989) worked on the Albian/ 1960 at grid reference 3492 152/58 44943. One year Cenomanian boundary succession and calibrated the later the excavation of the 6.75 m wide shaft was aranaceous microfauna against the electric borehole started, 39 m south of the Staffuorst trial borehole at logs. By means of the boreholes of the Staffhorst grid reference 3492 152/58 44 904. The Barbara area, KOCKEL (1998) demonstrated certain effects of Erzbergbau GmbH (now Barbara Rohstoffbetriebe the northern German inversion tectonics in the GmbH) was able to prove reserves of oolitic iron Coniacian to Santonian. BALDSCHUHN & al. (1998a) ores of the phosphorite-rich chamositic-sideritic dealt with salt intrusions into the bedrocks. type of ca. 500 Mio. tonnes over an area of ca. 60 km2 (THIENHAUS 1960). Because of the technical problems involved in mining this deposit, the pilot 2. OBJECTIVES (B. NIEBUHR) plant was abandoned in August 1965 and the Staffuorst shaft was closed (ROHRS 1992). This paper deals with the Upper Cretaceous suc Weare grateful for permission to use the logging cession of the shaft, which spans the interval from ca. data and fossil content of the shaft of the Barbara 240 - 790 m. Because of its structural position, the Rohstoffbetriebe GmbH (Porta Westfalica). The fos section mediates between the different facies areas of sil and lithologic material was collected by SPIEGLER the "proximal" Lower Saxony Block, to the south, & SPIEGLER (1964) from the heaps of rock excavat and the "pelagic" Pompeckj Block, to the north. Due ed from the shaft, but not directly from the shaft to the close proximity of the shaft and the the trial itself. Normally each unit of excavated material borehole, Staffhorst provides a unique opportunity, spanned about 4-7 m of strata. The collections of using a variety stratigraphic methods (1) to investi Bundesanstalt flir Geowissenschaften und Rohstoffe gate the appplicatbility to the shaft succession of the (BGR) and the Niedersachsisches Landesamt flir Stage and Substage boundary criteria that were pro Bodenforschung (NUB), Hannover, contain the posed at the Second International Symposium on inoceramids and the microfauna. The supplementary Cretaceous Stage Boundaries, Brussels, 8-16 fauna (ammonites, bivalves, brachiopods, corals, September, 1995 (Cenomanian: TRaGER & KENNEDY UPPER CRETACEOUS OF THE STAFFHORST SHAFT 177 1996; Turonian: BENGTSON 1996; Coniacian: fig. 5) to the left and right of the SP log of the KAUFFMAN & al. 1996; Santonian: LAMOLDA & Staffhorst trial borehole respectively. In chapter 10, HANCOCK 1996); (2) to calibrate the electric logs of "Mulstistratigraphic correlation and conclusions" the trial borehole against the lithostratigraphy and the interpretation of the stratigraphy and the ratio biostratigraphy of the shaft; (3) to apply the recali nale behind the revised positioning of the Stage and brated electric logs to the interpretation of the electric Substage boundaries is comprehensively discussed. logs of the numerous other north German boreholes. This recalibration will be of particularl value to the German oil/gas companies, since the Upper 3. STRUCTURAL DEVELOPMENT IN THE Cretaceous in the older boreholes was almost invari STAFFHORST AREA (R. BALDSCHUHN) ably never cored and the positioning of the Stage and Substage boundaries was mostly based on electric The Staffhorst shaft is situated on the lower logs calibrated by means of foraminiferal biostatig northern flank of the Staffhorst inversion and thrust raphy, using now outdated stage concepts. In chap structure (Text-figs 1-2), which continues towards ter 4, "Borehole log peak stratigraphy and lithos the east into the Blenhorst structure and towards the tratigraphy", the previously applied (BALDSCHUHN west into the Scholen structure. This elongated & JARITZ 1977; KOCH 1977a) and the herein revised structure is part of a thrust fold belt 70 km long and Stage and Substage boundaries are shown (see Text- 15-20 km wide, on the northern margin ofthe invert- go I I Upper Cretaceous ~ subcrop of the Upper Cretaceous ~ " ~ ....•• 0<""""'" ......... ~()______ Upper Cretaceous isocontour lines .::::::::::::::: Lower Cretaceous /' in 100m below mean sea-level r--'('" /, -::-" ~.\/- I ......... ,.",~,,~ I: ._ I - "-, !, I Triassic and Jurassic normal fault o 10km ! I. 1Zechstein (salt dome) .. .. v reverse fault or thrust I Fig. I. Structural location map of the Staffhorst area, Lower Saxony 178 BIRGIT NIEBUHR & al. ed western Lower Saxony Basin, which can be fol The structural development began as early as the lowed from the Steinhuder Meer lineament at the Triassic. In Middle Buntsandstein and Lower Weser river in the east to the Cloppenburg area in Gipskeuper (km1) times, an active synsedimentary, the westnorthwest