BibTex format
@inproceedings{Jordan:2012,
author = {Jordan, N and Allison, PA and Hill, JH and Sutton, MD},
title = {Carbonates, ammonites and the fate of aragonite: a new perspective from the Lower Jurassic of Lyme Regis},
year = {2012}
}
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Citation
RIS format (EndNote, RefMan)
TY - CPAPER
AB - The Lower Jurassic Blue Lias Formation at Lyme Regis, Dorset, preserves a diverse assemblage of invertebrate and vertebrate fossils within rhythmic packages of shales, marls and carbonates. One limestone bed in particular, Bed 29, preserves a unique pavement of very large (up to 72 cm) ammonites, initially buried in carbonate mud before diagenetic cementation. The ammonite accumulation is most likely due to sedimentological condensation but the mechanisms for preserving an aragonitic shell long enough for it to be neomorphosed to calcite on the seabed are a challenge for conventional taphonomic models. It has been suggested that early dissolution of aragonite is a major process in offshore deeper ramp settings, resulting in the removal of sediment prior to lithification. We present field-based evidence for a new model of aragonite preservation within a cyclic oxic-anoxic carbonate environment, using ammonite preservation to track the fate of aragonite in different depositional environments. The carbonate sediment provides a short-term geochemical buffer that militates against the dissolution of aragonite sediment and molluscs, allowing neomorphism to calcite under some conditions. The broader implications of this model for the preservation of molluscan shells and reduced sediment dissolution in carbonate environments under variably oxygenated conditions are evaluated.
AU - Jordan,N
AU - Allison,PA
AU - Hill,JH
AU - Sutton,MD
PY - 2012///
TI - Carbonates, ammonites and the fate of aragonite: a new perspective from the Lower Jurassic of Lyme Regis
ER -