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LIMONITIC CONCRETIONS FROM THE EUROPEAN JURASSIC, WITH PARTICULAR REFERENCE TO THE “SNUFF‐BOXES” OF SOUTHERN ENGLAND
Author(s) -
GATRALL MICHAEL,
JENKYNS HUGH C.,
PARSONS COLIN F.
Publication year - 1972
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.1972.tb00004.x
Subject(s) - geology , sedimentology , waves and shallow water , paleontology , geochemistry , carbonate , oceanography , materials science , metallurgy
Large discoid (1–30 cm), carbonate‐rich limonitic concretions or “snuff‐boxes” are contained in stratigraphically condensed limestones from the Jurassic of southern England and parts of Europe. Their general association with conglomerates and algal stromatolites suggests formation in turbulent shallow water on submarine swells, or a shallow marginal shelf. The surprisingly uniform growth‐form of the “snuff‐boxes”, together with their gradation into obvious calcareous oncolites and stromatolites, is taken as evidence that they too may have been formed, at least partially, under algal influence. The geochemistry of the concretions, dominantly ferruginous, with subordinate phosphate, suggests deposition in an epicontinental environment, probably under the influence of considerable river drainage. They therefore contrast with the more trace‐element rich ferromanganese nodules which occur in some condensed pelagic sequences.