Lateral variation within a hiatal-condensed bed and the controls on the formation and occurrence of berthierine ooids: a case study from the Middle Jurassic of NE England, UK
✍ Scribed by M.E. Williams
- Book ID
- 102222411
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 459 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0072-1050
- DOI
- 10.1002/gj.915
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✦ Synopsis
Abstract
Shallow‐marine sandstone and berthierinic, ooidal, sandy limestone form the Hackness Rock Member (HRM), a Callovian‐age hiatal‐condensed bed in NE England. The HRM was deposited in response to a rise in relative sea‐level. Apart from the major hiatal surfaces represented by two significant non‐sequences, it contains a number of other hiatal surfaces representing shorter periods of time. Although the HRM has its own distinctive bioclastic concentrations, early diagenetic mineral assemblages and specific types and degrees of bioturbation, the expression of this bed is variable even over short distances.
Variations in the topography of the sea floor produced local hollows and highs, which account for the lateral variability of the HRM and controlled where berthierine ooids formed. Hollows created ‘clastic/colloidal’ traps where finer‐grained sediment accumulated and had low physical mobility; these conditions favoured intra‐sedimentary growth of berthierine ooids in an early (sub‐oxic) diagenetic environment. In contrast, highs were more susceptible to storm reworking and material was more mobile; these conditions resulted in a lower overall rate of accumulation and a lower degree of shallow, sub‐surface diagenesis. Copyright © 2002 John Wiley & Sons, Ltd.