Lacustrine Carbonates and Pedogenesis: Sedimentology and Origin of Palustrine Deposits from the Early Cretaceous Rupelo Formation, W Cameros Basin, N Spain

  1. V. Paul Wright2 and
  2. Maurice E. Tucker3
  1. Nigel H. Platt

Published Online: 8 APR 2009

DOI: 10.1002/9781444304497.ch18

Calcretes

Calcretes

How to Cite

Platt, N. H. (1991) Lacustrine Carbonates and Pedogenesis: Sedimentology and Origin of Palustrine Deposits from the Early Cretaceous Rupelo Formation, W Cameros Basin, N Spain, in Calcretes (eds V. P. Wright and M. E. Tucker), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304497.ch18

Editor Information

  1. 2

    Postgraduate Research Institute of Sedimentology (PRIS), University of Reading, UK

  2. 3

    Department of Geological Sciences, University of Durham, UK

Author Information

  1. Geologisches Institut, Universität Bern, Baltzerstrasse 1, CH-3012 Bern, Switzerland

Publication History

  1. Published Online: 8 APR 2009
  2. Published Print: 13 JUN 1991

ISBN Information

Print ISBN: 9780632031870

Online ISBN: 9781444304497

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Keywords:

  • lacustrine carbonates and pedogenesis - sedimentology and origin of palustrine deposits;
  • open lacustrine facies, containing non-marine biota;
  • marginal lacustrine facies, showing subaerial exposure;
  • vadose zone diagenesis;
  • Rupelo Formation, example of extensional rift setting;
  • ‘laminar calcrete’

Summary

The Berriasian Rupelo Formation of the W Cameros Basin consists of a 2–200 m thickness of marginal and open lacustrine carbonate and associated deposits. Open lacustrine facies contain a non-marine biota with abundant charophytes (both stems and gyrogonites), ostracods, gastropods and rare vertebrates. Carbonate production was mainly biogenic. The associated marginal lacustrine (‘palustrine’) facies show strong indications of subaerial exposure and exhibit a wide variety of pedogenic fabrics. Silicified evaporites found near to the top of the sequence reflect a short hypersaline phase in the lake history. The succession was laid down in a low gradient, shallow lake complex characterized by wide fluctuations of the shoreline.

Carbon and oxygen stable isotope analyses from the carbonates show non-marine values with ranges of δ13C from – 7 to – 11‰ and δ18O from – 3 to –7.5‰. Differences in the isotopic composition of open lacustrine carbonates are consistent with sedimentary evidence of variation in organic productivity within the lake. Analyses from the entire sample suite plot on a linear trend; isotopic compositions become lighter with increasing evidence of pedogenic modification. This suggests progressive vadose zone diagenesis and influence of meteoric waters rich in soil-derived CO2. The stable isotope data thus support evidence from petrography and facies relations that ‘palustrine’ limestones form through pedogenic modification of lake carbonates.