A SEQUENCE-STRATIGRAPHIC INTERPRETATION OF A MUDSTONE-DOMINATED SUCCESSION - THE LOWER JURASSIC CLEVELAND IRONSTONE FORMATION, UK

Citation
Jhs. Macquaker et Kg. Taylor, A SEQUENCE-STRATIGRAPHIC INTERPRETATION OF A MUDSTONE-DOMINATED SUCCESSION - THE LOWER JURASSIC CLEVELAND IRONSTONE FORMATION, UK, Journal of the Geological Society, 153, 1996, pp. 759-770
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary
Journal title
ISSN journal
0016-7649
Volume
153
Year of publication
1996
Part
5
Pages
759 - 770
Database
ISI
SICI code
0016-7649(1996)153:<759:ASIOAM>2.0.ZU;2-3
Abstract
Microfacies analysis (using optical and backscattered electron imagery ) has been undertaken on 37 samples from the Cleveland Ironstone Forma tion, Staithes, Yorkshire, UK. Four lithofacies were encountered: clay -rich mudstones, silt-rich mudstones, sand-rich mudstones and concreti onary carbonates (two types: berthierine/siderite-rich ironstones and apatite-rich concretionary horizons). Successive units were Found to s tack systematically into upward-coarsening units on a small (0.1-1.0 m ) scale. Upward-coarsening and upward fining packages were also found on a larger (1.0-3.0 m) scale. The small-scale upward-coarsening units are interpreted to be parasequences; while the large scale upward-fin ing and upward-coarsening packages are interpreted to be retrogradatio nal and progradational parasequence sets respectively. The ironstones occur at the level where the stacking patterns change from being overa ll progradational to retrogradational, while the apatite-rich concreti onary units occur al the level where the stacking patterns change from being retrogradational to progradational. The concretionary carbonate s are interpreted to have formed close to/at major stratal surfaces. T he ironstones are interpreted to be either the correlative equivalent of sequence boundaries or part/all, of the forced regressive system tr act; while the apatite-rich units are interpreted to have precipitated close to/at maximum flooding surfaces (condensed sections) and/or maj or transgressive surfaces.