Derryvree’s Rosy Saxifrage – Emerald Archives

Dateline

31,520 BCE is not a date at which Irish history can be reconstructed as a sequence of events. No community on the island kept a calendar, wrote an account, named a leader or left a settlement that can be assigned to this single modern year. The responsible frame is the Late Pleistocene, in Marine Isotope Stage 3: a long, climatically volatile part of the last Ice Age. In archaeological convention the label lies roughly 33,470 calendar years before AD 1950, but that conversion is only a way of locating a modern year-number within deep time. It is not evidence for something happening in one season, or even one lifetime.

A Date Range, Not an Anniversary

The best Irish evidence that can illuminate this notional point comes from Derryvree townland, near Maguiresbridge in County Fermanagh. Roadworks in 1969 cut through a drumlin and revealed a remarkable sequence: one body of glacial till below, water-laid silts and fine sands with organic remains in the middle, and another thick till above. The order matters. First ice deposited the lower till; afterwards the locality was ice-free long enough for freshwater sediments, plants and small animals to accumulate; then a later glacier overrode and sealed the deposit.

Organic material from the freshwater series produced a conventional radiocarbon age of 30,500 years before present, with a substantial published uncertainty. Modern calibration does not sharpen that result into a particular year. Rather, scholarship places the Derryvree deposits broadly at about 36,900–31,700 calibrated years before present, approximately 34,950–29,750 BCE. Thus 31,520 BCE falls within the wide calibrated span associated with this local archive, but cannot be pinned to a specific layer, plant, pool or episode within it. The deposit offers an interval of evidence, not a snapshot.

Fresh Water Between Ice Advances

Derryvree’s middle beds are unusually valuable because glaciers have removed or disturbed so much older evidence elsewhere in Ireland. Their fossil contents show that, during the period represented by the sediments, this part of Fermanagh was not continuously entombed beneath ice. It was an open, cold and wet periglacial landscape. Periglacial means shaped by severe frost and ground freezing at the edge of, or beyond, glacier ice; it does not mean that glaciers were absent from the wider region for all time.

The sediments preserve a freshwater setting: shallow pools, saturated ground and silty water rather than woodland soil or a settled lakeshore. Moss remains, sedges and aquatic plants indicate a tundra or muskeg-like mosaic. Among the recorded plant fossils are mountain avens (Dryas octopetala), bogbean (Menyanthes trifoliata) and rosy saxifrage (Saxifraga rosacea). These are not decorative details. They are direct biological traces of the kinds of ground cover able to persist through short summers, long winters and waterlogged hollows. The presence of such plants does not allow a painted panorama of every hillside in Ireland, but it firmly rules out a landscape of continuous temperate forest around Derryvree.

Grasses, sedges, herbs, dwarf shrubs and mosses would have created low, patchy cover. Snow, frost-heave, seasonal thaw and wind exposure probably kept much soil unstable. Pools could form in shallow depressions, while better-drained ridges and gravelly ground supported different plants. The drumlin in which the beds were found was therefore not simply a relic of one ice advance: it enclosed evidence of an intervening watery world that later ice concealed.

An Unstable Island-Edge Climate

Ireland’s climate during Marine Isotope Stage 3 changed abruptly on millennial scales. Evidence from Crag Cave in County Kerry is especially useful for this broader context. Growth of cave calcite, or speleothem, requires liquid water to percolate through ground and rock. U-series dating shows that deposition in this shallow south-western cave occurred episodically during the last glacial cycle, broadly in step with warmer Greenland Interstadials. Interruptions in growth are consistent with colder phases in which sustained freezing restricted infiltration.

Derryvree should consequently be understood within a restless North Atlantic world, not as proof of a single stable climate. At one time its locality could sustain freshwater vegetation; at another, advancing ice could bury it beneath till. The island’s ice margins were neither fixed nor necessarily identical in every region. Conditions in lowland Fermanagh cannot be projected without qualification onto Cork caves, Atlantic headlands, upland Donegal or the basin of the Irish Sea. Later evidence demonstrates that the British–Irish Ice Sheet reached its maximum much later, around 25,000–23,000 years before present, but its growth had a long and geographically uneven prehistory.

Animals in the Open Country

Southern Irish caves provide a complementary, though more complicated, record of Ice Age animals. Castlepook Cave near Doneraile in north Cork has yielded remains of reindeer, giant deer, brown bear, spotted hyaena, foxes, lemmings and woolly mammoth from deposits accumulated across more than one period. Improved radiocarbon pretreatment has shown that several older cave dates needed revision, a warning against treating old collections as simple, undisturbed layers. Still, the assemblage establishes that Ireland supported, at various Late Pleistocene moments, a cold-open-country fauna rather than only the animals of later wooded Ireland.

For the Derryvree interval, reindeer are a plausible part of the wider ecological picture, but no herd can be placed at Fermanagh in 31,520 BCE. Nor do cave bones by themselves show the exact habitats or seasons in which animals lived. Carnivores could carry carcass parts into caves, water could move bones, and nineteenth- and early twentieth-century excavations did not always record contexts to modern standards. The strongest conclusion is modest: Ireland contained usable, though harsh and changing, habitats for cold-adapted plants and animals before the later maximum expansion of the ice sheet.

The Human Question

A reindeer femur from Castlepook has attracted particular attention because it bears a deep linear mark interpreted by zooarchaeologist Ruth Carden as consistent with cutting or chopping by a sharp stone implement while the bone was fresh. County Cork heritage interpretation has presented the bone as approximately 31,000 BCE. If the mark is indeed human-made, it raises the possibility that people visited Ireland during the earlier Upper Palaeolithic, perhaps while moving through the north-western edge of Europe and exploiting large game.

That possibility must not become a fictional settlement story. The bone’s age dates the animal, not independently the instant when the mark was made. The cave collection is mixed, no matching stone tool has been recovered in Ireland, and there is no securely excavated camp, hearth, dwelling, burial, artistic object or human skeletal remain from this period. The femur is important precisely because the evidence is so slight: it may preserve a rare trace of carcass processing, but it cannot identify a people, language, route, number of visitors or length of stay.

There is likewise no basis for describing political institutions, diplomacy, warfare, chiefs, territorial boundaries or organised religion in Ireland at this date. Such categories belong to much later evidence. Small mobile hunter-gatherer groups, if present, would have depended on practical knowledge of animal movements, stone resources, weather and safe shelter. That is an interpretation drawn from comparable Upper Palaeolithic lifeways elsewhere in Europe, not a demonstrated Irish social arrangement. Exchange or travel between Ireland and neighbouring lands is conceivable in a period of lower sea level and altered coasts, but no Irish artefact assemblage currently documents a trade network.

What Derryvree Makes Visible

Derryvree’s rosy saxifrage and other tiny remains are more historically secure than grand narratives. They reveal an Ireland in which ice, frost, freshwater and tundra vegetation repeatedly remade the ground. The local landscape was habitable for specialised plants and, at least regionally and intermittently, for animals adapted to open cold country. Human presence remains a serious but unresolved question at this depth of time. The most truthful account of 31,520 BCE is therefore not an invented episode, but a carefully bounded landscape: wet tundra in Fermanagh, preserved between two advances of the ice.

Primary Sources

Tags: Castlepook Cave, County Cork, Derryvree, Ireland Year by Year, Late Pleistocene, Marine Isotope Stage 3