Carbonate tidal rhythmites from the Middle Jurassic of Britain
Article first published online: 14 JUN 2006
Volume 28, Issue 5, pages 689–698, October 1981
How to Cite
ASHTON, M. (1981), Carbonate tidal rhythmites from the Middle Jurassic of Britain. Sedimentology, 28: 689–698. doi: 10.1111/j.1365-3091.1981.tb01929.x
- Issue published online: 14 JUN 2006
- Article first published online: 14 JUN 2006
- (Manuscript received 4 February 1980; revision received 24 October 1980)
Newly discovered carbonate laminites are described from the Lincolnshire Limestone Formation (Middle Jurassic, Britain). These occur in the upper peloidal unit of fining-upward rhythms which comprise much of the lagoonal lower Lincolnshire Limestone in south Lincolnshire. The flat, millimetre-scale laminations are of three types: (1) alternating peloid-rich, peloid-poor laminae; (2) alternating bioclastic and peloidal laminae; (3) alternating bioclastic and micritic laminae. In all three types, small-scale cross-laminated sets (usually < 40 mm thick) also occur. The laminite horizons are usually < 150 mm thick and have, in some cases, been traced laterally for ∼100 m.
The close analogy of these carbonate laminites with siliciclastic counterparts favours their interpretation as tidal rhythmites, mechanically deposited in a low intertidal/shallow subtidal setting. The associated sedimentary features and overall stratigraphic-sedimentologic position of the deposits support this conclusion.
According to the literature, mechanically deposited as opposed to algally induced carbonate laminites are rare outside the supratidal realm. Possible reasons for the real or imagined scarcity of intertidal/ subtidal carbonate laminites in ancient sedimentary regimes are discussed.