St Monans Fossil Hunting

1859–1861 – Early coastal stratigraphy described
T. Brown distinguished the limestone-bearing part of the St Monans coastal succession from adjacent strata and published further observations. The historical ‘Mountain Limestone’ grouping included beds later placed below the Lower Limestone Formation.

1902 – Detailed shore succession compiled
J. W. Kirkby’s measured coastal section and fossil lists were incorporated into A. Geikie’s account. This established a durable bed-by-bed framework, although the White Limestone was then incorrectly correlated with the Hurlet Limestone.

1917 – White Limestone correlation challenged
P. Macnair proposed that the White Limestone lay below the Hurlet horizon, identifying the next major limestone, now called the St Monans Brecciated Limestone, as the Hurlet equivalent. Later borehole correlations supported that distinction.

1923 – Lateral variation and fault effects clarified
D. Tait and J. Wright examined the Pathhead exposures, documenting changes in the White Limestone and its associated beds across the foreshore. They also related the striking brecciation of the Brecciated Limestone to local faulting.

1943 – A St Monans trilobite named
F. R. C. Reed named Weberides parilis var. cuspidata from material east of St Monans. Later revision treated this distinctive trilobite as a separate species. This is a naming milestone, not a known date of collection.

1966 – Neilson Shell Bed recognised in the succession
R. B. Wilson’s shell-bed work identified the distinctive marine assemblage above the Charlestown Main Limestone. It provided an additional way to correlate the shore succession using fossils rather than appearance alone.

1968 – Boreholes strengthen the correlation framework
I. H. Forsyth and J. I. Chisholm integrated the east-Fife boreholes with coastal sections, including St Monans. The work reinforced the Brecciated–Hurlet correlation and clarified the position of the higher limestone horizons; the boreholes were regional evidence, not all drilled on this shore.

1970 – Trace fossils studied in detail
J. I. Chisholm published a study of Teichichnus and related fossils from St Monans. The burrowed beds became an important part of interpreting the sedimentary environments, alongside shells, corals and crinoids.

1970 – Trilobite type material revised
Halszka Osmólska treated the species as Paladin cuspidatus and identified a head shield, RSM 1958.1.2683, as its lectotype. Her revision illustrated the east-of-St-Monans material and distinguished it from related forms.

1977 – Revised geological synthesis published
Forsyth and Chisholm combined the measured beds, shore structure, regional correlations and fossil-locality records in a detailed geological account. The synthesis distinguished the White Limestone from the base of the Lower Limestone succession and documented substantial lateral variation.

1996 – Field excursion synthesis updated
The third edition of A. R. MacGregor’s field guide presented detailed bed tables and descriptions of the pool, Pathhead faults and syncline. The account remains useful for relating fossil-bearing horizons to the shore, while its historical measurements need to be read with their local qualifications.

Scope, measurements and formation boundary
This account follows the harbour-to-Pathhead shore, with the older Pathhead marine bands included only as nearby stratigraphical context beyond the White Limestone stop. It does not import the west-of-harbour, Newark or Ardross exposures. Thicknesses below are published local descriptions, principally the 1996 excursion tables; they are not a new survey or a promise of present-day exposure. Faulted packages are not summed into a total thickness. Named limestones, coals and marine bands here are beds and horizons rather than formal members.

STRATHCLYDE GROUP

Pathhead Formation

Modern definition and older usage
The modern formation begins at the West Braes Marine Band and ends at the base of the Hurlet-equivalent St Monans Brecciated Limestone. Its formal base lies above the base of the older ‘Pathhead Beds’ used in the 1977 account; old whole-unit thicknesses therefore do not define the modern formation. The St Monans White Limestone remains within the Pathhead Formation. The beds described here belong to its upper part, in the Brigantian.

Pathhead Lower Marine Band: nearby lower context
The excursion records 1.2 m of shale with thin limestone and carbonate nodules, yielding corals, brachiopods, bivalves and crinoids. This band lies below the White Limestone succession and may require continuing beyond the core guide endpoint. It is followed upwards by 3.6 m of thinly bedded, rooted sandstone, indicating a change from marine deposition towards vegetated ground.

Pathhead Upper Marine Band and overlying rooted beds
The next marine interval is described as 6.0 m of contorted shaly and sandy beds with Lingula in the excursion. The Survey gives 5.5 m for its mudstone development; these descriptions should not be presented as identical measurements. Above it the excursion logs 7.3 m of sandstone with a seatearth near the base and bioturbation towards the top, then 6.5 m of interbedded sandstone and shale with ironstone and calcareous bands.

Coal and the beds immediately below the White Limestone
Ascending towards the White Limestone, the excursion distinguishes a 0.7 m package of thin coal and seatearth, 2.5 m of sandstone and shale with the upper 2 m bioturbated, 0.9 m of partly thin-bedded sandstone, and 1.2 m of bivalve-bearing shale. The 0.7 m figure is not the coal thickness alone. The locality description identifies intensely Teichichnus-burrowed sandstone about 4 m below the limestone, overlain by about 1 m of fossiliferous grey shale whose upper 5 cm is oil shale with yellow jarosite efflorescence at high-water mark.

St Monans White Limestone
The excursion gives a total of 4.3 m, including a basal 0.7 m crystalline dolomitic band and a conspicuous central brown dolomitic band listed as 0.7 m in its table but described as 0.8 m in its prose. Lower beds are brownish, crinoidal and dolomitic; the pale upper beds are rich in colonial coral, historically Lithostrotion junceum, now Siphonodendron junceum. Brachiopods are also recorded under historical generic names. The Survey describes about 5 m at high-water mark, NO 5381 0212, with a nodular, greenish-clay-patched top, but only 2.4 m towards low-water mark, where the rock is mainly crinoidal and corals concentrate near the top. Fossiliferous mudstone there replaces part of the upper limestone laterally. This variation is geological, not a single thickness to be averaged.

Beds above the White Limestone
The excursion table distinguishes 7.3 m of shale with ironstone bands, including a historically Camarotoechia-rich band about 2 m above the base, then 3.0 m of strongly bioturbated sandstone and seatearth, and 5.0 m of dark grey shale below the succeeding Lower Limestone Formation. Its locality prose refers more generally to about 10 m of mainly marine shale above the limestone. The Survey also records a pale-grey mudstone and thin coal below roughly 4 m of varied marine strata at the approach to the Brecciated Limestone. These accounts reflect a variable, fault-affected transition and should not be forced into one exact total.

CLACKMANNAN GROUP

Lower Limestone Formation

St Monans Brecciated Limestone: Hurlet equivalent
The base of this bed marks the formation boundary. At Pathhead on the eastern limb of the syncline, the limestone is about 3.5 m thick, nodular and crinoidal, with branching thin shaly or clayey seams around nodules. The excursion describes nodules up to about 25 cm thick and 25–50 cm long. Much of the conspicuous fragmentation is confined to the vicinity of the Pathhead Fault; it is not evidence that the entire bed was deposited as rubble. The relatively erodible limestone commonly forms a trough rather than a prominent reef.

Shales and fault-interrupted sandstone below the Little Limestone
Above the Brecciated Limestone, the excursion lists 2.7 m of micaceous sandy shale, then a combined 11 m package of grey shale with ironstone nodules, sandy shale with sandstone laminae, and sandstone with cross-bedding, ripple cross-bedding and convoluted bedding. Much of this package is cut out at high-water mark by the Pathhead Fault, although more is seen lower on the shore. A further 1.5 m of sandy shale lies below the Little Limestone. The 11 m is a combined package, not a single uninterrupted bed.

St Monans Little Limestone
The excursion gives 0.9 m and describes crinoids and large productid brachiopods, pale grey or buff weathering, and an uppermost 5 cm stained by hematite. The Survey measures about 0.8 m on the east limb, at the type locality NO 5376 0210, and describes patchy dolomitisation with less resistant non-dolomitic areas. The slightly different published values are retained as source-specific measurements rather than a new precise thickness.

Radernie coal-bearing interval
Above the Little Limestone lie 4.3 m of micaceous sandy shale with ironstone nodules and thin sandstone near the top, followed by 4.6 m of sandstone, mudstone, seatearth and thin coals. The latter is the mixed Radernie coal package, not 4.6 m of coal. The excursion notes that the coal seams at the shore are only a few centimetres thick, unlike much thicker inland seams. A 2.3 m massive sandstone with large plant fragments near its top follows, then 0.9 m of shale with a seatearth at its base below Charlestown Main.

Charlestown Main Limestone
This limestone, equivalent to the Blackhall Limestone in the wider correlation scheme, is about 1.5 m in the excursion and 1.5–1.6 m in the Survey’s shore description. The excursion separates a lower 0.6 m bed from an upper 0.9 m bed by an impersistent shale seam about 3 cm thick. The grey limestone is crinoidal and commonly dolomitised, with bioturbation; the Survey records non-dolomitic patches and layers as well. It is a bed within the Lower Limestone Formation, not a formation that interrupts and then replaces it.

Neilson Shell Bed and succeeding shale
The excursion table records 1.5 m of shale containing the Neilson Shell Bed above Charlestown Main, followed by 22 m of grey shale with ironstone nodules and increasingly abundant sandy beds. The locality prose describes about 21 m of dark grey shale and carbonate nodules, with the shell-bed assemblage near the base. Treat 21 and 22 m as approximate, differently described published intervals rather than matching independent measurements. Historical shell-bed records include Straparollus carbonarius and Posidonia corrugata gigantea; their names and horizon are recorded historically rather than offered as newly revised determinations.

Sandstone and Mill Hill Marine Band
Above the thick shale interval, the excursion logs about 12 m of sandstone, silty towards its base, followed by 1.5 m of shale containing the thin sandy Mill Hill Marine Band. Sedimentary structures in the sandier succession include starved ripples, an erosion surface with shale clasts and flute casts; black pyritous shale and sandstone with large concretions also occur. The marine band provides evidence for renewed marine conditions among the sandy beds, rather than an entirely new formation.

Largoward Black Coal and Seafield Marine Band
The table places a 15 m sandstone-and-coal package above Mill Hill, including the Largoward Black Coal at the seaward wall of the bathing pool. The Survey records a lower coal leaf 0.3–0.4 m thick and an upper leaf 4.5–6 m above it: the latter was historically reported as 1.8 m but only 0.6 m remained visible in the Survey account. Marine grey shale and nodules above the coal contain the Seafield Marine Band. The excursion gives 12 m for that shale package in the table but about 10 m in its pool description. These local/source differences should not be converted into a precise new measurement. The Geological Conservation Review identifies this Seafield Marine Band locality beside the pool as the type locality of the trilobite recorded as Paladin cuspidatus; the type-specimen history is separate from routine abundance claims.

Beds above Seafield and the Lower Kinniny horizon
A 2 m well-jointed sandstone is followed in the excursion table by a 25 m mixed package of sandstone, seatearth, coals up to 0.7 m and shales up to 2 m. Sandstone near the pool is strongly burrowed, including Teichichnus and Planolites at the west steps. The Largoward Splint Coal is poorly displayed because of old workings. Its overlying marine mudstone represents the Lower Kinniny Limestone horizon; the limestone itself is absent in east Fife. The Survey records further marine bivalve-bearing mudstone and well-developed Teichichnus in the succeeding sandy interval. The 25 m package is neither one sandstone bed nor a coal thickness.

Mid Kinniny Limestone and the upper exposed beds
The excursion table gives 1.5 m for the Mid Kinniny Limestone, while its local description, approximately 160 m west of the bathing pool and 4 m south of the path, gives about 1 m. The upper 15 cm carries abundant Zoophycos markings. The Survey describes the shore bed as hard dolomitised crinoidal limestone. Above it, the excursion records 5 m of fossiliferous marine grey shale with ironstone nodules and at least 1 m of sandstone. This is an open-ended exposed section, not proof that the complete formation top is visible. BGS correlates Mid Kinniny with the Second Hosie Limestone. Later foraminiferal work places the base of Second Hosie at the Viséan–Serpukhovian boundary, so an early Serpukhovian (Pendleian) age is applied here by regional correlation, rather than by a new dating study of this exposure.

St Monans Syncline and Pathhead faults
Near the synclinal axis the excursion records a change in dip from 38° north-west to 70° east-south-east within about 3 m, with shattered limestone and a shallow eroded trough along the axial trace. Beds repeat in reverse order towards the harbour, and a small anticline is visible near the harbour mouth only at sufficiently low tide. At Pathhead the main fault has about 18 m of apparent left-lateral outcrop offset; a west-south-west branch offsets the Little Limestone by about 6 m in the opposite sense. These are mapped outcrop offsets, not automatically true vertical throws. Faulting makes the high-water section incomplete.

Raised beaches and route limits
The path near the pool and Mid Kinniny exposure follows a low post-glacial raised beach, backed by a relict cliff. A higher late-glacial raised-beach surface supports the windmill and nearby housing. These are much younger coastal landforms, separate from the Carboniferous succession. The Lower and Upper Ardross limestones and the St Monans volcanic neck are important in wider excursions, but are not silently added as fossil stops on this east-harbour-to-White-Limestone route.

References
Forsyth, I. H. & Chisholm, J. I. (1977), The geology of east Fife, chapters 3–4 and 9
MacGregor, A. R. (1996), Fife and Angus geology, Pittenweem–St Monans excursion
BGS formal Pathhead Formation definition
BGS formal Lower Limestone Formation definition and correlations
Aretz & Nudds (2005), coral systematic account, p.176 (nomenclature only; specimens from Cumbria)
Osmólska (1970), trilobite revision, p.142 and Plate XXI: historical type material from east of St Monans
JNCC: British Lower Carboniferous Stratigraphy, Elie–Anstruther section, pp.38–41
BGS Carboniferous framework (1999), Table 4: Mid Kinniny–Second Hosie correlation
Cózar, Somerville & Burgess (2008): regional Viséan–Serpukhovian boundary evidence