Isotopic and Trace Element Evidence for Submarine Lithification of Hardgrounds in the Jurassic of Eastern England

  1. Maurice E. Tucker3 and
  2. Robin G. C. Bathurst4
  1. James D. Marshall and
  2. Michael Ashton

Published Online: 29 APR 2009

DOI: 10.1002/9781444304510.ch9

Carbonate Diagenesis

Carbonate Diagenesis

How to Cite

Marshall, J. D. and Ashton, M. (1990) Isotopic and Trace Element Evidence for Submarine Lithification of Hardgrounds in the Jurassic of Eastern England, in Carbonate Diagenesis (eds M. E. Tucker and R. G. C. Bathurst), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304510.ch9

Editor Information

  1. 3

    Department of Geological Sciences, University of Durham, UK

  2. 4

    Derwen Deg Fawr, Llanfair DC, Ruthin, Clwyd, North Wales, UK

Author Information

  1. Department of Geology, The University, Leicester, LE1 7RH, UK

  1. Department of Earth Sciences, University of Liverpool, Liverpool L69 3BX, and Badley, Ashton & Associates Ltd, Winceby, Horncastle, Lincs LN9 6PB, UK

Publication History

  1. Published Online: 29 APR 2009
  2. Published Print: 21 AUG 1990

ISBN Information

Print ISBN: 9780632029389

Online ISBN: 9781444304510

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Keywords:

  • isotopic and trace element evidence - submarine lithification of hardgrounds;
  • geochemical and petrographic data, suggesting early submarine cementation;
  • Leadenham, early lithification being superficial;
  • hardgrounds, surfaces of synsedimentary lithification;
  • carbonate succession of Lincolnshire Limestone Formation, reflecting landward migration;
  • Lincolnshire Limestone, major marine carbonate formation within Middle Jurassic;
  • Lincolnshire Limestone hardgrounds, undergoing synsedimentary submarine lithification

Summary

Geochemical and petrographic data suggest early submarine cementation of hardgrounds from the Lincolnshire Limestone Formation, Middle Jurassic, England. The three hardgrounds, from Cow-thick, Castle Bytham and Leadenham quarries, developed in tidal-inlet, on-barrier and lagoonal sub-environments of a carbonate barrier–island complex. At Cowthick early composite (acicular-bladed) radial-fibrous cements, which pre-date aragonite dissolution, completely fill intergranular pore-space at the hardground surface; away from it isopachous fringing cements decrease in thickness. Microprobe analyses demonstrate zoning within the fringes with magnesium concentrations (> 2 wt % MgCO3) higher than those in allochems or later, ferroan cement (≏0.5 wt % MgCO3, 1·7 wt % FeCO3). At Castle Bytham early granular isopachous cements, which post-date aragonite dissolution, occur within 5 cm of the surface. At Leadenham early lithification is superficial and represented by ferruginous crusts and micritic internal sediment. Late blocky cement fills residual pore-space in all three examples. Carbon and oxygen isotopic composition of whole-rock samples taken at intervals away from each hardground surface demonstrate the increasing proportion of late 18O depleted cements (δ18O−8 to −10). Early cements must have a marine isotopic composition; different δ18O values from each hardground reflect the intensity of early lithification and exclusion of late cements at the hardened surface. There is no isotopic evidence for subaerial cement precipitation during possible emergence at Castle Bytham. Oyster samples (with δ18O, −2·9 and δ13C, 2·4) give estimated palaeotemperatures of 22–25°C. Early cements from Cowthick are enriched in 18O and 13C (δ18O = 0 δ13C ≏ 3‰) compared to the oyster values. In conjunction with trace element data this is interpreted as evidence for high-magnesium calcite precursor cements which underwent replacement in a system with a low water: rock ratio. The intensity of early lithification is related to depositional environment: maximum circulation of sea-water producing the most lithified hardground (Cowthick). This is directly analogous to the formation of Recent hardgrounds.