FURTHER EVIDENCE OF LATEST SILURIAN WILDFIRE ACTIVITY: CHARRED MESOFOSSILS FROM THE WINNICA FORMATION OF THE HOLY CROSS MOUNTAINS, POLAND

Wildfire in the latest Silurian and earliest Devonian is an important taphonomic factor that has allowed anatomical investigations of charred fossils and led to an enhanced understanding of early land plant evolution. Fire also affords paleoenvironmental insights into both ecosystem structure and atmospheric composition. Compressed rhyniophytoids, of basal Přídolí age occur in the Słupianka Member of the Winnica Formation exposed at Winnica in the Holy Cross Mountains of Poland. These sediments contain an open marine fauna as well as marginal marine and terrestrial elements, and were deposited during delta lobe progradation into a marine environment at sub-tropical latitudes comparable with those of the Anglo-Welsh Basin at this time.

Preliminary macerations of the rhyniophytoid-bearing beds of the Słupianka Mbr. have yielded abundant mesofossils. These three-dimensional fossils include an as yet undescribed cryptophyte, arthropod coprolites and common nematophytic material, some with anatomy comparable to Prototaxites/Nematasketum, but as yet no definitive rhyniophytoid remains. This pre-Devonian flora is comparable with that of other sub-tropical localities in southern Laurussia that typically preserve small and relatively simple embryophytes. As at Ludford Lane in the UK, many of the mesoscopic, anatomically preserved fossils of Winnica appear to be preserved as charcoal and, as such, are further indicative of wildfire activity in the Přídolí. Given the paucity of Přídolí age plant-bearing localities and the diminutive, hydrophilic, nature of the vegetation, especially in the sub-tropics, a second report of wildfire activity suggests that modeled predictions of elevated atmospheric oxygen levels at this time are probably accurate.