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A meander‐belt sandstone of the Lower Cretaceous of Southern England
Author(s) -
STEWART D. J.
Publication year - 1981
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.1365-3091.1981.tb01658.x
Subject(s) - geology , meander (mathematics) , conglomerate , facies , cretaceous , erosion , geomorphology , point bar , accretion (finance) , paleontology , geometry , sedimentary rock , structural basin , mathematics , physics , astrophysics
The meander‐belt deposit comprises a sandstone resting on an erosion surface and bounded above and below by massive varicoloured mudstones with rootlet traces. The sandstone unit is composed of six bodies separated from one another, horizontally, by erosion surfaces; together the bodies form a single multilateral sand body. Internally each body is composed of lateral accretion units inclined at up to 6° from the horizontal. Vertical sequences of facies show significant variations but the grain size generally fines upwards. The principal lithofacies within the sandstones are, in common ascending order, intraformational conglomerate, large‐scale cross‐bedded, horizontal bedded and small‐scale cross‐laminated sandstone, and alternate sandstones and mudstones. Current directions are normal to the true slope of accretion surfaces and show insignificant scatter within individual bodies but are very diverse overall. Five of the sand bodies are believed to represent individual point bars, and one body an abandoned channel. Together they comprise the meander belt. The river was subject to very variable discharges and carried high suspended loads. Analysis of vertical profiles indicates that grain size segregation along the length of the point bars caused differentiation of the bars into coarse‐grained heads and sandy tails.