Skip to main content Accessibility help

Mixed-layer illite/smectite diagenesis in Upper Jurassic claystones from the North Sea and onshore Denmark

  • P. L. Hansen (a1) and H. Lindgreen (a1)


Claystones of Kimmeridgian-Volgian(-Ryazanian) age are the main source rocks for oil in the Central Trough, North Sea, but they are too immature for oil generation in the Norwegian-Danish Basin. This paper describes the diagenesis of mixed-layer illite/smectite (I/S) in these source rocks as investigated by X-ray diffraction and high-resolution electron microscopy, interpretation for both methods being supported by computer simulations. Randomly-ordered I/S with ∼70% illite layers, together with discrete illite, kaolinite, and traces of chlorite and vermiculite, are detrital. The clay mineralogical data suggest the existence of an island at Gassum during part of the Upper Jurassic. Mixed-layer illite/smectite originating from volcanic ash is found in two wells in the Central Trough. The volcanism may be related to a period of stretching in the North Sea graben system during Jurassic-Lower Cretaceous time. Diagenesis has not altered the I/S in the Norwegian-Danish Basin. In the Central Trough, however, the amount of illite layers in I/S increases from ∼70% to ∼90% and the I/S becomes ordered. The volcanic clays have been changed to randomly ordered I/S with ∼50% illite layers. These changes occurred in the Central Trough simultaneously with oil generation.



Hide All
Ahn, J.H. & Peacor, D.R. (1986a) Transmission and analytical electron microscopy of the smectite-to-illite transition. Clays Clay Miner. 34, 165179.
Ahn, J.H. & Peacxdr, D.R. (1986b) Transmission electron microscopy data for rectorite: Implication for the origin and structure of 'fundamental particles'. Clays Clay Miner. 34, 180186.
Anderson, J.U. (1963) An improved pretreatment for mineralogical analysis of samples containing organic matter. Clays Clay Miner. 10, 380388.
Biørlykke, K., Dypvik, H. & Finstad, K.G. (1975) The Kimmeridgean shale, its composition and radioactivity. Pp. 120 in: Jurassic Northern North Sea Symposium 1975 (Finstad, K. G.& Selley, R. C., editors). Norwegian Petroleum Society, Stavanger.
Buzagh, A. & Szepesi, K. (1975) A colloid-chemical method for the determination of the montmorillonite content in bentonites. Acta Chim. Hung. 5, 287298.
Cowley, J.M. & Moodie, A.F. (1957) The scattering of electrons by atoms and crystals. I. A new theoretical approach. Acta Cryst. 10, 609619.
Cradwick, P.D. & Wilson, M.J. (1978) Calculated X-ray diffraction curves for the interpretation of a three- component interstratified system. Clay Miner. 13, 5365.
Dixon, J.E., Fitton, J.G. & Frost, R.T.C. (1981) The tectonic significance of Post-Carboniferous igneous activity in the North Sea Basin. Pp. 121137 in: Petroleum Geology of the Continental Shelf of North West Europe (Illing, L. V. & Hobson, G. D., editors). Institute of Petroleum, London.
Dypvik, H. (1983) Clay mineral transformations in Tertiary and Mesozoic sediments from North Sea. Am. Assoc. Petroleum Geol. Bull. 67, 160165.
Eberl, D.D. (1984) Clay mineral transformation in rocks and soils. Phil. Trans. R. Soc. Lond. A311, 241257.
Gibbs, R.J. (1967) Quantitative X-ray diffraction analysis using clay mineral standards extracted from the samples to be analysed. Clay Miner. 7, 7990.
Hower, J., Eslinger, E.V., Hower, M.E. & Perry, E.A. (1976) Mechanism of burial metamorphism of argillaceous sediments: I. Mineralogical and chemical evidence. Geol. Soc. Am. Bull. 87, 725737.
Howitt, F., Aston, E.R. & Jacque, M. (1975) The occurrence oWurassic volcanics in the North Sea. Pp. 379387 in: Petroleum and the Continental Shelf of North-West Europe 1 (Woodland, A. W., editor). Applied Science Publishers, London.
Hughes, R.E., DeMaris, P.J., White, W.A. & Cowin, D.K. (1987) Origin of clay minerals in Pennsylvanian strata of the Illinois Basin. Pp. 97104 in: Proc. Int. Clay Conf., Denver, 1985 (Schultz, L. G., van Olphen, H. & Mumpton, F. A., editors). Clay Minerals Society, Indiana.
Hurst, A. (1982) The clay mineralogy of Jurassic shales from Brora, NE Scotland. Pp. 677684 in: Proc. Int. Clay Conf. Bologna and Pavia, Italy 1981 (van Olphen, H. & Veniale, F., editors). Elsevier, Amsterdam.
Iijima, S. & Buseck, P.R. (1978) Experimental study of disordered mica structures by high-resolution electron microscopy. Acta Cryst A34, 709719.
Jeans, C.V., Mbrriman, R.J., Mitchell, J.G. & Bland, D.J. (1982) Volcanic clays in the Cretaceous of Southern England and Northern Ireland. Clay Miner. 17, 105156.
Jensen, P.K. (1982) Formation temperatures in the Danish Central Graben. Geol. Survey Denmark Yearbook 1982, 91106.
Jensen, T.F., Holm, L., Frandsen, N. & Michelsen, O. (1986) Jurassic-Lower Cretaceous lithostratigraphic nomenclature for the Danish Central Trough. Geol. Survey Denmark Ser. A, 12, 65 pp.
Knox, R.W.O.B. & Fletcher, B.N. (1978) Bentonites in the lower D beds (Ryazanian) of the Speeton Clay of Yorkshire. Proc. Yorkshire Geol. Soc. 42, 2127.
Larsen, G. (1966) Rhaetic-Jurassic-Lower Cretaceous sediments in the Danish Embayment. (A heavy-mineral study.) DSc thesis. Geol. Survey Denmark. II. Series. No. 91, 127 pp.
Madsen, L. (1974) Approximate geothermal gradients in Denmark and the Danish North Sea sector. Geol Survey Denmark Yearbook 1974, 516.
Michelsen, O. (1978) Stratigraphy and distribution of Jurassic deposits of the Norwegian-Danish Basin. Geol. Survey Denmark Ser. B. 2, 35 pp.
Nadeau, P.H. & Reynolds, R.C. (1981) Burial and contact metamorphism in the Mancos Shale. Clays Clay Miner. 29, 249-259.
Nadeau, P.H., Wilson, M.J. , McHardy, W. J. & Tait, J.M. (1984) Interparticle diffraction: a new concept for interstratified clays. Clay Miner. 19, 757–769.
O'Keefe, M. A. (1973) w-beam lattice images. IV Computed two-dimensional images. Acta Cryst. A29, 389401.
Pearson, M.J., Watkins, D. & Small, J.S. (1982) Clay diagenesis and organic maturation in Northern North Sea sediments. Pp. 665675 in: Proc. Int. Clay Conf., Pavia and Bologna 'Italy' 1981 (Olphen, H. van & Veniale, F., editors). Elsevier, Amsterdam.
Perry, E.A. & Hower, j. (1970) Burial diagenesis in Gulf Coast pelitic sediments. Clays Clay Miner. 18, 165177.
Roth, C.B., Jackson, M.L. & Syers, J.K. (1969) Deferration effect on structural ferrous-ferric iron ratio and CEC of vermiculites and soils. Clays Clay Miner. 17, 253–264.
Schmidt, B.J. (1985) A coat petrographic source rock evaluation of the Rhaetic-Jurassic-Lower Cretaceous sediments of the Berglum 1 and Uglev 1 wells, Denmark. Bull. Geol. Soc. Denmark 33, 239–252.
Scotchman, I.C. (1987) Clay diagenesis in the Kimmeridge Clay Formation, onshore UK, and its relation to organic maturation. Mineral. Mag. 51, 535–551.
Sellwood, B.W. (1972) Regional environment changes across a Lower Jurassic stage-boundary in Britain. Palaeont. 15, 125–157.
Thomsen, E. (1984) A coal petrographical investigation of the well 2/11-1. Geol. Survey Denmark. Internal Report 38, 28 pp.
Thomsen, E., Lindgreen, H. & Wrang, P. (1983) Investigation on the source rock potential of Denmark. Geol Mijnbouw 62, 221–239.
Veblen, D.R. (1983a) Microstructure and mixed-layering in intergrown wonesite, chlorite, talc, biotite, and kaolinite. Am. Miner. 68, 566–580.
Veblen, D.R. (1983b) Exsolution and crystal chemistry of the sodium mica wonesite. Am. Miner. 68, 554–565.
Vollset, J. & Dore, A.G. (1984) A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD Bull. 3, Stavanger, 53 pp.


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed