Lemanaghan, County Offaly [PDF 1.96 - The Heritage Council

3.5 G E O L O G I C A L S E T T I N G
The geological situation of Lemanaghan is within a faulted syncline of muddy
limestone of Lower Carboniferous age; the syncline is surrounded by Waulsortian
mudbank (‘reef’) limestone, and further to the east by a pure fine limestone
(one of the Irish ‘grey marbles’). Large drift blocks of sandstone also abound
in the area, especially in the wooded area, known locally as ‘The Rocks’, about
2km (1.25 miles) to the north-east of the monastic settlement. These come from
the Basal Sandstone unit of the Lower Carboniferous which is encountered in
boreholes rather than in outcrop in the Ferbane area.
Stonework
Most of the stone used in the buildings at Lemanaghan is of local drift origin;
numerous very large blocks of limestone are characteristic of the local hummocky
drift. The sandstone seems to be of more directly local provenance; drift-derived
boulders of sandstone are generally less rounded but some of the material may
derive from sub-outcrop in the wood to the north-east of the site.
All except the most recent tombstones in the graveyard are limestone, sourced
by local headstone makers outside the immediate area. The early carved slab
in the graveyard is sandstone, as are the few stones that seem to have been
footstones. The cut limestone in the windows and elsewhere in the church is not
of immediately local origin.
3.6 E C O L O G Y
Hedgerows
There is very little out of the ordinary in the ecological heritage of the immediate
site. The hedges by the toghar at the side of the St Managhan's site and
along the Lemanaghan/Pollagh road are of little interest, being predominantly
blackthorn and bramble, with a little elder and birch. The herbaceous vegetation
is mainly weedy species: cleavers, creeping buttercup, couch grass, dandelion,
white clover, perennial rye grass, broad-leaved plantin, ribwort plantin, nettle,
common bent, red fescue, ivy, butterbur, creeping thistle and broad-leaved
dock.
Grassland
There are two grassland communities in the graveyard: one of improved
grassland in the graveyard proper, and a semi-natural grassland at the lower end
dominated by false oat-grass.
The species in the hedge along the togher include sycamore, blackthorn,
whitethorn, elder and privet, with a flora similar to that around the graveyard.
The ditch along the side of the togher has the usual common species for this
type of habitat: wild iris, fool’s water parsley, water horsetail etc. The most
interesting plants are the few specimens of bay willow to the side of the togher
just where it heads across the field.
A noteworthy feature of St Mella’s Cell is the abundance of hemlock, a
poisonous plant that has been widely used in herbal medicine. However,
there is nothing to suggest that its presence here has anything to do with the
archaeological context.
35