The BGS Lexicon of Named Rock Units — Result Details
Belfast Marls Formation
| Computer Code: | BLFM | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Cenomanian Age (KE) — Cenomanian Age (KE) | ||
| Lithological Description: | Pale grey strongly bioturbated silty marls with a scattering of dark green glauconite grains (not exceeding 40%). Transitional "zone" at the top contains relatively little glauconite. Fossiliferous with concentrations into discrete laterally continuous shell-beds. | ||
| Definition of Lower Boundary: | The lower boundary is unconformable, oversteps various older units, principally Triassic rocks. | ||
| Definition of Upper Boundary: | The upper boundary is at a conformable junction arbitrarily drawn at the base of the lowest persistent hard calcareous siltstone of the overlying Island Magee Siltstones Formation. This junction appears at the top of a transitional zone showing an upward decrease in glauconite content. | ||
| Thickness: | Maximum thickness of a little less than 3m known from a borehole near Magheramorne, Reference Number 84NW/7 [342972 397818] in the Larne (sheet 21) area. Minimum thickness of 1.6m over the Knockagh Axis north of Belfast. | ||
| Geographical Limits: | East Antrim Basin and Southern Uplands area of Northern Ireland. Numerous localities on the Larne, Antrim, Carrickfergus and Belfast sheet areas (see Griffith and Wilson, 1982, p.48, fig.16A). | ||
| Parent Unit: | Hibernian Greensands Group (HBG) | ||
| Previous Name(s): | Belfast Marls Member [Obsolete Name and Code: Use BLFM]
(-1990)
Glauconitic Sands (-65) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Carrs Glen near Belfast. | ||
| Type Section | Cloghfin Port area where three exposures of the formation occur, Woodburn Glen South and 503m northwest of Knock Lodge. | ||
| Reference Section | Borehole near Magheramorne Reference Number 84NW/7 [342972 397818] (NI Sheet 21) Notation J above is replaced by an initial 3 for both the easting and northing in full National Grid References. See reference to borehole in Griffith and Wilson (1982). | ||
| Reference(s): | |||
| Griffith, A E and Wilson, H E. 1982. Geology of the country around Carrickfergus and Bangor. Memoir of the Geological Survey of Northern Ireland. Sheet 29 (Northern Ireland). | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| none recorded or not applicable | |||