The BGS Lexicon of Named Rock Units — Result Details
Belfast Marls Formation
Computer Code: | BLFM | Preferred Map Code: | notEntered |
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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) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
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 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(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 |